Integrating Sentinel-1 SAR and Hydrometeorological Data for Flood Risk Mapping and Ecological Impact Assessment in Alluvial Regions

Flooding is a recurring hydrometeorological disaster affecting low-elevation coastal areas, yet real-time monitoring is often hindered by thick cloud cover on optical sensors. This study aims to conduct a spatial and temporal analysis of extreme flood events using the integration of radar satellite imagery and hydrometeorological data. The research focuses on the northern coastal region of Aceh, Indonesia (North Aceh Regency and Lhokseumawe City), which experienced severe flooding in November 2025. Flood extent was extracted using change detection analysis of Sentinel-1 Synthetic Aperture Radar (SAR) imagery processed through Model Builder, an automated workflow in ArcGIS Pro 3.6. The derived inundation maps were subsequently integrated with precipitation, land-cover, and population datasets to assess ecological and socio-economic impacts. The results indicate that the total inundated area reached 23,964.51 hectares, affecting 329 villages and more than 12,000 people. The cultivated crops sector was identified as the most extensively affected area, covering 20,559.10 hectares or 85.8% of the total affected area. Hydrometeorological analysis shows that, in addition to extreme rainfall exceeding 150 mm/day, upstream degradation due to tens of thousands of hectares of oil palm concessions and Forest Utilization Permits (PBPH) exacerbated water accumulation in the downstream alluvial plains. This study demonstrates that Sentinel-1 SAR is highly effective for rapid flood monitoring under adverse weather conditions and highlights the importance of integrated, watershed-based disaster risk management that transcends administrative boundaries