Hydrology and Hydraulics Model

The Ventura County Watershed Protection District developed a complete watershed model of the Calleguas Creek system, including Revolon Slough, using the Modified Rational Method. Sub-watersheds were carefully digitized; imperviousness compared to latest aerial photos, and routing reaches measured from Rocky Peak to Mugu Lagoon. The majority of the sub-areas are less than 100 acres, but in some rural areas, larger sub-areas seemed appropriate. For each sub area, the input has these parameters: area in acres, time of concentration in minutes, percent effective imperviousness, hydrologic soil type, and rainfall zone with storm frequency.

The model produces a 200-point hydrograph for each sub-area, which it adds to the next area downstream. In this way it accounts for changes in Times of Concentration between sub areas. Channel storage from routing point to routing point also is accounted for, treating each reach as if it were a reservoir. Timing at junctions between two laterals or the main channel and a lateral can be requested to help in doing hydraulic analysis.

In March of 2003, the Ventura County Watershed Protection District completed an assessment of Present Conditions utilizing this model. In April 2005, they completed a assessment of Future Conditions with Projects implemented.