Climatic controls on hillslope angle and relief in the Himalayas

Comparison of rainfall data and mean hillslope angles in the Himalayas of central Nepal shows that mean hillslope angles decrease with increasing mean annual rainfall. Higher pore pressures and higher rates of chemical weathering in the wetter regions may decrease the threshold angle of hillslopes prone to landsliding. When valley spacing is held constant, the sensitivity of mean hillslope angle to climate implies that relief, in the absence of limits due to rock strength, is also dependent on climate. These results suggest that wet-to-dry climatic changes increase relief in regions with incising bedrock channels and that dry-to-wet climatic changes reduce relief. Keywords: threshold hillslopes, climatic geomorphology, relief, Himalayas, Nepal, landslides.