Comparison of One- and Two-Dimensional Hydraulic Habitat Models for Simulation of Trout Stream Habitat

Abstract

In the 1990's, the number of brown trout (Salmo trutta) in Rapid Creek (within the city limits of Rapid City) have declined and the South Dakota Department of Game Fish and Parks initiated a study to identify potential limiting factors that affect the Rapid Creek Fishery. One component of the study is characterization and analyses of the hydraulic habitat. Historically, instream habitat characterization has been done using one-dimensional hydraulic analysis. One of the most common one-dimensional techniques is the Physical Habitat Simulation System (PHABSIM). PHABSIM uses the methodology known as the Instream Flow Incremental Methodology (IFIM) and is one of the most widely used tools for assessing flow management practice. IFIM was designed for analysis of alternative management practices, and includes a framework for the decision-making process as well as techniques for quantifying instream habitat at different flow regimes. Recently, two-dimensional models (RIVER 2D and SMS) have been developed for detailed hydraulic analysis of spatially explicit habitat units at the microhabitat scale. River 2D was chosen for this project because of the ease with which the model reaches a steady-state solution without compromising accuracy. River 2D also contains a fish habitat module based on the IFIM and provides for a direct comparison between one- and two-dimensional models.