BRI-STARS (Bridge Stream Tube Model for Alluvial River Simulation)

This NCHRP digest describes the BRIdge Stream Tube model for Alluvial River Simulation (BRI-STARS), Version 3.3, an innovative, operational computer program developed for NCHRP Project 15-11, Computer-aided Analysis of Highway Encroachments on Mobile Boundary Streams. It is a semi-two-dimensional model capable of computing alluvial scour/ deposition through subcritical, supercritical, and a combination of both flow conditions involving hydraulic jumps. This model, unlike conventional water and sediment routing computer models, is capable of simulating channel widening/narrowing phenomenon as well as local scour due to highway encroachments. It couples a fixed-width stream tube computer model, which simulates the scour/deposition process taking place in the vertical direction across the channel, with a total stream power minimization algorithm. The decision making algorithm, using rate of energy dissipation or total stream power minimization, determines whether the simulated sediment erosion satisfying the sediment continuity equation should take place in the lateral or vertical direction. It is this second component that allows the lateral changes in channel geometries. Finally, the bridge component allows computation of the hydraulic flow variables and the resulting scour due to highway encroachments. The model also contains a rule- based expert system program for classifying streams by size, bed and bank material stability, platform geometry, and other hydraulic and morphological features.