Learn: What is Room for the River?
The Room for the River program is a Dutch flood mitigation initiative that focuses on creating “room for the river” by increasing the depth of rivers, storing water, relocating dikes, creating high water channels, lowering floodplains, lowering groynes (structures built into the river that disrupt water flow) and/or removing polders (tracts of land entirely surrounded by dikes). Making “room for the river” allows landscapes along rivers to be restored in order to act as “natural water sponges” in the event of a flood.
Two people crossing of the flooded Elftweg in 1930.
Photo "Watersnood in Grave / Flood in Grave" is by Brabant Bekijken (CC BY-NC-SA 2.0).
In 1993 and 1995, the Netherlands experienced severe flooding that resulted in mass evacuations and left farmland inundated with water. The floods prompted the Dutch government to explore how to safeguard flood-prone areas by "enabling the rivers to safely discharge far greater volumes of water". This marked a shift in flood mitigation; prior to these major floods, the Dutch relied primarily on the construction of dikes and berms for flood mitigation.
In 2006, the Dutch government approved the Room for the River program and work began the following year. The program is expected to conclude in 2015. The Dutch government invested significant funds into the program: in total, 2.3 billion Euros were allocated to this work. The Dutch government in partnership with the Dutch provinces, regional water boards and municipalities, leads the program.
Effective flood mitigation is a national priority in the Netherlands as flooding is a regular occurrence and of significant concern. The country lies in a delta where three rivers – the Rhine, the Meuse and the Scheldt - intersect and spill into the ocean. The majority of the Netherlands is also below sea level.
The primary goal of the Room for the River program is flood attenuation, but the program also recognizes the importance of aesthetics and cultural and ecological elements and has worked to incorporate these factors into work carried out under the program. The intent of the program is to make Holland’s rivers safer and more attractive by stepping back from the river and allowing water to flow through the river system without hindrance. This ultimately will result in more “room for the river” to travel through the floodplain during high-flow events.
A photo taken by NASA of the city and harbor of Den Helder. Extensive gray mudflats can be seen in the top right of the photo.
Photo "Den Helder, Netherlands (NASA, International Space Station, 05/01/07)" is by NASA's Marshall Space Flight Center (CC BY-NC 2.0).
Flood Mitigation Measures
Under the Room for the River program, there are nine measures for flood mitigation that are intended to create more room for the river:
- Deepening the Summer Bed: The “summer bed” refers to the main river channel. This area can be excavated or deepened to make more room for water to flow directly in the channel. In order to deepen the summer bed, dredging must occur. Dredging is particularly important in the Netherlands because transport vessels regularly navigate the main river channels. Sediment usually returns to the summer bed quickly, so dredging must be repeated regularly.
- Water Storage: Most of the Room for the River measures are designed to move water through the floodplain quickly. Water storage, however, holds back fast-flowing water. In the Netherlands, the Volkerak-Zoommeer lake is used for temporary water storage if required
- Dike Relocation: Dikes can be moved back from the river. This allows more room between dikes to convey more water during floods.
- Strengthening Dikes: Strengthening dikes is a last resort measure in the Room for the River program. Dike reinforcement is only done in areas where dike relocation is not possible. Dike relocation may not be possible in higher-density areas or places that have iconic buildings of national or cultural importance.
- High Water Channel: A high water channel can be created in the floodplain along the river to accommodate the higher flows seen during a flood event. A high water channel is a secondary channel that diverts some of the excess water through the floodplain. In some cases, these channels remain empty at all times so that they can accommodate the largest amount of water possible during floods. In some cases, high water channels are filled with riparian plants or other vegetation so that the water-flow can be slowed and water can be absorbed into the ground.
- Lowering Floodplains: Rivers in the Netherlands carry a lot of silt. During seasonal floods this silt is deposited into the floodplain near the river. In order to maintain room for the river, this silt is removed by lowering/excavating the floodplain.
- Lowering Groynes: Groynes are structures in the river channel that ensure water stays in the channel in order to maintain high flows so boats can navigate upstream. Groynes can be lowered to below water level so that in flood events, the water is not held beyond a groyne.
- Depoldering: Polders are sub-sea or sub-river tracts of land that are surrounded by dikes. During high flows, excess water can spill into a polder. This measure, much like dike relocation, involves removing all of or a portion of the shorter dike, so that water can flow into the area behind the dike. This creates more room for the river, because the river has the entire area in between the main dikes to flow through.
- Removing Obstacles: Obstacles in the floodplain that restrict flow can be removed or they can be reduced in sized. For example, bridges with large abutments can be redesigned so they have a wider span.
Additional information of the Room for the River program is available online at http://www.ruimtevoorderivier.nl/english/.
Since inception, the Dutch have implemented the Room for the River program across the globe, and other countries, like the Philippines [http://www.worldbank.org/en/news/feature/2014/10/08/a-paradigm-shift-for-guarding-delta-cities-against-floods], have developed similar strategies for flood mitigation.