2012 Annual Report
1a.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.
1b.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.