Frequently Asked Questions (FAQ)

Question:
I am designing a private stormwater network for the Los Angeles City College (LACC) and I am in need for the corresponding undeveloped runoff coefficient (Cu) in order to determine the actual runoff coefficient to use in the calculation of the runoff flow (using the rational method). But the determination of Cu depends upon the relevant soil type and there is a table in Appendix D of your Hydrology/Sedimentation Appendix, that lists these soil types. My problem is that the names of these soils are not generic but relate to specific places such as Altamont Clay Loam, Chino Silt Loam and others. Do you have a map including the above-mentioned College area, and which gives the relevant soil type as listed in the table mentioned above?

I would highly appreciate your answer

Regards

Amine



ANSWER:
Our Hydrology Manual, which is available online at the link below, contains maps that show the 50-year rainfall depth, the soil type number, and the debris production area classifications. An index map using the USGS quadrangle maps allows users to select the quadrangle map which includes the area of interest. The soil number that relates to the area of interest (LACC in your case) can then be used to look up the correct runoff coefficient relationship.

Links:
  DPW Hydrology Manual
WRD SWE hydrology sedimentation hydraulic hydrological wells groundwater rainfall conservation depth precipitation alert gauges stormwater engineering