Flooding poses significant challenge to urban communities, particularly in tropical regions prone to extreme weather. While most studies analyse pluvial and fluvial impacts separately, hydrodynamically differentiated assessments of the two based on a validated historic compound event remains scarce, especially in the Indian context. This study presents a return period based hydrodynamic assessment of both pluvial and fluvial flooding for the downstream Periyar River Basin (PRB) in Kerala, India, using the 2018 Kerala flood as a validation base model. The aim of this study is to isolate and compare pluvial and fluvial drivers within an input data-controlled hydrodynamic framework, enabling a defensible attribution of the dominant flood mechanism, revealing how each driver behaves across return periods when assessed independently. Results show that, on average, pluvial flood impact (92.66 km²) is significantly greater than fluvial flood impact (22.17 km²) in terms of areal extent across the analysed return periods. The dominant flood class for pluvial events was ‘very high depth’ category (D>1.2m∼49.93 km²), with minimal change in extent across return periods, suggesting topographic saturation and drainage infrastructure limitations. The study underscores the need for differentiated flood management strategies emphasizing pluvial mitigation in urbanizing areas and wetland conservation for fluvial risk reduction.
Puthanveed et al. (Sun,) studied this question.