This guide is designed to help you retrofit and apply existing CWMS watersheds to compute AFDR. It begins by introducing two primary approaches for using CWMS in combination with HEC-FIA (Flood Impact Analysis software) to calculate AFDR, and provides criteria for selecting the most suitable method based on your watershed’s characteristics. The guide then walks through how to set up CWMS watersheds and their component models to support AFDR computations across a variety of scenarios, addressing both typical and more complex situations that may arise during analysis.
Assumptions
This document assumes the CWMS models you are using were developed following the Mapping, Modeling, and Consequence (MMC) Production Center's guidance, and that each model is capable of accurately simulating flood events across a range of durations and magnitudes. That said, calculating AFDR introduces certain model-specific challenges that may not have been considered during the original model development process. This guide highlights those issues and offers practical solutions to ensure your models produce reliable and defensible AFDR results.