Evaluating Flood Hazard Mitigation through Sustainable Urban Drainage Systems in Bor, Jonglei State, South Sudan

Abstract

In response to the escalating pressures of urbanization and population growth on the ecosystems and flood risks in Bor County, Jonglei State, South Sudan, this study proposes the implementation of Sustainable Urban Drainage Systems (SUDS) as a resilience-building measure. Through the design of open drainage channels featuring non-uniform flow, inclusive of main and sub-channels alongside infiltration wells, the research aims at mitigating flooding, enhancing water quality, and fostering sustainable development within the region. The necessity for managing substantial runoff volumes has been identified, with a decade of rainfall data employed to accommodate annual variability. The evaluation of SUDS techniques to mitigate flooding entails a customized design approach, integrating cost estimation with flood mitigation strategies and the assessment of short-and long-term co-benefits. Hydrological analysis of ten years of rainfall data facilitated the sizing of channels for storm events ranging from 2 to 5 years, with precipitation intensities between 73.82 and 93.08 mm/day, resulting in the planning of open trapezoidal channels with dimensions to support 5 m 3 /s flows. Moreover, infiltration wells, with diameters of 2-3 meters and depths of 3-5 meters, have demonstrated potential in reducing runoff volumes by up to 70% in a 0.5-hectare modelled area. The incorporation of drop structures aims to control slopes ranging from 6-15% in channels, thereby preventing erosion for flows up to 20 m 3 /s. The adaptability of SUDS approaches, commonly applied in developed nations, to the tropical environment of Bor is scrutinized, highlighting the necessity for localized adaptation due to data limitations and modelling simplifications. The potential barriers posed by capital costs underscore the importance of a life cycle analysis. The success of SUDS implementation in Bor County is contingent upon community engagement, ensuring acceptance and ownership. It is recommended that low-cost, simplistic pilot projects, focusing initially on rain gardens and permeable pavements, precede large-scale implementation. Through strategic planning, SUDS hold the potential to enhance climate resilience in the expanding community of Bor County. An integrated technical analysis provides actionable solutions for flood mitigation, advocating for further monitoring and community-driven initiatives to transition SUDS from concept to reality.

Modeling Surface Runoff in Al-Mohammadi Valley: Influence of Climate and Soil Parameters

“…For instance, evapotranspiration and the volume and quality of runoff can be directly impacted by variations in temperature and precipitation. As a result, control of the runoff should begin at the most miniature area, such as a household, or what is known as "site control and regional control" [4].…”