Quantification of flood-occurrence risks in the middle reaches of the Yellow River under climate and land-use changes

Study region The study area is the Middle Reaches of the Yellow River (MRYR), China. Study focus Flood-occurrence risk under concurrent hydroclimatic and land-use change remains poorly quantified in the MRYR. We developed an AHP–FCE–GIS framework integrating 19 climatic, hydrological, topographic, and land-use indicators to reconstruct risk evolution during 1990–2020 and project 2050 conditions under SSP1–1.9, SSP2–4.5, and SSP5–8.5. The framework was evaluated using historical flood/non-flood reference locations, ROC–AUC, and spatial-block cross-validation. New hydrological insights for the region Historical FORI showed an overall increase, but the 1990–2000 reconstruction was weakly constrained. Between the better-validated 2001–2010 and 2011–2020 periods, mean FORI increased from 0.494 to 0.578 and the high-risk area from 26.7% to 46.6%. This shift coincided with a 20.2% increase in annual precipitation and a 111.09% expansion of urban land during 2000–2020. Future mean FORI reached 0.520, 0.551, and 0.603 under SSP119, SSP245, and SSP585, respectively. Under SSP585, 59.14% of the basin was classified as high or very high risk, compared with 28.57% under SSP119 and 28.30% under SSP245. Despite the largest annual precipitation increase under SSP119, its overall risk remained lowest, indicating that annual precipitation alone cannot explain future risk. The Yiluo and Wei basins remained persistent hotspots, while SSP585 extended severe risk toward the Fen River Basin and Yellow River mainstream. These findings support spatially differentiated, climate-adaptive basin management.