Application of an Index-Based Approach in Geospatial Techniques for the Mapping of Flood Hazard Areas: A Case of Cape Coast Metropolis in Ghana

Abstract

Floods remain one of the disasters that destroy properties, livelihoods, and in extreme situations, take lives. As a way of prevention, geospatial applications have been employed in many cities to map flood zones and predict floods. For a country such as Ghana, floods have been ranked as the second fatal disaster after epidemics leading to several kinds of research to resolve them. To date, the Cape Coast Metropolis (CCM) has received little attention in terms of research, though flood cases in the area continue to escalate. This study, therefore, examines the use of geospatial techniques as tools in addressing flood problems in the CCM of Ghana. From a Digital Elevation Model, hydrologic variables were generated using the ArcGIS software (Esri, Redlands, CA, USA). The soil drainage classification for the study was generated from a downloaded African Soil Grid Drainage map, while other important factors that influenced flooding in the CCM were obtained from Landsat 8 imagery. Over 21% of the CCM was classified as high flood hazard zones with areas around the river Kakum estuary being flood hotspots. It is, therefore, recommended that the CCM Assembly fund dredging of streams/rivers and promote afforestation along river banks to reduce the risk of flooding within the metropolis.

Changes in urban green spaces in coastal cities and human well‐being: The case of Cape Coast Metropolis, Ghana

“…Cape Coast Metropolis is found in the coastal savannah ecological zone, which is characterised by two distinct seasons (wet and dry) annually, with annual rainfall ranging between 90 and 110 mm. It is mostly humid (relative humidity ranging from 60% to 80%) due to its proximity to the sea, with temperatures ranging between 24°C and 32°C (Danso et al, 2020). The metropolis stretches 13 km along the central coast.…”

“…It currently has an estimated 189,925 people according to the 2021 population and housing census. Previous studies suggest its population grows at an annual rate of 3.1% (Danso et al, 2020). The metropolis is rapidly expanding to accommodate the increasing population and associated socio-economic activities.…”

Assessment of Land Use/Land Cover Change and Morphometric Parameters in the Keta Lagoon Complex Ramsar Site, Ghana

“…In this study, morphometric characteristics of KLCRS landscape, like elevation, slope, aspect, flow direction, stream network and order, and stream density, were modelled with the help of the Spatial Analyst tools in ArcGIS [26,45,46]. The Fill tool in ArcGIS was used to create depressionless DEM to prevent any interruption of continuous flow paths [46]. Using the inbuilt D8 method in the Spatial Analyst tool, the flow direction of KLCRS was modelled out of the fill DEM.…”

“…The flow direction was used as an input material to create a flow accumulation raster image. Following the procedures described in [46,47], the watershed was delineated, and stream network and stream density maps of KLCRS were produced. Based on Strahler's system of stream order [45,48] as a built-in tool in QGIS version 3.16, six stream orders of the study area were revealed.…”

A GIS-based flood risk mapping of Assam, India, using the MCDA-AHP approach at the regional and administrative level

“…Over the past few decades, remote sensing has played a crucial role in monitoring floods, and it has also solved the challenges related to the availability of data (Sharma et al 2018;Wang and Xie 2018;Rong et al 2020). In recent times, GIS has been widely used in vulnerability and risk assessment studies as a decision support system for its database and analytical ability (Lyu et al 2018;Choubin et al 2019;Danso et al 2020). Armenakis et al (2017) developed a flood risk map for the Don River watershed, Toronto, using high spatial resolution data and incorporated demographic indicators to enhance mitigation and preparedness planning.…”