Influence of hydrograph characteristics and littoral sandbars on flooding dynamics in a small-scale estuary

Study Region: This study examines the Maipo River estuary in central Chile, a small bar-built estuary where littoral sandbars can reach several meters in height and narrow the inlet to 60–80 m. These systems are representative of many Mediterranean-climate estuaries that support valuable ecosystems and local activities. Study Focus: Flood hazard assessments in estuaries often emphasize peak discharge while overlooking hydrograph variability and morphological controls. We use the TELEMAC-2D model with the GAIA sediment transport module to simulate flooding under realistic and synthetic hydrographs and different sandbar configurations. We analyze the influence of peak discharge (700 to ¿5,000 m 3 s -1 ), hydrograph volume and duration, and time to peak on flood extent and water depths, and evaluate how these factors interact with sandbar morphology. New Hydrological Insights for the Region: Peak discharge is the dominant control on maximum flood extent and depth, while hydrograph volume mainly affects flood persistence. Hydrograph duration and time to peak show negligible effects on inundation. The presence of a littoral sandbar markedly increases flooding during low-return-period events, expanding inundated areas by approximately 60–70 %, but has little influence during extreme floods, when flows erode or overtop the sandbar. Maximum flood depth increases linearly with peak discharge regardless of sandbar configuration. These results underscore the importance of accounting for sandbar dynamics and basic hydrograph characteristics in estuarine flood assessments.