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A new two-dimensional hydrological model has been developed that 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. Sensitivity analyses of the model have been carried out to assess the relative importance of topographic linkages, surface characteristics and rainfall characteristics on catchment hydrological response. Attribute sensitivity analyses 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, variability in output discharge at the catchment outlet increases with an increase in the spatial variability of infiltration. Rainfall intensity is thus an important factor in controlling the overall coupling characteristics. Catchment runoff production is affected by a complex interaction of topographic, surface and rainfall characteristics. Copyright (C) 2002 John Wiley Sons, Ltd.