Prediction of River Meandering and Habitat Formation
* Can state-of-the-art methods to predict bank erosion and channel migration be used to inform Reclamation descisions on river management and water operations?
* Can we increase the amount of available riprian habitat on rivers affected by Reclamation operations?
* Can we predict future sites of bank erosion along rivers affected by Reclamation operations?
* Can we predict the channel migration zone for restoration projects?
Need and Benefit
There is a critical need for Reclamation to understand and predict bank erosion and river meandering processes, because these processes directly affect Reclamation operations and maintenance.
Commonly applied one-dimensional (1D) models are insufficient to model the bank erosion or meandering process because they cannot resolve the complicated flow field that occurs in meandering rivers. There has been some work to develop methods specifically to model river meandering (Johannesson and Parker 1989, Howard 1995, Randle 2004), but the methods have not been formalized into tools generally applicable to a variety of rivers. There also has been some development of multi-dimensional models that simulate bank erosion and or point bar growth (Nelson and Smith 1989, Duan et al. 2001), but these models are in the research stage and have not been applied beyond the domain of the researcher who developed them.
There are several projects in several different Reclamation regions where bank erosion, river meandering, and/or habitat development directly affect Reclamation operations and maintenance. A few of the major examples are listed below. All of the projects listed here are current projects in which the project team members are directly involved. These tools developed in this research project will be immediately applied to these projects.
On the Sacramento River, the North-of-Delta-Offstream-Storage (NODOS) project, facilitated by Reclamation, is considering methods to modify reservoir operations of Shasta Dam on the Sacramento River to benefit the ecosystem. One of the primary needs for a healthy riparian ecosystem is natural river meandering that creates new habitat along the riparian corridor. Larsen (1995, 2002) has already applied analytical methods to predict bank erosion along the Sacramento and he will be directly involved with this work. We will seek to build upon his previous work to improve and generalize these methods so that Reclamation can apply it to other rivers as well.
The Rio Grande is eroding banks near levees or other infrastructure at many locations. A tool is needed that will predict the future locations of bank erosion problems. Currently, a simple extrapolation of current bank erosion rates is done, but this method ignores the dynamic nature of bank erosion and channel migration. A method based on the physics of flow and bank erosion is needed to accurately predict locations of bank erosion.
The Trinity River Restoration Project is modifying flow releases from Lewiston and Trinity River Dams partly to increase the development of point bars along the Trinity River. The critical factors to point bar development are ensuring adequate sediment supply and bank erosion. A predictive tool of bank erosion and point bar growth is necessary to plan flow releases.
The Yakima River has been affected by gravel mining in its floodplain. Many of these abandoned gravel pits are now protected by levees that constrict the natural flow in the river and prevent natural river meandering--resulting in a degraded fish habitat. Removing some of the levees and allowing the river to resume its natural dynamic adjustments would improve fish habitat. However, when the river recaptures gravel pits, it could have large impacts on the sediment dynamics of the river. No currently available tools adequately model this process.
Reclamation is working for the U.S. Army Corps of Engineers (Corps), Los Angeles District to perform the hydraulic and sedimentation analysis for the Matilija Dam Ecosystem Restoration project. The preferred alternative calls for the removal of Matilija Dam and the creation of a channel through the reservoir sediments. The primary mechanism for sediment erosion will be bank erosion and slope failure. Multi-million dollar flood protection and diversion structures are being designed based upon the predicted rates of bank erosion and slope failure. Therefore, we must accurately predict these proce
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Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Description of Meandering model (final, PDF,
By Blair Greimann and Victor Huang
Report completed on May 30, 2014
model that simulates the bed topography, flow field, and bank erosion rate in a curved channel with an erodible bed. In each time step, SRH-M first calculates the flow field based on the standard step method or normal depth method. It then computes the channel bank erosion rate. Finally the channel alignment is updated with the erosion rate, followed by a channel cutoff if needed.