Communities are provided flood hazard maps for managing development. Engineering models are used to generate the flood elevations used to develop the mapping. Historically, the engineering models used to develop the flood elevations were one dimensional – since the data inputs were slices (cross sections) along stream corridors. More recent engineering models are two-dimensional – in that the data inputs are grids that cover the entire surface area being mapping. 2D modeling has various levels, and the data developed at each of the levels is useful for community management of development.
Communities are routinely provided these data, from 1D and 2D models, including information on floodways, without clearly understanding the impacts or how to utilize all the data available to them. FEMA has funded ASFPM to develop outreach materials related to floodways and 2D modeling to help communities understand the floodway and how to use 2D modeling data to better managing development.
Link to 2D Modeling Guidance