Hydrologic-hydraulic response of swales to stormwater runoff

Abstract

Urban areas face high pluvial flood risks due to intense storms from climate change, more impervious surfaces from urbanization, and inefficient drainage systems. The consequences include damage to infrastructure, public health risks, economic losses, and environmental impacts. Stormwater control measures (SCMs) based on Low Impact Development (LID) principles which employ systems and practices that mimic natural processes, are used to manage urban runoff and to reduce flooding risks. A vegetated swale is a shallow roadside channel that aids stormwater flow and natural filtration, setting it apart from other SCMs. Swales are a cost-effective SCM option, requiring minimal construction and maintenance. In this review, a comprehensive approach was followed where various studies such as field experiments, hydrologic modeling-based studies, and other studies such as laboratory experiments have been critically investigated to evaluate the hydrologic-hydraulic performance of vegetated swales. An initial search in Google Scholar, Web of Science, Scopus, and ResearchGate using relevant keywords yielded 460 articles. After filtering for topic relevance, 368 articles were selected for this review. The review includes categorization of relevant literature, methodology, important results, vegetated swale description, critical acclaims, and potential limitations of various studies. At the end, critical remarks and future recommendations are presented. In conclusion, swales are effective for stormwater conveyance and management, while, their performance varies with factors such as rainfall, soil moisture, and slope. Optimizing these factors can enhance hydraulic processes like infiltration, minimize soil erosion, and lead to efficient swale design. Depending on these factors, runoff volume and peak flow reductions of up to 100% are possible. Enhancements like check dams, pre-treatment filter strips and engineered soils improve swale efficiency, due to processes like increasing retention time for infiltration and increased permeability. Additionally, there is a need for more laboratory research and adoption in developing countries.