County Hydrology, Regional Approach

by Abdullah D. Saah, Santa Clara Valley Water District, San Jose, United States,

Document Type: Proceeding Paper

Part of: Engineering Hydrology


The effort to update the regional hydrology methods of the Santa Clara Valley Water District (District) entails a series of tasks that are long and difficult. This paper enumerates the tasks and provides a quick look at the problems and the progress that has been achieved towards finding solutions. The hydrology methods cover all types of watersheds, small, large, urban, rural, gaged, ungaged, regulated and unregulated. This is done to provide consistent design flow values for storm drains and major flood control facilities, for small detention ponds as well as major multipurpose reservoirs. The first part of this paper addresses project management, funding, the difficulties encountered, and the back-up plans. The second part of the paper addresses the gathering and qualification of basic hydrological raw data, the extraction of maximum annuals from that data, and the development of mathematical and statistical tools for the analysis of the resulting time series. In addition, the paper addresses the use of HEC-1 to develop hydrographs from rural and urban areas. For urban areas, an extra effort was made to develop an urban hydrology technique. This technique is used to evaluate the impact of increased imperviousness and channelization, due to various types of land uses, on the hydrologic responses of watersheds. Lastly, this paper addresses the design criteria for detention ponds and their use as multipurpose facilities for flood and non-point source (NPS) pollution control.

Subject Headings: Hydrology | Watersheds | Rural areas | Building design | Hydraulic design | Floods | Detention basins | Soil pollution

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