Frequently Asked Questions (FAQ)

We are doing hydrology study for an area in the City of Santa clarita, LA county. Does the county prefer to use a specific method, such as Rainfall-runoff method (HEC-1/HEC-HMS)and Modified Rational Method, over others. Also where can I get a software for Modified Rational Method (MORA)?

Thank you

Los Angeles County requires that hydrologic studies reviewed by the County must be completed using the Modified Rational hydrology method. This method is described in the 2006 Hydrology Manual which is available on-line at the following link:

The MORA program is no longer supported for Modified Rational hydrology studies. Several approved software packages that include the Modified Rational method are available. They are listed below with the vendor and webpage addresses:

Watershed Modeling System (WMS)

XPSWMM or XPSTORM ver. 9.0 and above
XPWSPG2011 and above

CivilDesign Corp.

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