| Geomorphologic instantaneous unit hydrographs (GIUHs) have been proposed by several researchers to produce runoff hydrographs from rainfall for ungauged, predominantly undeveloped watersheds with third-order and higher stream networks. Their work used equations that expressed the GIUH as a function of Horton's numbers RA, RB, and RL; an internal scale parameter LQ; and, a mean velocity of streamflow v. Their work has indicated that there is potential for use of this model in the types of areas tested. However, little work has been done for urban areas and for smaller watersheds with lower stream orders.; In this study the term geomorphology was used in the sense of drainage composition (Horton's laws, etc.). A model using a more general form of equations to represent drainage basin geomorphology was developed for use in urban areas. Also, in this study, (1) the National Resource Conservation Service (NRCS) Method was used to determine the travel times for overland and channel flows in a stream-ordering subbasin system, (2) the velocity for each order stream in a basin was allowed to vary, and (3) zero-, first-, second-, fourth- and fifth-order watersheds were considered.; The model was tested for three small urban basins in three of the four physiographic provinces of South Carolina. No gauged data was available for the fourth province. Comparison between the shape of the simulated and observed unit hydrographs gave good results for two of the three watersheds. The third watershed had significant storage in it. This resulted in poor agreement between predicted and observed unit hydrographs. The implied free flow assumption of the model was violated by the storage. Based on the tests performed, the model has potential as a useful tool in watershed rainfall-runoff analysis. |
