Water We Talking About // Eve Nnaji _ Master in Advanced Architecture Thesis

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WATER WE TALKING ABOUT? A city, citizen, and water dialogue

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Natural flood management in Lagos, Nigeria, through participatory river strategies

by Eve Nnaji

_ Advisors: Mathilde Marengo + Gonzalo Delacámara _

IAAC, 2021

_ Wat e r We Tal k in g Ab o u t ? _

WATER WE TALKING ABOUT?

]

A city, citizen, and water dialogue Natural flood management in Lagos, Nigeria, through participatory river strategies

Research Thesis Developed by

_ Eve Nnaji _

Thesis Advisors

_ Mathilde Marengo + Gonzalo Delacámara _

Institute for Advanced Architecture of Catalonia Master in Advanced Architecture

Barcelona September, 2021

_ Water We Talking About? _ MAA02: Eve Nnaji

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_ Wat e r We Tal k in g Ab o u t ? _

ACKNOWLEDGEMENT _

Thank God. Second of all I would like to thank my thesis advisors Mathilde Marengo and Gonzalo Delacámara, who mentored me through the inception, development, and completion of my thesis. With great encouragement, praise and criticism, patience, and humor, they guided me towards the realization of a truly passionate and informed project.

Next, I would like to thank the Institute for Advanced Architecture of Catalonia for their full support by providing apt advisors and facilities to carry out this project, as well as their efforts made through the transition to a COVID-compliant education process.

I would like to thank my family and friends for their support through the hours spent listening to me rant about nothing but water.

_ Water We Talking About? _ MAA02: Eve Nnaji

Last, but absolutely not least, I’d like to thank the city of Lagos, Nigeria.

The time spent in this city has led to life-changing decisions due to the intense realities it has presented to me. I owe my drive and motivation to the impossibilities I have witnessed to be possible in this city. The people that have sprouted from the extremely trying conditions of Lagos, are the pure inspiration for the effort mustered to develop and execute this project.

It is an absolute honor to call myself a Lagosion, and a Nigerian. Thank you for the insanity you have gifted to me.

This thesis illustrates the issues resulting in the environmental problem of urban flooding in

_ Wat e r We Tal k in g Ab o u t ? _

Lagos, Nigeria in order to propose solutions that encompass democratic flood risk management.

The solutions proposed in this thesis focuses on practical applications that can be implemented in the study region. This thesis is a combination of theoretical approach and applied research that combines a holistic vision of the insertion of the research in a broader scenario with a specific description and analysis of the own research process and the results obtained. This research was developed with the intention of delivering a phased project implementation program to be for Lagos, Nigeria.

CONTENTS _

01 - Abstract 02 - INTRODUCTION - Climate Change and Water Risk 03 - REGIONAL STUDIES - Nigeria’s Water Networks

3.1 - Oyo, Osun, Ogun, & Lagos State

3.2 - Regional Flood Causes Conclusions

04 - LAGOS URBAN ANALYSIS - Identification of the contributors to urban flooding

4.1 - Water as a resource (city and citizen water relationship)

4.2 - Urban activities along the waterway (city and citizen

water relationship)

4.3 - Impact analysis and an identity crisis; the river as a

residual space 05 - STRATEGY - Renature, Reculture

5.1 - Democratic Flood Risk Management

5.1.1 - Renaturalization strategy; quality, quantity,

hydromorphology

5.1.2 - Reculturalization (deifying the river to create

an identity)

5.2 - Establishing a dialect using flows

5.2.1 - River dialects; making the invisible visible and

legible (Case studies; Makoko, phumdis)

5.2.2 - Mapping the hydrological processes of the

waterway and floodplain 06 - PROPOSAL - What We’re Talking About

6.1 - Designing for bund microcatchments

6.2 - Application and implementation strategy 07 - CLOSING - A New Dialogue...

_ Water We Talking About? _ MAA02: Eve Nnaji

08 - REFERENCES

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Fig. 01. Google Earth - Oyan Dam. Abeokuta, Ogun State

01 . ABSTRACT _

SCIENTIFIC INTEREST _

Lagos, Nigeria and rapidly developing cities like it are destined for a life spent largely underwater unless reformational measures are put in place. Lagos is undergoing rapid urbanization with a 13 million population growing at 3.2%. This leads to environmental problems such as poor infrastructure and increased flooding. Urbanization has led to a 35% increase in flood economic risks and €500 million euros in economic damage (Komolafe, Adegboyega and Akinluyi, 2015).

AIM _

Water we talking about? reconnects a dialogue between the city, the citizens, and their water by creating natural, democratic flood risk management systems perpetuated by the inhabitants of Lagos, Nigeria.

How can the understanding of hydrological aspects and the decentralization of this information be used to transcend recurring problems plaguing the region’s ecological systems.

EXPECTED RESULTS _

_ Water We Talking About? _ MAA02: Eve Nnaji

This research was developed with the intention of delivering a phased rehabilitation program to be implemented in Lagos, Nigeria. The implementation of natural environmental rehabilitation, environmental control, and cultural intergration strategies for flood mitigation in Lagos, Nigeria was developed to serve as a model for the neighboring cities facing the same problem in the country.

_ Wat e r We Tal k in g Ab o u t ? _

Fig. 02. Google Earth - Magboro Soil. Magboro, Ogun State

01 . ABSTRACT _

METHODOLOGY _

The first part of this research investigates the waterways and the cities in order to identify the main cause of urban flooding in relation to the bodies of water. The northern states are used as the starting point for tracing the activities occurring from upstream to downstream, ending at the Atlantic Ocean. This region’s water relationship is also investigated by understanding how the city and citizens manage and interact with their water sources. An analysis of the ground conditions taking place around the waterways is conducted to understand how the citizens are utilizing and changing these waterways on a daily basis.

This research then analyzes the hydrodynamic effects occurring due to the changes in the environment and the changes spurred by citizen activity within the waterways. The linear urban structure currently hinders progress towards flood mitigation, thus a democratic flood risk management system is developed in order to engage the most important stakeholders, the citizens. A strategy of applying communication to the river is ensured through computational methods. By understanding and utilizing the historical measures once used to enable and uninhibit the river’s function, a series of communication forms are catalogued by simulating the movements of the river and translating them into a formal language, river dialects.

_ Water We Talking About? _ MAA02: Eve Nnaji

The final part of the research illustratres how micro-catchments can be used to create natural flood controls by understanding the hydrological processes of the floodways and the floodpain and proposing microcatchment strategy maps. Finally, an implementation plan is proposed in order to direct the engagement of the citizens and ensure the intergration of the proposal with its environment.

02 . INTRODUCTION _ Climate Change and Water Risk

_ Water We Talking About? _ MAA02: Eve Nnaji

02 . INTRODUCTION - Climate Change and Water Risk _

CLIMATE CHANGE _

Less than 1% of all freshwater available for people to use is about 12,500 km3 of water, amounting to 6,600 m3 per person/year. Only 48% of the inhabitants of the urban and semi-urban areas of Nigeria and 39% of rural areas have access to potable water supply.

Global water demand for all uses, presently about 4,600 km3 per year, will increase by 20% to 30% by 2050, up to 5,500 to 6,000 km3 per year.

Global water demand for agriculture will increase by 60% by 2025.8 By 2050 the global population will increase to between 9.4 to 10.2 billion people, an increment of 22% to 32%.1 Most of the population growth will occur in Africa, +1.3 billion, or +108% of the present value, and Asia, +0.75 billion, or +18% of the present value (Boretti and Rosa, 2019).

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Climate change is an increasingly acute issue with impacts devastating some of the most vulnerable regions worldwide. Impacts of climate change include increasing rainfall, rising temperatures, irregular seasonal patterns, and environmental deterioration from extreme natural disasters such as constant forest fires. These occurrences are not only decimating the economies that survive of these landscapes but are hindering the growth and recovery of vulnerable ecosystems that need to develop over long periods of time.

Fig. 03. Global Water Crisis

_ Water We Talking About? _ MAA02: Eve Nnaji

Source: Afolabi Sotunde/Reuters. Flooding in the Nigerian state of Kogi on Monday.

02 . INTRODUCTION - Climate Change and Water Risk _

CLIMATE CHANGE IN LAGOS _

Lagos, Nigeria is undergoing rapid urbanization with a 13 million population growing at 3.2%. Urbanization has led to a 35% increase in flood economic risks and 5.3 billion euros in economic damage (Komolafe, Adegboyega and Akinluyi, 2015). Lagos can be divided into three socioeconomic typologies, upper, middle, and low income areas. Approximately 70% of the city’s population lives in lower income areas characterized as slums (Adelekan, 2010). These vulnerable areas consisting of structures composed with temporary and second-hand elements suffer the most during floods.

Lagos, Nigeria has two major climatic seasons, wet and dry. The dry season spans from the months of November to February. In these months the dust from the Sahara desert blows southwards covering the counties in its path to the Atlantic Ocean with a blanket of red dust. The environment dries out due to the dust and the average temperature lowers. In later years, the dry season has not been confined to its usual months. This has impacted various sectors of the economy and the impact has been felt greatly in the agricultural industry along with other sectors depending on a predictable supply of water.

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The wet season spans from the months of March to October with the peak months spanning from May to September; June being the month with the highest amount of rainfall. Increased rainfall in these months have been sporadic and unpredictable. With unreliable prediction comes unpreparedness. Severe storms and flooding have come both expededly and unexpectedly, the latter causing more damage to human life through flash floods. Flooding has altered the landscapes, in particular the rivers and water transportation systems, hindering the environment from draining built up silt, sediments, chemicals, and solid obstructions. These elements in turn are dispersed all over the urban and rural areas, contaminating natural resources. Not only are surface water resources compromised, but this dispersal of contaminants also affects the groundwater resources.

Lagos extracts most of its domestic water from the ground, putting it in critical danger of water depletion, ironically from flooding. Increasing rainfall brings a surplus of decemating waters, yet 36% of Nigerians still don’t have access to improved drinking water (Progress on Drinking-Water and Sanitation, 2014). With increasing floods, an increasing population, and decreasing water stability, there is a clear water disconnect and an imminent water crisis.

_ Water We Talking About? _ MAA02: Eve Nnaji

Source: Nairaland. Men drinking beer in lagos flood.

Source: Business Day. Flood experience in Lagos.

03 . REGIONAL STUDIES _ Nigeria’s Water Networks

_ Water We Talking About? _ MAA02: Eve Nnaji

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

4 STATES _

In order to identify the flood causes in Lagos, it is important to understand the waterways. Studying these rivers and tributaries within Lagos alone isolates the investigation and ignores the potential contributors that lay beyond the city limits. In order to avoid this, the waterways were followed upstream, and the major cities they intersected were added to the investigation, creating the regional studies of southern Nigeria. The following questions were posed to direct the efforts of the investigation.

Are these cities experiencing flooding? If so, is the flooding related to natural or unnatural causes? This information is needed to further focus the investigative direction pertaining to Lagos and determine if the problems and solutions in Lagos are applicable to its neighboring cities upstream.

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The four major waterway intersecting states are Oyo, Ogun, Osun, and Lagos State. The Ogun river runs from Oyo state, to Ogun state, and Lagos state, the Osun river runs from Osun state to Lagos state, the Ogbere river runs from Ogun state to Lagos state, and these three major rivers feed water into the Lagos and Lekki Lagoon which finally feeds into the Atlantic Ocean. The chosen study cities in which these waterways intersect are Ogbontosa, Ibadan, Abeokuta, Magboro, Mokoloki, Osogbo, Ede, Ikire, Iwo, Lagos Mainland, Lagos Island, and Lekki (the last three compose Lagos).

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Fig. 04. Study states and cities map.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

4 STATES : DATA TABLE _

A data table was created in order to record important characteristics of each city. General information, geographic information, water input and output, and anthropogenic behaviors were recorded. The general information was used to understand the city at a glance along with its economic driver.

The geographic information was used to understand the natural factors that may contribute to flooding, while anthropogenic behaviors were used to understand unnatural factors that may contribute flooding, and the water intake and output was used to understand the city and citizen’s relationship with their water.

The common economic drivers in small towns include agriculture and

_ Wat e r We Tal k in g Ab o u t ? _

timber products. In a small town like Ede, agriculture is rapidly declining due to poor soil conditions and lack of resources to propel the industry.

The major economic drivers in the study cities include agriculture, trade, manufacturing, and commercial business. The average town has a size of 232 square kilometers and a population of 105,438. The plot dispersion in these towns are often more sprawled than the plots in a city; neighbors may live 1 km away from each other as opposed to sharing a plot fence.

The average city has a size of 1,391 square kilometers and a population of 3,254,645. The plots are often densely packed together, utilizing every available land for commercial development. It is important to note that most of these large cities once shared a similar identity to their neighboring small towns. The rapid development of these cities forced both inward and outward growth.

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Fig. 05. Regional studies data table.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

OYO STATE _

Looking at Oyo state, two locations were closely studied; Obgontosa, a fairly small town, and Ibadan, a large city.

Ogbontosa, with a population of 384 and a size of 0.25 square kilometers, is a sparsely populated town that may even be considered a village. Its elevation spans from 160-168 meters above sea level and an average yearly rainfall of 1200 mm. Ogbontosa residents gather most of their domestic and drinking water from the Ogun river surface water and a small percentage from rainwater. The town has not recorded any major urban flooding event. South of Ogbontosa is the large city of Ibadan with a population of 3,552,000 and a size of 3,080 square kilometers. Its elevation spans from 177-270 meters above sea level and an average yearly rainfall of 1233 mm, indicating a variation of topographic transformation from hills to lowlands.

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Ibadan relies on boreholes and hand dug wells to provide most of its water, while its secondary source derives from pipe borne and sachets (Lade and Oloke, 2018). Although Ogun river tributaries sprawl across the city, it does not rely on surface water. Lake Eyeleye, which feeds the Ogun river, is located north-west of the city’s boundary; however, this water source is directly linked to the recorded flooding that plagues the city. Development around the lake has led to soil erosion and degradation of the lake’s water quality with high amounts of heavy metal contamination. Deforestation around the city in order to make room for more development has hindered this region’s ability to prevent its tributaries from flooding despite the heavy forestation north of the city.

ogbontosa

ibadan Fig. 06. Ogbontosa and Ibadan map.

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Fig. 08. Google Earth - Ibadan

Fig. 07. Google Earth - Ogbontosa

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

OGUN STATE _

Looking at Ogun state, which is south of Oyo, three locations were closely studied; the large city of Abeokuta, the small boom town of Magboro, and the small town of Mokoloki.

Abeokuta is a prosperous developing city; however, dwarfed in comparison to Lagos. It is roughly 872 square kilometers with a population of 533,000 and an average rainfall of 1822mm per year. Its major economic drivers are agriculture, fishing, and sand mining, which is ideal due to the amount of water resources in and around the city. The Ogun river’s two major tributaries connect just north of the city. Lake Eyeleye feeds into a tributary approaching from the northeast while the Oyan Lake feeds into a tributary approaching from the northwest. These two major waterways join to form

_ Wat e r We Tal k in g Ab o u t ? _

the Ogun River, and this collision point just north of Abeokuta is directly linked to the city’s flooding. The Oyan River dam was commissioned in 1983 to supply water for agriculture to Lagos and Ogun State as well as electricity to Ogun State but was then decommissioned in 2007 due to lack of long-term planning and lack of a financial structure (Oyegoke and Sojobi, 2012). It covers 4,000 hectares and has a catchment area of 9,000 km2 which contains water that is released once a year during the rainy season.

This invites several hazardous problems. The first of these problems is one of health safety. Because the dam is defunct and devoid of maintenance funding, it is not maintained to a sanitary condition that regards the health of its surrounding environment. The water in the dam is teeming with excessive amounts of bacteria, attracting snails that carry viruses harmful to the human body. Once the dam is open, these snails are released into the environments downstream. Because snails are a delicacy in this region, locals catch them and consume them, ingesting the diseases and viruses they carry within their body. The second and more formidable threat of the defunct Oyan dam is the amount of water that is released from the dam. The surplus of contaminated water released at once from the dam overwhelms the city’s drainage system creating devastating flash floods.

The amount of water is so overwhelming that it travels south through the Ogun river and floods the city of Magboro, the second study site.

abeokuta Fig. 09. Abeokuta map.

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Fig. 11. Google Earth - Abeokuta

Fig. 10. Google Earth - Abeokuta

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

OGUN STATE _

Magboro is a satellite town of Lagos that experienced explosive urbanization due to the developmental opportunities it advertised to Lagosians. In 2000, plots of land in Magboro were being sold for N5,000, an opportunity too cheap to be ignored by Lagosians, and within 4 years the price had jumped to N75,000 for a plot of land (Alimi, 2017). By 2015 the number of houses had increased by 10 times and industrial development began taking place.

The most notable being WEMPCO Steel, a Chinese steel manufacturing company that occupied a sizable portion of Magboro. Deforestation around the city was a result of the lumber industry clearing and selling lumber due to the development along with the selling of the topsoil north of the city. This latter development teamed with the floodwaters coming from the Ogun river due to the release of the Oyan Dam north of the city led to catastrophic flooding events that eventually turned Magboro into a ghost town. At first, the inhabitants of Magboro juggled back and forth between cities, residing in a friend of family’s house during the rainy season and residing in Magboro during the dry season; however, by 2017 Magboro witnessed a loss of the majority of its boomtown residents. With all of its water problems, it is not an additional help that Magboro received 1900mm of rainfall per year; the highest amount compared to the previously listed study locations.

_ Wat e r We Tal k in g Ab o u t ? _

Mokoloki, a small town which Magboro once resembled lays north of the city; however, it has not recorded any major flood devastation, despite the influx of water coming from Ogun River as a result of the dam release, despite it being located closer to the Ogun River. It remains a self-sufficient agricultural town which relies on solar power and receives the majority of its water from a nearby water corporation which in turn receives its water directly from the Ogun River (Areola, Faniran and Akintola, 1985). It can be assumed that Mokoloki is not affected by the influx of water from the river due to the heavy forestation surrounding it as well as the permeable surfaces used as transportation routes in and around the town.

mokoloki

magboro

Fig. 12. Mokoloki and Magboro map.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 15. Google Earth - Mokoloki

Fig. 14. Google Earth - Magboro Soil 2006 - 2020

Fig. 13. Google Earth - Magboro 1984-2015

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

OSUN STATE _

Looking at Osun state, which is west of Ogun state, four locations were closely studied; the towns Ede, Ikire, and Iwo. Ede, with a population of 169,866 and a size of 330 square kilometers, has an agricultural products driven economy; however this industry is steadily declining. Its elevation spans from 445-269 meters above sea level and an average yearly rainfall of 1200 mm. The Osun River sits to the east of the town and is fed by the Erinle Reservoir. Unlike most of the study locations, this town relies on the reservoir as a main source of water along with rainwater. It also has a water scheme that supplies to 57% of the households, another unusual feat for water corporations in Nigeria (Badiane and Mbye, 2014). The town suffers from fires which dismantle its vegetative systems that cover its hilly landscapes. During the rainy season, the water rushes from the hills and due to the lack of forestry, it creased landslides and devastates the town. The town has committed to the greening of its floodplains as a strategy to combat flooding, a focus that is quite unusual for cities and towns in Nigeria. Ede is an exceptional town that suffers from flooding mostly due to its geological position rather than its anthropogenic activities.

Ikire and Iwo are both similar towns; however, Ikire receives more rainfall, 1700mm per year, than its northern counterpart which receives 1400mm of rain per year. Ikire and Iwo have both reported flooding, although the floods events are not extreme and the events do not destroy the towns nor result in loss of property or lives, despite being located a few kilometers from the Osun River.

ede _ Wat e r We Tal k in g Ab o u t ? _

ikire

Fig. 16. Ede and Ikire map.

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Fig. 18. Google Earth - Ikire

Fig. 17. Google Earth - Ede

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

LAGOS STATE _

Looking at Lagos state, 3 locations were closely studied; Lagos Mainland, Lagos Island, and Lekki. These three locales are usually summed up as ‘Lagos’. For this section the locales will be referred to by their individual names.

Lagos Mainland, which is located directly below Magboro, has a population of 14,368,000. It receives 2000mm of rainfall per year from flows through its elevation from north to south spanning from 71 to 0m above sea level. The Ogun River, Osun River, Aye waterway, Owo waterway, Yewa waterway, and Iju waterway all flow through Lagos mainland and outlet into the Lagos and Lekki Lagoon. This rapidly urbanized city with an economic focus on oil and commerce has expanded to a size of 3,577 square km, mostly composed of tightly packed buildings and impermeable surfaces. This environmental make-up coupled with a low elevation and high rainfall has created the perfect scenario for devastating flood events.

With its extensive labyrinth of roadways comes it’s even more extensive and complicated labyrinth drainage system which is mostly compared to open gutters.

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Lagos Mainland has recently been experiencing a short burst of heavy rainfall leading to flash floods that rapidly inundated the region, resulting in the loss of lives and the damage of property, especially automobiles. The use of cars and generations in almost every household has contributed to the increase of CO2 in and around the city. This increase in CO2 is attributed to the short bursts of heavy rainfall. Lagos Island, which is surrounded by the Lagos Lagoon has also recorded unprecedented flood occurrences. This small island with a size of 8.7 square km, roughly twice the size of Mokoloki, has a population of 212,700, more than Iwo, which is 24x its size.

Lagos Island hosts the city’s banking, finance, and hospitality driven economy and houses the upper socio-economic group. This region was initially colonized by the British and can account for most of the oldest and historical buildings in the city, as well as drainage networks. With the heavy rains, poor drainage, impermeable surfaces, all while surrounded by a lagoon, it is no surprise that Lagos Island, although disconnected from Lagos Mainland, is also under severe flooding.

lagos island Fig. 19. Lagos island and Lagos mainland map.

lagos mainland

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Fig. 22. Google Earth - Lagos Island

Fig. 21. Google Earth - Lagos Mainland

Fig. 20. Google Earth - Lagos Mainland

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.1 - Oyo, Osun, Ogun, & Lagos State

LAGOS STATE _

Lekki is the most recent addition to Lagos, and is currently expanding at an unprecedented rate. It is the piece of land that borders the Atlantic ocean with an elevation spanning from 21 to 0 m above sea level. What was once a sandy stretch of land covered in dense mangroves and palm trees is now a blanketed surface of real estate development sitting on concrete sitting directly on top of sand. Lekki is home to the new middle to high socio-economic groups who sought large estates for a price lower than the properties in Lagos Island, with square-footage higher than the properties on Lagos Mainland.

The extremely rapid development of Lekki has left some of its major roadways without a drainage network. These extensive roadways have become a highway for water, carrying flood waters into some of the most expensive real-estate developments in the entire city, leading to extreme flood economic damage. Not only have the effects of rapid urbanization added to flooding, ocean waves and storm surges, high tidal levels, and unregulated modifications of shoreline have also created coastal flooding in the island of Lekki. The coast has largely been ignored by the city as a disaster front, leaving Lekki to fend for itself at the height of the rainy season as it battles flooding from the inside out.

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lekki

Fig. 23. Lekki map.

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Fig. 25. Google Earth - Lekki Phase 1

Fig. 24. Google Earth - Lekki Phase 2

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.2 - Regional Flood Causes Conclusions

FLOOD HOTSPOTS _

A map was created in order to identify the region’s flood hotspots, according to data collected from the regional studies. These flood spots are mostly located in major cities and areas closer to the sea level. This is parallel to the geographic location of each city; the lower the terrain, the closer it is to the Atlantic Ocean, the more tropical the climatic conditions, the higher the amount of rain it receives. The major flood spots are also relevant to anthropogenic events in the region such as the abandonment of dams, the deforestation of vegetative barriers, and the size of urban development.

A diagram created by U. C. Nkwunonwo indicates the most common causes of urban flooding (Nkwunonwo, Whitworth and Baily, 2016). This

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was used to rate the cities in order to understand which has the most to least anthropogenic causes for urban flooding. To help visualize the collected geographic data from the regional studies, a metric was created to show the city’s size, average rainfall, and elevation along with its water consumption to create an understanding of its relationship with rainwater.

The causes of flooding were then used to rate each city. It’s interesting to see cities with roughly the same amount of rainfall and elevations having different flood causes.

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Fig. 26. Flood hotspots map.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.2 - Regional Flood Causes Conclusions

CAUSES OF FLOODING _

A diagram created by U. C. Nkwunonwo indicates the most common causes of urban flooding (Nkwunonwo, Whitworth and Baily, 2016). This was used to rate the cities in order to understand which has the most to least anthropogenic causes for urban flooding. To help visualize the collected geographic data from the regional studies, a metric was created to show the city’s size, average rainfall, and elevation along with its water consumption to create an understanding of its relationship with rainwater.

The causes of flooding were then used to rate each city. It’s interesting to see cities with roughly the same amount of rainfall and elevations having different flood causes.

One of the most notable flood enhancers can be attributed to the alteration of the environment. The most direct example is taken from Magboro. The deforestation north of the city decimated land’s porosity and allowed surface runoff to carry large volumes of sediments, compromising the soil as well as the Ogun river’s performance. The selling of the top soil further worsened the conditions of the land’s porosity, exposing subsoil, which consists of clay, a soil type with a slow absorption rate. This, in turn, allowed for large volumes of water to flow south, inundating the town of Magboro.

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Another common environmental alteration is the construction of the dams. The economic and political structures of Nigeria did not allow for a sustainable continuation of the dam projects. These defunct dams had to release their surplus of water during the raining season and in turn caused tremendous flooding that crossed borders from Ogun to Lagos State.

WATER CONSUMPTION FLOOD CAUSES

SIZE POTENTIAL WATER ELEVATION YEARLY RAINFALL

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Fig. 27. Flood Causes Ogun state.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _

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3.2 - Regional Flood Causes Conclusions

Fig. 28. Flood Causes Osun and Oyo state.

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Fig. 29. Flood Causes Lagos state.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.2 - Regional Flood Causes Conclusions

CAUSES OF FLOODING _

Another notable cause of flooding that plagued almost all of the study cities was the blockage of drainage systems due to poor waste disposal.

It is unknown if the current drainage networks are sufficient enough to handle the enormous amounts of water created by the dam release and deforestation. These networks are constantly overwhelmed with solid waste which hinder the water from discharging at a rate capable of decreasing flooding.

The blockage of drainage systems from solid waste is a common dilemma, so it is no surprise that the most common effort for tackling flooding is the dredging of drainage networks. Most of the studied cities listed dredging as their primary effort to combat flooding. Unfortunately this strategy is not sustainable being that these efforts must constantly and consistently be applied in order to be successful. With minimal amounts of funding being allocated to these projects and the complete eradication of these projects at the change of political positions, these efforts have not been successful throughout the region. This strategy also fails to address the cause of solid waste blocking the drainage systems; the lack of accessible, public waste disposal facilities. Until this infrastructural issue is addressed, the drainage will constantly require dredging.

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Other efforts to combat flooding include the removal of homes from areas susceptible to flooding, flood education and awareness programs, the construction of dikes along the river and drainage ducts underground, and the funding of flood management programs. These efforts aim to tackle flooding using visual strategies that can be easily recognized by the public as governmental engagement in the community. Unfortunately, these demonstrative acts fail to address some of the less visible and most detrimental contributors to urban flooding such as high CO2 emissions.

This environmental alteration happens at the domestic level. Roughly 26% of households and 86% of operating businesses in Nigeria use generators to produce their domestic and commercial electricity (Ochieng, 2017).

Efforts have not been put in place to address this issue which has been linked to the short heavy burst of rain creating flooding in large cities such as Lagos and Ibadan.

_ Water We Talking About? _ MAA02: Eve Nnaji

ADEJUWON, JO; ADEKITAN, AA; OLADUNMOYE, SL, 2018.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.2 - Regional Flood Causes Conclusions

CAUSES OF FLOODING _

All of the listed common and uncommon causes of flooding can be grouped into one major cause, rapid urbanization. The explosive growth of cities and towns in Nigeria has resulted in lack of urban planning. Only 3 of the 12 study locations had an available urban plan. Most of the study cities grow without a proper plan which is necessary to plan and map drainage networks for current and future development. The expansive growth of cities creates explosive economic pressures which can lead to the creation of dams in order to support an expanding population or the selling of topsoil as a source of income for newcomers. The most notable effect of rapid urbanization is the creation of impermeable surfaces. The use of concrete for transportation routes have created increased surface runoff which overwhelmed the already blocked drainage, leading to flooding.

Impermeable surfaces are also used as groundcover for residential and commercial plots. Concrete is also used to construct the open drainage systems which seem to be constructed with inadequate measurements regardless of the size of the road or neighborhood it is serving. Where there are no funds for concrete, clay is exposed as the ground cover, which when wet and constantly rammed downwards by vehicles, turns into a tough impermeable surface that acts similar to concrete.

Rapid urbanization not only creates impermeable surfaces, it cripples a city’s natural drainage systems, the rivers, from functioning. The urbanization of Lagos has led to the solidification of waterways that need room to transform and accommodate for changes in flow velocity.

Straightening of these waterways has disabled this ability.

_ Wat e r We Tal k in g Ab o u t ? _

The last step of the regional studies required the investigation of the rivers and waterways in order to understand how they play a part in urban flooding. When studying a section of the Ogun river that runs from Abeokuta to Lagos, the river’s transformation can be seen clearly through the use of sequenced Google images from 1990-2020. The waterway downstream the urban area meanders substantially due to the high discharge output coming from the straightened channels. The pastoral waterways meander less due to the heavy forestation that stabilizes the river’s planform. This illustrates the linear impacts of upstream activities on downstream environments.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 30. Abeokuta to Lagos, mapping Ogun River changes.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.2 - Regional Flood Causes Conclusions

CAUSES OF FLOODING: RIVER PLANFORM _

A river needs to constantly transform by meandering as sediment is moved from side to side due to the velocity of the flow. Because one side has a higher velocity, sediment on the other side builds up and reshapes the river. Without meanders, rivers can have increased flow velocity, thus creating flood risk further down the river. The development of impermeable surfaces have solidified the shape of the river. The hard edges disable the river and tributaries from adapting to the flow of the water. The river then spills beyond flood plains in urban areas resulting in the inundation of these vulnerable spaces.

Buffington and Montgomery state, ”Interactions between the river and its surrounding floodplain can exert strong controls on physical

_ Wat e r We Tal k in g Ab o u t ? _

processes, morphology, response potential, and the quality and diversity of habitat for both the river and its floodplain...Because channel–floodplain approaches focus on overbank flows that are capable of eroding banks and doing work on the floodplain, they tend to describe longer term processes and recognize that channel and floodplain conditions represent a distribution of flood events, with smaller floods modifying and sculpting the morphologic legacy of

Fig. 31. Abeokuta to Lagos, Ogun River changes analysis.

larger floods....Many channel–floodplain classifications are inherently process based, but they are limited to unconfined, or partly confined, alluvial rivers. Nevertheless, their explicit inclusion of channel– floodplain interactions allows the development of stronger linkages between fluvial processes, riparian ecosystems, and human uses of floodplain corridors” (Buffington, J.M., Montgomery, D.R., 2013). In this case, the channel coming into Abeokuta is discharging water at an extremely rapid rate due to the instantaneous release of the Oyan Dam. The water has no way of escaping into the floodplain due to the paved development and thus it can be assumed that the vast meandering of the channel coming out of abeokuta is compensating for the velocity of the water. Again, it can be seen how development due to rapid urbanization has put extreme stress on the waterways.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 32. Abeokuta to Lagos, Ogun River changes sequence images.

03 . REGIONAL STUDIES - Nigeria’s Water Networks _ 3.2 - Regional Flood Causes Conclusions

CONCLUSIONS _

_ Wat e r We Tal k in g Ab o u t ? _

The regional studies confirmed that anthropogenic activities are a large contributor to urban flooding as opposed to natural geographic and climatic formations. They also hint towards the investigation of the river as a network that links the activities in one area to the flooding in another area.

Investigating the upstream to downstream effects is key to developing a holistic solution towards flood risk mitigation.

Fig. 33. Regional studies conclusion images.

_ Water We Talking About? _ MAA02: Eve Nnaji

Source: Fela by Lemi Ghariokwu

But, what about the citizens?

04 . LAGOS URBAN ANALYSIS _ Identification of the contributors to urban flooding

_ Water We Talking About? _ MAA02: Eve Nnaji

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.1 - Water as a resource (city and citizen water relationship)

DOMESTIC WATER SOURCE _

As stated previously, there is a disconnect between the region’s society and their water source. This disconnect is evident within the narrative of the city being overwhelmed by excessive amounts of water yet not having enough access to improved drinking water. So, it is important to understand the city and citizen’s relationship with their water in order to understand where this disconnect is taking place.

In Oyo State, Ogbontosa receives most of its water supply directly from the Ogun river. Meanwhile, Ibadan extracts most of its water from groundwater aquifers (supplied by rain water). The Oyo Water Corp supplies only 6% of Ibadan’s water demand.

In Ogun State, Abeokuta also extracts most of its water from domestic wells and boreholes, due to the Akaranga water scheme not producing adequate amounts of water to supply the city (Ufoegbune, Oyedepo, Awomeso and Eruola, 2010). The town of Mokoloki, on the other hand, relies on Ogun state water corporation (OGSWC) to supply its water, mostly for irrigation of farms. Just south of Mokoloki, Magboro receives no government support for the supply of water, rather the boom town relies on boreholes.

In Osun State, households in the town of Ede rely on interior and exterior pipes to supply households with water from the Ede-Osogbo Scheme which supplies to 57% of households; the rest rely on hand dug wells.

In the towns of Ikere and Iwo most households rely on domestic wells, boreholes; however, the Osun State Water Corporation (OWC) was initially proposed as the main supplier for Ikire, but payment disputes lead to the cancelation of its operation.

_ Wat e r We Tal k in g Ab o u t ? _

In Lagos Mainland the Adiyan, Iju, Isashi, and Odomola waterworks supply pipe-borne (70% of water usage), whereas boreholes, wells, tankers, and disposable water sachets supply 30% (Oyebod, 2018). This is a stark difference to Lagos Island and Lekki which have no governmental water supplier. The households rely on boreholes, tankers, and sachets for their water supply.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 34. Regional studies water as a resource.

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.1 - Water as a resource (city and citizen water relationship)

DOMESTIC WATER SOURCE _

When looking at water as a source, most of the cities rely heavily on hand dug wells and boreholes rather than surface water. It is evident that high income areas rely on boreholes, while low income areas rely on pipe-borne, which also rely on sachet water if pipe-borne supply is unavailable.

Looking at the Lagos map, the circles highlight the only 3 fully functioning water corporations. Assuming they all have a reticulation network of 5km, it is evident that a large portion of the city, more than 30%, does not have access to public water. Most of these areas are mid and high income which extract their water from the ground. This independence of water supply extraction using boreholes and wells creates unaccountable variables for the city’s water supply. It is difficult to calculate how much water is drawn from the aquifers and water table on a daily basis, and even harder to understand if this rate is gradual enough for the water table to replenish the water supply. Rapid extraction of water from the ground can lead to geographic malformations such as gully erosions, which are currently killing inhabitants and causing large economic damages during the rainy season.

_ Wat e r We Tal k in g Ab o u t ? _

In terms of surface water, Lagos does not consume it due to extremely low quality. This is common for most of the study cities and towns. Ogbontosa, a small town, is the only city that has recorded its reliance on the surface water of the Ogun River. This leads to the conclusion that the waterways and rivers are polluted enough to produce very discernable signs of its poor quality. This is enough to deter the citizens as well as the city from depending on surface water which in turn puts extreme pressure on groundwater.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 35. Lagos water scarcity map.

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.2 - Urban activities along the waterway (city and citizen water relationship)

WATERWAY ANALYSIS _

It is evident that groundwater is the most dependable source of water; however, this does not disqualify the fact that the surface water resources, the rivers and waterways, are being used by the citizens. In order to investigate the relationship between these waterways and the city, a deeper and more vivid picture of the activities happening around the waterways needs to be understood. Google Map Street View was utilized as a tool for virtually exploring and traveling through the immediate and extended surroundings of the waterways. By following the rivers downstream, the evolution of usage from the different neighborhoods revealed unique findings.

This urban analysis was conducted by splitting all the waterways into segments and plotting notable characteristics or events taking place around the waterways. The observations were divided into 4 categories; general land use, land characteristics, waterway characteristics, and economic activities.

_ Wat e r We Tal k in g Ab o u t ? _

Notable land usage around the waterways included landfills, abandoned plots, the international airport, farmland and plains, and low to very low income commercial and residential plots. Notable land characteristics consisted mostly of landscapes with tightly packed plots lines with low, single-story buildings, with little to no vegetation. The roadways were either paved, partially paved, or unpaved with exposed, compressed clay.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 36. Lagos urban analysis plotting.

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.2 - Urban activities along the waterway (city and citizen water relationship)

WATERWAY ANALYSIS _

There were several waterways observations that hinted towards causes for urban flooding. The waterways are heavily polluted with solid waste.

Every studied waterway harbored small to large piles of solid waste. These objects seem to make their way into the canals and tributaries by travelling through the gutter. The design of the gutter system revealed itself to be an extreme impediment to the drainage of water and a top contributor to the passage of solid waste into the canals and tributaries. Most of the neighborhoods in Lagos utilize an open gutter design. The closed gutter systems can also be considered open because they are covered with removable concrete blocks that also serve as the sidewalk. These blocks often break or are removed by citizens, exposing the gutter system and allowing for solid waste to enter and block the drainage network. The gutters then outlet into canals, tributaries, and eventually rivers with a simple open gape. They are allowed to discharge all they contain without any sort of structure to filter or trap solid waste or even screen particles that can be hazardous to the greater water network. The solid and chemical waste are then free to enter the rivers, lagoons, and ultimately, the ocean.

Another design flaw lies in the transition from gutter to waterway.

_ Wat e r We Tal k in g Ab o u t ? _

The gutters seamlessly blend into streams, canals, tributaries, and even open plains. This is an extremely dangerous flaw because it allows for citizens to settle upon what seems like an open field, or a floodplain, but is actually a large gutter capable of discharging tonnes of water per minute in the event of a heavy storm. The appearance of small shows, gardens, and miscellaneous valuable items being stored in these ambiguous gutters is the evidence for this observation.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 37. Lagos urban analysis images evaluation.

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.2 - Urban activities along the waterway (city and citizen water relationship)

WATERWAY ANALYSIS : ECONOMIC ACTIVITIES_

There are various economic activities taking place in and around these waterways. Gardens, flower shops, and miscellaneous storage are just a few. A section of the Osun River harbours an animal farm, nestled between the chaos of the city and the open plain on the opposite side of the river.

This animal farm most likely takes advantage of the river as a drinking water source for the animals or even a water source for cleaning the pens.

Crop farming is the most common economic activity taking place around the waterways, due to a free source of irrigation water. The farms are scattered in various urban typologies, from partially rural plains to urban low-income residential neighborhoods. These crop farms are fairly small and owned by individuals looking to earn supplementary capital in addition to their various revenue streams.

_ Wat e r We Tal k in g Ab o u t ? _

Fish farming is also a common economic activity around the waterways.

The farmers carve our small rectangular pools next to the waterway. These pools then fill up with water due to the saturation of the soil. This cheaper alternative to purchasing fish tanks allows for low socio-economic citizens to capitalize on free resources. The abandonment of these pools, however, creates unhealthy conditions in which stagnant water harbors bacteria which can easily spread through passing wildlife. Less organic economic activities taking place around the river are landfills.

Fig. 38. Google Maps - Lagos Roadside Animal

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 41. Google Maps - Lagos Animal Farm

Fig. 40. Google Maps - Lagos Crop Farm

Fig. 39. Google Maps - Lagos Fish Farm

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.2 - Urban activities along the waterway (city and citizen water relationship)

WATERWAY ANALYSIS : ECONOMIC ACTIVITIES_

Sanctioned city landfills are placed close to the river which is an extreme health hazard. The chemical leachate from these landfills make their way into the waterways as well as the groundwater which also makes releases into the waterways. Unsanctioned landfills pop-up in low-income neighborhoods which have insufficient to no means of public waste disposal. These are more dangerous than sanctioned landfills as they have no regulations and often allow waste piles to overflow into the waterway.

The chemical leachate produced by these piles are so concentrated that they can be seen and recognized using Google Street View.

Another hazardous activity taking place is the dredging of soil. Heaps of silt and sand can be seen lined up along the waterways. Next to these

_ Wat e r We Tal k in g Ab o u t ? _

piles are large trucks that are used to transport the sediment to various construction sites to be used for concrete mix. On the other side of these piles, in the water, canoes line the waterway. These are the vessels used to venture into the middle of the waterway and anchored while the diver swims to the channel bed with a bucket to retrieve the sediments.

Fig. 42. Google Maps - Lagos Economic Activities Around Waterway

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 45. Google Maps - Lagos Dredging

Fig. 44. Google Maps - Lagos Dredging

Fig. 43. Google Maps - Lagos Unsactioned Landfill

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.2 - Urban activities along the waterway (city and citizen water relationship)

WATERWAY ANALYSIS : LAGOON_

The Lagos Lagoon is the unfortunate recipient of the waste and pollution provided by the gutters and waterways. These gutters move water to the streams which turn into tributaries, supplying water to the river, which eventually outputs its discharge into the Lagos Lagoon. The waste accumulating in a neighborhood in Magboro can potentially end up in the Lagos Lagoon. This puts extreme pressure on the ecological balance of the Lagoon which is in constant deterioration.

Makoko, a floating village situated on the lagoon, has witnessed a decline in the fish population and a takeover of invasive species. The village relies on fish and lumber as its primary economic support. Makoko stores its lumber on the lagoon by floating the logs in the water. The sawmills that

_ Wat e r We Tal k in g Ab o u t ? _

are located directly next to the water, sit on years old sawdust that has accumulated in a quantity large enough to form a land mass. This pile of sawdust also contributes to the degradation of the water’s ecological balance.

Fig. 46. Google Maps - Lagos Lagoon Border

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 49. Google Maps - Makoko Sawdust

Fig. 48. Google Maps - Lagos Lagoon Ogun

Fig. 47. Google Maps - Lagos Lagoon Community

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.2 - Urban activities along the waterway (city and citizen water relationship)

WATERWAY ANALYSIS : CONCLUSION_

The activities around the river such as animal farming, car repair, and dredging for soil, revealed that the river was being used as a miscellaneous resource simply because of its openness. The river has become the backyard of the city, making it susceptible to an uncoordinated range of activities, while the Lagoon is the end recipient of the harsh effects of this unchecked discoordination. The waterways blend from gutter to canal to river through the facade of solid waste, making it hard to connect it as one functioning body.

The dysfunction of the waterways has offset a chain of environmental problems ultimately leading to devastating flood impacts in the urban landscape.

_ Wat e r We Tal k in g Ab o u t ? _

Fig. 50. Lagos urban analysis summary.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 53. Google Maps - Waterlogged Community

Fig. 52. Google Maps - Waterlogged Street in

Fig. 51. Google Maps - Waste Infested Waterway

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.3 - Impact analysis and an identity crisis; the river as a residual space

ACTIVITY IMPACT : QUALITY, QUANITY, HYDROMORPHOLOGY DECLINE _

The river and waterways today hold the same conversation as they did less than 60 years ago, yet tell a very different story. What was once the forefront of economic responsibility has become the background of economic damage. Lagos once relied heavily on fishing as a pillar of its economic stability. Fishing villages were once the city’s backbone, spurring the creation of fish markets in and around the city. Lumber and cane production was also an economic pillar. These activities were fostered in a manner that was easily sustainable due to the scale at which they operated. Today, these industries have been outcompeted by commerce and oil, leaving the trade of fish and lumber to be adopted by low socioeconomic citizens who can seek to make a profit using the free resources of water and wood.

_ Wat e r We Tal k in g Ab o u t ? _

The sawmills of Makoko have produced enough sawdust, over a number of years, to dismantle the lagoon’s ecological balance. The sawdust serves as a food source for bacteria, the zooplankton then increase as a result of increased bacteria and phytoplankton to feed off of. Yakub states, “The higher phytoplankton abundance and species richness recorded during rainy than dry season could be attributed to influx of allochtonous nutrients as the river drains into the Lagoon (Yakub et al., 2011). This increase in plankton then results in a decrease in oxygen in the water and the creation of harmful algal blooms which creates an environment that benthic cannot survive in. It also invites invasive species such as blue crabs from the ocean into the lagoon. These resilient predators feed on any available food source and invite more invasive predators as the blue crab then becomes a thriving prey.

Vintage Lagos Postcard - Hausa Pedlars

_ Water We Talking About? _ MAA02: Eve Nnaji

Vintage Lagos Postcard - Ebuta Metta Waterside, Lagos Fish Market on Beach Road, Sunset on the Lagoon, Fishing Village Near Lagos

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.3 - Impact analysis and an identity crisis; the river as a residual space

ACTIVITY IMPACT : QUALITY, QUANITY, HYDROMORPHOLOGY DECLINE _

The Lagoon has also suffered from the invasion of water hyacinths.

Factories located along the river are known to dump their waste directly into the river in order to cut cost on waste extraction. Car mechanics located along the river also dump hazardous waste in the river for the same reason. These two events have been linked to the increase of Cadmium in the waterways and lagoon, as well as the increase of other heavy metals.

Farming along the river is directly linked to the increase of nitrates and phosphates in the waterways and lagoon. These chemicals are all a food source for water hyacinths, resulting in the explosive takeover of the waterways and lagoons by these floating plants.

The overpopulation of hyacinths in the water has resulted in the blockage

_ Wat e r We Tal k in g Ab o u t ? _

of the waterways as well as the blockage of sunlight and the decrease of oxygen in the waterways and lagoon (Ndimele, 2012). This decrease of sunlight and oxygen has also resulted in the decrease of benthic fish and the increase of algae. The decomposition of the algae further decreases the amount of oxygen in the water as it settles to the bottom of the channel. In the dry season, the water hyacinths then sink to the bottom in search of nutrients which they receive from the decomposing algae, supplying them with enough food to survive the dry season until they float up to the water surface again to receive direct sunlight and oxygen in the rainy season. This vicious cycle and the thriving of hyacinths has not only resulted in an environmental decline, but an economic decline as well. The blockage of these waterways hinder fishermen from reaching fishing grounds where benthic fish are still surviving. The blockage also hinders water from discharging at a rate that is suitable for the channel, thus resulting in flooding.

Source Unknown - Lagos Fishermen Clearing Water Hyacinths

ACTIVITY IMPACT : QUALITY, QUANITY, HYDROMORPHOLOGY DECLINE _

The dredging of the waterways by individuals seems to be an action that can offer relief to the channels in order for them to discharge at an appropriate rate.

T.A. Wesche states, “Dredging is mostly used for the lowering of a river to allow boats to pass by. After a river is dredged, its banks will become prone to erosion. Eroded banks will stimulate further build-up of silt, exacerbating rather than improving problems with navigation (boat flow). On one hand disturbance of bank vegetation caused by erosion will remove cover and shade. This will increase light penetration and hence water temperature increases, which will cause fish to migrate. On the other hand, dredging also disturbs particles, reducing visibility and increasing the turbidity of water to the point where the amount of photosynthesis that can occur in the water is curtailed with the result that there will be an overall impairment of the function of the ecosystem. Since dredging loosens up the soil, these carcinogens will find their way into the water and will cause substantial degradation of the environment. There is documented evidence showing clearly that rivers which have been dredged, silt-up more frequently and return to their pre-dredged state. Thus, dredging is an unsustainable activity since it needs to be repeated frequently (Wesche, 1985).

Source: VisitNigeriaNow - Ekpe Fish Market

_ Water We Talking About? _ MAA02: Eve Nnaji

This account refers to dredging executed by a coordinated governing body, which is not the case in Lagos. If dredging by river authorities and stakeholders creates this kind of environmental damage, it is imaginable what sporadic and opportunistic dredging is doing to the water ecology in the city.

04 . LAGOS URBAN ANALYSIS -

Identification of the contributors to urban _

4.3 - Impact analysis and an identity crisis; the river as a residual space

ACTIVITY IMPACT : CONCLUSIONS _

The major reason these activities and impacts have taken place is due to the fact that the waterways have been left out of the jurisdiction of city planning and regulation. Revisiting the causes of urban flooding, we can expand the list even further by adding the effects of the floodplain becoming a residual space. The river has taken on a disconnected function and with various unaligned usages the river undergoes an identity crisis.

This statement is true and not at the same time. From the perspective of the individual, there’s a clear identity, but from the perspective of the city, there’s an identity crisis, a dysfunction leading to flooding.

Perhaps the way we have designed and built our waterways were actually inappropriate for young countries and cities facing rapid urbanization.

_ Wat e r We Tal k in g Ab o u t ? _

The major question now becomes how do individuals create a collective identity that restores the function of the waterways and river?

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 54. Lagos urban analysis cause-effect conclusion.

05 . STRATEGY _ Renature, Reculture

_ Water We Talking About? _ MAA02: Eve Nnaji

05 . STRATEGY - Renature, Reculture _ 5.1 - Democratic Flood Risk Management

RIVER IDENTITY : INDIVIDUALISM _

For many tribes the river was a deity, one body, able to give, take and communicate. Most of these forms of communication were actually just signs of a healthy ecological system. We can use this strategy to restore the river by restoring the communication between the man and the river.

This is the strategy of democratic flood risk management, the restoration of the river’s function through the development of the river’s identity by the city and citizens.

The major cause of rapid urbanization was individualism. The lack of a collective structure to govern and guide the development of the city and coordinate citizen participation in the urban development is the root of the problems that have led to extreme urban flooding. Democratic flood risk management is split into two goals; restoration of the function of the river and definition of identity of the river.

_ Wat e r We Tal k in g Ab o u t ? _

The restoration of function can be achieved through the renaturalization of the river. These goals, in a nutshell, aim to maximize water retention, prevent obstruction, and filter waste in order to maintain an hydro ecological balance. The definition of identity can be achieved through the reculturalization of the citizens. There needs to be a clear medium that will serve as the infrastructure to direct the citizen’s engagements with their water.

Source: Unknown. Celestial Church members worship at beach.

_ Water We Talking About? _ MAA02: Eve Nnaji

Source: Reuters. Girl fishing in Lagos

Source: Formereside. Protest in Lagos Lagoon

Source: Unknown. Men in Makoko builing canoe.

05 . STRATEGY - Renature, Reculture _ 5.1 - Democratic Flood Risk Management

RIVER FUNCTIONALITY _

Rowiński states, “The need for sustainable, cost-effective solutions for river management is pressing: rivers, streams, and flood-plains are hydroenvironments which are most severely affected by human alterations...

Most notably, geomorphic alterations changing the shape of rivers as well as hydrologic alterations modifying their water balance have dramatically increased sediment and nutrient transport rates and have resulted in losses in habitat, biodiversity and ecosystem services. Climate change will impose additional challenges on the management of rivers and streams by modifying e.g. the hydrographs, vegetation, and loading from the catchment areas and consequently by altering riparian habitats)”(Rowiński et al., 2018).

736

Geomorphic Classification of Rivers

Increasing sediment supply Bed material dominated channels Boulders, cobbles

Step-pool, Cascade

Sand

Meandering channels

_ Wat e r We Tal k in g Ab o u t ? _

Braided channels

Increasing channel gradient

Wandering channels

Decreasing channel stability

Increasing sediment caliber

Gravel

Anastomosed channels

Fine sand, silt

Silt

Wash material dominated channels Decreasing channel stability Figure 5 Schumm’s (1977, 1981, 1985) classification of channel pattern and response potential as modified by Church (2006). Reproduced Channel Wesche, T., The Restoration of Rivers and Streams Experience. from Church, M., 2006. Classifications.

Bed material transport and1985. the morphology of alluvial rivers.

Annual Theories Review ofand Earth and Planetary Sciences 34, 325–354, with permission from Annual Reviews, Inc.

RIVER FUNCTIONALITY _

The natural functionality of a river can be redeveloped by focusing on three parameters; water quantity, water quality, and hydromorphology. The quantity of water being discharged by the channel needs to be appropriate for its size, roughness, location, and so forth. Several parameters can be used to keep a balanced quantity in order to prevent flooding, excessive quantities. The focal parameter this project will focus on are a.) sediment control, b.) planform flexibility, c.) obstruction control, and d.) flood plain porosity. a. Sediments are particles that are broken down from rock and land formations which make their water into the river through streams.

These streams can carry rocks from northern mountains to coastal beaches. The buildup of sedimentation can be good and bad for a river. On one hand, sediment build-up during flood events can create natural dykes, mounds of earth on each side of the river, which can act as a natural elevated barrier wall, preventing flooding. On the other hand, the buildup of sedimentation can elevate a river’s floor, making it more shallow, thus decreasing its capacity to hold more water which could lead to flooding. Cities often dredge their rivers and waterways in order to remove sediments and promote water flow. b. A river alters its planform, shape and sinuosity, in order to accommodate for changes in water discharge amount and velocity.

The urbanization of Lagos has led to the solidification. Straightening of these waterways have disabled the river’s ability to accomodate for high water discharges. Looking at a section of the Ogun river that runs from Abeokuta to Lagos, the channel downstream the urban area meanders more than the channel in the rural area due to the high discharge output coming from the straight urban channels. The rural channel meanders less due to its accommodation upstream, that is able to control the discharge rate with the meanders. The river needs to maintain its malleable edges in order to transform its planform.

d. Floodplain porosity refers to the floodplain’s capability of retaining water. The retention of water is dependent on factors such as the soil type, vegetation type and dispersal, as well as ground cover of the floodplain and surrounding environments. The floodplain needs to be able to maintain its water balance along with retaining incoming water from rain, surface runoff, and river overflow. The retention will allow the river channel to flow downstream.

_ Water We Talking About? _ MAA02: Eve Nnaji

c. Obstruction control is essential for allowing water to flow through a channel. If the channel is obstructed, water will accumulate and overflow, causing the surrounding areas to flood. Obstruction control not only refers to solid waste created by urban waste, but to solid organic matter such as branches and fibrous debris.

05 . STRATEGY - Renature, Reculture _ 5.1 - Democratic Flood Risk Management

RIVER FUNCTIONALITY _

The quality of the water in the river needs to be able to sustain a healthy ecosystem which in turn will maintain several important structures of the river. Chemical waste needs to be managed in order to prevent diseases and contamination from spreading into the biological systems of organic lifeforms. Solid waste also needs to be controlled in order to ensure an appropriate water quantity balance. Solid waste is also a contributor to chemical waste. Tackling this visible problem before it becomes an invisible threat is essential to sustaining healthy water quality.

The hydromorphology of a river pertains to the ecological balance of the river; the maintenance of habitats for animals and organisms to survive and contribute to the environment. In order to get an understanding of the current ecological system in and around the river, a data table was used to research important ecological loops that have been disrupted by the presence of solid and chemical waste.

_ Wat e r We Tal k in g Ab o u t ? _

Water quality, quantity, and hydromorphology can all be considered by understanding and controlling a few parameters; flow direction, flow velocity, river profile, vegetation, and sediment deposition. These parameters were chosen because they can be translated into a formal design that can then bse implemented as a design strategy towards the renaturalization of the river.

_ Water We Talking About? _ MAA02: Eve Nnaji

Vintage Lagos Postcard - Mangroves

05 . STRATEGY - Renature, Reculture _ 5.1 - Democratic Flood Risk Management

RIVER FUNCTIONALITY _

Mami Wata, meaning mother of water, is a popular water deity that is known by most of the tribes in Nigeria. Her story has been able to transcend the eradication of aborigonal religions due to her likeness to the mermaid and Nollywood’s exploration of mystic female villains. This water deity was once prayed to but is often feared for her power and skills of seduction. She controls the river and uses the water and ecology in order to reward or punish participants. The anger of Mami Wata can be expressed through the drying up of the river, the hunger of alligators, and flooding, to name a few. Her affection can be expressed with the abundance of fish, the steady flow of fresh water, lush vegetation, and the presence of multiple species of wildlife. These expressions are indications of a river’s health. The message is that man gives to the river, by taking care of it, and the river will give back to man by taking care of him.

The river must be reestablished as a living entity by creating a unified network that is able to directly display its function, display its development, and reward its participants. The usage of the river varies according to economic groups. The lower income group has the highest impact, dependence, and ownership of the river, making it the appropriate group for the highest priority of engagement.

_ Wat e r We Tal k in g Ab o u t ? _

As noted from the urban studies, the river has become a residual space.

The events and impacts of the activities taking place in and around the waterways and lagoon are evidently resulting in the deterioration of the environment and ecology. The waterways are unable to serve as a water supply, drain water, sustain wildlife habitats, or act as a transportation route, thus resulting in the complete deterioration of function.

One of the shocking discoveries of this research is the fact that most of the rivers and waterways in Lagos have not been named. Upon the settlement of the British in the colonial era of Lagos, development was focused around major roadways within Ikoyi island, along with the railway which cut across Lagos Mainland. The settlements in these areas developed basic infrastructure to support industrial and governing activities. The surrounding areas were mapped under general classifications such as “swamp land” or “mangroves’’. After the independence of Nigeria was gained, the rapid urbanization of Lagos boomed outwards from the major roadways and railways. Due to the rapid growth, with the lack of detailed maps, and the multitude of water networks, the waterways and major geological formations were ignored or eradicated, leading to the current situation. The absence of names is evidence of the lack of cultural integration of the river and waterways. The simple act of giving the rivers a name is a strategy towards deification and reconnection.

Giving the waterways multiple forms of personification, such as deification and naming, can create a connection to the citizens in a manner that allows them to understand the river as a body and a living entity.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 55. Democratic flood risk management strategy diagram..

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.1 - River dialects; making the invisible visible and legible (Case studies; Makoko, phumdis)

LOKTAK LAKE PHUMDIS _

In Manipur, India, a very unique lake harbours an example of citizens living with a deep knowledge and control of their water environment. Loktak Lake is covered in floating biomasses called phumdis. These masses, which float due to their vegetative composition, are gathered and arranged by the fishermen in order to create bio havens that attract fish. These biomasses are referred to as ‘phumdis’ and they are the staple of life for the inhabitants in and around the lake. In the wet season, the biomass floats along the surface of the lake. They are composed of seagrass, hyacinth, and other amphibious vegetation with sponge-like, buoyant roots and stems. In the dry season, the lake loses its water content and the phumdis attach their long roots to the bottom of the lake bed where they can receive nutrients.

The fishermen are able to manipulate their environment with these floating structures in order to promote biodiversity and sustain an environment suitable for the fish to multiply. There are several formations that can be noted, the most prevalent are the circular rings of phumdis. They allow fish to create shelter within the circle, which makes it easy for the fishermen to feed and capture them. There are several rectilinear formations that can also be noted. These suggest larger, more permanent fishing grounds because they typically have houses built on one of the phumdi links.

_ Wat e r We Tal k in g Ab o u t ? _

One of the most interesting feature of Loktak Lake’s phumdis-scape is the way the phumdi formations transition from circular to rectilinear; the circular arrangements can be found in the middle of the lake, while the rectilinear arrangements can be found around the perimeter of the lake.

This is because the phumdis have to transition from informal territory to more formal territory that has a distinct ownership and is linked to plots of land. This is an amazing example of ownership within the water and around the water. Land can be divided into plots, but the inner section of a body of water is constantly moving and therefore cannot be sectioned into rigid boundaries, but rather shared landscapes with shared responsibilities for the greater body. Loktak isn’t just a precedent for what we now call floating wetlands, it’s a precedent for how we can create control using citizen driven engagement, giving an identity to this environment once seen as an uncontrollable residual space.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 57. Google Earth - Lokatk Phumdi Rings

Fig. 56. Google Earth - Loktak Phumdi Plots

Source: The Culture Gully - Loktak Lake

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.1 - River dialects; making the invisible visible and legible (Case studies; Makoko, phumdis)

LOKTAK LAKE PHUMDIS : LEKKI PHUMDIS _

These floating biomasses can also be found in the Lekki Lagoon. A small village located off the island of Lekki has also been noted to use floating biomasses in order to create a controlled region within the inner sections of the Lekki Lagoon. Amazingly, these phumdis are also arranged in circular formations, more similar to ovals. Unlike the phumdis in Loktak Lake, these units are divided into smaller sections within the oval. The division of these sections range from 3-8 subsections. It is not yet identified if these units are used for the same reason, fishing control; however, it can be assumed that some form of control over the environment is being utilized. Like the formations in Loktak Lake, some of these units are also attached to houses on the perimited of the Lekki Lagoon. Further investigation on the use and composition of these phumdis should be carried out and compared to the findings in Loktak Lake.

_ Wat e r We Tal k in g Ab o u t ? _

By analyzing these phumdis, several parameters that can be used to control water can be noted. Phumdis are able to indicate the direction of waterflow by contorting into ovals and aligning parallel to the flow of water.

They can also indicate sedimentation build-up. The phumdis located bby a waterway have been arranged in linear rows. The color of the water changes from brown to dark green as the water moves from the outlet into the inner section of the lake. This indicates that sediments are being trapped or slowed down from row to row. The strategy of fighting erosion and rebuilding the lake’s perimeter is implemented by creating these rows in the regions where the lake is susceptible to erosion. This is a display of massive control using natural resources in a sustainable manner that does not remove of add to the environment, but simple utilizes what is available.

The mapping of invisible forces such as water flow, wind direction, and sediment deposition and erosion is key to understanding and implementing natural methods of environmental control in and around the waterways.

Fig. 58. Phumdi analysis diagram.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 61. Google Earth - Lokatk Phumdi Transition

Fig. 60. Google Earth - Loktak Phumdi Rows

Fig. 59. Google Earth - Lekki Phumdis

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.1 - River dialects; making the invisible visible and legible (Case studies; Makoko, phumdis)

MAKOKO LOGS _

Looking at Lagos, there needed to be an investigation of the people who have the closest and oldest relationship to the river, the floating village of Makoko. This community relies on fishing and lumber as their major economic drivers. Lumber from the forested regions closer to the Niger Delta are cut down and transported through the Atlantic Ocean, into the Lagos Lagoon, and delivered directly to Makoko. This method of transportation keeps the wood wet, a requirement preferred by Makoko being that they store their logs by floating them on the water in order to avoid drying them out. The logs are then collected by the sawmill buyers, who have created sections within the water that are dedicated as their personal area of storage. These massive links of floating lumber can be seen from the third-mainland-bridge and even Google maps.

_ Wat e r We Tal k in g Ab o u t ? _

An interview was conducted with a resident in Makoko to assess their knowledge of their water environment as well as gather more information about the floating logs. The interview proved that their major understanding of the water dealt with water levels and seasonal tides. In regards to the logs, a hint was given that only the fishermen utilize and manipulate them.

They propose a precedent for communicating with the water through a formalized medium; a surface facade capable of function, expression, and control.

Fig. 62. Google Earth - Makoko Logs Overview

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 64. Source: Unknown - Mkoko Floating Logs

Fig. 63. Makoko map.

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.1 - River dialects; making the invisible visible and legible (Case studies; Makoko, phumdis)

MAKOKO LOGS : MAPPING INVISIBLE FORCES _

When looking at the logs from Google Earth, an interesting observation was gathered in regards to the formation of their arrangement. These are free-floating structures that are typically anchored only to each other, in an arrangement determined by the owner. Looking at them in plan view, their formation typologies are able to indicate several parameters. Single, looped, and clustered arrangements are able to indicate the direction of water flow as well as the direction of wind flow. Like the phumdis, they extend parallel to the flow of water, literally pointing towards the direction of water flow. This extension is also able to indicate water flow velocity; partially extended links are able to indicate mild velocities as opposed to fully extended links which indicate high velocities. This is able to determine if there is a high water discharge from the nearby waterways, which can also be noted as increased rainfall or surface runoff in areas upstream. The log formations can also suggest sediment control by resting on sandbars that are created as a result of sediment deposition.

_ Wat e r We Tal k in g Ab o u t ? _

By overlaying the formations created from the years 2000 to 2020 the logs show consistencies in pattern direction. This indicates accuracy and can serve as a physical dialect for these parameters. If the water can be visibly traced, then the flows can be understood, mapped, and controlled. What does the water say with these platforms?

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 65. Makoko log formation typologies

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.1 - River dialects; making the invisible visible and legible (Case studies; Makoko, phumdis)

MAKOKO LOGS : MAPPING INVISIBLE FORCES _

Using Kangaroo, a plugin for Rhino Grasshopper, a definition was created to simulate how a linked object would behave in a waterway as opposed to an open body of water such as the Lagos Lagoon. Various closed and opened link designs were used to understand various circumstances towards the possibility of using these structures as design solutions similar to phumdis.

The waterflow directions south, southeast, and southwest were used to observe how the links would interact with the waterway’s edge. Different velocities were also applied to simulate the full and partial extension observed in Makoko. Arrangements with one or two anchor points were also observed.

This exercise carried out an understanding of how suitable in-water design solutions can be used to indicate flows, velocities, and sedimentation. The exercise proved rather predictable findings in a waterway, this is because a channel has one direction of flow rather than multiple directions, which were observed in Makoko.

_ Wat e r We Tal k in g Ab o u t ? _

A further study should be done on a physical site in order to note how objects and debri can interact with these arrangements.

Fig. 66. Makoko log formation mapping : formation overlay

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 67. Makoko log formation mapping (2000-2020)

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.1 - River dialects; making the invisible visible and legible (Case studies; Makoko, phumdis)

LOG FLOW SIMULATION CATALOGUE _ SOUTH

SOUTH

SOUTHWEST

SOUTHWEST

SOUTHEAST

a.

anchor = 0.9

b.

anchor = 0.5

c.

anchor = 0.1

d. parallel anchor (set1) mid anchor (set 2) side anchor (set 3)

mid anchor obstacle (set 1) side anchor obstacle (set 2) sand deposition (set 3)

_ Wat e r We Tal k in g Ab o u t ? _

g.

a. Low wind speed + Low velocity b. Mid wind speed + Mid velocity c. High wind speed + High velocity d. Parallel anchor (set 1) e. Side anchor (set 2) f. Mid anchor (set 3) g. Mid anchor obstacle (set 1) h. Side anchor obstacle (set 2) i. Sand deposition (set 3)

Fig. 68. River dialects; waterflow simulation.

SOUTHEAST

SOUTHWEST

SOUTHEAST

SOUTH

a.

a.

b.

b.

c.

c.

e.

f.

h.

i.

SOUTHWEST

SOUTHEAST

_ Water We Talking About? _ MAA02: Eve Nnaji

SOUTH

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.2 - Mapping the hydrological processes of the waterway and floodplain

MAPPING HYDROLOGICAL PROCESS : MAKOKO LOG EXTRACTION _

Using the makoko log studies, a grid was overlaid on this map of flows and the vector directions were used to morph the grid, contracting the cells where the flows converge. This indicates a convergence of not only water but of sediments, nutrients, solid and chemical waste. These become pressure points, areas with high activities that can be used to implement high-impact solutions because they focus on extreme points rather than deploying solutions evenly through an environment. The pressure points are the starting point of intervention towards the location for implementing interventions for the quality, quantity, and hydromorphology goals in an optimal manner.

The water flow in the lagoon is quite different from the flow in the linear

_ Wat e r We Tal k in g Ab o u t ? _

floodways. The simulation of floating masses in a channel could be used to give an understanding of how floating elements could indicate flow convergences. The findings suggested that different arrangements of links and anchor points illustrate interesting behaviors but never converge.

This simulation alone cannot provide pressure points, because they only acknowledge one direction of flow, whereas the Makoko map shows a history of convergence from multiple directions. In order to understand and map the pressure points in the linear direction, the flows from the lateral direction need to be mapped as well. It is the convergence of flows in these two directions that indicate pressure points.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 70. Makoko log formation mapping : identifying pressure points

05 . STRATEGY - Renature, Reculture _ 5.2 - Establishing a dialect using flows 5.2.2 - Mapping the hydrological processes of the waterway and floodplain

MAPPING HYDROLOGICAL PROCESS : FLOODPLAIN _

By giving a formal language to the series of water flows in the lateral direction, the pressure points can be identified well before they converge with the flows in the linear direction. In order to do this, the hydrological process that constructs the floodplain needs to be understood. Typically, the floodplain can be split into zones; zone 0 being the floodway and zone 1, 2, and 3 being the flood fringes. In these zones, inland water needs to make it to the nearest floodway through runoff, infiltration and percolation, and interflow. Each zone has a different flow rate for these processes. At each step water has to make a decision; to infiltrate or to runoff, to percolate or to be absorbed, retained by soil and vegetation, to move forward into the next zone through interflow or to percolate downwards into the baseflow.

Each of these forks in the roads decreases the time it takes for water to reach the floodway in zone 0.

_ Wat e r We Tal k in g Ab o u t ? _

Currently, impermeable surfaces in and around the floodplain have hindered infiltration, thus decreasing percolation, interflow, and baseflow.

The water has only one decision to make, to runoff surfaces and converge in the floodway, causing flooding; therefore, surface runoff becomes the major flow we need to map in order to identify our pressure points.

This creates a silver lining because surface runoff, unlike percolating and interflow, is a visible process. It can be tracked and controlled using natural, low-cost, interventions that simply redirect runoff towards relief areas. This combination of retention, filtration, and distribution strategies are called micro-catchments.

Fig. 71. Linear and lateral connectivity diagram.

RETAIN

FILTER de c re ase

eva p ot ra n s p i t a t ion

ZONE 3

ZONE 2

ZONE 1

p rec ip i t a t ion v

over f low > ( r un off ) in f il t ra t io n v

i n c re ase

FI LTE R

RETA IN

DISTRIBUTE

gro u nd cove r i nf i l t ra t i o n eva p o ra t i o n ove r f low

in t er f low >

u ns a t u ra t e d s o il i nf i l t ra t i o n u pt a ke p e rc o l a t i o n i nt e r f l ow

b a s ef low V

p erc ola t io n v

p erc ola t io n v

s a t u ra t e d s o il i nf i l t ra t i o n p e rc o l a t i o n b a sef l ow

D I STR I B U TE

ZO NE 3

ZON E 2

ZON E 1 ZON E 0

RETAIN

FILTER de c re ase

ZONE 3

eva p ot ra n s p i t a t ion ZONE 2

H I G H R UN O F F OVE RSAT URAT I O N

ZONE 1

p rec ip i t a t ion v

over f low > ( r un off )

i n c re ase

FILT ER

RETAIN

DISTRIBUTE

gro u nd cove r i nf i l t ra t i o n eva p o ra t i o n ove r f low

in t er f low >

u ns a t u ra t e d s o il i nf i l t ra t i o n u pt a ke p e rc o l a t i o n i nt e r f l ow

b a s ef low V

s a t u ra t e d s o il i nf i l t ra t i o n p e rc o l a t i o n b a sef l ow

D I STR I B U TE ZON E 2

ZON E 1 ZON E 0

Fig. 72. Hydrological process, diagramming water flow.

_ Water We Talking About? _ MAA02: Eve Nnaji

ZO NE 3

06 . PROPOSAL _ What We’re Talking About

_ Water We Talking About? _ MAA02: Eve Nnaji

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

MICROCATCHMENT STRATEGY : BUNDS _

Micro-catchments redirect runoff through surface alterations. Bunds are a type of micro-catchment that optimize surfaces by using coordinated mound formations to direct runoff, allowing water to infiltrate the ground before it reaches the floodway. They dismantle large quantities of water and maximize surface retention quality.

Bunds are a type of micro-catchment. They are small mounds and barriers that are able to divert surface runoff water coming from other catchments along with precipitation. They are able to reduce the speed of water flow and allow it to flow on the ground surface in a manner that encourages infiltration and soil water absorption. The advantage of bund systems is that their effectiveness relies mostly on their location and general design.

They do not require heavy specifications that leave a tight margin of error in order to be operable.

“A water harvesting scheme will only be sustainable if it fits into the socioeconomic context of the area as described in the previous chapter and also fulfills a number of basic technical criteria.

SLOPE: The ground slope is a key limiting factor to water harvesting.

Water harvesting is not recommended for areas where slopes are greater than 5% due to uneven distribution of run-off and large quantities of earthwork required which is not economical.

SOILS: Should have the main attributes of soils which are suitable for irrigation: they should be deep, not be saline or sodic and ideally possess inherent fertility. A serious limitation for the application of water harvesting are soils with a sandy texture. If the infiltration rate is higher than the rainfall intensity, no runoff will occur.

_ Wat e r We Tal k in g Ab o u t ? _

COSTS: The quantities of earth/stonework involved in construction directly affects the cost of a scheme or, if it is implemented on a self help basis, indicates how labour intensive its construction will be.”

(Critchley and Siegert, 2013)

_ Water We Talking About? _ MAA02: Eve Nnaji

Source: Critchley, W. and Siegert, K., 2013. Water harvesting microcatchments

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

DESIGNING FOR MICROCATCHMENTS : RUNOFF CALCULATION _

In order to design micro-catchments surface runoff rates need to be mapped. A peak runoff rate essentially tells how much water is passing through a given plot of land per second. The equation Q=CiA can be used to solve for the peak runoff rate where Q represents the peak runoff rate, C represents the runoff coefficient, i represents the rainfall intensity, and A represents the area of land to calculate (Chin, 2019). The rainfall intensity was taken from a paper that calculated the intensity over a period of 2-200 years (A. S., 2018). The most important value being the runoff coefficient. These are fixed values given to different types of ground covers from woody to concrete (SWAMP, 2021). It’s important here to note that the runoff coefficients between woody and concrete are vastly different.

The amount of water passing through a concrete plot can be 20 times the amount of a woody plot. It takes a lot of plots to make a difference in converting an area from high to low peak runoff, showing the importance of optimizing all available land.

_ Wat e r We Tal k in g Ab o u t ? _

A section of a neighborhood close to a waterway in Lagos was selected to be used as the model site to map runoff. The site is divided into plots in order to map these rates from low to high peak runoff. A Grasshopper definition was created using the peak runoff rate formula in order to plot the runoff rate points on the map. Several parameters were used to further define runoff such as the slope of the topography, the amount of buildings clustered around the grid points, and the land cover in the area. To get a zonal perspective of the peak runoff rates, the plots are grouped and a gradient that spanned from white to black was used to indicate high and low rates, white being low and dark grey being high. The areas around the river, in white, which have the lowest peak runoff rates, allocated land that can be used as potential relief points.

316m3

runoff (L/s)

PEAK RUNOFF RATE ex: 100 L/s

time (hours) ** Q

1060m

*

= CiA C = runoff coefficient i = rainfall intensity A = area

woody = 0.05 grassy = 0.15 compact gravel = 0.85 concrete = 1.00

Q = (0.05)( 50)(0.078acres) Q = 0.195 cf/s = 5.5 L/s woody = 5.53 L/s grassy = 16.59 L/s compact gravel = 94.03 L/s concrete = 112 L/s

x x x

Low Peak Runoff Mid Peak Runoff High Peak Runoff

1060m potential relief points

Fig. 73. Calculating surface runoff

** The Clean Water Team Guidance Compendium for Watershed Monitoring and Assessment State Water Resources Control Board 5.1.3 FS-(RC) 2011

_ Water We Talking About? _ MAA02: Eve Nnaji

* Development of Rainfall Intensity Duration Frequency Curves for South Western Nigeria Awofadeju A. S., Akanni, A. O., Ojeleke T. A., and Oguntayo A. A., 2018

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

DESIGNING FOR MICROCATCHMENTS : PRESSURE AND RELIEF POINTS _

A water flow simulation was then used to identify where water flows converge. These areas become where the pressure points are located.

When running the simulation, it is known that the water flow will converge in the floodway; however, another point of convergence was noted at a lower elevation. The topology indicated that the water in the selected site flows into the waterway and continues to flow downwards into a neighborhood located at an elevation slightly lower than the waterway.

This means that there are two areas with pressure points, the floodway and an axis that runs through the neighborhood in the lower elevation area.

Two scenarios can explain this event, these developments are situated in a space that once belonged to the floodplain or these developments are situated in a region that is currently being carved out by surface runoff which, naturally would become the new path for a channel that would merge with the current waterway.

_ Wat e r We Tal k in g Ab o u t ? _

This scenario is currently being mirrored in neighborhoods throughout Lagos and the study cities. By indicating these pressure points along with identifying the runoff rates of the surrounding area, a strategy can be designed in order to mitigate flooding. The land must be altered to indicate the new relief zones and redirect water towards these zones.

Bunds, which create surface alterations that can control surface runoff, will be used to transform these two areas. In zone 2, incoming surface runoff from the paved land needs to be coordinated towards the relief zones. By following the natural process, the goal is to create multiple options for the water to take, this will decrease the amount of time it takes for the runoff to reach the relief point.

The surface design in zone 2 can be designed in a labrythined manner as long as the outlet is evenly dispersed along the border of zone 1. In zone 1, the incoming surface runoff from zone one needs to go through a more directional path towards the relief point. The bund patterns in zone 2 need to follow more specific guidelines that can be measured in order to make future alterations. Using the semi-circular bunds to create a series of steps towards the relief zone is appropriate. The semi-circles can be increased or decreased in size in order to accomodate for the amount of water and time it takes to reach the relief point. The relief point should be located in the central axis of zone 1. This is necessary in order to create a controlled release of the surface runoff towards zone 0, the floodway. The section of zone 1 that will distribute a controlled relief can mirror the same design used to attract the runoff to the relief point, but it must disperse the water evenly along the floodway. By the time the runoff reaches the floodway, it will be broken down into minute streams that will not overwhelm the floodway.

pressure points

relief points

250m

9m*

10m*

Fig. 74. Microcatchment zonal design

_ Water We Talking About? _ MAA02: Eve Nnaji

*elevation

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

DESIGNING FOR MICROCATCHMENTS : RELIEF STRATEGY MAP _

The system of bunds offers many design variations that can adhere to the distributive guidelines of the zones. Each zone is meant to distribute and capture the runoff water at different rates. While distribution is achieved through the geometric formation of the bund, retention is achieved through vegetation and ground cover. As previously discussed, the floodplain’s hydrological process is just a series of water in which water flows through various mediums. The percolation rate is the amount of time it takes for water to pass through earth substances such as soil, clay, and rock formations. This rate can be controlled through various ground covers.

Vegetation also increases percolation as well as provides another avenue for water to travel, this is through the root system of the plant and eventually through evapotranspiration. As the water flows through each zone, it can pass through ground covers and vegetation that moves from a rapid absorption and percolation rate to a more gradual rate as it reaches the center of the zone, the retention point.

_ Wat e r We Tal k in g Ab o u t ? _

Another layer was added to the micro-catchment strategy mapping by plotting vegetation and groundcover types. Three plant types were indicated for the strategic use of their uptake rate. As the runoff reaches each retention point, grassy vegetation and low shrubs that sit on porous soil covered with coarse pebbles are able to absorb the first incoming surface runoff; this ground cover typically has a percolation rate of 15-18 liters of water per day. As the water moves through the stone, it is met with high level shrubs and low level trees. These sit on sandy clay and or sandy clay loam which has a decreased percolation rate than the previous environment; this ground cover typically has a percolation rate of 6.5-10 liters of water per day. Finally, as the soil reaches the central retention point, it is met with woody vegetation that sits on clay with small sand or gravel; this ground cover typically has a percolation rate of 3-4 liters of water per day.

This strategy uses the frontlines of the retention zone to receive as much water as possible before passing the remainder runoff towards the center.

The center is meant to slowly receive the first liters of runoff which will come at a gradual pace. At the point where it is eventually inundated with water, these conditions will not do as much damage to woody vegetation as it can to shrubs. Overwhelming a small plant’s roots with water can cause it to die; however, larger plants are able to withstand flooding events. To represent this strategy on the map, a gradient of gray was used to indicate the ground cover; light grey being high percolation rates to dark grey being low percolation rates. The numbers 1-3 were used to indicate the vegetation type; 1 being grassy and 3 being woody vegetation.

Fig. 75. Microcatchment strategy map

250m

9m*

10m*

Fig. 76. Microcatchment vegetation planning

_ Water We Talking About? _ MAA02: Eve Nnaji

*elevation

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

_ Wat e r We Tal k in g Ab o u t ? _

Fig. 77. Microcatchment strategy map 01

The planning of relief points before the surface runoff reaches the floodway and before it reaches these pressure points can greatly reduce water attenuation and flooding in these vulnerable areas. A micro-catchment strategy map essentially plots a porosity scheme that increases in retention towards the center of the relief by using a grade of vegetation and soil types, taking uptake and percolation rates into account.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 78. Lagos flood zones map

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

_ Wat e r We Tal k in g Ab o u t ? _

Fig. 79. Microcatchment strategy map 02

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 80. Lagos pollution hotspots map

06 . PROPOSAL - What We’re Talking About _ 6.1 - Designing for bund microcatchments

_ Wat e r We Tal k in g Ab o u t ? _

Fig. 81. Microcatchment strategy map 03

This is the layered information that needs to be decentralized and democratized. It is crucial for this information to be visibly communicated to the community in order for them to carry out and further develop this strategy within their environment.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 82. Lagos water discharge velocity map

06 . PROPOSAL - What We’re Talking About _ 6.2 - Application and implementation strategy

DESIGNING FOR MICROCATCHMENTS : RELIEF STRATEGY MAP _

How do we communicate these micro-catchment schemes that can maximize retention in heavy inundated areas, disperse and moderate flows in areas with high discharge velocities, reate interventions that confront water quality issues before they reach the floodways, And most importantly, engage the community in the restoration of their environment?

The coordination of water flows in the floodplains is the restoration of the function of the floodways, channel by channel. But an overarching body can further coordinate these efforts from the channels to the catchments to the Lagoons. This is where the city comes in as a platform of communication.

The city has the opportunity to establish a formal language that serves as a guideline from catchment to catchment, using a spatial framework that communicates these schemes and can be populated by each community.

Bunds are appropriate for this implementation because they offer an extremely visual means of communication. In the same way that a stop sign is the literal declaration of an order, bunds can be the declaration of a strategy because they are that visually simplistic.

_ Wat e r We Tal k in g Ab o u t ? _

Source: Demi-lunes. Men building semi-circle bund

Fig. 83. Lagos zonal income map

Low-income Mid-income

_ Water We Talking About? _ MAA02: Eve Nnaji

High-income

06 . PROPOSAL - What We’re Talking About _ 6.2 - Application and implementation strategy

DESIGNING FOR MICROCATCHMENTS : RELIEF STRATEGY MAP _

The first development of the indication of relief points can be implemented by the governing body in command of the floodplain. Simplified geometries can be used to indicate the direction in which water needs to travel and the destination it is trying to reach. Radial bunds can indicate the focus of relief zones, strong axis of contour bunds dictate the flow towards these fields, and denser contours create a gradual redistribution of runoff from these zones into a protected floodway. By demarcating these regions using these geometries, the city informs, “this is where water needs to go” , the citizens engage the implementation, and the water follows these directions. This partnership is the restoration and definition of the floodways and floodplains by the city and citizens.

Giving the citizens clear instructions, and trusting in their capacity to read the environment along with the permission to engage in their environment is essential to the success of such projects in developing countries. Citizens in Lagos, and cities of the like, have been forced into independence by the lack of a governing infrastructure. Providing a template that allows them to continue exercising their independence provides them a stake in the project and places the project in a position suitable for long-term implementation and success.

_ Wat e r We Tal k in g Ab o u t ? _

The advantage of the microcatchment system is that their effectiveness relies mostly on their location far more than their design. They do not require heavy specifications that leave a tight margin of error in order to be operable. This allows the participants to create their own identity and language using a wide array of geometrical formations. As long as the direction and destination of water flow is understood, the bunds and microcatchments can be utilized towards independent needs without causing harm to the greater system.

_ Water We Talking About? _ MAA02: Eve Nnaji

Source: TNAU Agritech, Engineering . Contour Bunds

Source: Justdiggit; Kuku, Kenya. Semi-circle Bunds

Source: Justdiggit; Kuku, Kenya. Semi-circle Bunds

Source: Justdiggit; Kuku, Kenya. Semi-circle Bunds

06 . PROPOSAL - What We’re Talking About _ 6.2 - Application and implementation strategy

_ Wat e r We Tal k in g Ab o u t ? _

Fig. 84. Natural flood mitigation design proposal 01

_ Water We Talking About? _ MAA02: Eve Nnaji

06 . PROPOSAL - What We’re Talking About _

_ Wat e r We Tal k in g Ab o u t ? _

6.2 - Application and implementation strategy

Fig. 86. Natural flood mitigation design phasing

_ Water We Talking About? _ MAA02: Eve Nnaji

06 . PROPOSAL - What We’re Talking About _

_ Wat e r We Tal k in g Ab o u t ? _

6.2 - Application and implementation strategy

Fig. 87. Deification of the landscape

_ Water We Talking About? _ MAA02: Eve Nnaji

06 . PROPOSAL - What We’re Talking About _ 6.2 - Application and implementation strategy

DESIGNING FOR MICROCATCHMENTS : RELIEF STRATEGY MAP _

In order to successfully execute this project, the implementation can be broken down into X phases. The first phase is dedicated towards identifying a pilot location and implementing the first bund framework.

The community residing in the immediate environment must be engaged in the implementation of the bund framework. By educating a handful of stakeholders, the community is empowered to carry out further development and maintenance independently. This pilot must be studied in order to collect data that can track the success of the implementation. The flow of water can easily be mapped by noting vegetation. Where water flows through, vegetation is most likely to grow in abundance. By noting where the vegetation is flourishing, the relief points can be assessed; those that are showing no signs of vegetation growth can be deemed useless to the strategy, while those regions showing vegetation growth can be developed further to either retain more water used to develop further dispersal channels.

The second phase focuses on the development of multiple channels towards monitoring the health of a catchment area. The findings and strategies recorded in the first phase are to be shared with the communities surrounding these channels. Focusing on a catchment area offers the opportunity to learn about the hydrological process and the hindrances on a larger scale. Parameters such as solid waste amount, precipitation, water discharge amount, and even sedimentation can be recorded. The goal of recording is not necessarily to control these parameters, because this will already be achieved through the microcatchements, but it is to initiate the development of a digital environment that can learn and predict the environment at the catchment scale.

_ Wat e r We Tal k in g Ab o u t ? _

The third phase focuses on the entire water network of the city. By implementation, the combination of data, and the development of a digital environment of Lagos, flood mitigation can be controlled at a level capable of relieving the city from disasterous scenarios. Events, such as flooding from the release of incoming water from the Oyan Dam located above Abeokuta, hundreds of kilometers away, can be easily avoided.

Implementing these strategies from channels to catchments in cities such as Magboro, Abeokuta, and Ibadan is key to addressing the causes of flooding in close proximities from upstream to downstream, from state to state.

RIVER

information: definition

renaturalization

information: translation

restoration

Fig. 88. DRFM loop

_ Water We Talking About? _ MAA02: Eve Nnaji

CITY + CITIZENS

06 . CLOSING _ A New Dialogue...

Fig. 89. «A new dialogue»

_ Water We Talking About? _ MAA02: Eve Nnaji

07 . CLOSING - A New Dialogue... _

What if we changed our linear ideas of our impacts, acknowledging that we are an extension of our environment?

We’ll find that as we exercise control that doesn’t try to fight water, but invites it into a meeting place, we create temples for nutrients, flora and fauna that serve beyond

_ Wat e r We Tal k in g Ab o u t ? _

the immediate region.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 90. This is what we’re talking about 01

07 . CLOSING - A New Dialogue... _

As we find our place within this framework in a continuously changing landscape, We collectively build a body that exemplifies a strong social ecological connection between our immediate selves and our extended

_ Wat e r We Tal k in g Ab o u t ? _

selves, our environment.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 91. This is what we’re talking about 02

07 . CLOSING - A New Dialogue... _

The communities and individuals that will benefit from this strategy are the ones that acknowledge the river, investigate its changes, and participate in the development of its new identity. Giving to the river, will give to the citizens, creating a narrative where function and identity are present not

_ Wat e r We Tal k in g Ab o u t ? _

only in the environment, but in the culture.

_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 92. This is what we’re talking about 03

This is democratic flood risk management.

This is the new dialogue between the city, the citizens and their water.

08 . REFERENCES _ Bibliography

A. S., A., 2018. Development of Rainfall Intensity-Duration-Frequency Curves for South Western Nigeria. International Journal of Engineering and Technology, 10(4), pp.373-379.

Adelekan, I., 2010. Vulnerability of poor urban coastal communities to flooding in Lagos, Nigeria. Environment and Urbanization, 22(2), pp.433-450.

Adelekan, I., 2015. Flood risk management in the coastal city of Lagos, Nigeria. Journal of Flood Risk Management, 9(3), pp.255-264.

Alimi, T., 2017. Magboro: Sad tales from abandoned community. [online] Medium. Available at: <https://medium.com/@taiwo_ alimi/magboro -sad-tales-from-abandoned- community2d1791a22523> [Accessed 5 September 2021].

Areola, O., Faniran, A. and Akintola, O., 1985. The farmer-based small-farm schemes of the Ogun-Oshun River Basin Development Authority, Southwestern Nigeria. Agricultural Systems, 16(1), pp.7-21.

Badiane, A. and Mbye, D., 2014. State of Osun Structure Plans Project.

STRUCTURE PLAN FOR OSOGBO CAPITAL TERRITORY AND ENVIRONS, [online] Available at: <https://unhabitat.org/structureplan-for-osogbo-capital-territory-and-environs-2014-2033state-of-osun-structure-plans> [Accessed 6 September 2021].

Buffington, J. and Montgomery, D., 2021. [online] Fs.fed.us. Available at: <https://www.fs.fed.us/rm/pubs_other/rmrs_2013_buff ington_ j001.pdf> [Accessed 18 September 2021].

Chin, D., 2019. Estimating Peak Runoff Rates Using the Rational Method. Journal of Irrigation and Drainage Engineering, 145(6), p.04019006.

Critchley, W. and Siegert, K., 2013. Water harvesting. Jaipur: Scientific Publishers (India).

_ Wat e r We Tal k in g Ab o u t ? _

Komolafe, A., Adegboyega, S. and Akinluyi, F., 2015. A Review of Flood Risk Analysis in Nigeria. American Journal of Environmental Sciences, 11(3), pp.157-166.

Lade, O. and Oloke, D., 2018. Performance Evaluation of a Rainwater Harvesting System: A Case Study of University College Hospital, Ibadan City, Nigeria. Current Journal of Applied Science and Technology, 25(5), pp.1-14.

Ndimele, P., 2012. The Effects of Water Hyacinth (Eichhornia crassipes [Mart.] Solms) Infestation on the Physico-Chemistry, Nutrient and Heavy Metal Content of Badagry Creek and Ologe Lagoon, Lagos, Nigeria. Journal of Environmental Science and Technology, 5(2), pp.128-136.

Nkwunonwo, U., Whitworth, M. and Baily, B., 2016. Review article: A review and critical analysis of the efforts towards urban flood risk management in the Lagos region of Nigeria. Natural Hazards and Earth System Sciences, 16(2), pp.349-369.

Ochieng, A., 2017. Nigeria’s Generator Addiction Is An Opportunity in Disguise. [online] emerge85. Available at: <https://emerge85. io/Insights/nigerias-generator-addiction-is-an-opportunity-indisguise/> [Accessed 5 September 2021].

OYEBOD, O., 2018. A Comparative Assessment of Water Corporations in Nigeria with Water Management in a Typical Developed Country.

European Journal of Advances in Engineering and Technology, 5(8), pp.535-542.

OYEGOKE, S. and SOJOBI, A., 2012. Developing Appropriate Techniques to Alleviate the Ogun River Network Annual Flooding Problems.

International Journal of Scientific & Engineering Research, 3(2).

Rowiński, P., Västilä, K., Aberle, J., Järvelä, J. and Kalinowska, M., 2018. How vegetation can aid in coping with river management challenges: A brief review. Ecohydrology & Hydrobiology, 18(4), pp.345-354.

SWAMP, C., 2021. Methods to Measure Rainfall. Guidance Compendium for Watershed Monitoring and Assessment, pp.5.1.3.

Ufoegbune, G., Oyedepo, J., Awomeso and Eruola, A., 2010. Spatial Analysis of Municipal Water Supply in Abeokuta Metropolis, South Western Nigeria.

Wesche, T., 1985. The Restoration of Rivers and Streams Theories and Experience. Laramie, Wyoming: Wyoming Water Research Center.

WHO, 2014. Progress on Drinking-Water and Sanitation. Geneva, Switzerland.

of Lagos Lagoon, Southwest Nigeria. International Journal of Biological and Chemical Sciences, 5(1).

_ Water We Talking About? _ MAA02: Eve Nnaji

Yakub, A., Balogun, K., Ajani, G., Renner, K., Ariyo, A., Bello, B., Nkwoji, J. and Igbo, J., 2011. Distribution of phytoplankton in some parts

08 . REFERENCES _

_ Wat e r We Tal k in g Ab o u t ? _

Image Appendix

Figure 01. Google Earth - Oyan Dam. Abeokuta, Ogun State Figure 02. Google Earth - Magboro Soil. Magboro, Ogun State Figure 03. Global Water Crisis Figure 04. Study states and cities map Figure 05. Regional studies data table Figure 06. Ogbontosa and Ibadan map Figure 07. Google Earth - Ogbontosa Figure 08. Google Earth - Ibadan Figure 09. Abeokuta map Figure 10. Google Earth - Abeokuta Figure 11. Google Earth - Abeokuta Fig. 12. Mokoloki and Magboro map

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Fig. 13. Google Earth - Magboro 1984-2015 Figure 14. Google Earth - Magboro Soil 2006 - 2020 Figure 15. Google Earth - Mokoloki Fig. 16. Ede and Ikire map Fig. 17. Google Earth - Ede Fig. 18. Google Earth - Ikire Fig. 19. Lagos island and Lagos mainland map Fig. 20. Google Earth - Lagos Mainland Fig. 21. Google Earth - Lagos Mainland Fig. 22. Google Earth - Lagos Island Fig. 23. Lekki map Fig. 24. Google Earth - Lekki Phase 2 Fig. 25. Google Earth - Lekki Phase 1 Fig. 26. Flood hotspots map Fig. 27. Flood Causes Ogun state Fig. 28 Flood Causes Osun and Oyo state Fig. 29. Flood Causes Lagos state Fig. 30. Abeokuta to Lagos, mapping Ogun River changes Fig. 31. Abeokuta to Lagos, Ogun River changes analysis Fig. 32. Abeokuta to Lagos, Ogun River changes sequence images Fig. 33. Regional studies conclusion images Fig. 34. Regional studies water as a resource Fig. 35. Lagos water scarcity map Fig. 36. Lagos urban analysis plotting Fig. 37. Lagos urban analysis images evaluation Fig. 38. Google Maps - Lagos Roadside Animal Farm Fig. 39. Google Maps - Lagos Fish Farm Fig. 40. Google Maps - Lagos Crop Farm Fig. 41. Google Maps - Lagos Animal Farm Fig. 42. Google Maps - Lagos Economic Activities Around Waterway Fig. 43. Google Maps - Lagos Unsactioned Landfill Fig. 44. Google Maps - Lagos Dredging Fig. 45. Google Maps - Lagos Dredging Fig. 46. Google Maps - Lagos Lagoon Border

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Fig. 59. Google Earth - Lekki Phumdis Fig. 60. Google Earth - Loktak Phumdi Rows Fig. 61. Google Earth - Lokatk Phumdi Transition Fig. 62. Google Earth - Makoko Logs Overview Fig. 63. Makoko map Fig. 64. Source: Unknown - Mkoko Floating Logs Fig. 65. Makoko log formation typologies Fig. 66. Makoko log formation mapping : formation overlay Fig. 67. Makoko log formation mapping (2000-2020) Fig. 68. River dialects; waterflow simulation Fig. 69. Makoko log formation mapping : pressure points Fig. 70. Makoko log formation mapping : identifying pressure points Fig. 71. Linear and lateral connectivity diagram Fig. 72. Hydrological process, diagramming water flow Fig. 73. Calculating surface runoff Fig. 74. Microcatchment zonal design Fig. 75. Microcatchment strategy map Fig. 76. Microcatchment vegetation planning Fig. 77. Microcatchment strategy map 01 Fig. 78. Lagos flood zones map Fig. 79. Microcatchment strategy map 02 Fig. 80. Lagos pollution hotspots map Fig. 81. Microcatchment strategy map 03 Fig. 82. Lagos water discharge velocity map Fig. 83. Lagos zonal income map Fig. 84. Natural flood mitigation design proposal 01 Fig. 85. Natural flood mitigation design proposal 02 Fig. 86. Natural flood mitigation design phasing Fig. 87. Deification of the landscape Fig. 88. DRFM loop Fig. 89. “A new dialogue” Fig. 90. This is what we’re talking about 01 Fig. 91. This is what we’re talking about 02 Fig. 92. This is what we’re talking about 03

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_ Water We Talking About? _ MAA02: Eve Nnaji

Fig. 47. Google Maps - Lagos Lagoon Community Fig. 48. Google Maps - Lagos Lagoon Ogun River Outlet Fig. 49. Google Maps - Makoko Sawdust Fig. 50. Lagos urban analysis summary Fig. 51. Google Maps - Waste Infested Waterway in Lagos Fig. 52. Google Maps - Waterlogged Street in Lagos Fig. 53. Google Maps - Waterlogged Community in Lagos Fig. 54. Lagos urban analysis cause-effect conclusion Fig. 55. Democratic flood risk management strategy diagram Fig. 56. Google Earth - Loktak Phumdi Plots Fig. 57. Google Earth - Lokatk Phumdi Rings Fig. 58. Phumdi analysis diagram

_ Wate r We Talk in g A bo ut ? _

MAA02: E ve Nn aj i

Research Thesis Developed by

_ Eve Nnaji _

Thesis Advisors

_ Mathilde Marengo + Gonzalo Delacámara _

Institute for Advanced Architecture of Catalonia Master in Advanced Architecture

Barcelona September, 2021