Scale-dependency, rainfall, and lithologic controls on the hypsometry of the Western Ghats, India

Basin hypsometry is a proxy of landscape evolution, providing insight into the role of geological factors and climate on topography. With reference to the Western Ghats in India, we investigated for the first time the roles of scale-dependency, rainfall, and lithology on hypsometric properties and discussed possible controlling factors. We computed the hypsometric integrals for 1048 catchments of different orders. We observed that their value strongly correlates with the area, perimeter, and relief in larger catchments (4th to 6th order). We did not observe a scale-dependency on hypsometry in smaller (3rd order) catchments; instead, we found a correlation with the age of lithology. Younger formations, in particular, were associated with higher hypsometric integrals, corresponding to a younger stage of drainage development and higher erosion rates. The effect of rainfall on the spatial distribution of hypsometric integral values did not stand out at any spatial scale.