Unit hydrograph estimation using digital drainage model for applicable Texas watersheds

Surface runoff and streamflow along with groundwater are the components of the hydrologic cycle that are typically of the most interest to water resources engineers. Watershed models are mathematical representations of hydrologic processes which partition precipitation into abstractions and runoff to streams. Such modeling requires the estimation of specific time-response characteristics of watershed. In the absence of observations, these characteristics are estimated from watershed physical characteristics. An exploratory assessment of a particle-tracking approach for parameterizing unit hydrographs from topographic information for applicable Texas watersheds is presented.;Unit hydrographs based entirely on topographic information were generated and used to simulate direct runoff hydrographs from observed rainfall events. These simulated results were compared to observed results to assess method performance. Unit hydrographs were also generated by a conventional analysis (of the observed data) approach to provide additional performance comparison.;Three loss models were selected to produce the effective runoff. They are the fractional loss model (FRAC), the initial abstraction constant loss model (IACL) and the Green-Ampt infiltration loss model (GAIN). The results show that loss models have minor effects on the timing parameters of hydrograph.;The final results demonstrate that the procedure is a reasonable approach to estimate unit hydrograph parameters from a relatively minimal description of watershed properties, in this case elevation and a binary development classification. The method produced unit hydrographs comparable to those determined by conventional analysis and is a useful synthetic hydrograph approach.;The study examined 92 watersheds in Texas, for which rainfall and runoff data were available. Drainage areas ranged from approximately 0.25 to 150 square miles; main channel lengths ranged from approximately 1 to 50 miles; and dimensionless main channel slopes ranged from approximately 0.0002 to 0.02.