Integrating frequency and duration in flood susceptibility assessment: a novel approach for the east coast of Tamil Nadu, India

A flood susceptibility assessment is crucial for identifying areas that are susceptible to flooding. This task usually uses models, but prior flood susceptibility assessment models focused on the frequency or duration of floods, not both. Integrating the frequency and duration of floods in susceptibility assessment could provide a more accurate picture of flood susceptibility. This study aimed to utilise and assess a novel integrated model that considers the frequency and duration of floods to categorise vulnerability/susceptibility zones. This study focuses on the multi-hazard zone between Cuddalore and Sirkazhi on the east coast of Tamil Nadu, India. Sentinel-1 A and RISAT-1 A Synthetic Aperture Radar (SAR) images were analysed using the Classification and Regression Tree (CART) classifier. Eight SAR images were used to study the persistence and temporal evolution of flooding over 49 days in 2015, along with multi-temporal datasets for 2015, 2018, and 2019. The classification of flood-susceptibility zones based on the frequency and duration of flooding yielded an accuracy of 0.87, whereas the integrated model scored 0.96 in all matrices. The hybrid integrated analysis provided a comprehensive understanding of the area’s flooding system, identifying the southern part of the study area as the most susceptible. The proposed model recommends a frequency-duration-based approach to demarcate flood susceptibility zones and potentially improve flood susceptibility assessments and management strategies.