Comparison of models to mitigate flood hazard to transportation alignments on alluvial fans

Julianne Joy Miller, University of Nevada, Las Vegas


Many investigators have suggested that available one- and two-dimensional, deterministic models may provide better discharge estimates for alluvial fan flood mitigation studies than the one-dimensional, stochastic Federal Emergency Management Agency (FEMA) model; A modified version of the one-dimensional, stochastic FEMA model (French, 1992), and the one- and two-dimensional, deterministic models, DAMBRK (Fread, 1984) and FLO-2D (O'Brien, 1995), respectively, are used to estimate peak discharges at railroad alignments crossing three alluvial fans in southern Nevada. Risk analyses calculate exceedance probabilities. Results are compared with railroad maintenance records documenting damage to these alignments; All three models generally predict peak discharges that are larger than the railroad maintenance records indicate have occurred; however, the two deterministic models yield more conservative results than the stochastic model. A combination of results from the modified-FEMA and the FLO-2D models may provide a cost-effective method for estimating design peak discharges for transportation alignments crossing alluvial fans.