SedVeg-Gen3 Platte River Model: A Sediment Transport and Riparian Vegetation Model

The plan and cross-section form of the central Platte River, and the presence or absence of vegetation, are important factors affecting habitat suitability for three threatened and endangered bird species that use the central Platte River: the Whooping Crane, Interior Least Tern and Great Plains Piping Plover. To understand the changes in river form resulting from modified flows, altered sediment transport, and more ubiquitous vegetation, the Bureau of Reclamation developed a one-dimensional numerical sediment transport model with vegetation subroutines written by Simons & Associates. A description of hydraulic, sediment transport, and vegetation computations are included here, in addition to descriptions of model input and output data. Information from the vegetation growth and removal routines continually adjusts the channel resistance values for the hydraulic and sediment transport computations. Vegetation information is also used to track the quality of habitat for the target species. Illustrative results from the SedVeg-Gen3 Platte River Model are presented. The Platte River model has 62 cross sections representing 80 miles of river beginning downstream of Lexington, Nebraska and ending at Chapman, Nebraska. Model runs simulated 61 years in daily time steps. The SedVeg-Gen3 model was used to optimize the proposed sediment and mechanical management actions, and to aid in the comparison of alternatives for the Platte River Recovery Implementation Program, Final Environmental Impact Statement (DOI, 2006).