The Maas (The Meuse River) requires navigable conditions and flood safety while improving ecological conditions with natural banks (note at both sides). (Source: Gonzalo Duró)
Insights on riverbank erosion of restored reaches: survey techniques, drivers, prediction and role of vegetation.
The management of multifunctional rivers requires the consideration of factors such as flood conveyance, ecology and navigation. This functions may conflict with each other, for which a holistic approach to compromise among interests becomes necessary. The restoration of riverbanks is implemented to improve riparian habitats but a deep understanding of the impacts to other uses is crucial to achieve a sustainable river system. This research provides insights on the erosion dynamics of restored banks to find a balance among all river functions.
Key goals: Fundamental understanding Innovative monitoring
Sequential surveys at eroding bank in the Meuse River over 2017, showing profiles and eroded volumes per event and cumulative series. (Source: Duró et al., 2018)
We apply structure from motion photogrammetry with an aerial unmanned vehicle (drone) to survey complex riverbanks along a mid-sized river reach. We evaluate the method’s precision to measure bank erosion processes and perform systematic campaigns along two years. Second, we investigate the factors that determine distinct bank erosion patterns, for which we measure and analyze the subaqueous bank topography thanks to a unique opportunity provided by a ship accident. Third, we study the morphological evolution of restored banks in navigable regulated rivers to characterize the mechanisms of erosion and test current modelling approaches.
For whom and where?
- Managers who need insights on where and how to restore banks along lowland rivers.
- Practitioners that want to know how well current models predict bank erosion in waterways.
Data-collection methods: Field survey measurements Remote sensing
Temporal scale: Seasonal measurements Yearly measurements
Application development and findings
Low-cost drones can be used to survey riverbank erosion with resolution and precision comparable to laser methods, covering long distances in relative short times. A single path along the bank with eight photo overlaps is sufficient to reach the highest precision. A RTK-GPS is used to reference to global coordinates the digital surface model and correct for non-linear distortions. This method is applicable to streams and rivers with high bank and distances up to 3 kilometers.
Field measurements, which include these topographic campaigns, explain the irregular erosion rates along short distances in the Meuse River. These patterns are caused by the former river migration which deposited sediments of varying compositions. Tree locally delay erosion rates but their fate is highly controlled by the substrate composition at regulated water levels. These results imply that floodplain heterogeneity and vegetation strongly determine bank erosion patterns, especially in rivers with regulated stages and navigation.
Status for day-to-day practice
The case studies in the Meuse River serve as benchmarks to design and understand how riverbanks respond to restoration. The consideration of the key elements that define the morphological response of riverbanks may help to define future projects dealing with natural banks in waterways.
Spatial scale: River section
Key locations: Maas River (NL) Rhine River (NL)
The next logical step is to improve current models for predictive purposes based on the new knowledge.
Last modified: 19/06/2019
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Delft University of Technology
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