Progress 10/01/12 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): The objective of this cooperative research is to develop computer model components, which can be coupled to CONCEPTS, for predicting the onset and continual development of river meandering. Approach (from AD-416): A linear model of the flow in the interior of sinous streams will be enhanced to include: (1) the near-bank domain, (2) transport of graded sediments, and (3) the formation of alternate bars and point bars including simulation of changes in transverse bed profile. The stresses exerted by the flow on the streambank as simulated by the above model will be used by the process-based streambank erosion algorithms of the channel evolution model CONCEPTS to predict streambank erosion and to adjust bank profiles. The predictive capabilities of the resulting model regarding hydraulics, non-uniform sediment transport, streambank erosion, and channel migration will be validated on selected laboratory experiments, field data of single bends of sand- and gravel-bed streams, and selected multiple-bend streams segments of Tahoe Basin streams. In FY 13 we completed: (1) the development of a submodel that explicitly accounts for failed bank material in bank erosion calculations; and (2) theoretical analyses with the model to study the effects of vertical heterogeneity of floodplain soils on meander migration rates and planform shapes. Substantial results were realized over the five years of the project. A new model, RVR Meander/CONCEPTS, was developed to both assess the planform evolution of existing meandering streams and design the planform of remeandered streams. The model combines the bank erosion algorithms of the USDA-ARS channel evolution computer model CONCEPTS with the lateral migration module of the RVR Meander toolbox developed by the University of Illinois. To improve the ease of evaluating meander planforms of rivers, an interface for the Geographic Information System (GIS) platform ArcGIS versions 9.3.x and 10.x was developed. The user can digitize channel centerlines and enter model input parameters through various menus. Tools were developed to preprocess and smooth digitized centerlines. Further, features were developed to visualize floodplain soil distributions and meander flow parameters. The new meander migration model is unique as it calculates migration rates based on measurable, resistance-to-erosion properties of floodplain and bank soils. Extensive testing of the new model for idealized river geometries and for the Mackinaw River, IL, showed that the new model more realistically predicts complex planform patterns observed in nature than the standard empirical migration methods based on calibrated migration coefficients in use today. Further, it was found that floodplain-soil complexity can greatly contribute to planform complexity of meandering rivers. The simulations performed allowed for highlighting three key parameters that characterize the effect of floodplain heterogeneity on channel planform complexity, respectively: the local randomness of soil resistance, the cross-valley increase of soil resistance, and the spatial scale of soil heterogeneity. To understand the effects of vertical floodplain soil heterogeneity on meander migration rates and patterns, computational studies of identifying the effects of bank collapse on long-term migration rates were conducted. A submodel was developed that explicitly accounts for failed bank material in bank erosion calculations. Cantilever failures, which occur continuously during migration, have an important impact on migration rates and on meander shapes. In particular, bend length and bend skewness can be modified, even with possible achievement of downstream skewness. Though planar failures are more episodic than cantilever failures, they still significantly affect meander migration rate, which depends on the planform-induced topography of the river, and can cause preferential directions of meander migration.
Impacts
(N/A)
Publications
|
Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): The objective of this cooperative research is to develop computer model components, which can be coupled to CONCEPTS, for predicting the onset and continual development of river meandering. Approach (from AD-416): A linear model of the flow in the interior of sinous streams will be enhanced to include: (1) the near-bank domain, (2) transport of graded sediments, and (3) the formation of alternate bars and point bars including simulation of changes in transverse bed profile. The stresses exerted by the flow on the streambank as simulated by the above model will be used by the process-based streambank erosion algorithms of the channel evolution model CONCEPTS to predict streambank erosion and to adjust bank profiles. The predictive capabilities of the resulting model regarding hydraulics, non-uniform sediment transport, streambank erosion, and channel migration will be validated on selected laboratory experiments, field data of single bends of sand- and gravel-bed streams, and selected multiple-bend streams segments of Tahoe Basin streams. We examined the robustness of the computer algorithms that handle the assignment of multi-layer bank materials to channel cross sections that have to be redistributed during channel migration when meander bends are elongating. Computer code was developed to cutoff meander bends when the channel sections at each end of the bend are immediately adjacent. To improve the ease of evaluating meander platforms of rivers, we developed an interface for the geographic information system (GIS) platform ArcGIS versions 9.3.x and 10. The user can digitize channel centerlines and enter model input parameters through various menus. Tools were developed to preprocess and smooth digitized centerlines. Further, features were developed to visualize floodplain soil distributions and meander flow parameters. To understand the effects of horizontal and vertical floodplain soil heterogeneity on meander migration rates and patterns, we completed computational studies of identifying the effects of bank collapse on long- term migration rates. We made progress on developing a model that will explicitly account for failed bank material in sediment transport calculations by improving the flow hydrodynamics through the inclusion of a secondary flow correction.
Impacts
(N/A)
Publications
|
Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) The objective of this cooperative research is to develop computer model components, which can be coupled to CONCEPTS, for predicting the onset and continual development of river meandering. Approach (from AD-416) A linear model of the flow in the interior of sinous streams will be enhanced to include: (1) the near-bank domain, (2) transport of graded sediments, and (3) the formation of alternate bars and point bars including simulation of changes in transverse bed profile. The stresses exerted by the flow on the streambank as simulated by the above model will be used by the process-based streambank erosion algorithms of the channel evolution model CONCEPTS to predict streambank erosion and to adjust bank profiles. The predictive capabilities of the resulting model regarding hydraulics, non-uniform sediment transport, streambank erosion, and channel migration will be validated on selected laboratory experiments, field data of single bends of sand- and gravel-bed streams, and selected multiple-bend streams segments of Tahoe Basin streams. Components were developed to enable the ARS channel evolution computer model CONCEPTS to simulate lateral channel migration using technology from the RVR-MEANDER toolbox developed by the University of Illinois. Extensive testing of the new model for idealized river geometries and for the Mackinaw River, IL, shows that the new model more realistically predicts complex planform patterns observed in nature than the standard empirical migration methods based on calibrated migration coefficients in use today. Further, it was found that floodplain-soil complexity can greatly contribute to planform complexity of meandering rivers. The simulations performed allowed for highlighting three key parameters that characterize the effect of floodplain heterogeneity on channel planform complexity, respectively quantifying the local randomness of soil resistance, the cross-valley increase of soil resistance, and the spatial scale of soil heterogeneity. This project was monitored by meetings, phone and e-mail communications between the ADODR and principal investigator.
Impacts
(N/A)
Publications
|
Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) The objective of this cooperative research is to develop computer model components, which can be coupled to CONCEPTS, for predicting the onset and continual development of river meandering. Approach (from AD-416) A linear model of the flow in the interior of sinous streams will be enhanced to include: (1) the near-bank domain, (2) transport of graded sediments, and (3) the formation of alternate bars and point bars including simulation of changes in transverse bed profile. The stresses exerted by the flow on the streambank as simulated by the above model will be used by the process-based streambank erosion algorithms of the channel evolution model CONCEPTS to predict streambank erosion and to adjust bank profiles. The predictive capabilities of the resulting model regarding hydraulics, non-uniform sediment transport, streambank erosion, and channel migration will be validated on selected laboratory experiments, field data of single bends of sand- and gravel-bed streams, and selected multiple-bend streams segments of Tahoe Basin streams. Components will be developed to enable the ARS channel evolution computer model CONCEPTS to simulate lateral channel migration. The lateral migration module of the RVR-MEANDER toolbox developed by the University of Illinois has been combined with the streambank erosion components of CONCEPTS. New modules were developed to update the schematization of the model to accurately capture a river�s evolving planform. Extensive testing of the new model for idealized river geometries and for the Mackinaw River, IL, shows that the new model more realistically predicts complex planform patterns observed in nature than the standard empirical migration methods based on calibrated migration coefficients in use today. The SCA was monitored by meetings, phone and e-mail communications between the ADODR and principle investigator.
Impacts
(N/A)
Publications
|
Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) The objective of this cooperative research is to develop computer model components, which can be coupled to CONCEPTS, for predicting the onset and continual development of river meandering. Approach (from AD-416) A linear model of the flow in the interior of sinous streams will be enhanced to include: (1) the near-bank domain, (2) transport of graded sediments, and (3) the formation of alternate bars and point bars including simulation of changes in transverse bed profile. The stresses exerted by the flow on the streambank as simulated by the above model will be used by the process-based streambank erosion algorithms of the channel evolution model CONCEPTS to predict streambank erosion and to adjust bank profiles. The predictive capabilities of the resulting model regarding hydraulics, non-uniform sediment transport, streambank erosion, and channel migration will be validated on selected laboratory experiments, field data of single bends of sand- and gravel-bed streams, and selected multiple-bend streams segments of Tahoe Basin streams. Significant Activities that Support Special Target Populations Components will be developed to enable the ARS channel evolution computer model CONCEPTS to simulate lateral channel migration. The lateral migration module of the RVR-MEANDER toolbox developed by the University of Illinois has been combined with the streambank erosion component of CONCEPTS. Initial tests of the model were conducted using data from Trout Creek in the Tahoe Basin, California. Monitoring activities were performed through quarterly progress reports with the cooperators and semi-annual site visits.
Impacts
(N/A)
Publications
|
|