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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. Research highlights: We investigated the roles of scale-dependency, rainfall, and lithology on hypsometric properties and discussed possible controlling factors for the entire Western Ghats escarpment. A total of 1048 sub-catchments were investigated individually. Strong scale-dependency was observed in high-order catchments (4th–6th order). Lower-order (3rd) catchments are controlled by lithology, particularly by younger formations. Hypsometry in the Western Ghats is independent of any rainfall control. [ABSTRACT FROM AUTHOR]

The Mahi—one of the major rivers in Western India—is subject to frequent major flooding, which severely affects the local economy and infrastructure. Little has been done, however, to assess the flood patterns and severity along its course. Here, the Mann–Kendall and Pettitt tests are used to identify long-term trends of precipitation and peak streamflow at multiple locations in the catchment. Then, flood susceptibility mapping is performed by the analytical hierarchy process, accounting for 14 geomorphic, hydraulic, and geologic factors. The analyses suggest a decline in total precipitation and peak flow discharges at most locations, consistently with the general climatic trend of the area, featuring a weakening summer monsoon. Nonetheless, a significant portion of the catchment area remains highly susceptible to flooding, with stream powers capable of mobilizing boulders up to 1 m in size in extraordinary floods. These results can support the work of engineers and policymakers dealing with floods in the study area, but the proposed methodology can also be applied to other fluvial catchments to evaluate the role of climate trends in modulating flood susceptibility. [ABSTRACT FROM AUTHOR]