Hydrodynamic and geomorphological processes in the hydrologic response of a watershed

Abstract

The effects of the geomorphological and hydrodynamic mechanisms in the hydrologic response of a watershed are well-studied phenomena. However, how such effects vary when the parameters of the run-off propagation model vary spatially has not been analyzed. This paper presents a methodology that combines models of propagation based on the kinematic wave diffusion equation and Digital Elevation Models (DEMs), obtaining analytical expressions for the variance of the travel time of water within the watershed. The variance allows us to analyze the diffusive effects in the response of the watershed, and DEMs introduce the spatial variation of parameters. This allows us to define the hydrodynamic dispersion coefficient of the watershed in such a way that the hydrodynamic term of the ‘variance is not altered, thus obtaining an expression for the geomorphological dispersion coefficient of the watershed when there is a spatial variation of parameters.

The relative importance of geomorphological and hydrodynamic mechanisms in the watershed response is analyzed through the parameter wich represents the ratio between and This methodology was applied in five South American watersheds considering two flow zones: overland and streams flow, determining the relationship between the coefficients and Y,, for different sizes and drainage network configurations. The effects of spatial variation of parameters in the peak flow and lag time are also analyzed.