Floodplain Mapping Using Continuous Hydrologic and Hydraulic Simulation Models

Abstract

A new approach for estimating floodplain limits using continuous-simulation modeling is proposed. A hydraulic model with flood-routing capabilities is coupled with a continuous-simulation hydrologic model to compute river stages. Simulations are made using historical precipitation data to produce long, continuous flow records. Simulations are also made using precipitation data for extreme storms to gain additional information on overbank flooding. A new statistical approach is then directly applied to the simulated peak stages to estimate peak stage exceedence probabilities. To illustrate the benefits of this approach, floodplain limits for an Illinois stream are estimated with the new method and compared to estimates based on a design storm approach and conventional frequency analysis applied to the peak stages.