Modelling the effects of hillslope–channel coupling on catchment hydrological response

Michaelides, K. and J. Wainwright (2002)

Earth Surface Processes and Landforms 27(13): 1441-1457

Abstract

A new modelling approach has been developed to capture the hydrological response of catchments to the effects of hillslope-channel coupling. The new two-dimensional hydrological model accounts for dynamic interactions between hillslope and channel flows. The model is specifically designed for semi-arid areas dominated by Hortonian overland flow, and has a dynamically active channel belt. The relative importance of several variables has been assessed by carrying out sensitivity analyses of the model. Sensitivity analyses of attributes suggest that hillslopes are more sensitive than floodplains to all parameters except surface roughness. However, decoupling through the presence of floodplains or other barriers will reduce the relative importance of the sensitivity of hillslope parameters. Spatial sensitivity analysis suggests that sensitivity to the spatial variability of infiltration decreases with an increase in the magnitude of the runoff event. On the other hand, if there is an increase in the spatial variability of infiltration the variability in output discharge at the catchment outlet will also increase. Rainfall intensity is therefore an important factor in controlling the overall coupling characteristics. A complex interaction of topographic, surface and rainfall characteristics affect the production of catchment runoff.

Key words

catchment hydrology; infiltration; rainfall rate and distribution; surface roughness; floodplain; hillslope; spatial variability.

Illustration of the two-dimensional model (a) at the reach scale, and (b) at the cross-section scale