Modeling Riparian Vegetation and Effects On Hydraulics and Sediment Transport In Support of River Restoration and Management

Predicting the effects of riparian vegetation on hydraulics and sediment transport within managed riverine systems is a growing challenge due to the increasing priority of maintaining ecosystem function while sustaining water conveyance. A modeling suite has been developed by the Bureau of Reclamation for simulating vegetation lifecycle and the effects on hydraulics and sediment transport in the riparian environment. The models are based upon the SRH-2D package (Lai, 2010), which contains a two-dimensional flow and mobile bed sediment transport model. The capabilities of the modeling suite are comprised of two distinct components: • A vegetation-hydraulic solver that uses measured vegetation parameters and calculated hydraulic variables to estimate a spatially-distributed, dynamic roughness coefficient that is coupled to the simulated hydrodynamics through the bed shear stress. • A cumulative stress lifecycle algorithm that predicts the establishment, growth, and removal of riparian vegetation based on measured parameters and calculated hydraulic variables. The components of the riparian vegetation modeling suite have been developed and enhanced through a series of individually funded projects, the utility of which have been demonstrated at the project level. Here we provide a background of development for the modeling framework, a review of literature on the topic, and the theory upon which the algorithms are developed. We provide conceptual guidance on how the modeling tools may be effectively applied and review common questions associated with challenges in managing water and riparian corridors in the West. References to application of the modeling suite are provided, drawn from Bureau of Reclamation case studies. The model components are in active development; testing, validation, and refinement of the riparian vegetation modeling suite is needed to improve the usability, workflow, and accuracy of the simulations. The model development has leveraged in-kind support through mutually-beneficial collaborations with other agencies and institutions, including the U.S. Army Corps of Engineers, Massachusetts Institute of Technology, and University of New Mexico.