A "Background-Dynamics-Loss-Resilience" framework to assess flood risk in the Shandong reach of the Lower Yellow River

Study region The downstream sub-basin of the Lower Yellow River in Shandong Province. Study focus Flood risk in suspended-river systems remains poorly understood due to their anomalous geomorphology and hydrodynamic behavior. This study integrates a two-dimensional hydrodynamic model with a multi-source Background-Dynamics-Loss-Resilience (BDLR) framework to assess flood risk in suspended river systems. Flood inundation processes for return periods of 5–100 years were simulated to quantify the spatiotemporal responses of inundation depth and flow velocity. A hybrid weighting approach, combining Analytic Hierarchy Process (AHP) and Entropy Weight Method (EWM), was applied to determine the relative importance of various factors in flood risk. Spatial risk distribution maps were generated, and dynamic threshold analysis identified risk-sensitive areas for targeted flood prevention. New hydrological insights for the region Floodwaters in suspended river systems overtop topographic ridges in stages, resulting in diminishing marginal increases in inundated area with increasing return period. Flood risk is controlled by geomorphic constraints and energy redistribution. Key risk factors include slope (14.868%-15.899%), inundation depth (16.371%-17.004%), flow velocity (14.380%-15.695%), population and GDP density (27.382%-28.570%). About 8.09% of the region exhibits higher- and high-risk values (> 0.279) under low return period (5-year) flood scenarios, indicating high sensitivity to such floods, particularly in the Jindi River basin, the Yellow River estuary. These findings offer new insights for flood management in the Shandong reach.