U.S.- Italy Research Workshop on the

Hydrometeorology, Impacts, and Management of Extreme Floods

Perugia (Italy), November 1995

THE DEPENDENCE OF HYDROLOGIC RESPONSE ON GEOMORPHOLOGIC CHARACTERISTICS OF THE BASIN

Glenn E. Moglen

Office of Hydrology

National Weather Service

Silver Spring, MA 20910 USA

Rafael L. Bras

Department of Civil and Environmental Engineering

Massachusetts Institute of Technology

Cambridge, MA 02139 USA

It is well known that the Instantaneous Unit Hydrograph (IUH) can characterize the response of a river basin and that the IUH, in turn, can be expressed in terms of the geomorphic structure of the basin. The object of this paper is to study how heterogeneities in basin erosivity and smoothing processes like diffusive erosion lead to different patterns of runoff production, different width functions and hence basin response. In other words, we want to study how, all else being equal, heterogeneous basins and diffusion dominated basins behave when compared to homogeneous and fluvially eroded basins. We use a physically based basin evolution model in order to generate our test beds. First we study the impact of heterogeneity and diffusive processes on runoff production using the concept of saturation indices. Second we study the impact of routing on the IUH shape.