Assessing the Impacts of Fluvial Flooding and River Bedform Geometry on Hyporheic Exchange Zones

 The dynamic interaction between surface water and groundwater in the hyporheic exchange zone (HEZ) is crucial for regulating water quality, nutrient cycling, and ecosystem health. Nonetheless, understanding the impact of changing river discharge conditions—especially during peak flow events—and the diverse geometries of bedforms on flow dynamics and biogeochemical processes in the HEZ continues to be a substantial research challenge. This study aims to address this gap using a multiphysic framework to simulate bedform responses to distinct river flow conditions. The model assesses water exchange, pressure distribution, and solute transport under steady and transient states, providing insights into HEZ dynamics. Our study is grounded in extensive field data collected from the Krycklan Catchment in Northern Sweden. Key datasets include piezometer readings of water level and pressure measurements, hydraulic conductivity profiles, and tracer movement through the subsurface, which are used to validate the numerical model. Variables such as discharge intensities, flow duration, and bedform aspect ratios are systematically varied to investigate their effects on hyporheic exchange and residence times. Preliminary results indicate that variations in flow conditions and bedform geometries affect pressure distribution, velocity fields, and flow streamlines within the HEZ. These variations lead to changes in hyporheic exchange extents, especially under peak flow regimes. The findings will enhance our understanding of the impacts of peak flow events on HEZ expansion, contraction, and nutrient cycling. They hold significant implications for river management, particularly in predicting the impact of flood dynamics and preserving freshwater ecosystems.