1. Create flood damage extent
The InfoSWMM Risk Assessment Manager is organized by risk assessment tasks. The risk assessment drop-down menu contains four commands. Each of these commands opens a new dialog box for further input. The following sections describe the functionality for each of these commands. Generally, these commands should be used in the order described below.
A flood damage extent map shows areas subject to flooding at the current simulation time of the network model. The current simulation time is shown on the InfoSWMM Output Toolbar, and it can be adjusted using the date and time drop-down selectors or the slider-bar.
InfoSWMM calculates a flood flow for each node where the hydraulic depth is greater than the sum of the invert elevation, the maximum depth and the surcharge depth, provided the simulation does not model ponding. With ponding, the total flood volume is assumed to be contained in the ponded area where it will safely reenter the storm drainage system.
The flood damage extent only utilizes nodes that have a flood flow greater than zero to compute the flood surface. For these points, the hydraulic grade line (HGL) is interpolated between flooded nodes according to an inverse distance weighting scheme. The result of this interpolation is a flood elevation which may or may not rise above the ground surface as defined by the elevation raster layer. Any parts of the flood elevation above the surface elevation are flooded, and any below are dry.