Integration of Remote Sensing Data in Rain-on-Grid Flood Modelling and Post-Event Validation Using Orthophotos

Abstract. This study explores the integration of remote sensing data into rain-on-grid flood modelling, with a focus on post-event validation using high-resolution orthophotos. The aim is to assess the hydrologic and hydraulic characteristics of the flood event that occurred on August 11, 2021, in Ezine Creek, which flows through the Bozkurt district center located in the north of Kastamonu, Turkey. By comparing the simulated flood extent with observed flood boundaries extracted from orthophotos, the hydraulic model was calibrated to better represent the actual flood behaviour. The resulting hydrograph was then used in the downstream section, where hydraulic structures and debris that contributed to the flooding were explicitly modelled and compared against observed outcomes. This calibration process enabled the derivation of a realistic hydrograph for downstream boundary conditions in subsequent flood event simulations. The approach demonstrates the value of combining remote sensing and traditional hydraulic modelling for enhanced flood risk assessment and decision-making.