WMS:MODRAT (Q&A)
Q: Is time concentration (tc) data built in to WMS or would a user have to read in their own tc data from a file?
A: Time concentration data is built in to WMS, but a user could develop tc data outside of WMS and enter it directly into the interface. There are essentially two ways of computing tc in WMS. One is based on general basin parameters and the other is based on tc arcs. The MODRAT Tc wizard uses tc arcs. There is a regression equation that requires some input parameters like length, slope, soil number, and rainfall depth that is used to automatically compute the tc. There are some other general equations used for developing tc, but LA County uses just one equation, which requires a few parameters. You can look at them by double-clicking on a tc arc and selecting the LACDPW Regression equation.
