Water detention structures as a flood mitigation strategy: A case study of the Elgin Creek Basin

Elgin Creek Basin, Manitoba, Canada, a rural, prairie watershed with limited hydrological data and a history of flood-induced road washouts. This study introduces a system-scale modelling framework for assessing flood risks and evaluating mitigation strategies in data-scarce environments. The framework uses MODSIM-DSS as its core modelling component and integrates HEC-HMS and HEC-RAS to simulate hydrologic and hydraulic interactions under multiple flood return periods and infrastructure configurations, complemented by LiDAR-based GIS analysis for reliability. Although demonstrated in the Elgin Creek Basin, the framework is designed to capture hydrologic and hydraulic processes characteristic of Prairie watersheds—such as low-relief terrain, snowmelt-driven runoff, and culvert-controlled drainage—making it readily transferable to similar basins and supporting region-wide flood resilience planning. This study provides regionally relevant insights for Prairie watersheds characterised by low-relief terrain, culvert-controlled drainage, and limited hydrological data. Evaluation of 16 detention structures proposed by local authorities shows that, although they reduce peak flows and spill volumes, they do not eliminate road washout risk under extreme events. Scenario-based optimisation identifies five strategically located detention dams that collectively prevent washouts for floods up to the 100-year return period. These results underscore the importance of integrated flood-routing and storage analysis for infrastructure planning in data-scarce environments and demonstrate that targeted interventions in small to medium-sized basins can yield substantial regional benefits. The proposed framework addresses common hydrologic challenges and supports evidence-based planning for rural transportation networks under increasing climate variability. • Efficient modeling framework for rural flood mitigation planning. • First application of MODSIM-DSS for distributed detention design in prairie basins. • Strategic detention dam placement eliminate washout risk for under 100-year floods.