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Nature-based solutions (NBS) as an urban flood mitigation measure: the case of Ga East Municipality, Accra, Ghana

Asare, Prince (2021) Nature-based solutions (NBS) as an urban flood mitigation measure: the case of Ga East Municipality, Accra, Ghana.

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Abstract:The rapid rate of urban expansion with its associated physical development in recent years sharply conflicts with the ecosystem and its services due to the natural landscape in most metropolitan regions of the world being transformed into the prevalence of hard surfaces. This hard surface development is very evident in the Ga East Municipality of Accra, Ghana. Hence, the rate with which these hard surfaces are increasing, coupled with climate change factors, has partly contributed to urban floods in the municipality. But attention has not been drawn to the impact of the decreasing natural and green environment on urban flood occurrences. As a result, flood mitigation strategies in Ghana are still geared towards the construction and desilting of drains and how proper solid waste management can help reduce the frequency and intensity of urban flood events. However, the flood mitigation strategies have not successfully resolved and mitigated urban floods in the country, including the Ga East Municipality. Studies have revealed that most cities in the western world have adapted “Nature-Based Solutions” (NBS) to restore the natural areas and ecosystem and reduce the environmental challenges linked with uncontrolled rapid urban expansion and hard surface development, including urban floods. The Ga East being one of the most affected Municipalities in Accra in terms of urban floods calls for a consideration of NBS measures as an alternative and complementary urban flood mitigation approach. Hence, this study aims to explain the need for urban flood-related NBS measures. The study also identifies target areas where specified NBS measures, including green roofs, vegetated swales, rain gardens, rainwater harvesting, detention basins, and porous pavements, can be implemented and how they can be integrated into spatial and flood mitigation schemes in the Ga East Municipality. A case study approach was adopted for this research. In this context, a mixed-method approach specifically, quantitative, and qualitative methods were used to address different aspects of the research. Specifically, land cover change analysis and the SCS model were used to determine the relation between land cover changes and urban flood occurrences. Also, a Spatial Multi-criteria Analysis (SMCA) was applied to identify target areas where specific NBS measures can be implemented in the Ga East Municipality. Additionally, content and text analysis of spatial and flood management plans and key informant interviews were used to determine how the NBS measures can be part of the municipality’s spatial development and flood management schemes. The study revealed that the development of hard surfaces had increased the likelihood of urban flood happenings in specific areas in the Ga East Municipality, hence a need for NBS measures. Also, the study revealed that different areas in the municipality require specific NBS measures to ensure effective urban flood mitigation. Additionally, the study disclosed that the municipality’s spatial plans and flood mitigation schemes reflect a possibility of NBS integration. Furthermore, the study also unveiled techniques of integrating the NBS measures as well as implementation barriers and facilitators in the Ghanaian flood management professionals' perspective. Therefore, for future research, it is recommended to empirically analyse and quantitatively determine how the specified NBS measures will reduce runoff depth and inundation volumes. Also, future research can also look at NBS integration from the perspective of the local people and inhabitants.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
Link to this item:https://purl.utwente.nl/essays/88792
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