Role of hydrometeorological variables and catchment area to flood generation over the monsoonal climate region of India

Abstract. Indian River basins experience frequent flooding during the Indian summer monsoon rainfall and pose several challenges to the large population of the region. To effectively manage flood risk in the region, a better understanding of flood-generating mechanisms is essential, yet hydrometeorological and catchment drivers controlling flood processes are poorly explored across India. In this study, we examine the role of hydrometeorological variables (such as precipitation and surface runoff) and catchment area in the flood occurrence in one of the largest river basins (Godavari River basin) of the Indian Subcontinent using observed and VIC-simulated datasets. Based on the temporal analysis of precipitation, runoff, and streamflow, we show that floods caused by multiple high-intensity precipitation days predominantly occur in the semi-humid sub-basins (Tekra, Pathagudam, Perur, and Polavaram) of the Godavari River. The majority of floods in the semi-humid sub-basins are associated with 10 to 11 days of accumulated precipitation, having multiple high-intensity precipitation events prior to the flood. In contrast, the majority of floods in the semi-arid region of Godavari (Mancherial sub-basin) are triggered by a single high-intensity precipitation day and associated with short-duration (2 days) accumulated precipitation. In addition to temporal analysis, we also performed Empirical Orthogonal Functions (EOF) analysis using precipitation, runoff, and streamflow data to identify the flood-dominant catchment area. Our results demonstrate that central and downstream areas of the basin contribute disproportionately to flood occurrence, with the Tekra sub-basin generating substantially higher runoff due to favorable catchment characteristics. Overall, this study advances understanding of flood-generating mechanisms over the Godavari River basin, which can be helpful for flood control and management during the monsoonal climate of the Indian Subcontinent.