This project is funded by TKI Deltatechnology UTW01
Insights into the morphological changes in rivers with and without river interventions.
The management of rivers requires the consideration of river functions such as flood conveyance, ecology, and navigation. River interventions, such as side channels and longitudinal dams, are constructed to benefit mainly one of these functions and should have minimal effects on the other functions of the river. For example, side channels are constructed to increase the ecological value of the river but side channels generally cause aggradation in the navigation channel and thereby affect the navigational function of the river. Better insight into the bed level changes that result from such interventions can help to improve their design such that the effect on conflicting river functions is mitigated.
Key goals: Fundamental understanding Integrated management
Several analytical and numerical models exist that can be used to estimate the river bed level changes as a result of interventions (top left side of the figure). However, field measurements of such development are rare. We use a large dataset to estimate the development of several types of interventions and characterize their bed level variation (top right side of the figure). We apply a method that can distinguish bed level changes that occur at different spatial scales. This allows us to identify the contribution of the interventions to the local bed changes. Second, we study the morphological variation of the river without interventions. This variation occurs as a function of the river’s geometry in combination with the discharge. Combining the morphological effect of the interventions with the morphological variation of the river can result in a more optimized design of river interventions. For example, a side channel locally increases the equilibrium bed level and local narrowing of the floodplain reduces the equilibrium bed level (bottom of the figure). If the side channel is constructed at the correct location, the bed level changes counteract each other.
For whom and where?
- Managers who need to design new river interventions and need to gain insight into the morphological behavior of their river
- Practitioners that want to optimize the design of river interventions.
Data-collection methods: Field survey measurements Historical approach
Temporal scale: 1-10years
Application development and findings
We derive several maps that indicate the bed level changes along the river as a function of the discharge. These maps can be used to characterize the bed level changes in the river and to evaluate suitable interventions. The location of the intervention can be chosen such that the resulting bed level changes are enhanced or mitigated. The proposed method is therefore relevant for both river interventions that should have minimal impact on the navigational function river and river interventions that need to reduce the degradation rate of a river.
Based on our results we propose changes to the current way of planning and designing river interventions. We apply our method to the Rhine branches, but it is generally applicable to other rivers. Taking into the seasonality of the bed level support planning and designing river interventions in multi-functional rivers.
Status for day-to-day practice
We developed a method to extract bed level changes that occur at different length scales. Using this method we can relate bed level changes with their causes. We are currently analyzing the bed level changes that occur at a range of discharges.
Spatial scale: Channel Reach
Key locations: Netherlands (NL) Rhine River (NL)
We link the observed bed level changes with bottlenecks in the river and give suggestions for new locations of river interventions.
Last updated: 04/02/2020
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Pepijn van Denderen
University of Twente
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Morphological evaluation of river interventions: progress reports
The management of multifunctional rivers requires the consideration of river functions such as flood conveyance, ecology, and navigation. River interventions are constructed to benefit these functions but these interventions should have minimal effects on the other functions of the river. Better insight into the morphological changes that result from such interventions can aid to optimize their design and improve the sediment management of the river.
11/02/2020 by Pepijn van Denderen
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