Impression of Willemspolder
Impression of Willemspolder

WaalWeeldeMidden

Tiel

Flood creation

Flood Protection Task


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Due to climate change, the amount of water that must be drained by the rivers in the Netherlands will increase in the coming years. It is expected (climate scenario WB21) that the maximum amount of water that enters Lobith, Netherlands will increase from 16,000 m3/s in 2015 to 17,000 m3/s in 2050 and 18,000 m3/s in 2100. For water safety (with a chance of exceeding it once every 1250 years) in the river area, a strategy has been chosen not to raise the river dikes in the first instance, but to reduce the water level as much as possible by giving the river more room (PKB Room for the River 2006). To reduce the chance of breakthroughs for existing dikes, it is being investigated at the same time whether they can be extended to delta dikes.

The river-widening measures for the WaalWeelde area (between Lobith and Gorinchem) for the short and long term are named and prioritized in the WaalWeelde spatial investment program (2010).

Delta scenarios

All river-widening measures with which the intended fall in water levels in WaalWeelde Central can be achieved in the short and long term have been mapped (quantitatively) and prioritized in the WaalWeelde Spatial Investment Program (2010). However, these measures have not yet been achieved. Important factors for this are: money, land and decision making. The revenue side for the realization of these projects is still limited. For long-term measures in particular, it is useful to take into account different future scenarios with large differences in economic situation, management, socio-demographic aspects, land occupation and climate change (deviating from WB21).

Water value creation

In our proposition we broaden the flood protection task (space for the river) with a search for spatial quality, possible use (productive, recreational) and thus for the yielding capacity of the outer dike area. We want to demonstrate that river-widening measures can easily be combined with a spatially differentiated and economically vital outer-dike area in which the presence of the river and local potential are optimally utilized and give meaning to the landscape. This also makes the (future) necessary dyke shifts more acceptable, both from an economic and social perspective. In addition, it is useful to move the dikes extra far where possible, so that robust, future-proof (climate) floodplains are created. These extra wide floodplains (wider than strictly necessary for flood risk management) can possibly be combined with broad (climate) dikes that create a water-retaining landscape with a strategic excess and an economic potential. In contrast to the current strategy whereby functional co-use of the outer dike area is discouraged and dyke relocation is accompanied by loss of valuable agricultural land, we propose a strategy whereby agricultural activity takes into account incidental flooding and is expanded with river-related activities such as fishing and algae cultivation. The possible hydraulic resistance associated with this (more than with nature development only) is compensated by the extra widening (or deepening) of the outer dike profile.

The proposal is not intended as a competitive strategy, but seeks to vary from the current strategy, which can also increase the spectrum of nature development and thus biodiversity. It is a strategy that, to a certain extent, is an extension of the way in which for centuries the floodplains have been used as a breeding ground for biomass, building materials and food production.

Use linked to water frequency

The space outside the dykes must be able to turn a maximum water level that occurs on average once every 1250 years. Much more often the water will be considerably lower and a large part of the area outside the dykes can be used for other activities. The average frequency of the different water levels is easy to predict and can be translated into vertical zoning of the outer dike space based on water frequency. The profile from dyke to dyke can be designed in such a way that maximum benefit is achieved from the water frequency. It goes without saying that every location in this profile applies: the higher, the less often there is water here. Just like with summer dikes, this can possibly be influenced with the help of thresholds. The significance of the water frequency for the possible use of a location is large. For example, an area that is regularly flooded is especially suitable for nature development or planting tidal rivers (including watercress), while an area that can only be flooded a few days a year can be equipped with other biomass or food-producing crops. Extensive and seasonal fish and algae farms that use the surplus nutrients from the river (and thus have a purifying effect) and residual streams from the brick factories (including CO2) can also be considered. The higher parts of the area outside the dykes can be arranged as a distinctive residential and residential area where parts of the public space and gardens undergo a controlled flood every few years.

Case for the water-retaining landscape

As a case study for this approach, we want to focus on the area around Tiel. Here a number of specific situations occur in a relatively small area that are partly exemplary for the rest of WaalWeelde. Together they can form an inspiring image of the future that shows the potential of a water-retaining landscape.

In the Willemspolder algae farming is combined with trout farming to create a varied, productive water landscape where space is given to ecosystems and a nutrient-rich habitat is created for various species of animals. The surplus of nutrients in the Waal and CO2 from the brick factory are local residual streams that are used for the cultivation of algae.

In the Wamelsche Uiterwaarden and Dreumelsche Waard, specific floodplain nature is used for natural water treatment and soil treatment. With the help of plants with a water-purifying capacity, a system is created in which river water is purified and collected in a clean water reservoir. This reservoir offers opportunities for recreation and irrigation of adjacent orchards. At high tide the reservoir acts as a secondary channel.

The municipality of Tiel intends to realize a climate dike in the area between the Willemshaven and the Amsterdam-Rhine canal. The aim is to realize a broad, break-free dike that can be built on with houses. By meandering shaping the dike body, more homes can be developed with a view of the Waal and the floodplains. The Kleine Willemspolder is at the same time partly excavated and transformed into a walking area that is influenced by the tides.

The current parking place on the Waalplaat will be transformed into a hydrodynamic river park where the fluctuations of the water levels of the river Waal can be experienced. Depending on the water level, parts of the park will flood. The design greatly reduces the hydraulic resistance at high water. The river park offers Tiel a place with quality accommodation that contributes to the cityscape and identity of Tiel. The function as an event location is also given an extra dimension by the stepwise design that creates stands and venues.
Impression of Wamelsche Uiterwaarden + Dreumelsche Waard
Impression of Wamelsche Uiterwaarden + Dreumelsche Waard
Impression of small Willemspolder
Impression of small Willemspolder
Impression of Waalkade
Impression of Waalkade
average waterflow
average waterflow
winterflow 1x in 10 years
winterflow 1x in 10 years
extreme low summerflow
extreme low summerflow
From fighting the water to living with water.
From fighting the water to living with water.
Water fluctuation in relation to the section
Water fluctuation in relation to the section
value adding system in outer dike area
value adding system in outer dike area
section algea farm
section algea farm
Safety level: 1/1250 a year
Safety level: 1/1250 a year
year
2012

team
ir. Marco Vermeulen, ir. Joost van der Waal, Antoine van Erp, Despoina Sapoutzi

programme
Biomass, algae and fish farms, homes, nature

client
IABR Atelier Making Projects

website
www.rijksoverheid.nl


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