Application of retention basins and on-contour swales for flood risk reduction

Abstract

This study evaluates the effectiveness of non-structural watershed management measures for flood risk reduction, with a focus on the Mirusha River catchment and the urban area of Malisheva. The research investigates the application of retention ponds integrated with contour-aligned channels (swales), following the principles of Keyline Design, as a strategy to control surface runoff, enhance infiltration, and mitigate urban flooding.

The methodology combines long-term climatic and hydrological data analysis, runoff estimation using multiple hydrological methods, and GIS-based spatial analysis to identify optimal locations for retention ponds. Sixteen retention ponds were strategically positioned at keypoints along contour lines to maximise water retention and runoff attenuation.

The results demonstrate that the proposed system is capable of retaining approximately 903,840.67 m³ of water annually, which corresponds to a reduction of the flood-prone area by approximately 180.77 ha under a 50-year return period flood scenario. Beyond flood mitigation, the system contributes to increased groundwater recharge, reduced peak flows, and enhanced hydrological resilience at the catchment scale.

The findings confirm that the integration of retention ponds and on-contour swales represents an effective and sustainable non-structural approach to flood risk management, offering simultaneous hydrological, ecological, and socio-economic benefits for vulnerable urban and peri-urban areas.