Assessment and mitigation of stormwater runoff in an informal settlement

Abstract

Urbanisation and global population growth are increasing rapidly, particularly in Africa and Asia; as a result, the formation of informal settlements in peri-urban regions and corresponding social and environmental hazards within these settlements are becoming more prevalent. Stormwater runoff is one such risk, which is relatively unexplored within the context of informal settlements, both in terms of flooding as well as the spread of pollutants and related health and environmental issues. The aims of this thesis were to i) to investigate how stormwater quality within an informal settlement is influenced by anthropogenic and environmental factors, and ii) to understand the inter-relationships between the hydrology, geochemistry and microbiology of stormwater within a settlement. This research was undertaken at the case study site of Enkanini informal settlement (Stellenbosch, South Africa). Water samples were collected and analysed during the wet winter seasons of 2016 and 2017 at six runoff sites: five sites within Enkanini informal settlement and one control site located outside the settlement in an area with little or no remote human activity. Sample site selection was based upon catchment analysis using DEM data to determine the most suitable and critical locations while also taking into account practical and logistic considerations. Data collection within Enkanini focused on two primary methodologies: water quality (geochemical and microbiological components) and water quantity (hydrological component). Key results include the measurement of significantly high levels of pollution in runoff water samples especially for the microbial indicator organisms, e.g., faecal coliforms ranged between 4 × 103 - 1.9 × 108 CFU/100 mL as compared to water standard guideline of 130 CFU/100 mL which ensures no health impacts. The remaining indicator organisms, microorganisms detected through PCR analysis, and geochemical analysis of common chemicals all followed a similar trend of extremely high levels detected above South African water standard guidelines, indicating health and environmental risk from Enkanini stormwater runoff. Due to sampling limitations, it was not possible to definitively determine a correlation between hydrological influences upon the runoff. Results indicate that the predominant influencing factor in runoff contamination in informal settlements is anthropogenic, more specifically population density. The significant impact of anthropogenic influences should therefore be considered in development of mitigation measures to reduce pollutant levels in runoff in informal settlements.

Date of Award	22 Jul 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Thomas Kjeldsen (Supervisor), Lee Bryant (Supervisor) & Wesaal Khan (Supervisor)