Master Thesis - Intergrative Environmental Design

PETIT SABLE 2018-06-26

INTEGRATIVE ENVIRONMENTAL DESIGN TOWARDS LOCAL IMPACTS OF CLIMATE CHANGE

BY R.R.LACHHMAN SUPERVISORS G.HARTMANN, J.FACH & L.BUSSE

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I would like to thank my supervisors Gunnar Hartmann, Krassimir Krastev and Joris Fach for the help and guidance during the project.

Special thanks to Aid Action, Non Governmental, Non Profit Organisation for their involvement in the project. As well as Lilian Busse from the German Environment Agency (Umweltbundesamt – UBA), for her valuable insights on the problems at hand.

Finally, I would like to thank my parents and friends for their helpful insights and support during the development of the project.

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TABLE OF CONTENTS 0-0. Introduction 0.1. Abstract 0.2. Studio Brief 1-0. Background 1.1. Mauritius 1.1.1. Colonial Architecture 1.1.2. Colonial Artitectural Evolution 1.1.3. Modernity Vs Cyclones 1.1.4. Climate Change 1.1.5. Soil Erosion 1.2. Agricultural Coastal Village 1.2.1. Petit Sable 1.2.2. Economy 1.2.3. Terrain 1.2.4. Soil Erosion 1.2.5. Initiatives

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2-0. Techniques 2.1. Soil Stabilisation 2.1.1. Terracing 2.1.2. Water Management 2.1.3.Retention Walls 2.2. Structural system 2.2.1. Cyclone Vulnerable Structure 2.2.2. Roofs 2.2.3.Concrete Masonry 2.2.4. Wall Openings 2.2.5. Foundations 2.2.6.Channel Crossings 3-0. Blue Print 3.1. Soil Stabilisation 3.2. Housing System 3.2.1. Water Rules 3.2.2. Wind Rules 3.3. Housing Plans & Dimensions 4-0. Outlook 5-0. Bibliography

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0-0.

INTRODUCTION

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0.1. ABSTRACT Changes in weather patterns, caused by solar radiations, movements in tectonic plates, volcanic activities, all the way to biotic processes and all that climate change entails. In this issue varsity of professionals have attempted to develop structural designs that they have been believed to be the solution, some have failed while others succeeded. However, is it enough to develop or simply redesign infrastructures in order to manage our involvement with climate change?

Stewart Brand in his book “The Whole Earth Discipline” does argue that urbanization should be rethought by taking into account emerging forces of climate change and some of society’s general positions on environmental design should be modified. “Cities are green with a huge room for improvement.”1 Traditional indigenous environments are the ones with the most room for improvement with their structural vulnerability while facing climate change.

Reference 1

Brand, Stewart. 2010. Whole Earth Discipline. London: Atlantic Books.

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Researcher David R Montgomery a geomorphologist and process professor of earth and space science is at the University of Washington talks in his book “Dirt: The erosion of civilization�, about the ill treatment of soil and how that has worked against the longevity of societies. Accumulated years of habitation and agriculture have worn out the so more precious soil. Looking into how to save a small community in Mauritius that has been suffering from soil erosion, affecting their structurally unsafe housing typologies, will enable to understand the broader topic of climate change and how this affects our surroundings. Digging deep into the blue and green infrastructures theory, the progression of architectural vernacular and environmental restrictions of a south equatorial site, through records, case studies, simulations, observations, and structural analysis we should somehow get closer to understanding how to live with the inevitable changes in our environment.

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0.2. STUDIO BRIEF Looking into various countries throughout the world with the same type of issues and their implemented actions to turn around the relation with their environment. Mostly where an unpredictitable increase in precipitation, due to a disrupted hydrological cycle has caused contaminated water run-off to damage the infrastructures and threaten the urban life.

These re-integrations of nature within the community are often seen in Blue-Green infrastructures, which seem to have found the balance in reconnecting the two along with the increase bio-diversity and walkability of an area.

Further on, the investigation of soil erosion, structural system of existing houses and understanding the broader dysfunction of the site's urban settlement, using programs simulating radiation analysis, rain water flow, solar and wind trajectory will allow better comprehension of the area and its issues and design a system that does not only deviate the water and soil flow, but also use it to help the community's progression along with a structurally safe designed house.

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1-0.

BACKGROUND

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Illustration of a colonial cannon along the south east of the island. The cannon was used during the big battle of Grand Port between the French Navy and the British Royal Navy

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1.1. MAURITIUS Mauritius encountered its' first colonies in 1638, who introduced new technologies of colonialism to its virgin lands. As time passes it get more habited by various global ethnicities that brought along new cultures and infrastructure. Developing the island to become what now is considered to be the most economically competitive country in the sub Saharan African area.2

Reference 2 "Mauritian economy ranked 'most competitive' in sub Saharan African". 2018. Africanews. http://www.africanews.com/2016/10/01/see-africa-s-top-10-economies-in-latestranking-of-global-competitiveness-index/

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1.1.1. COLONIAL ARCHITECTURE Traditional colonial architecture, composing of wood facades and slate roofing was built all around the island, starting from the south east of the island where the original port was based. The windy shores caused the inhabitants to replace the port to the north west of the island, where the current and wind is nearly not existent. The strong winds were not only caused by the Southen African current but also by the highly cyclonic tendencies of the Indian Ocean, which did not agree with the colonial structures.

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Illustration of colonial house with basalt stone walls.

Illustration of the colonial house evolution, introducing tin roofing during the industrialisation period.

Illustration of a tin sheet house using the basic structure of colonial structures, also known as creole houses.

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1.1.2. COLONIAL ARCHITECTURAL EVOLUTION They soon understood that they needed stronger structures that could withstand the uncontrollable weather. The use of volcanic rock as walls allowed the structures to not only be resistant but highly durable. Along with industrialisation came metal and tin sheeting allowing for cheaper and quicker roofing alternative.

As time went by the architectural style modernised itself getting rid of ornamental aspects of the colonial times.

Eventually, as modern precast basalt bricks came to be, some inhabitants made the choice of sticking with tin and metal sheeting. Tin housing was not only cost friendly, but also easily available materials and less time consuming to build.

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1.1.3. MODERNITY VS CYCLONES Unfortunately, their choice was miscalculated, as those structures are more vulnerable to cyclones often causing complete destruction of the whole unit. The structure of the tin housing and most specially the tin roofing, compose itself of various weak spots in the structure.

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Illustration of a tin roof collapsing.

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Illustration of weak points within tin roof structures.

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If those weak spots are not carefully treated, they can cause major damage. The windward facade (wind exposed side) could collapse under the pressure of the wind when the wall is not properly reinforced or the wood frames are too light and improperly connected to the footings or foundation. This may also prevent walls to resist the push and pull of the wind causing a tend to lean in the direction of the wind resulting to the roof to collapse first.

Cyclonic wind to entering the unit, increases the pressure on the internal surfaces. In combination with external suction causes the roof to blow off and walls to explode. When no air enters the house pressure on the inside of the house along with pressure on the windward side and suction on the leeward side cause wall failures.

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1.1.4. CLIMATE CHANGE The current environmental disbalance that is climate change entails several repercussions on the island. Climate change is as per the definitions in the Oxford dictionary as, "A change in global or regional climate patterns,..."3 This change has most importantly brings across more cyclones. According to the meteorological records of Mauritius, cyclones are a high risk on average every 5 years.

This average has been put to test not later than early 2018 where two cyclones passed over the island in less than a 2 month period. Causing high level of damage resulting mostly to flash flooding and soil erosions.

Reference 3

"Definition of climate change in English". 2018. Oxford Living Dictionaries. https:// en.oxforddictionaries.com/definition/climate_change

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Illustration of places at risk of soil erosion along the island

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1.1.5. SOIL EROSION Soil erosion has been an ever growing problem in Mauritius.

This is not only due to the soil type of the island (appendix 1) or the high wearing off of the land through centuries of sugarcane cultivation and exploitation of the land but also due to the depletion of green spaces with deep rooted plants.

While looking into other Sub Saharan African countries the ratio of green vs urban can be seen having a better ratio compared to Mauritius.4 Furthermore although the government has been implementing a forest preservation program the percentage of forest area has been depleted from 28% to 18%.5

Reference 4

The Green City Index A Summary Of The Green City Index Research Series. 2012. munich: Siemens AG.

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"Forest Data: Mauritius Deforestation Rates And Related Forestry Figures".

2018. Conservation News. https://rainforests.mongabay.com/deforestation/archive/ Mauritius.htm.

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1.2. AGRICULTURAL COASTAL VILLAGE A small coastal village in the district of Grand Port south east of Mauritius called Petit Sable is a typical native example of an agricultural coastal village. Its beautiful sloped landscape is home to sugarcane crops since 1735 with the arrival of French colonies who also introduced to the island their colonial architecture. This picturesque village with its panoramic view over the bay and horizon is not labeled on most maps and served by one coastal road 'B28'.

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Illustration of coastal road leading to the site

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Illustration of location of focus site

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1.2.1. PETIT SABLE Understanding that the village is an old colonial agricultural settlement area the structures have been built without any regards to what is now degrading marginal lands. The independence of the island caused the area to be taken over by the government, but the village was never considered as residential areas, even through the obvious.

Looking into the village architectural structures we see a variation of styles between modern housing, metal sheet housing and old volcanic rock structures. This huge gap between styles are not only seen in this particular village but all around Mauritius.

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Illustration of house type in the location

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Illustration of plantations along the bay

VARIOUS PLANTATIONS

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1.2.2. ECONOMY Its’ 300 inhabitants economy is mostly based on fisheries, small agricultural plantations and farming barns with no more than a few ducks, chickens and goats.

Fishries being their main source of income ever after the French and English left the island. Providing both for the population in terms of food and economically. Most of the time it is the man of the locality that holds this harsh task that is fishing and often this causes them to lose their life at sea. Leaving a family behind the women and children of the community needs to find other ways to provide for themselves.

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Illustration of retention basalt rocks along the bay

FISHERIES

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The village was a part of the millennium development goals (MDG) in terms of eradicating hunger & poverty which the locality was slowly leaning toward. The government helped by providing with proper sanitary facilities and adequate drainage system.

Nowadays the people of the village can be observed having better housing structures being built, all this by learning from the interventions brought by the government.

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GOAT FARMING Illustration of a child feeding goats

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Illustration of chickens inside a metal sheet shed

VARIOUS TYPE OF POULTRY FARMING

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The isolated village has also received amount of help and donations from Aid-action NGO. Providing them mainly with crops and poultry to breed, in order to boost and diversify their economy.

The results can be seen today with large amounts of chickens and ducks being breed responsibly with regards to sustainability and animal rights in a healthy environment non toxic environment.

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The millennium development goals (MDG) also focused on achieving universal primary education an there, hence introduce small community and learning centers as well as playgrounds in order to boost children learning process and influence them to pursue higher education beyond the limits of their village.

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Illustration of a children's playground surrounded by wooden barriers

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Illustration of aerial view of the village

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1.2.3. TERRAIN The south east village of Petit Sable has always been an area geographically prone to strong winds and strong currents.

Those strong winds often carried strong rain that would wash down the sloped terrain. Now with climate change, those naturally occurring events are taking a bigger impact of this already struggling community.

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1.2.4. SOIL EROSION Various sites along the island of Mauritius is prone to soil erosion. Most often due to over exploitation of the soil for sugarcane plantations since the 17th century and the village of Petit Sable is not an exception.

Petit Sable has a monthly rate on 120mm (appendix 2, pg 70-71) of rain per month with strong southeast winds. The wind is mostly the reason they are so affected by cyclonic movements they are the first area of the island to face torrential rain and flash floods.

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Illustration of water rippling down a set of stairs

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These constant soil erosions created major red sea pollution.

Red sea pollution is when soil and various sediments enters the sea bay. This eventually causes the sea life within the lagoon to deteriorate. The lack of fishes has caused a decrease in fisheries revenue as well as forcing fishermen to go beyond the lagoon and endangering their lives.

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Illustration of water flow over the terrain

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1.2.5. INITIATIVES The town has received various helps from the government and NGOs , such as ADAPTATION FUND & UNDP, which planted a large amount of mangrove helping to retain the soil and filter clear water into the sea. Creating a wider biodiversity, protection for small sea live, and allowing fishermen to slowly climb up the ladder.

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Illustration of a man planting mangroves along the shore

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Illustration of a fisherman. fishing in the shallow sea while the waves crashing along the reef.

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During the Second National Communication of the Republic of Mauritius under the United Nations Framework Convention on Climate Change in November 2010 the Mauritian government stated their plan to rehabilitate coral reef around the island in order to boost marine biodiversity.

In addition, various sea farming has been set up in the area.

But this has attracted other predators, such as sharks.

Endangering the workers and the indigenous sea life of the island.

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I have been following the community closely ever since my involvement with Aid Action NGO several years back, and something I have learned and observed from the community is that they are very productive and inventive. Their ability to rise up from their various difficulties and care for each other as a big family is a strength rarely seen in other societies.

With the right guide, instruction and information they would be able to create an environment that is self sustaining for their community.

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2-0.

TECHNIQUES

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Throughout this chapter a new page will be allocated to analysing each introduced technique in terms of their requirements advantages and disadvantages. These pages will be entitled:

‘IMPLICATIONS’ and those ‘implications’ to be highlighted in yellow allowing you to quickly refer to any page of your needs.Requirements needed for each technique will be assessed based on the following:

LEDGEND $ = CHEAP $$ = MODERATE $$$ = COSTLY *same applies to the others.

Maintenance: where the longevity and maintenance of the technique will be questioned. This will be represented by the icon displayed on the side, which if repeated thrice this would indicate high maintenance.

Cost: will englobe overall cost, of either transport if needed or additional labour. The higher the cost the higher the number of money icon.

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Labour: the amount of manpower needed to achieve the task. This can only be assumed on a small scale and to allow you to know how dreadful the task at hand will be. The more the man icon the more workmanship is required.

Tools: the basic tools required, will be listed and their availability within the community accessed. In the case where tools are already available on site at small amount the icon used only once.

Impact: the ecological impact on the environment will also be analysed. If an icon is placed only once, that means technique being analysed has a low negative impact on the environment.

Time: the amount of time required will be approximately stated, although the time frame for most will highly be determined by the amount of manpower available. If more manpower available less the amount of time required and eventually less amount of time icons.

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2.1. SOIL STABILISATION & EROSION CONTROL METHODS Bioengineering is the discipline that applies engineering principles of design along with the analysis of biological systems. They take in consideration basic laws of physics(such as; kinetics, biocatalysts, heat transfer, uid mechanics, thermodynamics, and so much more) combining with surrounding living circumstances, through which they attempt to mimic biological systems in order to control further biological and natural occurrences. Bioengineering methods are easy, cheap and grow stronger with time. But on the other hand, some of those methods may not withstand mass cases of mass failure or might not be suitable of all circumstances.

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Illustration of terracing technique used on a small scale around an apple tree

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Illustration of terracing system above a village area

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2.1.1. TERRACING The south east village of petit sable has always been an area geographically prone to strong winds and strong currents.

Those strong winds often carried strong rain that would wash down the sloped terrain.

Terracing is the action of converting a slope into a series of horizontal steplike structures, with the aim to control and guide water ow or surface runoff across the slope to a suitable outlet with a non erosive velocity. Thus, this technique reducing soil erosion by trapping it on a uniform level, and creating a at suitable land for cultivation.

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Terracing methods are a set of very easy steps to be followed, although very time consuming.

STEP 1 Start with the lowermost terrace by compacting the soil thoroughly, creating an even ground.

STEP 2 The topsoil from the area of the next higher terrace is removed and distributed evenly over the lower terrace.

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Illustration of terracing steps 1 & 2

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Illustration of terracing steps 3 & 4

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STEP 3 The second terrace is formed and compacted then covered with topsoil from the area of the third terrace.

STEP 4 Work progresses up the slope, each newly formed and compacted terrace is covered with top soil taken from the slope immediately above. Grass is planted along the rises of all terraces to prevent the slanted slope to run off during heavy rain and this even if it is not too steep.

Although if built in the rainy season it would be less time consuming and more appropriate to start near the drainage area and even from the uppermost terrace in order to allow rain water to drain off without damaging and eroding the terraces.

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Accessibility, we often forget about it is an important aspect of terracing. While creating sensible plateaux to be cultivated we have to also think of safe ways to access those areas.

There are various natural ways to create steps that are ecofriendly and cost nearly nothing. The first one would be using wood logs alreading found around the site. Or even a trip of wood brought from the local hardware store. The trips and logs of wood are secured by being half buried into the soil while long strips of wood rods or steel are hammered through the wood into the soil.

An even easier way would be to place large stones found during excavation of terracing, at regular alternation with riser not more than 175 mm height (height of regular steps).

Obviously riser could be higher if we admit to the fact that this is a rough terrain, but comfort is key when designing for farmers that are most probably exhausted after a day of work.

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Illustration of terracing steps along sloped terrain structures

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IMPLICATIONS Terracing as it can be seen in the information illustrated can be used in various circumstances, in small or in big scale.

The most costly component of terrace construction is labour which will depend on average local daily wages. Local daily wages in Mauritius is 87 Mauritian Rupees for a non skilled worker. But since the villages are to perform the tasks by themselves this technique does not require much cost.

The villages and farmers will be using their own available tools, such as shovels, pickaxes, hoes and rakes. Additional tools can be needed depending on the precision of the terracing, such as measuring tape, laser level or a normal level.

Once built, annual minimal maintenance.4 Reference 4

Treacy, J. M. (1989) “Agricultural Terraces in Peru's Colca valley: Promises and problems of an ancient technology.� Monographic Source: Browder, J.O. (Ed.) Fragile lands of Latin America: Strategies for sustainable development. Imprint: Boulder (USA).

Westview Press. 1989. ISBN 0-8133-7705-6. pp. 209-229

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Since only natural resources are being used in this process, there is no external negative impact on the environment on the other hand the plant and crops planted on the slope and the terrace will strenghten the soil and natural habitat.

Research indicates that two people can build 7m² of wall in one day. Assuming a common size terrace wall of dimensions 1.8m high and 50m long, two people could restore an entire terrace in two weeks, or build an entirely new one in a slightly longer period of time.5

The time required to construct a slow-forming terraces will depend on available manpower, the type of soil and the time of year. Refer to appendix 2 to view the weather average in Mauritius.

Reference 5

Antle, J. M., J. J. Stoorvogel and R. O. Valdivia (2004) Assessing the economic impacts of agricultural carbon sequestration: Terraces and agro-forestry in the Peruvian Andes, Agriculture, Ecosystems & Environment 122(4), 435-445

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APPENDIX 1 Types of terrace: -Bench Terraces (slopes 33%) Where water ows along the contour line, but also accross the terrace, allowing it to feed various crops on it’s way down.

-Level & Contour Terraces Terraces constructed along slope traps water and sediments within its bed while its contours are lined with plants or trees with deep roots.

-Parallel & Channel Terraces This particular graded terraces with constant slope and gradient along the length, are used in areas prone to heavy rainfall. It coveys excess runoff at a safe velocity in a grass waterway or channel.

Reference Redrawn by: Reety Lachhman, 2018

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Shoulder bund Filling Cutting Outward slope 5% Original Slope

Shoulder bund Filling

Channel Cutting Inward sloping 5%

Original Slope

5% 0 5% 15%

3 2

3

2

1

1

3

3

2

2

1

1

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APPENDIX 2 TEMPERATURE max min

MONTH

HUMIDITY %

January

29.9

23.0

81

February

29.5

23.1

83

March

29.1

22.7

83

April

28.2

21.8

83

May

26.8

20.2

81

June

25.2

18.7

78

July

24.2

18.1

77

August

24.2

17.8

78

September

25.5

18.0

77

October

26.2

19.2

78

November

28.5

20.4

78

December

29.6

21.9

80

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NO. OF AVERAGE AVERAGE RAINFALL RAINFALL DAYS WITH SUNSHINE SEA RAINFALL Hrs per TEMP. SOUTH EAST EAST day °c (mm) (mm) (>5mm) 237 261.3 9 7.7 26.7 267

334.1

10

7.0

27.5

203

231.2

9

6.9

27.6

211

240

9

6.5

26.9

153

167.7

8

6.5

25.9

95

104

7

6.1

24.7

100

102.5

6

5.5

23.8

88

104.9

6

5.9

23.2

60

70.1

4

6.7

23.2

60

62.2

3

7.6

23.8

77

82

4

8.8

25.0

172

201.8

7

8.4

26.4

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2.1.2. WATER MANAGEMENT Drainage ditches are an important point of managing soil erosion. The village already has some basic integration of a drainage system. The drainage system is constantly prone to clogging due to the huge amount of waste being washed down the canal. The appropriate size and shape for a particular site depends upon such factors as the expected runoff, site condition, and availability of resources and construction materials. For example; Petit Sable village consist mostly of soft marginal land, sugarcane crops, volcanic stones, and minor forest area, which results to a lot of soil runoff as well as waste from plants.

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Illustration of metal sheet house in between sugarcane fields with forest at the far back.

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Weepholes Lined drain Weepholes Rectangular lined drain

Drain made of hollow concrete blocks or bricks Illustration of three drainage system present on site

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Several drainage systems are available on site, but the issue with those types of drainage is that most of them are not porous enough or do not filter the heavy components being washed down along with the water run off. The drainage system also lacks in terms of frequency and capacity, they are not able to retain the volume and velocity of the storm water runoff as efficiently as it used to in the past.

But failure also occurs when water drainage network has a minimum velocity flow less than the minimum allowable velocity for deposition control. Creating thus a stagnating water flow in a nonporous channel attracting insects and creating a lost space to be filled with man made trash and other natural sediment.

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2.1.2(a). TRENCHING Water trench along terraces allows to manage and irrigate surrounding crops, and redirect rain water to collection ponds. The use of big heavy materials such as rocks of others acts as a filter system for heavy run offs. These porous trenching systems are easy to form the and multiple networks around the networks can be created in order to filter larger amounts of rain water.

They can also be combined with other drainage systems on a much larger scale in order to canalise and filter heavier storm runoffs during cyclones and torrential rains.

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Porous filter fabric (porous as to allow water to be absorbed at every point)

Line bottom of trench with sand to support pipe and protect fabric from punctures.

4 diameter perforated pipes with holes on sides sloped to daylight, dry well or holding tanks etc.

Fold filter fabric over top of cobbles

Pile more cobbles and rocks on top of exposed fabric filter fabric

water collects in trench

Fil around pipes with larger cobbles to allow more air space for water to drain easily bottom of the trench

water flows down hil through rocks.

Fabric filters out sediment. Water fil s up bottom of trench, enters hole through sides of the pipes.

Illustration of trenching system

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2.1.2(b). CONTOUR DITCHES (Drainage and inďŹ ltration ditches) Useful for small-scale hillside farming contour ditches are created along terraces in order to stop downslope water movement as the water falls into the ditch. They tend to require less work than terraces as they are very simple to build, and can be used to either divert or to retain water.

Allowing the ditch to have a 1% slope will create a natural diversion of excess water to protect drainage ways or retention ponds while also reducing soil erosion and leaching of nutrients.

The ďŹ rst step in the construction is to excavate a 300 mm wide by 300 mm deep ditch (ditches can be constructed of any size, if desired). Then the banks are formed by cutting a slanted wall on each side. The removed earth is placed in a mound 155 mm - 230 mm below the lower lip of the ditch.6

Reference 6

Crozier, C. (1986). Soil conservation techniques for hillside farms. Washington, D.C.: Peace Corps Information Collection and Exchange.

Redrawn: Reety Lachhman

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Illustration of a man tending to his crops on a sloped terrain with a contour ditch.

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Illustration of a man digging a contour ditch with stone retainment walls

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Contour ditches can also be accompanied by loose stone barriers, creating retainment areas, allowing the water to slowing get absorbed within the soil. If loose stones are not available on site earth dikes can be left at several intervals in the ditches with a 0% slope so that the water is not only retained but also not diverted outside the ďŹ eld.

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Loose stone is often used in order to create a temporary catchment area as those are porous as they often allow water to filter into the soil and water flow to keep on at a constant slow rate. Water that filters in between the rocks along the drain prevents the water to stagnate while still giving time to the small sediments to settle down and other big debris to get filtered away.

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Illustration of ditch with loose stone retainment walls

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L 0. 5

0. 5 1/2

D

spil way

1/2

(Max.) H = 1 . 3

Foundation = H/2

Illustration of loose stone retainment wall

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Loose stone retention walls within the ditch are easy to build as they are only a compilation of rocks staggered over one another without further retaining material. Although in case the rocks found on the site are more like gabion, smaller rocks a metal netting system could be placed over to contain them.

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Although these canalisation methods are ideal to provide catchment areas for water absorption it is also to divert excess water to another location in order to minimise soil erosion and slow down water velocity. Yet special care are to be taken at connecting area to which all diverted drainage water gets deposited. These intersections should be preferably placed at natural drainageways. While adding ways to break down water velocity while running down the slope, by lining the bottom with rocks and adding planting deep rooted plants acting as a securing network for the soil.

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Illustration of slope vegetated drain lined with loose stones and framed by berms.

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IMPLICATIONS Trenching and contour ditches have been strategies used by farmers for centuries, using natural resources to the best.

Nowadays people rely too much on prefabricated bricks that are not porous.

Taking into account that no additional material is being used and the labour is the local farmers themselves no high cost should be involved in this process.

The villages and farmers will be using their own available tools, such as shovels and pickaxes.

Once built, annual minimal maintenance, although it would require regular leaf and branches unclogging specially after the heavy storm to prevent any water overflow.

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Since only natural resources are being used in this process, there is no external negative impact on the environment while the plant and crops planted on the berm will strenghten the soil and create a natural habitat in a healthy environment for biodiversification.

A man can cut and fill 3.5 to 4 cubic m a day under average conditions. Expressed another way, it means a 17 to 19 m length of 2 m wide hillside ditches on a 25% (14 degree) slope can be completed in a man-day.7

It will take about 50-60 man-days to construct a hectare of hillside ditches under normal conditions.

A small machine (70 to 80 H.P.) can complete 20 cubic m per hour.7

Reference 7

"M30E10.Htm". 2018. Fao.Org. http://www.fao.org/docrep/006/ad083e/AD083e08.htm.

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Stif -stemmed plants in filter strips Grassed waterway

Illustration of a low scale grassed waterway.

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Flexible grass in channel

Filter strips to trap sediment

2.1.2(b). GRASSED WATERWAY Grassed waterways are a good way to manage water runoffs, the vegetation slows down the ow down the slope while naturally ďŹ ltering the big sediments. Good outlets to prevent rill and gully formation, it also allows the ground and surrounding plants to absorb water. Sometimes those drainages convey the water to a conservation pond; a technique that has been suggested through Blue and Green Infrastructure projects as well as in smaller scale individual projects such as rain water gardens.

Reference Author: Shrestha, A.B, E GC, R.P Adhikary, and S.K Rai. 2012. Resource Manual On Flash Flood Risk Management. Kathmandu: International Centre for Integrated Mountain Development (ICIMOD).

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IMPLICATIONS Grassed waterways has must more to it than the brief statement presented. In the case it would be an important addition to the location worked with here is a few things to consider.

Grassed waterways can stretch over meters on either a at ground or a slope. In the case of Petit Sable the area of use for grassed waterways is acting as an addition to the drainage system, thus the cost involved in the design will mostly surround the aquatic plants being involved in the design

The villages and farmers will be using their own available tools, such as shovels, pickaxes and smaller gardening tools such as a trowel, rake and hand fork for planting aquatic plants.

Timely maintenance is important for keeping a waterway in good working condition.

Recommended maintenance generally includes mowing of waterways and removing vegetation so as not to retard water flow and cause excessive sedimentation in the channel.8 Reference 8

Meyer, Daniel. 2007. Part 650 Engineering Field Handbook. Washington, DC: Natural Resources Conservation Service (NRCS).

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Since only natural resources are being used in this process, there is no external negative impact on the environment while the plant and crops planted on the berm will strenghten the soil and create a natural habitat in a healthy environment for biodiversification

Taking into account the same measurement given in to the ditch it is to be assumed the same amount of manpower would be needed for a certain amount of area to be covered. In addition, having planters for the aquatic trees will automatically mean more hands at work.

Taking into account the same measurement given in for the ditch implications, it is to be assumed the same amount of time would be needed for a certain amount of area to be dug, in addition to the amount of time one takes to plant specific aquatic plants. It it to be noted some seeds of aquatic plants can be simply aerially spread across the are thus saving time.

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2.1.2(c). RAIN WATER GARDENS The bachelor thesis of Julia Roder at Anhalt University in Dessau portraits, various projects or techniques that has been used around the world, involving waterways and ecological gardens. But a simpler way to explain those projects are to label them under rain water gardens. Rain water gardens are often used on a small scale technique to produce a self sufficient garden that grows naturally in the most ecological way possible. This diagram from the blog “Better Ground” is the best illustration of how such an environment is created.

A simple water bath with gravels and rough sand is created from any gutter or natural rain water path and directed towards a retention zone where the plants are planted. The retention zone is lower ground than its surrounding ring in order to prevent soil erosion in case of water overflow. If on an inclined ground the side down the slope should have a slight higher bump.

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selected native plants and hardy cultivars filter strip

impervious surface water flow retention and filtration zone

planting soil mix

no liner or filter fabric Illustration of rain water garden system Reference Source: "Better Ground | Sound Ideas For Your Land". 2018.

Betterground.Org. http://www.betterground.org.

Redrawn by: Reety Lachhman

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IMPLICATIONS Rainwater gardens have varying implications depending on how big and efďŹ cient it is aimed to be. Taking the insight with the most cost efďŹ cient proposal possible.

Rainwater gardens highly depend on the amount of plants and the size of the area to be worked with.

The cost involves the cost of the type of plant, soil aggregate, drain piping and overow piping,and some loose rocks to prevent water from eroding the soil.

The villages and farmers will be using their own available tools, such as shovels, pickaxes and smaller gardening tools such as a trowel, rake and hand fork for planting

Daily, maintenance is required, like for any garden to ensure the well being of the crops. But the design in itself would only need yearly gutter maintenance.

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The use of extra PVC (Polyvinyl chloride) piping is evidently not ecological with its life span of 140 years during which it releases microplastics that soaks up persistent organic pollutants. No external negative impact on the environment and the plants or crops can be seen, although these pollutants will be ingested by the insects advantaging from the rainwater garden.

Assuming that rainwater gardens would be additions to each household on a small scale, each house owner will have the responsibility of their own crops and environment.

A small personal rainwater garden should not take more than a day to dig, compress the soil and connect the waterways; and from then on a daily process of cultivating and plant the land.

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Illustration of a retention pond

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2.1.2(d). CONSERVATION PONDS Everywhere around the world people has grasped the importance of rain water, for their own survival during dry seasons, for their crops, for simple daily use. Each culture has developed a way of conserving rain water either through; reservoirs connected to the gutters, or through, conservation ponds / retention ponds.

There are various types of conservation or retention ponds, varying from the simplest to the most complex form their main aims are to; a) control heavy water runoffs. b) settle pollutants in the water. c) retain water from their holding area unless it crosses a ďŹ xed level. d) increase biodiversity and puriďŹ cation of water through the algae, bacteria, biological beings in the water.

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Retention or conservation bonds may consist of several stages with the first stage most often been to allow the settling down of heavy sediments and big debris.

The retention pond discharge can be placed at any point as this allows for better filtration of the water from one retention space to the other. In order to prevent too much water absorption into the ground a network of aquatic plants or waterproof fabric lining and concrete can also be used as a quick alternative although these are less ecological.

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Storm water runoff Retention pond discharge

water level

Sediment forebay Concrete base/ Embankment

Illustration of retention pond section Reference Source: "Detention Ponds Vs. Retention Ponds". 2018. Helpsavenature. https:// helpsavenature.com/detention-ponds-vs-retention-ponds.

Redrawn by: R.Lachhman, 2018

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Illustration of retention pond plan

Top of Berm

sediment forebay

Inflow Energy dissipator Riprap Baffle

sediment forebay

peak attenu storag

Rundown with Baffles 102

Riprap Baffle

Low flow Channel (optional)

Trash Rack

spillway water quality storage Trash Rack

uation ge

embankment water quality storage Low flow Channel invert

Outlet Energy dissipator

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IMPLICATIONS Retention ponds, although helping with the bio-diversiďŹ cation of an area and providing in terms of resources to the community it comes with a few sacriďŹ ces.

Retention ponds are highly costly either during construction time; with a large digging area requiring heavy machinery, ground lining, concrete, reinforced retention walls and plants; as well as after construction with regular maintenances.

Large self-propelled scrapers, bulldozers, and motor graders are the preferred equipment that will do the job more time efďŹ cient.The villages and farmers will be using their own available tools, such as shovels, pickaxes and smaller gardening tools such as a trowel, rake and hand fork for planting aquatic plants.

Reference 9

Obropta, Christopher, and Jeremiah Bergstrom. 2010. "Detention Basin Retrofits And Maintenance". Presentation, Sussex County, , 2010.

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Retention ponds require both routine maintenance and non routine maintenance such as: vegetation management, debris and litter removal, mechanical component maintenance, inspections, Stabilization and erosion control repairs, sediment removal, outlet repair or replacement.9

Several materials and machinery will be used in this design with an obvious impact on the environment while on the other hand the plant and crops planted on the berm and at the bottom of the retention pond will strenghten the soil and create a natural habitat for bio-diversification to take place.

Given the amplitude of the task at hand a high amount of man labour as well as skilled workers will be needed.

Unfortunately, this is not a one day job, this might take several days, even months in order to dig, install the equipment, line the terrain with aquatic plants and much more detail work.

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2.1.3. RETENTION WALLS Retention walls can already be seen along the road, using locally available volcanic rocks found in this mountainous ground. The wall will not only retained the soil, but also allow breakdown the velocity of the water and allow sediments to be deposited at each step, leaving a softer stream cascade down the wall to the street.

Backfill

Backfill

a) Gravity retaining wall

Backfill Backfill Reinforcement Backfill

b)Semi-gravity retaining wall 106

Backfill

c) Cantilever retaining wall

STRUCTURE

FUNCTION

a) Gravity:

a) Gravity:

-Stacked locally available material.

-Depends on its own weight & mass to retain the soil.

-Strong bearing capacity foundation.

-Wall base (0.5 or 0.75 x H) width & thinner width on top.

-Stacked material exceeds force of the earth.

-low in height. b) Semi-gravity

b) Semi-gravity

-Wall thinner than 'gravity retaining wall' .

-same as 'gravity retaining wall'.

-Reinforced facade. c) Cantilever

c) Cantilever

-steel reinforced concrete.

-design to resist the sliding forces of earth upon the wall.

-Reinforcement in footer extends into the wall structure, creating one integral unit.

-6-8 m Height.

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Backfill

Illustration of various retension walls

Backfill

Counterfort

d) Counterfort retaining wall Backfill

Buttress Backfill

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e) Buttressed retaining wall

STRUCTURE

FUNCTION

d) Counterfort

d) Counterfort

-Triangular shaped support walls placed regularly at right angle to the main wall on the back soil filled facade.

-Reduce shear force and bending moments in the steam and the base of the structure.

-Stabilise overall wall.

-Footing, retaining wall & support wall is steel reinforced to each other.

-6-8 m Height. e) Buttressed

e) Buttressed

-Triangular shaped support walls placed regularly at right angle to the main wall on the front facade.

-Same as 'Counterfort retaining wall'.

Reference Source: Shrestha, A.B, E GC, R.P Adhikary, and S.K Rai. 2012. Resource Manual On Flash Flood Risk Management. Kathmandu: International Centre for Integrated Mountain Development (ICIMOD).

Redrawn by: R.Lachhman, 2018

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IMPLICATIONS Concrete retention walls are sometimes necessary in order to retain and secure some environment, even though they might not be the more environmentally friendly.

Concrete, retention walls are costly due to the high amount of construction materials, skilled workers as well as speciďŹ c machinery and transport.

Given the fact we are dealing with concrete and may be even reinforced concrete special tools such as mobile mortar mixer, wheelbarrows (if no concrete pumps), maybe even compactors to level the ground, along with conventional tools like saws, shovels and so on.

On the other hand, regular maintenance of the wall will not be needed unless if a failure in structure occurs.

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Several materials and machinery will be used in this design with an obvious impact on the environment while on the other hand the wall will be a strong component that will be able to retain the soil for years, with concrete's life span being about 50-100 years and steel reinforcements of 65 to 70 years.

Given the amplitude of the task at hand a high amount of man labour as well as skilled workers will be needed.

This might take several days in order to dig, do the reinforcement metal structure and pour the concrete and further detail work if wanted.

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2.1.3(a). STONE While looking into various materials used in retention walls (appendix 3), it can be observed that most of these materials are natural resources that requires extraction, which could lead to destruction of a perfectly functioning habitat or ecosystem. Processing of raw materials cost labour and heavy machinery.

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Illustration of stone retention wall

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Illustration of existing stone retention wall

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Volcanic rock walls can be seen on the site as well as in various other historical buildings around the island. Basalt rocks have proven to be reliable natural materials that lasts for centuries. The image here illustrated is of a stepped retaining wall along the edge of a local house.

The step like structure enables the water to be broken down to slower velocity and to eventually safety ow down the drain and street into the sea, without eroding not only the soil but also the asphalt.

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Step 1 - Determine the lenght and the height of the retention wall.

Step 2 - Establish the face of the retaining wall by hammering a piece of rebar into the ground at both ends, to which tie a piece of nylon string tightly making sure it is level.

Step 3 - Use a tape measure to determine the distance from the top point of the completed wall down to the ground.

Step 4 - Mark and dig the footing , concrete can also be used to secure the stone into the ground.

Step 5 - Place the stones with a slight pitch backward so that water will run off.

Step 6 - Fill the back the wall with small loose stone before covering and compressing it with the soil in order to create a porous ground where rainwater can be ďŹ ltered and absorbed into the ground.

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304.8mm top course should be mortared basalt stone 76.2 mm - 152.4 mm set back per 304.8mm rise

porous ground loose stone

compact ground 609.6 mm Illustration of stone retention wall section

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Illustration of machinery on a stone crushing query

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Volcanic rocks are the main natural resource for construction throughout the island. It is turns into basalt precast bricks, and other building materials. Nowadays, most of these nicely cut rocks are used for luxurious facades, causing a massive exploitation of natural lands.

Embeded cost for a rock wall: Excavator for derocking query 1hr - 25 tons - 6L diesel Tractor for loading truck 10min - 25 tons - 1L diesel Truck Travel from Beemanique, Rose Belle to Petit Sable 39km - 15.3 L diesel Diesel cost (Mauritius,April 2018) - 70.12 Mauritian Rupees

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Heavy machinery that is involved in the extraction as well as transport and placement of the rocks on the site are eventually producing more CO² pollution, and much more other add on cost that affect our environment. It is to be understood that even with the use of natural available resources we are bound to have negetive impact on the ecological aspect, it is up to us to observe and decide what is the less impactful and more relevant to the environment being worked with.

According to the ‘Department of Soil Conservation and Watershed Management’, Kathmandu in 2004, there is a table of other materials and their specificities that could be alternatives to volcanic rocks. (appendix 3)

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Illustration of machine laying out stone

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APPENDIX 3

Type of check dam

General characteristics

Advantages

Disadvantages

Transportation of big Uses local materials boulders is difficult (if not available upslope Stability and strength Simple of the site) If large depends on the size of the voids are not properly Low cost boulders or rocks and quality filled they, may create of construction If properly made, are water jets, which almost permanent Commonly used in gully can be destructive if and durable control where boulders or directed towards the rocks are abundant bank Made of big boulders or rocks

Boulder

Made with wire gabions of different sizes filled with stones Gabion

Flexible

Flexible and permeable Suitable where the land mass is unstable

Preferred where big boulders Economical compared to other are not available solid structures Made of cement masonry or concrete Masonry

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Generally, only used to protect important infrastructure such as roads and buildings

More expensive than loose stone or boulder structures The gabions have to be brought from outside which increases the cost Need skilled labour for construction High cost

Permanent solid structure Good appearance

Materials not locally available (cement, rods) Need a more engineering design, and skilled labour for construction

Type of check dam

General characteristics Made of wooden poles and brush

Advantages

Disadvantages

Simple Uses local materials

Brushwood Suitable for small gullies 1–2 Low cost m deep If the roots and Low cost where materials are shoots develop, they can form a longlocally available term barrier Made of loose stone or rock Uses local materials Stability and strength Simple depends on the size of Low cost (where Loose stone rocks and the quality of the the stones are construction abundantly Commonly used in gully available) control where boulders or rocks are abundant

Least permanent of all types if not rooted Takes a long time for the dams to develop roots and become established

If not done properly or stones are too small, they can be washed away

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IMPLICATIONS Basalt retention walls, although easily available around the country and also a natural resource, its processing makes it not be more environmentally friendly material.

The cost of such a wall includes the price per truck of 25 tones as well as the transport to the locality.

Tools and machinery rely on the amount, weight and stretch of terrace to be covered with stone.

On the other hand, regular maintenance of the wall will not be needed unless if a failure in structure occurs.

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Heavy machinery used in this design will have a CO2 impact on the environment while on the other hand the wall will be a strong component that will be able to retain the soil for years.

Given the amplitude of the task at hand a high amount of man labour as well as skilled workers will be needed.

Depending on the stretch of land being worked with this process will take several days to months in order to dig, and do the stone wall one by one.

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2.1.3(b). TIRES After looking at classics of concrete and rock retention wall we are to think if there might be better solutions. Then, how about looking into ways of recycling that do not involve so much pollution while at the same time dealing with waste and giving them a second life.

Observing several structures that are made both of natural and upcycled materials also known as Earthship Biotecture, the use of earth ďŹ lled tires is often repeated. This repetition of tires is mostly due to its availability worldwide and the inabilty to recycle such a complexly build material.

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Illustration of tire retention wall

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Illustration of tire structure Reference Source: "Tire Manufacturing | How A Tire Is Made | Michelin US". 2018. Michelinman.

Com. https://www.michelinman.com/US/en/help/how-is-a-tire-made.html. To tenis doluptasit et aut volore militatis accabor eserum fuga. Odicab iliberiae conem int intis

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Tires are composed of: 1. Inner liner: An airtight layer of synthetic rubber.

2. The layer above the inner liner, consisting of thin textile fiber cords (or cables) bonded into the rubber.

3. Lower bead area: This is where the rubber tire grips the metal rim.

4. Beads: Metal wire clamp firmly against the tire’s rim to ensure an airtight fit and keep the tire properly seated on the rim.

5. Sidewall: Rubber protects the side of the tire from impact with curbs and the road.

6. Crown plies (or belts): It’s made up of very fine, resistant steel cords bonded into the rubber.

7. Cap ply (or “zero degree” belt): reinforced nylon based cords are embedded in a layer of rubber and placed around the circumference of the tire 8.Tread: Rubber is designed to resist wear, abrasion and heat.

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Tires are a great example of a material that is strong, resistant, flexible and are easily available. According to Sekhar presentation about 1 billion waste tires produce each year worldwide, out of these 3-15% is recycled; 5-23% are reused in some way for new products; 25-60% is used for energy recovery; 20-30% are sent to landfill. Not forgetting that along the way of producing those tires further wastes are produced, such as; 20-40% waste from sured sheet rubber; 30-50% waste of moulding ‘flash’; and 2-5% waste extrusion of the final product process.

With all this waste already being produced find ways to recycle or upcycle this object has become more and more important. Unfortunately, at each process of construction of the tires more materials are introduced within one another making the final product an impure and very difficult material to recycle.

Reference Source:G.B. Sekhar in Proceedings of the Tire Technology Expo, Cologne, Germany, 2014.

Forrest, Martin. 2014. Recycling And Re-Use Of Waste Rubber.

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Illustration of tire mount

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Illustration of tire section

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All these additional materials that make it so difficult to recycle is also what makes it so reliable and strong as a building material. On a playground project by the Dessau International Architecture program, in Haiti the strength of these objects has been put to test. Although the project in Haiti was not subject to soil erosion testing the technique used are the same used for Earthships and retaining wall structures that can be seen in ‘the bluff country of Lowa’, a steep hillside plot of land in America, by William Hogan in 1981-1982.10

Reference 10

"I Built Terraced Retaining Walls With Old Tires - Homesteading And Livestock MOTHER EARTH NEWS". 1983. Mother Earth News. https://www.motherearthnews.com/ homesteading-and-livestock/retaining-walls-zmaz83mjzraw.

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Step 1 Dig the area in from of the terraced wall to be secured in order to allow the first row of tires to be anchored in the soil.

Step 2 Place a permeable fabric or net over the terrace face in order to hold and secure the earth in place during the construction period Step 3 Arrange tires side by side . Two rows could also be used as the first layer in order to allow the upper layer of tires to be more stable and also to naturally provide a ground for the soil to compact and supports loose rocks that are to be placed behind the tires forming a porous ground.

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Illustration of tire wall first step

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Illustration of tire wall building

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Step 5 A layer of rock chippings can be placed at the bottom of the tire before soil is then shoveled into the tire and compacted by repeated blows with a sledge hammer.

Step 6 Once packed with dirt, the tire walls bulge, interlocking with the tire row below.

Step 7 As you move up the rows some tires might have areas where the bottom of the tire is not resting on the lower tire. Thus these would require additional permeable fabric lining at the bottom of the tires in order to hold the earth compacted in place.

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Step 8 In some cases, while stacking up tires additional reinforced connections, for example: rope, metal wires or zip ties are used to secure the tires and shape together.

Step 9 Additional soil can be rammed and compacted at various places in between the tires were deemed necessary Step 10 Plants can be integrated in the tires to not only act as a decorating factor, but also to create more resistance and tension within the tire as the roots grow bigger

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Illustration of tire wall lined with chicken wire

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IMPLICATIONS Tire retention wall, although easily available, its structural composition that makes it so strong is also that makes it highly harmful to the environment.

Most of the tires could be sourced for free at dumping ground found in the same district as the village. On the other hand the transport cost of the tires along with loading and unloading comes at a cost. Not forgetting the ever increasing cost of diesel on the island. (Mauritius,April 2018) - 70.12 Mauritian Rupees

Tools to work the soil along with transportation machinery such as tractor and trucks increases with the stretch of terrace to be retained by the tires.

Annual maintenance of the wall will be needed to refill and compression, additional soil in areas where soil has eroded. Unless if a failure in structure occurs during a heavy storm or a mudslide.

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Heavy machinery used in this design will have a CO2 impact on the environment. Another point to be noted is that ruber takes 50 years to disintegrate while the other components found in tires , slowly separate into small particles of wires and fibres.

Small particles that are absorbed into the ground and progressively washed away into the sea, causing endangerment of the fragile ecosystem around. On the hand the wall will be a strong component that will be able to retain the soil for half a century.

Given the amplitude of the task at hand a higher amount of manpower will be needed.

Depending on the stretch of land being worked with this process will take several days to months in order to dig, place and fill the tires correctly

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Illustration of earthbag wall section

4 - point barbed wire internal floor earth bag 18 inch earth bag 24 inch rubble trench 142

plaster flashing stone

French drain

2.1.3(c). EARTHBAG Earthbag techniques have been present in Nepal as resistant and easily building techniques used by villages with remote access and facilities. This technique involves introducing earth into rice bags that are then placed and pressed after being securely connected together.

This technique is ecological as it uses the soil already acquired from the excavation and yaka or coconut ďŹ bre bags that are biodegradable.

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An earthbag wall was constructed and tested by student volunteers from the University of Florida11 using two rows of barbed wire as reinforcement between each course of earthbags. The test wall was not built using the best practices recommended by earthbag construction guides, and thus represents a lower bound for capacity and behavior. Key observations and conclusions are as follows: 1. The wall did not collapse during testing. It supported a maximum out-of-plane pressure of 3.16 kPa and a maximum out-of-plane displacement of 50 mm.

2. Wall deformation was primarily plastic and occurred due to shear deformation between courses of earthbags. This result supports Pelly’s conclusion that earthbag structures undergo large deformations and highly plastic behavior before collapse.

Reference 11

Ross, Brandon, Michael Willis, Peter Datin, and Ryan Scott. "Wind Load Test of Earthbag Wall." MDPI. August 07, 2013. Accessed June 08, 2018. http://www.mdpi. com/2075-5309/3/3/532/htm.

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Illustration of earthbag wall pressure test

3.16 kPa

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Illustration of first step earthbag wall

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3. Barbed wires were not initially thought, but were engaged in tension as the wall displaced during load testing. Tension in the barbed wires transferred load horizontally in the test wall to the perpendicular supports. After the barbed wires were engaged, they impeded additional displacements and contributed to wall capacity.

Test results demonstrated the strength and ductility of earthbag wall systems, and conďŹ rmed the structural viability of this construction system for hurricane prone areas.

Steps to building an earthbag wall: Step 1 In the case you are building an earthbag wall upon the ground, mark your walls with the help of construction rope stretched over by rebar

Step 2 Dig a path where you image your walls to be. Optional, layer the bottom with gravels or small rocks (chippings).

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Step 3 Fill your first layer of the bag with gravels, this will work as a foundation for your wall. After the bag is filled at 90% sew the bag close using “15 gauge wire about 9” long with one end cut at a sharp angle; make one stitch on one side and bend the end over; make a stitch in the center and pull the corner over; make a stitch in the other corner and pull the corner over; poke the remaining wire into the earthbag. This technique facilitates handling, prevents spills and enables bags to be filled to capacity”12

Step 4 Align bags to stringline with sewed area are connected together; tamp the bags solid and level.

Step 5 Add barbed wire: is used two strands of 4-point barbed wire in-between each course of bags; bricks or stones temporarily hold the barbed wire in place.

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Illustration of earthbag wall

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Illustration of earthbag wall compressed and retained by wired bricks Reference 12

"Step by Step Earthbag Constructuion." Earthbag Building Index. Accessed April 08,2018. http://www.earthbagbuilding.com/articles/stepbystep.htm.

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Step 6 Use a sheet metal slider to place additional courses so bags do not snag on the barbed wire12

Step 7 Continue with gravel-ďŹ lled bags until you are safely above grade to avoid risk of moisture damage. Repeat the process using earth-ďŹ lled bags, but with a few minor changes: turn bags inside out to avoid protruding corners; use lightly moistened soil; tamp the contents slightly after each bucket load is added; pre-tamp each bag after it is aligned in position.

This last step lengthens each bag to ensure good overlap.

Step 8 The last step is to let the wall to set in place with the help of bricks and then start covering the walls with lime plaster.

Humid areas often damage the wall and cause them to slide and collapse. to prevent such occurrences lime plaster may be used to absorb and prevent humidity from getting trapped in the wall. Lime plaster has to be renovated every two years on average.

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IMPLICATIONS Earthbag walls whether used as retention wall or housing system, it is a sustainable and strong structure that can be relied upon.

Earthbag walls are composed of metal barbed wires and polypropylene/yaka/coconut bags that may cost some money if bought. On the other hand, if coconut bags are weaved using traditionally produced coconut rope, this will save costs and help perpetuate a lost art. Rocks and soil that can be naturally sourced on site during terracing.

Tools to excavate, ďŹ ll earth bag and damn them into place should comparatively to other techniques be less intensive in size and amount. Most of the tools, shovels and so on can be easily provided by the villagers themselves.

Maintenance of the wall will not be needed on average every two years, mostly because of the limestone rendering.

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Several materials used in this design such as metal barbed wires and polypropylene bags is not the most ecological materials that could be used, but are neverthe less the least impactful in terms of sourcing materials due to the fact that most materials from the site itself is being used.

Manpower depending on the area to be built and the time limitation, although this technique is quite easy to undergo and thus one person with a bit of determination could single handedly perform this task.

Like any important structure this technique might take several days in order to dig, fill the earthbag, place, compress and do the finishing touches.

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2.1.3(d). VEGETATION Vegetation has been used for centuries as natural soil retainment systems, yet with modernisation we often make use of man made systems thinking they are better. It is true that some plants do not resist during heavy storms and end up getting washed away along with the soil.

One type plants that fail to withstand the water pressure from heavy precipitation are often composed of mostly superďŹ cial roots, same like sugarcanes. Sugarcane has been a part of the Mauritian life style and economy since the 17th century and although it is a plant that grows well in the local climate, its root system is not adequate for sloped terrains such as in Petit Sable. Their high length is also counter balancing the root system and when faced with high winds and eroding soil, a lot of them get damaged and destroyed.

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prop / adventurous roots

superficial roots

Illustration of sugarcane and sugarcane roots.

Buttess roots 155

Illustration of lemon grass roots

lemon grass

weepholes

deep roots

Illustration of traditional fish dish and rice

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loose rocks

On the other hand plant like manioc and lemon grass has the benefit of having very deep root networks , that retain not only top soil, but also over time helps comprising the whole terraced facade together through a comprex nextwork of roots. Roots that help biodiversify life in the soil, which slowly help the soil retain its fertile properties.

Furthermore, these types of plants and roots have many more properties that can be useful to any community.

Lemon Grass (Vetivert) 1. Absorb a lot of water

Cassava (Manioc) 1. Tolerate water stress

2. Consumable as added seasoning, tea and oil

2. Consumable as an alternative to rice

3. Natural repellent to mosquitoes

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IMPLICATIONS All the plants listed are easily found around the island and has been integrated in the life style of Mauritians.

Sourcing the plants to ďŹ t the amount of facade to be covered might result to a large amount of money, but on the other hand the cultivation of these plants will be an additional revenue to the locality.

Tools to needed to plant are already available by the farmers of the village.

Maintenance of the vegetal wall will be the same routine these farmers have been used to. Taking care of crops and live stock is an every day full of work, but on the other hand the wall itself will be constantly growing in strength by the root network.

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Instead of impacting the environment in a negative way this system will highly help to increase the biodiversity and fertility of the land

Manpower will depend on the area to be covered and yet this technique not something new to the local people. Thus, it can be assumed one person with a bit of determination could single handedly perform this task or the areas could to be divided among the people to be responsible of.

Planting crops and cultivation are the locality's area of expertise, thus this should take a few days for each person to fully plant their assigned areas and start caring and cultivating the crops.

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2.2. STRUCTURAL SYSTEM In Chapter 1 the brief introduction of the architectural history of Mauritius gives an insight to better understand the problem of housing structure within the village. The island has quickly moved from classical colonial structures to modern precast brick structures.

Although it is to be agreed that modern buildings show good resistance to the cyclonic weather of the island, it is to be pointed out that no indigenous structure has ever been tried in relation to its speciďŹ c climate. An omission that has lead communities with low resources to live in self made modern houses that does not ďŹ t the security norms that these modern structures implicates. Making this a big safety hazard in times of climatic crisis.

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Illustration of the destruction of Immaculate Conception Church by cyclone Jenny 1962.

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Illustration of aerial view over petit sable into the horizon

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The site of Petit Sable does not make it better for the structural limitations faced by the people of the village.

A site is considered vulnerable when it does not provide a natural barrier to regular wind direction. Given that cyclonic winds direction and velocity are unpredictable and random due to rotating motion, natural wind direction is the preventative information available. For instance, houses should be placed away from a tree at least 1.5 times its height in order to avoid the destruction of the house.

When a site is placed behind a mount the hillock already provides natural shielding, but in the case that the mount is not high enough or the valley is too narrow this may cause an accentuation of wind velocity. On the other hand, if the site is placed near a river or ocean the rising of the ground or a natural higher ground should be chosen to protect the house form ďŹ tting.

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2.2.1. CYCLONE VULNURABLE STRUCTURES

Looking into “Cyclone Resistant Building Architecture”

by Ankush Agarwal with the UNDP in 2007 a lot can be understood. His focus analysis taking part along the coast of India allows a very relatable climate to Mauritius. Although being more north India shares the same ocean and is affected by more or less the same cyclones as the island does.

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Vulnurable Structures:

Longitudinal splitting of rafters

Slight difference in slope increases or decreases pressure and suction forces on the roof structure

Inproper latches blots and hingers for doors and windows.

Unreinforced concrete/ masonary walls

Wood Frames are light weight

Inadequate roof sheet thinknes and insufficient fasteners

Constant heavy rain and flooding damages the structure

Improper connections to the footings or Innadequate foundation for gravity loads (The lighter the structure the larger or heavier the foundation should be)

Steel Frames are weekest at thier connection points

Illustration of Mauritian creole house

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1

2

3

4

5 Illustration of house failures

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1. Windward side of the house may collapse under the pressure of the wind.

2. Windward facade allowing cyclonic wind to enter, increases the pressure on the internal surfaces. In combination with external suction causes the roof to blow off and walls to explode.

3. Internal pressure can be relieved by providing an opening on the leeward side.

4. Wrong foundation or inappropriate connection to the foundation prevents the walls to resist the push and pull of the wind. House tend to lean in the direction of the wind causing the roof to collapse first.

5. When no air enters the house pressure on the inside of the house along with pressure on the windward side and suction on the leeward side cause wall failures.

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Square (best)

Rectangle

Simple, compact, symmetrical Smaller rectangles are still able shapes are the best in creating to overcome winds but not as aerodynamic tendencies allowing good as square shapes wind to go around

Funnel effect increases the wind speed. Row planning creates wind.

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Long Rectangle

L-Shape

Longer shapes should not be more In more complex shapes, conners than 3times the width in order to are to be reinforced and withstand the wind. strengthen in order to provide better resistance to wind.

Zig-zag planning avoids wind

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Roofs angles do not only determine solar radiation within the building, but also wind’s effect upon the whole structure.

1. The higher the hip roof the more it has room for air to expand.

2. Hip roof has been observed to be more cyclone resistant than gable roof.

3. Overhangs and canopies are weaker spots of the roof, thus these should be braced by ties held to the main structure.

4. Pitched roof with less than 22° in order to be more resistant to cyclonic winds.

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22 ° not less

Illustration of Mauritian creole house failures

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Illustration of Mauritian creole house lined with lambrequin

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2.2.2. ROOFS Roof - Overhangs, Patios & Verandas These roof extensions are often found in creole Mauritian houses are the actual weak points of pitched roofs. Large overhangs allow high wind force to build under them and rip apart the whole roof. In order to prevent these overhangs should not be more than 18 inches at verges or eaves.

The picture above shows a creole patio with metal sheeting and ‘lambrequin’ this structure has been treated as a separate structures rather than extension. Thus preventing the structure to pull apart the main roof in case of high winds.

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2.2.2(a). RIDGES When rafters are not secure, the ridge may fall apart during cyclonic weathers. There are many ways a ridge can be secured to prevent damage: 1. Timber connecting the raters called collar ties, are nailed to the side of the rafters.

2. Using steel or plywood gussets that are fixed on the bridge board connecting the two rafters.

3. Metal straps can also be placed over the top of the rafters.

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Illustration of roofing system

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Wrongly fixed capping is often the starting point of a roof failure.

Too thin sheeting and too few fitting nails/ screws may cause the sheet to tear or roll up, starting from the sides of the gable during strong winds.

Illustration of Mauritian creole house roof failures

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Galvanized sheets are measured in gauge, where the higher the number the thinner the sheet.

The sides are the weak spot as they have higher local wind suctions. But this can be prevented by using connections U-bolts or straps fixing cladding and purlings together.

2.2.2(b). GALVANISED SHEETS FAILURES Fixings should be placed at every two / three corrugated sheets at ridges and overhangs, with regular intervals along the sheet using galvanised iron flats under the fixes.

Fixings such as zinc nails/ galvanised coated nails with wide heads can be used by putting the laths at closer centers, where the distance of the laths varies with the gauge. The thinner the sheet, the more regular are the lath and nail fixings.

Screws more secure than nails should be used with large washers and be at least 50 mm, in order to ensure stability and prevent sheet from tearing.

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concrete strips 10 dia HSD bar sheet

rafter 30 x 24 gauge GI/MS strap

Illustration of roof fixings

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Steel straps Corrugated Sheeting

Nut

metal strip

bolt fixed with ditumen washers

30x30x6 gauge M.s. washer purlin

bolt flattenned and nailed to purlin with lap

U-bolts connectors

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Galvanised sheets with 24 gauge is recommended, higher than 28 gauge can result in roof failure.

Best gauged to be used and the spacing for the laths: 26 gauge - 450 mm - 600 mm laths spacing 25 gauge - 600 mm- 750 mm laths spacing 24 gauge - 600 mm- 900 mm laths spacing With consideration of all these details and weak spots to carefully take care of, one should be able to build a near to perfection resistant metal sheet roofing that would withstand wind. Now it is to be aware that during a cyclone, wind direction becomes unpredictable and one should be ready for all scenarios. The impact of the wind over a building can also be overcome through a more aerodynamic building shape and structure.

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Ridge

corrugated sheets overhang

end

eaves

Illustration of metal sheet roofing

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3. Vertical reinforcement at corners

1. Longitudinal reinforcements

Illustration of siesmic reinforcement

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2. Lateral ties

2.2.3. CONCRETE/MASONARY WALLS Cyclonic weathers often put to test the structure of our habitations. Most of the time they are concrete structures that are assumed to be highly resistant to strong winds. what is not taken into consideration is that these structures may fail due to mistakes in construction.

Houses in the locality are often built without the supervision or planning from experts. They are self built units by the villages or by cheap contracted labour. In addition the structure fails often fails to meet regulations for cyclonic prone buildings.

According to “Cyclone Resistant Building Architecture� prepared by Ankush Agarwal builds found in cyclone prone areas, it is necessary to reinforce the walls by reinforced concrete bands and vertical reinforcing bars as for earthquake resistance.

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Recomended size of longitudinal steel in seismic band in Cyclone Prone Areas For cyclone For cyclone prone areas prone areas where wind where wind speed is > speed is < Internal Size of 47m/s 47m/s length of wall Band Reinforcement Reinforcement 5m or less

10cm X 2 bars of wall width 10mm dia.

2 bars of 8mm dia.

6m

10cm X 2 bars of wall width 12mm dia.

2 bars of 10mm dia.

7m

15cm X 4 bars of wall width 10mm dia.

4 bars of 8mm dia

8m

15cm X 4 bars of wall width 12mm dia.

4 bars of 10mm dia.

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Recomended size of vertical steel in seismic band in Cyclone Prone Areas

No. of storeys

Floor

For cyclone For cyclone prone areas prone areas where wind where wind speed is > 47m/s speed is < 47m/s Reinforcement

Reinforcement

1

-

10mm dia. bars

12mm dia. bars

2

Top

10mm dia. bars

12mm dia. bars.

Bottom

12mm dia. bars

16mm dia. bars

Top

10mm dia. bars

12mm dia. bars

Middle

12mm dia. bars

16mm dia. bars

Bottom

12mm dia. bars

16mm dia. bars

3

NOTE: Last cyclone, Berguitta in Mauritius 2018 was recorded at 200km/hr - 55.556m/s

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2.2.4. WALL OPENINGS Doors and windows are vulnerable to flying objects and given that their failure often leads to adverse uplift pressures proper measures should be taken to ensure their structural resistance. a) Opening in load bearing walls should not be within “h (height of the storey) / 6” from the inner corner b) Two small vents right bellow the roof level could be provided to prevent suffocation in case of water fill up. c) Strong holdfasts as well as closing/locking arrangement. d) Thicker glass panes. e) Reduce panel size. f) Pasting thin film or paper strips to help hold debris of glass panes while also introducing some damping that reduce vibrations.

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Illustration of window reinforcement

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Illustration of pad foundation

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2.2.5. FOUNDATIONS During cyclonic weathers foundations are often put to test in various ways. One of these ways are during heavy top soil erosion and tidal surge, that may come up the shore from10 to 15km. As it is observed in Petit Sable soil erosion results into affecting the safe bearing capacity of the foundation and its regularity with time weakens the structure of the building; like it can be observed in the above picture.

Foundations determine the stability of the building as its weight is being transferred to the ground, thus the importance of determining the right foundation for an area, canâ&#x20AC;&#x2122;t be stressed enough.

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Stilts Houses - Barce both principal directions while the "knee bracings" with its diagonal direction does not obstruct the passage of floating debris.

Step Foundation - Used on sloping ground and where the foundation supports a wall.

Strip Foundation - Used on a variety of soil types where the foundation supports a wall.

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Slab or Raft - Used mostly on soft soils to spread the weight over a wider area possible.

Pile Foundation - Used on expansive clay or alluvial soils, the foundation has deep reamed piles connected to a slab.

Pad Foundation - Used on firm soil types where the foundation supports columns and poles.

Illustration of foundation styles

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2.2.6. CHANNEL CROSSING When dealing with a site prone to ďŹ&#x201A;ooding and soil erosion channel crossing and their functionality is imperative in order to allow the course of life in the town to go on.

Channel crossing need to: 1. allow passage for the maximum amount of water.

2. not degrade the water quality.

3. not degrade any other structure, e.g. roads.

4. not endanger inhabitants.

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Illustration of small wooden bridge over rain water drain

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energy dissipator cut away to show apron

Illustration of fords crossing channel

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stream bed

Channel Crossing failures 1. Water is backing up behind structure, creating a saturation of the fill and water overflow that may cause damage.

2. Inadequate design may cause a constricting flow and increase water pressure, leading to excessive downstream erosion and road failures.

3. Location of crossing should be placed in a natural stream line. This can be determined by observing signs of excessive erosion or deposition near the bay area.

195

Fords are used in areas: 1. Prone to ďŹ&#x201A;ash ďŹ&#x201A;oods.

2. High storm runoff peaks.

3. Frequent heavy passage of debris.

Ford enables: 1. The passage of water and debris without diverting onto the road surface.

2. Debris to be deposited on the top of the ford, allowing the debris to be cleared out after instead of polluting and endangering the aquatic ecosystem.

3. Road grade can be brought down to channel bottom.

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flow

15 - 30 cm

road surface

stream gravel rock filled gabion 1x1x2cm

flow

concrete apron 4h

paved / road way

h (max) low water drain pipe

8°

stream bed

stone paving h/4

gravel drain into solid material

stream bed

2° drain thru cutoff

road drain section

Illustration of fords crossing channel section

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Illustration of earthbag house design

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3-0.

BLUEPRINT

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200

PETIT SABLE SOUTH EAST OF MAURITIUS 300 INHABITANTS

PRONE TO: STRONG WINDS FLASH FLOODS SOIL EROSION

201

202

The site is highly sloped. Terrain line indicates every 1m in height with darker lines suggesting terracing platforms at every 3m in height.

Along the coastal line volcanic rocks are used as wall retention and protection from waves during heavy storms.

In addition a salt water communal pool lead by paved pathways can also be found.

scale 1:3000

203

204

3.1. Water Flow Simulation of water flow along terrain indicates natural water pathways running down the slopes into the sea bay.

scale 1:3000

205

206

Most dense water pathways are identified as main streams where all the smaller ones convey to connect.

scale 1:3000

207

208

Along the dense water pathways, retention ponds can be placed allowing water to be collected for various uses and channels are broadened to safely direct large amounts.

scale 1:3000

209

210

Various drain channels are added along the inner part of each terrace and directed towards the main channels by a a slight slope of 1°.

211

212

Retention or conservation ponds sizes can vary and multiply in amount to accommodate the most amount of water collected.

scale 1:1000

213

Retention and conservation ponds are easily placed anywhere along the terrain. Whether on a plateau or on a sloped terrain. The only key aspect to not forget on a sloped terrain is to increase the height of the berm placed on the downhill side to prevent high overflow that may cause more damage.

214

Best place for retention and conservation ponds are on natural dent or pond along the terrain as illustrated above.

Using natural ditches decreases the work while also ensuring the workability of the retention pond.

215

scale 1:400

216

Retention Ponds can combine several areas in sets of alternating levels, causing the water to stay in motion while still conserving as much rain water as possible. Thus preventing the water from staying too stagnant, which would cause it to be subject to the proliferation of pests.

scale 1:100

217

The addition of plants around or along the retention pond will encourage natural filtration and absorption of water through the roots ensuring clean and safe water.

Not forgetting that during all this process water is being retained and collected in every channel along plantations.

Thus irrigating as well as slowing down the water velocity to better canalise it into a mainstream into the retention pond allowing both nature and the community to profit through this process.

218

scale 1:50

219

scale 1:1000

220

Conservation ponds leads to channel crossing system as it gets closer to the road in order to allow passage for the maximum amount of water in a safe way towards the sea. This will also create a collection area for all debris and other trash.

This collection area will allow the community to safety, dispose of any unwanted components while protecting their lagoon. On the other hand biodegradable debris could be composted in order to create natural fertilisers.

221

222

Another key aspect in terracing which is often not talked about is accessibility. In order to provide access to each terrace there is no need to create a concrete or paved staircase.

Using natural resources such as wood logs or rocks are still the best, as they are available on site and easy to work with.

A simple cut through the 3m earth terrace of approximately 5m length should accommodate 16 steps of 300mm wide and 150-175mm height.

scale 1:30

223

224

225

3.2. HOUSING SYSTEM After looking into all the techniques to enhance and better structural systems in the village, an ideal structure along with various alternative building details will be introduced and explained. These alternatives will allow people with different means and needs to have secure home structures.

As a general rule this house system is aimed to withstand high winds, and structural damages caused by them, while still using easily available materials. The structure is also meant to allow natural water flow without damaging the housing unit and instead provide for it.

226

scale 1:50

227

228

3.2.1. WATER RULES Starting with water, there are various ways where water has been taken into consideration in the housing design.

3.2.1(a). PLACEMENT The first one is the placement of the house. Assuming the house is to be built on the newly terraced slope; the house should be ideally placed near the edge of the slope, allowing a small overhang above the vegetal retaining wall. This will enable rain water to safely run down the curved wall down the vegetal wall into the rain water drain on the next terrain.

Vegetal wall that will not only provide new crops to be cultivated and help with the economy of each house, but crops that are filtering the water through their dense roots and foliage before entering the mainstream.

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3.2.1(b). GUTTER The last water management consideration taken by the design is found with the gutters. Every house should have an adequate gutter system. There are various gutter types and fixations that are available on the market. Any of them could be used on any house typologies but in this case where an attempt to analysing the best design a combination not only gutter to provide a gutter but also a safety net for the structure.

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scale 1:5

An original design for the gutter consisting of a corrugated aluminium curved bottom to act as a conveyer for the water transported by the dents in the waved metal sheet roofing.

Followed by the continuation of the aluminium structure forming then a 'U' shape to be fixed over the top of the metal sheet. This specific design is meant to allow the collection of water while securing the ends away from the wind. Which, as stated before may cause suction pressure under the sheet, ripping away the roof.

231

At the bottom of the curved roof an additional classical gutter can be added to act as an additional water collection point if need be.

232

Each gutter is then connected to a down pipe safely secured to the side of the slab; carrying the water to a natural path above ground lined with rock to prevent soil damage, or to a pipe continuing down the ground into the main rain water drain.

233

roof drain

native grasses & shrubs

downspout

compost amended flow path

opening downhill leading to main drain

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The drainage can be discharged to a rainwater garden which is not only an efficient natural water purification practice, but also an irrigation system for crops that do not require human intervention.

The water from the gutter is redirected by a small trench in the ground lined with stones to prevent the bottom soil to be washed away; into a slight ditch filled with layers of fertilised soil compressed at each layer in order to provide the best soil quality to grow crops. The ditch is surrounded by a berm preventing water to overflow out from all sides, with the highest berm placed on the downhill side. A small opening into the berm is created on the downhill side, lined with loose stones enabling the overflow to be directed towards the main drain.

scale 1:30

235

3.2.1(c). FOUNDATION The other design that helps with the management of water is the elevated platform the house is placed on. This prevents water to infiltrate the house and at the same time allow the natural flow of water without deviation or obstruction with sometimes increase water velocity. In addition the terrain has a 1° inclination toward the inside of the terrain leading to the rain water drain.

As we have seen previously there are several types of foundations that can be used for housing structures. Here the decision to work with pad foundations to raise the structure from the ground seems to be the best option in terms of water and water infiltration into the concrete that often causes the wall to swell and crack in a lot of Mauritian houses.

In addition pad foundation works nicely with securing earth bag walls without having to be dug in the ground as it is usually done.

236

237

238

3.2.2. WIND RULES The wind rules used for this design are very straight forward as it englobes basics that was observed at the start; mainly in regards of the weak points in a structure but also what is the best structure to withstand wind pressure.

3.2.2(a) FOUNDATIONS & WALLS When looking at structure failures it can be often argued that a concrete wall is the best. Although it was noted that seismic bands are to be placed in concrete structures facing cyclonic wind velocity of at least 47m/s and as it was last recorded in Mauritius by Berguitta with a wind velocity of 55.6m/s. This highly underlining the need for such reinforcement. Which would lead to additional material and expertise workmanship.

On the other hand, through the pressure test over earthbag walls it was observed that displacement occurs at 13kPa, which translates to 141.84m/s, making earthbag a cheaper and definitely safer structural system.

239

In this detail the pad foundation is reinforced with a galvanised thread bar while the earthbag wall above is secured over a wood structure that is itself bolted to the concrete floor slab.

This detail could be used for already existing foundations or for households with low incomes, as this design requires less expertise.

scale 1: 5

240

12mm galvanised threaded bar

457 mm minimum 203 mm

457 mm

203 mm concrete blocks Concrete strip footing

Combining both pad foundation, structural systems and old earthbag techniques we are able to create a structure with an earthbag wall that is secure and stable.

241

This particular detail on the other hand underlines the use of much more reinforcement and concrete. The foundation in this detail is twice the thickness of the previous one, with 600mm. This is because the foundation is extended above the slap to englobe the first row of earthbag. This ensures complete stability of the eathbag wall, it could be compared to the original technique to build and earthbag structure where the first row is dug and placed into the ground.

In addition a 12 mm rebar that is anchored in both the earthbag wall and foundation acts as an extra vertical reinforcement along the whole height, in other words acting as a column. In addition, in this detail the plastering is bigger as it composes itself of; galvanised chicken wire to retain the eathbag structure ; a 25cm cement earthen plaster; and optionally additional U connectors reinforcement running along the whole wall length.

There is one structural detail that does not change in both design and this the main important reinforcement in an earthbag wall, the 4 point barb wire.

242

scale 1:5

243

scale 1:25 3.2.2(b) STAIRCASE Eventually a staircase is needed to access the housing unit and this compared to the terrace need to be properly secured to ensure safety in any weather condition. While on the other hand a terrace can be viewed as an addition to the house that can be extended, removed or modified. The extension can be seen as a playful aspect of the design that gives an identity to the house the bigger the extension is the bigger the family unit or the more social they are.

244

A staircase on the other hand cannot afford to be playful its reinforcement is what will enable residents to safety get in and out of their unit in harsh weather. It ensures that no structural failure will occur if a heavy flash flood arise or if a strong cyclonic wind hits. If on the other hand the stairs were made out of wood the structure could be easily damaged by various debris or pressure against the structure.

245

3.2.2(c) ROOFING Roofing has been viewed as a main structural failure during cyclonic disasters around the island. Although as we have learnt roofing can be secured by using appropriate materials such as; adequatate connectors at regular distance.

246

24 gauge and above metal sheeting

sealing off all edges to ensure that wind will not penetrate and create suction pressure.

247

Additionally the use of a curved roofing structure on the windward site if the site, allows a more natural wind flow over the structure; compared to a flat wall that receives constant wind pressure against the facade and which could eventually lead to structural failure.

It can also be noted that the windward curved facade does not have any opening. This is to ensure that the structure stays air tight during a cyclone. As we have learnt openings are often the second cause of structural failure during harsh cyclones. They are vulnerable to debris and a chance for the wind to enter the structure and causing structural pressure.

248

scale 1:50

249

3.2.2(d). Openings All openings are placed on the leeward side of the building protected by the terrace slope lined with vegetation. Although cyclonic wind directions are often unpredictable the vegetal wall acts like a natural barrier that slows down wind velocity.

On the other hand, what is known to us is the natural wind direction on the site, being a frontal wind coming straight from the sea and this side of the building creates a natural sheltered space for communal and leisure interractions.

250

The doors are aiming to be as simple as possible while being a secure air tight structure while having the advantage of a wide entrance bringing is ample light and ventilation when open. Here an metal frame is suggested due to its high resistance and durability.

A wooden frame or door can also be used if wanted, but wood structures and workmanship has been highly costly and often for a poor quality around the island. Not forgetting that if the wrong wood or water proofing used, this may cause the wood, to retain humidity which can be transferred into the earthbag structure and cause the proliferation of various fungi harmful to the health. Or eventually additional cost in replacing the wooden door. door 40

metal frame

251

scale 1:10

252

Windows are placed above eye level between the first roofing part and the curved roof. Creating a safe area where the probability of the window pane to be hit by a debris is minimized. Its position also creates a natural reflected light along the middle section of the building. Ensuring light throughout the day with specially warm setting sunlight as it moves beyong the hill slope.

Additionally, along with the windows, ventillation shafts are integrated to allow constant wind flow from the main doors through the house and out above. The constant air renewal helps not only to bring in cooler air and get out warmer air, but also helps the health of its inhabitants by preventing the stagnation of airborne bacteria.

253

254

3.3 HOUSING PLANS & DIMENSIONS

255

House version 1 scale 1:50

256

257

258

This house module is of standard size. In this version the earthbag wall is connected and sealed to along with the foundation reinforced by rebar crossing the whole length.

Additionally, the internal walls are also made out of eathbag creating a structurally safe environment and already defined structural spaces that the inhabitants can easily work with.

4 bedroom

5 common

6 bedroom

bathroom

1 living room

2 open kitchen

3 dinning room

House version 1 Section B scale 1:50

259

House version 2 scale 1:50

260

261

House version 2 is of standard size. The earthbag wall is connected to the concrete slab through the intermediance of a wooden frame bolted to the floor.

Internal walls are also made out of eathbag creating a structurally safe environment and already defined structural spaces that the inhabitants can easily work with.

House version 2 Section A1 scale 1:50

262

4 bedroom

5 kitchen

6 living room

1 master bedroom

2 bathroom

3 dinning room

3

2

1

263

House version 3 scale 1:50

264

E

265

3

266

2

1

This house module is of standard size with earthbag external wall connected to the concrete slab through the intermediance of a wooden frame bolted to the floor.

While internal walls are either thin wooden or metal columns that allow more fluidity in personalising the interior.

IMAGINE

House version 3 Section A2 scale 1:50

267

House version 3 is of extended sizes in order to accommodate larger families. This version helps illustrate house design can be elongated to provide for a higher amount of people.

The earthbag wall is connected to the concrete slab through the intermediance of a wooden frame bolted to the floor.

Internal walls are also made out of eathbag creating a structurally safe environment and already defined structural spaces that the inhabitants can easily work with.

House version 4 scale 1:75

268

269

F

E A1

A1

D

C

B

A

1

2

3

4-0.

OUTLOOK

270

OUTLOOK Earth and soil are a precious commodity on an island such as Mauritius and our role as humans is to protect it. Mauritius is a volcanic island that has caused its soil to be highly fertile and prosperous in terms of agriculture. But centuries of over cultivation of the lands , rock extracting and deforestation has put to peril our ecosystem. Making villages like petit sable ever more precious when it comes to tackling their problems. We are bound to do make our best to positively contribute to the ecosystem of the area, and eventually show the way for a better future around the island.

This book is my way of contributing to this future. Creating a tool box for us to come back to, when we forget the simple implications of our actions and at the same time be able to further develop the tool box together.

This book is an inspiration to look into many other, less impactful ways of building, that has not been talked about.

Broadening our knowledge for at the end be able to create a living environment that beneďŹ ts and unite humans to nature.

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5-0.

BIBLIOGRAPHY

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“Detention Ponds Vs. Retention Ponds”. 2018. Helpsavenature. https://helpsavenature. com/detention-ponds-vs-retention-ponds “I Built Terraced Retaining Walls With Old Tires - Homesteading And Livestock MOTHER EARTH NEWS”. 1983. Mother Earth News. https://www.motherearthnews.com/ homesteading-and-livestock/retaining-walls-zmaz83mjzraw.

Lib.Icimod.Org. Accessed April 19. http://lib.icimod.org/record/27709/files/Chapter%20 5%20Physical%20Methods.pdf.

“Manual For Building An Earthbag Shelter”. 2018. Earthbagbuilding.Com. http://www. earthbagbuilding.com/articles/akiohowto.htm.

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Brand, Stewart. 2010. Whole Earth Discipline. London: Atlantic Books.

Montgomery, David R. 2007. London: University of California Press Ltd. Armour, Tom, Chris Lubebkeman, and Josef Hargrave. 2014. Cities Alive Rethinking Green Infrastructure. London: Arup.

Smith, Peter F. 2005. Architecture In A Climate Of Change. oxford: Architectural Press.

Mohammed, Essam Yassin, and Zenebe Bashaw Uraguchi. 2013. Global Food Security, Chapter 4 Impacts Of Climate Change On Fisheries: Implications For Food Security In SubSaharan Africa. Nova Science Publishers, Inc. Bank, World. 2017. The Little Green Data Book 2017. Washington, DC: The World Bank.

The Green City Index A Summary Of The Green City Index Research Series. 2012. munich: Siemens AG. Shrestha, A.B, E GC, R.P Adhikary, and S.K Rai. 2012. Resource Manual On Flash Flood Risk Management. Kathmandu: International Centre for Integrated Mountain Development (ICIMOD).

Forrest, Martin. 2014. Recycling And Re-Use Of Waste Rubber.

Governmental Publications “MDG Report 2015: Assessing Progress In Africa Toward The Millennium Development Goals”. 2018. Addis Ababa, Ethiopia: Economic Commission for Africa.

“First National Report Of The Republic Of Mauritius: United Nations Convention To Combat Desertification (UNCCD)”. 2004. Mauritius: Government of the Republic of Mauritius.

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This book focuses on a small village named Petit Sable, found along the south east coast of Mauritius. Looking into their various environmental problems caused by climate change and centuries of land exploitation.The book attempts to solve and illuminate its reader through analysis of local and other native techniques from around the world.

MASTERS OF ARTS IN INTERNATIONAL ARCHITECTURE ANHALT UNIVERSITY OF APPLIED SCIENCES (DEPARTMENT 3)