Managed diversion lead time effects on flood response in a tidal freshwater river

Abstract

River diversions are a commonly used water management tool throughout the world. Low‐gradient coastal rivers exhibit complex floodplain interactions and are subject to multiple uncertain drivers of future flood risk. The interacting factors make quantification of downstream diversion effects on ambient flood hazards in coastal riverine ecosystems challenging. This article analyzes the effects of a managed ecological diversion (MED) on downstream flood hazards in the flood‐prone tidal freshwater Vermilion River system situated within the Atchafalaya Basin region of Louisiana, USA. A flexible and efficient hydraulic and hydrologic (H&H) modeling setup and counterfactual approach is utilized to develop and analyze 60 simulation scenarios aimed at quantifying the effects of an existing baseflow augmentation program on downstream flood hazards under uncertain future conditions. The analysis demonstrated the significance of preemptive diversion closure on the downstream flood levels in downstream rivers. The role of wetland topography and residual floodplain storage on MED‐induced flood response was also highlighted. A variety of uncertain parameter/forcing scenarios were also evaluated to establish robustness of the findings and to extend the results to more general settings. The study provides insights on downstream flood response induced by MEDs, which are expected to become more prevalent in the future.

Preparing for severe flooding: Flood risk management research leading to better flood preparedness

“…Effective flood preparedness relies on a greater understanding of flood-vulnerable areas to better anticipate flooding events, increase flood warning capabilities and guide in flood risk infrastructure investment. Several aspects of flood vulnerability are explored in this issue, including an investigation into the effect of flood diversions on the timing of downstream flood hazards in a flood-vulnerable area (Miller, 2023), and consideration of the data quality, data sources and fundamental relevant processes required for effective flood risk assessments (Sieg et al, 2023). New approaches are also being continually applied and developed to help identify floodvulnerable areas.…”