Sensitivity of channel profiles to precipitation properties in mountain ranges

The stream power erosion law, which describes the erosion rate as a function of channel discharge and gradient, has often been used for modeling landscape evolution in regions dominated by fluvial processes. However, most previous studies utilizing the stream power erosion law simply use drainage area as a surrogate for channel discharge. Despite its convenience this simplification has important shortcomings. Specifically, it ignores the effects of precipitation properties on channel discharge and hence erosion rate, and it ignores the interactions between mountain ranges and precipitation properties. By using the stream power erosion law together with the geomorphoclimatic instantaneous unit hydrograph we provide a method for linking the landscape evolution and precipitation properties directly. Our results demonstrate that the channel profile is sensitive not only to the total precipitation but also to precipitation properties like the rainfall frequency, intensity, duration, and their distribution in space. The channel profile is most sensitive to the variation of rainfall intensity and less sensitive to rainfall frequency and duration. Shorter and more intense rainfall could lead to significantly higher erosion rate and flatter profiles compared to longer and less intense rainfall. The spatial variation of precipitation can also influence the evolution of channel profile. Even if the total precipitation remains spatially homogeneous, different spatial behavior of rainfall intensity and rainfall duration may lead to different steady state river profiles. The channel profile tends to be flatter under the conditions of increasing rainfall intensity and decreasing rainfall duration with elevation and vice versa.