Safety for four million people in the Dutch delta
Room for the River From higher dykes to river widening Working together towards a safe and attractive river region
Room for the River facts Reasons Extremely high water High water levels in 1993 and 1995. Rivers are processing increasingly more rainfall, snow and ice.
Objectives A safer river region. In 2015 additional room for rivers will enable the Rhine to safely carry 16,000 m3/s to the sea. The current figure is 15,000 m3/s. A more attractive river region. River widening will be taken as an opportunity to reinforce spatial quality in the river region. This could include beautification of towns and landscape, more recreational facilities, and a boost to the economy.
Start 2006 Completion 2015 Activities Additional room will be created for the rivers IJssel, Rhine, Lek and Waal, at more than 30 locations. Of the nine techniques deployed, dyke relocation and floodplain excavation will be included.
ZOMERBEDVERLAGING BENEDEN-IJSSEL KETELMEER
Implementation The work will be carried out by the central government in collaboration with the provinces, regional water boards and municipalities.
UITERWAARDVERGRAVING SCHELLER EN OLDENELER BUITENWAARDEN
UITERWAARDVERGRAVING BOLWERKSPLAS, WORP EN OSSENWAARD
DIJKVERBETERING LEK / BETUWE / TIELEREN CULEMBORGERWAARD
UITERWAARDVERGRAVING DE TOLLEWAARD Amersfoort
W AT ER
DIJKVERBETERING OUDE MAAS / HOEKSCHE WAARD
MUNNIKENLAND KRIBVERLAGING BENEDEN-WAAL MERWEDE
DIJKVERBETERING NEDERRIJN / ARNHEMSEEN VELPSEBROEK
DIJKVERBETERING STEURGAT / LAND VAN ALTENA
KADEVERLAGING ZUIDERKLIP KADEVERLAGING BIESBOSCH DIJKVERBETERING AMER / DONGE
KRIBVERLAGING WAAL FORT ST. ANDRIES
UITERWAARDVERGRAVING HUISSENSCHE WAARDEN
DIJKVERLEGGING HONDSBROEKSCHE PLEIJ
DIJKVERBETERING NEDERRIJN / GELDERSCHE VALLEI
UITERWAARDVERGRAVING AVELINGEN UITERWAARDVERGRAVING
DIJKVERBETERING OUDE MAAS / VOORNE PUTTEN
OBSTAKELVERWIJDERING MACHINISTENSCHOOL ELST
DIJKVERBETERING LEK / LOPIKER- EN KRIMPENERWAARD
UITERWAARDVERGRAVING DOORWERTHSCHE WAARDEN
N M IEUW ER W E ED E
UITERWAARDVERGRAVING BOSSENWAARD, PONTWAARD EN HEERENWAARD DIJKVERBETERING LEK / ALBLASSERWAARD EN VIJFHEERENLANDEN
UITERWAARDVERGRAVING KEIZERS-, STOBBEN- EN OLSTERWAARDEN Deventer
HOOGWATERGEUL VEESSEN-WAPENVELD Almere
Total budget € 2.3 billion
OBSTAKELVERWIJDERING SUIKERDAM / GENDTSE WAARD KRIBVERLAGING WAALBOCHTEN
DIJKVERBETERING NEDERRIJN / BETUWE / TIELER- EN CULEMBORGERWAARD
RIVIERVERRUIMING OVERDIEPSE POLDER DIJKVERBETERING BERGSCHE MAAS / LAND VAN ALTENA
Bergen op Zoom Eindhoven
current projects additional reduction achieved in water levels for neighbouring projects means implementation no longer required
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Safety for four million people in the Dutch delta
Room for the River Working together towards a safe and attractive river region 4 Reversing the trend 5 Unique cooperation among national and local governments 6 Top Team Water 8 Long-term view 8 International cooperation 9 Room for the River: work in progress 10 Stayers and movers 11 Examples of projects 12 A menu of measures 19
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Working together towards a safe and attractive river region The Netherlands is a river delta. Europe’s rivers discharge via the Netherlands out to sea. With less room available to its rivers, this country faces increasing flood hazards. The rivers are sandwiched between ever-higher dykes protecting a burgeoning population. Meanwhile, there’s subsistence in land behind the dykes, and with more frequent and harder rainfall the rivers are dealing with greater amounts of water. Because the Netherlands’ river delta functions as Europe’s overflow facility, it (also) receives a lot of waters from abroad. This means rising water levels and ensuing flood danger causing a major impact on people, livestock, infrastructure and the economy. The Dutch government is res ponding with forward measures to ensure improved flood protection for the river region. Room for the
river will be created at more than 30 locations; projects forming a unique nationwide ‘Room for the River’ programme. The parties involved, ensuring safety for four million residents are the Rijkswaterstaat (DirectorateGeneral for Public Works and Water Management), regional water boards, municipalities and provinces. It is an integral, areabased development programme, which will enhance the beauty of the river region and afford more space for new economical potential, nature and leisure facilities. As a result, a safe and visually pleasing river region in 2015.
Europe’s drainpipe This country’s high safety standards often suprise people from abroad. Our river dykes needs to contain extreme high water levels occurring once in 1250 years. These high safety levels are crucial because of the low elevation and high population density. Moreover, the Netherlands is a river delta, acting as Europe’s drainpipe, carrying the water from its rivers to the sea. Combined, these factors make the Netherlands relatively vulnerable to flooding.
Ochten 1995 – emergency sand-bagging to combat high water levels
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Reversing the trend While ongoing dyke reinforcement will certainly reduce the risks, any flooding that does occur will have an even greater impact: more water will flow onto the low-lying land behind these very dykes. If the Netherlands is to be a safe, comfortable and pleasant home for all its inhabitants, the trend needs to be reversed, and the Dutch government’s plan to make more room for the river provides the solution. This involves elevating safety levels to ensure flood protection for residents and the land areas behind the dykes. Under the Room for the River programme, The river will have more room at more than thirty locations. The programme’s key objective is to complete flood protection measures by 2015, while simultaneously enhancing overall environmental quality in the river region.
Worst case scenario:
the Netherlands 50% submerged At worst, a breach in the dykes along the coast, the rivers or in the IJsselmeer region could inundate half the country. The lives and livelihoods of ten million people living in areas below the benchmark (NAP– Amsterdam constant level) would be endangered. Flood damage could mount to € 165 billion. Major flooding in the area south of the great rivers could give rise to fatalities in excess of 1000.
The city of Arnhem in 1830 and 2000
Making room for the river In 1993 and 1995 the river region and its residents were confronted with extremely high water levels. The dykes only just managed to resist the impact. With repetition likely, it was decided to safeguard the area by enabling the rivers to safely discharge far greater volumes of water without the danger of flooding. This initiated the Room for the River project, which in 2007 met the approval of the Dutch government. The programme has three objectives: - By 2015 branches of the Rhine may need to accommodate discharge volumes of 16.000m3/s without the risk of flooding - Safety enhancing measures must also improve overall economical and environmental quality in the river region - Over the next several decades the rivers will require additional room for higher discharges due to predicted climate change. This must be available on a permanent basis. A range of measures is being implemented to create more room for the river while reducing high water levels. This will include lowering floodplains, relocating dykes further inland, lowering river groynes, and deepening summer beds. Dykes will only be reinforced where other options are either too costly or below optimal requirements. Improving the environmental quality is done in different ways. The Millingerwaard nature reserve is one example of leisure facilities being developed. In Nijmegen river widening is part of the city’s plan for a dedicated recreational area. In the Overdiep polder reorganisation of agriculture intensifies operational profitability, and at the Avelingen business park water-borne transport gets a boost.
A hundred-plus floods in Europe Europe suffered more than one hundred major floods between 1998 and 2004. When the rivers Danube and Elbe overflowed their banks in 2002 there were 700 fatalities and 250.000 people left homeless. The extent of the damage stood at around € 25 billion.
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History of water management in the Netherlands The Dutch hold an impressive track record in water management that stretches as far back as the 9th Century. Right up until the 13th Century large portions of land engulfed by floods was a common occurrence, and the only safeguards for people and property were artificial dwelling mounds, called ‘terpen’. In the west of the country reclamation of peatlands started to develop which, though ensuring a drop in water levels, also caused land masses to subside, particularly those below sea level. These ‘polders’ were open to flooding – the worst being the St. Elizabeth flood in 1421: a deluge of gigantic proportions claiming tens of thousands of lives.
Unique cooperation among national and local governments Municipal, regional and national governments are uniting to implement Room for the River. Ultimate responsibility for the programme lies with the Dutch Ministry of Infrastructure and the Environment. Using their ground-level expertise and ability to finely tune adjustments in accordance with regional developments, provincial executives, regional water boards, and Rijkswaterstaat (Directorate-General for Public Works and Water Management) detail plans and implement projects. Room for the River’s programme directorate (PDR) is the link between national government and the regions. It verifies that plans are compatible with Room for the River policy, monitors cohesion between measures, facilitates processes and promotes exchange of expertise and experience among more than thirty projects.
St. Elizabeth Flood
rift to conquer Resolute in their determination bijsch oto + 3)built dykes. 5 the threat of water,(f thedDutch 9 1 in Floo Peatlands were protected, and so were the densely populated inland clay regions. The opportune introduction of windmills between 1250 and 1600 guaranteed continuous use of agricultural land and were also operational in the drainage of lakes.
Maintenance of dykes and sluices, however, proved costly. Communities banded to share the financial burden; predecessors of the regional water boards of today. Local farmers held responsibility for the upkeep of a section of the dyke. In time, water boards, funded by local landowner taxes would take over the task of maintenance and quality control.
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Administrative reform Freedom for regional and local governments to plan and implement plans within national boundary conditions; monitoring plans and decisions made by the regions; regular, informal consultation towards pro-active problem solving while sharing knowledge and experience. These are the modernising elements of cooperation by governments within Room for the River – an approach to governance that means improved quality planning, and less likelihood of delays.
Alderman Jan Luteijn, Werkendam
‘Maximizing impact on the end result’ ‘I suspect that most Noordwaard residents reckon they’re giving up more than they’re getting back. But looking at it from the macro level, I see a positive balance. And I’m happy to give the Room for the River organisation a full ten point score for going that extra mile to get support and find solutions that are fair.’ ‘Werkendam municipal council interprets signals received from residents and businesses into demands we can add
to the administrative agenda and exert influence. Sometimes the result is negative, sometimes positive. Like an entrepreneur with a double operation who now has more space to take the company forward, individualised opportunities are offered. And, in my opinion, the potential for customised solutions makes Room for the River unique.’
Ingwer de Boer, programmedirector
‘Making plans with the people concerned’ ‘I find interest from abroad regarding the managerial approach particularly significant. China, Vietnam, United States, Brazil… They all want to know how we do it. Our approach is to make plans together with the people concerned. And with local committees who draw public attention. They have, after all, been elected, are close to the people and can, therefore, achieve so much more. Take, for instance, Nijmegen/Lent where the plans were not originally well received.
When they were presented, however, the municipal council was applauded. In a relative short space of time a threat was turned into an opportunity. That’s the power of Room for the River. Councils, officials, residents and businesses work together. And it is precisely this collaboration that enables a large and complex programme such as Room for the River to be realised quickly and within the available budget.’
Piet IJssels, Mayor of Gorinchem
‘Clustering permits saved us a year’ ‘This approach to cooperation is a success – that is a fact. Rather than following a blueprint the process involves keeping eyes and ears open for mutual problems and interests. Right from the start we’ve been looking for win-win situations. Here in Gorinchem there’s broad awareness of the need for river widening. Indeed, this area had to be evacuated in 1995 because of the high waters. At the same
time we can use the opportunities offered by the washland excavation to boost the Avelingen business park. What also works neatly is clustering all the permits within a single procedure – plus rapid problem-solving thanks to regular consultation with permit granting authorities. This working formula was specially developed for Making Room for the River. I reckon that it has won us an extra year.’
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The flourishing Golden Age of Dutch economic and political power in the 17th Century contributed to boosting land reclamation. Society was modernising and making progress. Drainage of the 18,000 hectare Haarlemmermeer lake, in which sudden, violent storms claimed many ships, provided the location of Amsterdam Airport Schiphol. The name Schiphol literally translates to ‘Ship Grave’, a reference to the number of ships lost. The 20th Century heralded the completion of the Afsluitdijk enclosure dam, a major 32 kilometres causeway constructed between 1927 and 1933. It separated the Zuiderzee from the North Sea to form the IJsselmeer, turning a salt-water inlet into a fresh water lake and cutting the flood risk to the central part of the country. However, water would still make regular inroads. On the fateful night of January 31st 1953, a catastrophic combination of a high spring tide and a severe north-westerly storm inundated large areas of Zealand and South Holland provinces with the water level exceeding 5.6 metres above mean sea level. The death toll reached 1,835 with more than 70,000 evacuees and massive damage to homes and property. The Delta Plan would set out measures to prevent a recurrence of such a disaster.
Top Team Water The government has indicated ‘water’ as one of the main sectors that should give a boost to the Dutch economy. Top Team Water comprising governmental, scientific and business representatives was established for this purpose. The objective is to double foreign profit of the Dutch water sector in 2020. A leading programme such as Room for the River is a major contributor. The expertise gained by an integrated area approach and administrative cooperation goes down well on the international market. And the success of which reflects particularly well on Dutch companies abroad.
Floods in 1953
Based on the Delta Plan, the Netherlands constructed the Delta Works to demonstrate that the threat of a hazardous sea could and would be overcome. In doing so, safety from flooding was ensured for a large portion of the country. Despite this, in 1993 and again in 1995, the perils of flooding were only narrowly averted. On both occasions this was due to major volumes of melted snow and ice, and rainwater from upstream boosting the level of river discharges. This spurred a new approach to water management. Rather than continually adding to the height of their dykes, the Dutch are now affording water more space – making room for rivers.
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Long-term view Room for the River’s ambition is to create a safe and attractive river region in 2015. Meanwhile, as an integral part of the Delta programme, it is also involved in taking action in anticipation of future flood protection beyond 2015. All of which underlines our unique position as the country with a 100-year forward-focused vision on living safely with water.
Floods in 1995
The Dutch approach to water management This country retains a long track record in water management. Sophisticated innovation regarding water has always been key to survival. A population density of 402 per square kilometre makes careful management of space and environment mandatory. With the main hub of economic activity centred in the lowest lying part of the country, a new and essential approach to water management is spurred. Rather than continually heightening the dykes, more space is created for water. Knowledge sharing by Room for the River includes two EU operations. FloodResilienCity (FRC) involves Nijmegen and several other European cities sharing experience with improved flood protection in urban areas. Meanwhile, five European managers of floodplains, such as Overdiep, share knowledge and experience in Adaptive Land Use for Flood Alleviation (ALFA). Room for the River is Lead Partner for these projects and close cooperation with national and local governments is a priority. Sharing knowledge with our European neighbours spurred cooperation in our home country. The Netherlands is also working together with countries that have common river basins. One example is the International Commission for the Protection of the Rhine where Room for the River coordinates flood management measures with Germany. The Netherlands has close contacts in China, and in the USA with whom river management and flood protection knowledge and experience is shared. There are also similar programmes in place with five delta nations: Bangladesh, Indonesia, Vietnam, Egypt and Mozambique. Regarded as a role model in water management, Room for the River expertise is also reflected in the changes made in the Mekong-Delta. International media focus Making Room for the River regularly hits the international headlines. Two articles in the Washington Post hailed the Dutch approach to flood protection as visionary. The ‘Post’ also suggested that our river widening measures could help along the Mississippi. Also, Making Room for the River featured in an edition of the BBC’s Horizon science programme on the global issue of flooding.
Dutch water related statistics: Population: 16.7 million Average population density: 402 per km2 Main urban conurbation: The Randstad (urban agglomeration) includes Amsterdam, Rotterdam, Utrecht, and The Hague Highest elevation: 322 m above sea level at Vaalserberg (south-east) Lowest elevation: 6.74 m below sea level at Nieuwerkerk aan de IJssel (west) Annual rainfall: 800 mm
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Room for the River: work in progress The programmeâ€™s innovative approach is working. The planning process is Âcomplete and most projects are in the implementation stage. Room for the River is on schedule and work will be completed in 2015.
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Stayers and movers Room for the River is a far-reaching programme. Around 150 homes and 40 businesses will have to step aside for the river. There is continual, close cooperation with the people involved to arrive solutions – like at Overdiep where poldering (land reclamation) is to be reversed. Eight companies will ensure continuity by relocating to dwelling mounds known as ‘terps’. The other nine will either close down or move away.
New dweller / cattle farmer Nol Hooijmaijers
‘I’d like to experience a flood sometime’ ‘There was a lot of anger and frustration back in 2000 when we heard that our operations would have to make way. But, one Sunday afternoon, rather than digging our heels in the sand, we sat underneath the chestnut tree and came up with a terp-plan. My wife and I negotiated with North Brabant for two years to reach an agreement on the sale of our farm. It was then a really intensive time, but now we’re looking ahead. We’ll probably be celebrating Christmas 2012 on our new, up-to-date operational terp. At high tide the fields and meadows could become flooded. One time I’d like to see that from high up where we and the cows are safe and dry. Even without Room for the River, we would have had to make major investments to stay ahead. Now, that’s gone into turbo-drive and we’ve had great support from the government. When the farm operation is in place, we’ll have something to be proud of. What will happen to the chestnut tree? Sadly, it’ll have to go, but maybe we’ll plant another one.’
The van Beek family, ‘movers’ from the Overdiep polder
‘Initiative rewarded’ ‘The terp plan didn’t appeal to us’, says Adje van Beek. ‘It was too complicated. And with three sons with their hearts set in the farming world, we went looking for a new place to expand and redevelop. We found a great location in Terheijden with a brand new dairy operation twice the size of our old farm. But it didn’t come as a gift. We had to fight for it and invest. And we had to leave the place where we had lived and worked for 26 years. Looking back, we hadn’t realised at the time what that would involve. Negotiating with the North Brabant province for permission to build a new house and to start up the farm was a real headache! But, because we did a lot ourselves, all turned out well in the end, and our initiative paid off.’
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© inZicht, Henri Cormont
River widening at Overdiep A metamorphosis is underway at the Overdiep polder where most of the farms will be relocated and rebuilt on man-made, raised areas (terps) along a new dyke. This will ensure flood protection and additional room for the river.
Once the farms have been rebuilt on the ‘terps’, the dyke on the north side of the polder will be lowered. A new primary dyke to be built along the river Oude Maasje will be a mirror image of the current dyke on the north side of the polder. On average, water from the river will flow into the polder once every 25 years. This will lower the high water level in the Bergsche Maas river by some 27 centimetres in the Overdiep polder area, which will also have an impact on levels far upstream.
provided the final solution together by building on raised areas (terps). Their plan was based on accessing information early in the planning process. Cycling and walking Completion of the project’s new paths will offer a round-the-polder route to walkers and cyclists. By the end of 2015 the new Overdiep polder will be available for sustainable agriculture, as well as providing additional room for discharge from the Maas.
Residents develop plan What makes the Overdiep polder project special is that local residents and farmers
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Lowering of groynes in the Waal Groynes have a significant visual impact on the Dutch river landscape. Their main function is to stabilise the Waal (a branch of the Rhine) while ensuring a navigable route for river traffic. The downside is that they obstruct the river and hence increase water levels. Groynes on both sides of the river between the Pannerdensch canal and Gorinchem will be lowered by one metre on average. While freeing-up the water this will ensure an adequate depth for shipping. A total of 750 groynes will be lowered on this 75-kilometre section of the river. The initial stage (70 groynes) was completed in 2010, while stage two (120 groynes) was launched in autumn 2011.
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Lowering groynes will mean a 6 to12 centimetre reduction in extreme water levels occurring when 16,000m3/s. Water arrives at the Rhineâ€™s portal to the Netherlands (Lobith). As from 2015 the groynes are expected to be submerged for two-thirds of the year, and with normal discharge rates this will make the Waal look much wider. Currently the groynes are visible for most of the year.
Water storage at Volkerak-Zoommeer Water storage in the Volkerak-Zoommeer lake is a special Room for the River project. Implementation is confined to periods of very high sea level, combined with abnormal river discharges. High sea levels signal closure of the storm surge barriers in South Holland. Closure of the storm surge barriers stops water from flowing out to sea and when this coincides with extreme river discharges, water levels in the Haringvliet and Hollandsch Diep rise to an unacceptably high level. Temporary storage of river water in the VolkerakZoommeer can limit water levels in the Hollandsch Diep and Haringvliet. When the storm surge barriers reopen, river water can flow back out to sea again. Water storage in the Volkerak-
Zoommeer is confined to periods when closure of the storm surge barriers coincides with extreme river discharges. Although the chances of this happening are estimated at only 1/1400 per year, climate change and the impact on water levels and river discharge could increase the risk. Looking ahead, water storage may have to be implemented more often to ensure flood protection in the area around Hollandsch Diep and Haringvliet.
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Dyke relocation at Lent This project illustrates how Room for the River can act as a catalyst for integral development of the area. Nijmegen is using the opportunity provided by dyke repositioning to boost expansion plans on the north shore and give the city a new look. Located on one of the narrowest river bends in the country, opposite Nijmegen on the south bank of the Waal, is the village of Lent. The Waal is just 450 metres wide at this point, compared with 1000 metres elsewhere. In high water incidents this bottleneck signifies that large volumes have to force their way through a narrow passage. New water channel More room will be generated for the Waal by relocating the dyke, thus protecting the village of Lent, which is some 350 metres inland, opposite Nijmegen. This will reduce water levels by 35 centimetres along the Waal from
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Nijmegen. Shifting the dyke will be combined with excavation of a new channel in the floodplain on the Lent side of the river. Nijmegen welcomes the Waal Excavation of the channel will create an island between the Waal and the channel. Two new bridges will provide a link to the ‘mainland’ and there will be a unique new river park with space for nature and recreation. The dyke relocation will be melded into the newly constructed residential neighbourhood on the north shore, affording the village a new quayside and a sunny, attractive waterfront.
Depoldering Noordwaard Reverting reclaimed land of the Noordwaard polder to water is designed to prevent flooding by increasing the river’s discharge capacity at high water levels. A key principle here is that on request residents will be able to stay. Meanwhile, plans also feature an innovative green, wave-inhibiting dyke. The water level at Gorinchem, 40 kilometres east of Rotterdam needs to be reduced by 30 centimetres. The depoldering project will be the major contributor, featuring partial lowering of the dykes to create inlets and outlets. The aim is to divert some of the volume at high water levels as far as possible upstream from the Nieuwe Merwede canal. Discharge will be at a greater distance westwards in the direction of Hollandsch Diep. This ‘through-flow’ area will be submerged several times a year, notably in the winter months, but much less frequently than in other parts of Noordwaard enclosed by dykes. These additional areas will accommodate some of the volume occurring in high water level situations once every 100 to 1000 years.
‘Through-flow’ area Current agricultural operations will not slot in with the through-flow, although farming can continue in other sections of Noord waard. Basic to the project is that residents can stay in the polder, whereby some homes will be adapted and others relocated. Green, wave-inhibiting dyke Innovation within the project includes a green, wave-inhibiting dyke at Fort Steurgat, and the willow bed means the new dyke can be 65 centimetres lower at 4.6 metres. Although this will have a considerable impact on residents behind the dykes, the environment will be more natural and greener.
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Hondsbroeksche Pleij The Hondsbroeksche Pleij at Westervoort has a key function in distributing water between the lower Rhine and the IJssel rivers. A notable aspect of the project, which has drawn considerable interest from abroad, is that redevelopment of the area will also focus on nature, cultural and historical aspects, as well as recreational facilities. Once a floodplain, the area is to be reconfigured as flood protection for the low-lying Dutch delta, which is vulnerable to extreme water discharges. To this end the river will be widened and checks put in place on discharge levels of the lower Rhine and IJssel. This will reduce extremely high water levels by 40 centimetres. Innovative cut-off The main task at the Hondsbroeksche Pleij was to move the dyke 250 metres inland. An innovative cut-off was installed underneath to counter any loss of strength. Plus points included a reduction in clay shipments and ensuing local disruption.
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Regulating A high water channel was positioned at the northern end of the Hondsbroeksche Pleij to ensure additional discharge capacity in high and extreme high water situations. An engineering construction at the southern end of the high water channel will regulate water distribution between the lower Rhine and the IJssel. The area between the new Pleij dyke and the Rhine dyke has been renamed the Pleij polder. A water garden on this location will consume any groundwater that passes the new Pleij dyke, and a new pumping unit will return the groundwater to the IJssel river.
A menu of measures
Lowering floodplains Lowering/excavating part of the floodplain increases room for the river in high water situations.
Lowering groynes Groynes stabilise the location of the river and ensure its correct depth. However, in aÂ high water situation, groynes may obstruct the flow to the river. Lowering groynes speeds up the rate of flow.
Dyke relocation Relocating a dyke inland widens the floodplain and increases room for the river. Removing obstacles If feasible, removing or modifying obstacles in the riverbed will increase the rate of flow.
Depoldering The dyke on the riverside of a polder is lowered and relocated inland. This creates space for excess flows in extreme high water situations.
Water storage The Volkerak-Zoommeer provides temporary water storage in extreme situations where the storm surge barrier is closed and there are high river discharges to the sea.
Deepening summer bed Excavating/deepening the surface of the riverbed creates more room for the river. High water channel A high water channel is a dyke area branching off from the main river to discharge some of the water via a separate route.
Dyke reinforcement Dykes are reinforced at given locations where river widening is not feasible.
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Room for the River. Safety for four million people in the Dutch delta. From higher dykes to river widening, Working together towards a safe...