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University of Colorado-Denver: "Hydrologic database development techniques: Unit hydrograph procedures"

Final Report

This project is an extension of an earlier Partners Project (S9143) which resulted in a procedure for deriving synthetic unit hydrographs for headwater basins which are located in regions with very low density precipitation gage networks. Typically, the historic precipitation data from these basins are not adequate for standard hydrologic techniques of deriving headwater unit hydrographs; thus the development of synthetic unit hydrographs is required. Synthetic unit hydrograph methods use the physical characteristics of a drainage basin to derive a unit hydrograph, rather than historic rainfall runoff information. The procedure developed in 1991 was based on the Time-Area concept from hydrology which is well-suited for basins in which precipitation data are inadequate. During the 1991 study, Geographical Information System (GIS) software was adapted to perform the extensive geographic and topographic analysis required in the Time-Area technique.

The objectives of this second phase of the project are to: 1) verify the procedure developed in 1991 using data from existing headwater basins, and 2) develop necessary coding so that the final product will interface with standard digitized geographical data sets. The verification task involves developing the synthetic unit hydrograph for selected a headwater basin which has a sufficiently dense precipitation gage network to accurately define both the amount and the temporal distribution of storm rainfall over the basin. The unit hydrograph is used to compute flood hydrographs for selected historic storm events which can then be compared with the measured flood hydrographs for the same events. The second objective involves researching sources of digitized geographic/topographic information to obtain interfacing requirements.