# Browsing by Subject "hydrograph"

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Item Application of an electronic analog computer to the evaluation of the effects of urbanization on the runoff characteristics of small watersheds(1968) Narayana, V.V.D.; Riley, J.P.Show more In the synthesis of hydrograph characteristics of small urban watersheds, the distribution of the water among the various phases of the runoff process is attempted by the concept of "Equivalent Rural Watershed". The criteria for transforming the urban watershed into an equivalent rural watershed requires that, for a given input into both the models (urban and its equivalent rural watershed), the outputs must be identical. The hydrograph of outflow from an urban watershed is obtained by chronologically deducting the losses due to interception, infiltration and depression storage from precipitation on the equivalent rural watershed and then routing it through the surface and channel storages. This procedure of computing the synthetic outflow hydrograph is accomplished with the analog computer at the Utah Water Research Laboratory, Utah State University at Logan. Testing and verification is done with rainfall and runoff data from the Waller Creek watershed at Austin, Texas. In the verification process, coefficients representing interception, depression storage, and infiltration are determined by trial and error so that the simulated hydrograph is nearly identical to the measured hydrograph of the prototype. The variation in the values of these coefficients from year to year is assumed to be due to the corresponding variations in the characteristics of urbanization defined by the percentage impervious cover and the characteristic impervious length (ratio of the mean length of travel between the center of the impervious area and the discharge measuring point to the maximum length of travel on the watershed). This study attempted to develop the relation between these coefficients and the urbanization parameters.Show more Item Geographic Information Systems (GIS)-based spatially distributed model for runoff routing(American Geophysical Union, 1999) Olivera, Francisco; Maidment, DavidShow more A method is proposed for routing spatially distributed excess precipitation over a watershed to produce runoff at its outlet. The land surface is represented by a (raster) digital elevation model from which the stream network is derived. A routing response function is defined for each digital elevation model cell so that water movement from cell to cell can be convolved to give a response function along a flow path and responses from all cells can be summed to give the outlet hydrograph. An example application of analysis of runoff on Waller Creek in Austin, Texas, is presented.Show more Item Hydrograph Synthesis for Watershed Subzones from Measured Urban Parameters(Utah Water Research Laboratory, 1970) Evelyn, Joseph B.; Narayana, V.V. Dhruva; Riley, J. Paul; Israelsen, Eugene K.Show more An analog computer program was developed to simulate the outflow hydrographs at four locations within the 38th Street Waller Creek urban watershed at Austin, Texas. Actual outflow was gaged at the final outlet of the watershed. This provided a checkpoint for comparing the simulated and observed final outflow hydrographs. The outflow hydrographs for each subzone were obtained by chronologically abstracting interception, infiltration, and depression storage from their precipitation hyetographs. These outflow hydrographs were then routed through Waller Creek channel to obtain the hydrographs at the four desired locations. The advantages of this model are the flexibility in varying the precipitation inputs to each subzone and the ability to obtain the contribution to the final flood hydrograph of each subzone.Show more Item Hydrographs by Single Linear Reservoir Model(The Hydrologic Engineering Center, 1982) Pederson, John T.; Peters, John C.; Helweg, Otto J.Show more A single linear reservoir (SLR) model is presented which provides a simple means for developing runoff hydrographs for small, urban watersheds. The model only requires one parameter, K, which can be estimated from watershed and precipitation characteristics. Several methods for estimating K and the results of testing the model on various watersheds are presented.Show more Item Unit Hydrograph Estimation for Applicable Texas Watersheds(Texas Department of Transportation, 2006) Fang, Xing; Cleveland, Theodore G.; Thompson, David B.; Asquith, William H.Show more The unit hydrograph is defined as a direct runoff hydrograph resulting from a unit pulse of excess rainfall generated uniformly over the watershed at a constant rate for an effective duration. The unit hydrograph method is a well-known hydrologic-engineering technique for estimation of the runoff hydrograph given an excess rainfall hyetograph. Four separate approaches are used to extract unit hydrographs from the database on a per watershed basis. A large database of more than 1,600 storms with both rainfall and runoff data for 93 watersheds in Texas is used for four unit hydrograph investigation approaches. One approach is based on 1-minute Rayleigh distribution hydrographs; the other three approaches are based on 5-minute gamma-distribution hydro-graphs. The unit hydrographs by watershed from the approaches are represented by shape and time to peak parameters. Weighted least-squares regression equations to estimate the two unit hydrograph parameters for ungaged watersheds are provided on the basis of the watershed characteristics of main channel length, dimensionless main channel slope, and a binary watershed development classification. The range of watershed area is approximately 0.32 to 167 square miles. The range of main channel length is approximately 1.2 to 49 miles. The range of dimensionless main channel slope is approximately 0.002 to 0.020. The equations provide a framework by which hydrologic engineers can estimate shape and time to peak of the unit hydrograph, and hence the associated peak discharge. Assessment of equation applicability and uncertainty for a given watershed also is provided. The authors explicitly do not identify a preferable approach and hence equations for unit hydrograph estimation. Each equation is associated with a specific analytical approach. Each approach represents the optimal unit hydrograph solution on the basis of the details of approach implementation including unit hydrograph model, unit hydrograph duration, objective functions, loss model assumptions, and other factors.Show more