Enhancement of the Channel Evolution Model Concepts for Predicting Water Quality Benefits of Rretention of Riverine Sediments by Floodplains
Watershed Physical Processes Research Unit
2012 Annual Report
1a.Objectives (from AD-416):
Develop an algorithm to link the channel evolution computer model CONCEPTS to two-dimensional flow and sediment transport models of overbank flow that allows for improved prediction of sediment exchange between stream and floodplain; and.
2)Evaluate the resulting modeling system for selected streams in the Piedmont or Coastal Plain Physiographic Provinces and the Lake Tahoe Basin.
1b.Approach (from AD-416):
An improved modeling system for inbank and overbank sediment transport will be developed by coupling the one-dimensional (1D) ARS channel evolution model CONCEPTS to a two-dimensional (2D) model of flow and sediment transport. The two-dimensional model will be stacked on top of the one-dimensional model. Formulations will be developed that relate the vertical flux of water and sediment particles between 1D and 2D models as a function of flow and sediment concentration in the inbank and overbank sections of the stream channel. The enhanced modeling system will be utilized to evaluate the water quality benefits of water-retention measures on floodplains.
We completed the comparison of various two-dimensional (2D) computer models of river morphology to be coupled with the one-dimensional (1D) channel evolution computer model CONCEPTS. We selected the TELEMAC2D model because: (a) it uses a flexible mesh structure that can accurately represent diverse channel and floodplain topographies; (b) it uses a similar method to advance the solution in time as CONCEPTS; (c) it is coded in the same programming language (Fortran) as CONCEPTS; and (d) it is widely used and supported. We completed the derivation of the mass and momentum fluxes required to couple the 1D and 2D models.