Opulation Dynamics, Land Use/Cover Change and Flood Risk in the Greater Accra Metropolitan Area (GAMA).

Abstract

Flood disasters have become universal, causing damage to human lives and properties. The occurrences of flood disasters also impede social and economic growth. Accra is facing floods and flood disasters annually with impacts on the poor and vulnerable which cannot be overemphasized. The relationship between population growth and land use/land cover (LULC) changes is well-documented. However, there is a dearth of knowledge on their joint effect on flood disaster risk in Ghana. Using a quantitative approach, this study examined the impact of changes in population growth and LULC on future flood risk of the Greater Accra Metropolitan Area (GAMA). The GAMA is an agglomeration of districts which are typically low-lying, coastal, and urbanized. The seven selected districts are Adenta, Ashaiman, Kpone Katamanso, La Dade-Kotopon, Ledzokuku-Krowor and Tema. Data used were multiple, including a cross-sectional survey, Geographical Information Systems (GIS) and remote sensing such as Landsat and NASA imagery, weather data, i.e., rainfall and temperature data from the Ghana Meteorological Authority and population census data from the Ghana Statistical Service (GSS). The land use/ land cover classes were determined using an unsupervised land use/land cover classification of historical Landsat imageries in an ERDAS software environment. Furthermore, an Ordinary Least Square (OLS) regression model was executed in ArcGIS to obtain the predictors of flood risk. In forecasting future flood risks, three scenarios- trend, liberalization, and self-sufficiency - were built based on assumptions on changes in LULC, population and economic growth. The Modules for Land Use Change Simulations (MOLUSCE) was used to project changes in LULC. This data used together with projected population, economic growth, and other predictors of flood risk in the OLS were used to forecast flood risk. Presently, almost half (45.2%) of GAMA is prone to high flood risk. Predictors of flood risk included population, slope, rainfall, built-up spaces (human settlements), areas covered by impervious surfaces, wealth, and proximity of a building (human settlement) to a water body. In 2010, there was a 15.7% increase in the population of GAMA. Between 1990 and 2020, built-up area coverage increased by 31.9%. In the future, there is a possibility of exacerbated flood risk in GAMA given high population growth, rapid uncontrolled urbanization, and poor land use practices. Flood risk was forecasted for 2030, 2040 and 2050 and on average, medium flood risk was dominant. However, comparatively, under the trend scenario, high flood risk will be relatively pervasive in the future. Most parts of GAMA are likely to encounter medium flood risk which has the highest likelihood under the liberalization scenario. Low flood risk is more likely to be experienced under the self-sufficiency scenario especially at later dates as there were assumptions of high economic growth and prioritization of sustainability of the environment. This study has shown that there is high population growth in GAMA. There was evidence of accelerated changes in LULC visible in the spatial analysis of the city. The impact of changes in population growth and LULC might be dire if efficient planning of the urban space of GAMA is not expedited. Therefore, based on the forecast, the impacts of flood disasters in GAMA can be lowered in the future by employing appropriate policies and strategies for population growth and LULC. The improvement in land use by penalizing poor land use practices and promoting the building of space-saving accommodation types are recommended.