Issues
Areas
Solutions
TRL Level
SRL Level
Urbanisation and agriculture in the Rhine basin have driven loss of water storage capacity in floodplains and marshes and soils of smaller valleys and have caused ecosystem degradation. Changing precipitation patterns due to climate change are expected to lead to increased peak flows as well as critically low water levels. The combination of both developments increase the chance of severe impacts on society. Precipitation falling on the plateaus and slopes in the Middle Rhine region comes down as throughflow (water flowing through the soil) and passes the valley floor before entering the stream. Drained valley floors accelerate this process, i.e. artificial drainage “empties” the hydrological column of entire slope and plateau, contributing to flood peaks in the tributaries to the Rhine.
Developed by Wetlands International
Natural Water Retention through restoration of the ‘sponge’ function of currently drained soils in the middle-mountains of the Rhine basin is a locally applied nature-based solution to flood mitigation with potential impacts at basin scale. We argue that the benefits of the proposed solution are not only local, but will also favour end-users further downstream. This solution fits a systems approach and contributes to achieve water, agriculture and nature policy objectives as well as delivering societal benefits such as recreation and carbon capture.
See more information about this level and the TRL and SRL levels.
The most suited location for restoring the natural sponge function is at the foot of slopes in U-shaped valleys. Removing drainpipes and ditches would slow down the runoff response of a much larger area than the space needed for the measure itself. Calculations for local catchments in the Mosel basin (the case study area) shows potential for local peak reductions of 5 – 8% in the tributaries to the Rhine, and provide partial evidence for the hypothesis that natural retention can result in substantial reduction of flood peaks. Critical to bridging the gap between our innovative approach and the end-users is to provide more clarification regarding the location and scale of implementation as well as the expected effects of the measure.
Limitations/conditions under which this innovation does not work or is less effective
The method has gradually been developed and elaborated since 2004 in several publications. Our most recent study analyses costs, impacts and stakeholder opinions. We conclude that opinions differ on the scale of impact that can be achieved across the basin. A commonly heard argument is, that just a few restored areas cannot hold the water of a 100-year flood. Many of the questions asked boil down to the following: yes, natural retention works on a local scale and several water authorities apply it to solve local problems – but how many of these projects do we need to have meaningful impact on a river basin scale? Is the required surface area of relatively flat valley floor available and if so, would land users or landowners be willing to allow the removal of drainage and at what cost?
Added value
Our solution is an example of a nature-based measure contributing to water safety for urban areas, water quality and climate change challenges. Our suggested approach of restoration of the sponge function delivers benefits at local and river basin scale and will thus also have impact on downstream urban deltas. One of the great advantages of nature-based solutions (such as Natural Water Retention Measures) is that they provide multiple benefits. The co-benefits alone should provide an incentive to implement the suggested measures. Restoring the natural water retention capacity of currently drained soils will help achieve water, agriculture, and nature policy objectives. The approach will deliver socioeconomic benefits such as recreation, improved water quality, and carbon sequestration. In addition, it contributes to restoration of biodiversity. However, these are potential side-effects of the interventions. The main objective or the main means for reaching flood mitigation is the slowed down hydrologic response of the subbasin. This being said – if removal of drains is combined with development of peatlands, marshland and wetlands, the rough, year-round cover with natural vegetation will further increase the retention capacity of a sub-basin.
Urbanisation and agriculture in the Rhine basin have driven loss of water storage capacity in floodplains and marshes and soils of smaller valleys and have caused ecosystem degradation. Changing precipitation patterns due to climate change are expected to lead to increased peak flows as well as critically low water levels. The combination of both developments increase the chance of severe impacts on society. Precipitation falling on the plateaus and slopes in the Middle Rhine region comes down as throughflow (water flowing through the soil) and passes the valley floor before entering the stream. Drained valley floors accelerate this process, i.e. artificial drainage “empties” the hydrological column of entire slope and plateau, contributing to flood peaks in the tributaries to the Rhine.
Developed by Wetlands International
Natural Water Retention through restoration of the ‘sponge’ function of currently drained soils in the middle-mountains of the Rhine basin is a locally applied nature-based solution to flood mitigation with potential impacts at basin scale. We argue that the benefits of the proposed solution are not only local, but will also favour end-users further downstream. This solution fits a systems approach and contributes to achieve water, agriculture and nature policy objectives as well as delivering societal benefits such as recreation and carbon capture.
The main components of the system have been tested separately, and an initial integration exercise has been conducted.
The most suited location for restoring the natural sponge function is at the foot of slopes in U-shaped valleys. Removing drainpipes and ditches would slow down the runoff response of a much larger area than the space needed for the measure itself. Calculations for local catchments in the Mosel basin (the case study area) shows potential for local peak reductions of 5 – 8% in the tributaries to the Rhine, and provide partial evidence for the hypothesis that natural retention can result in substantial reduction of flood peaks. Critical to bridging the gap between our innovative approach and the end-users is to provide more clarification regarding the location and scale of implementation as well as the expected effects of the measure.
Limitations/conditions under which this innovation does not work or is less effective
The method has gradually been developed and elaborated since 2004 in several publications. Our most recent study analyses costs, impacts and stakeholder opinions. We conclude that opinions differ on the scale of impact that can be achieved across the basin. A commonly heard argument is, that just a few restored areas cannot hold the water of a 100-year flood. Many of the questions asked boil down to the following: yes, natural retention works on a local scale and several water authorities apply it to solve local problems – but how many of these projects do we need to have meaningful impact on a river basin scale? Is the required surface area of relatively flat valley floor available and if so, would land users or landowners be willing to allow the removal of drainage and at what cost?
Added value
Our solution is an example of a nature-based measure contributing to water safety for urban areas, water quality and climate change challenges. Our suggested approach of restoration of the sponge function delivers benefits at local and river basin scale and will thus also have impact on downstream urban deltas. One of the great advantages of nature-based solutions (such as Natural Water Retention Measures) is that they provide multiple benefits. The co-benefits alone should provide an incentive to implement the suggested measures. Restoring the natural water retention capacity of currently drained soils will help achieve water, agriculture, and nature policy objectives. The approach will deliver socioeconomic benefits such as recreation, improved water quality, and carbon sequestration. In addition, it contributes to restoration of biodiversity. However, these are potential side-effects of the interventions. The main objective or the main means for reaching flood mitigation is the slowed down hydrologic response of the subbasin. This being said – if removal of drains is combined with development of peatlands, marshland and wetlands, the rough, year-round cover with natural vegetation will further increase the retention capacity of a sub-basin.
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