In HEC-FIA, a watershed configuration describes a modeled physical state of the watershed. The modeled physical state can represent a without project condition or a modeled alternative state. The elements used to describe the physical state of the watershed are listed below:
- terrain grids
- reservoirs
- stream alignment
- cross sections set
- storage areas (with or without corps projects or leveed areas)
- common computation point (CCPs) set (standard or with holdout distribution areas)
These model elements are used to represent a state of the watershed being modeled. Not all of the elements are required for HEC-FIA to compute hydraulic information at a location, but there are minimum requirements dependent upon the desired methodology selected to evaluate hydraulic information at a location.
- When providing all gridded data for evaluating hydraulic information at point locations; all that is required for the watershed configuration is a terrain grid.
- When gridded depths are provided but cross sections are being used for arrival times, the watershed configuration needs to include terrain data, and a cross section set.
- When data is provided as hydrographs at cross sections, the watershed configuration needs terrain and a set of cross sections.
- When hydrographs are provided at common computation points, the watershed configuration requires a stream alignment, a terrain, and a set of common computations points.
- When the Flood Damages Reduced compute option is used, the watershed configuration needs to include terrain data, a stream alignment, and a flood reduction project: either levees (designated storage area elements) or reservoirs. If reservoirs are included, then a reservoir set and CCPs with holdout distribution areas must also be included in the watershed configuration.