Climate Change and Its Impacts on Flooding In Accra-Greater Accra Metropolitan Assembly
Climate change resulting in high precipitation is of utmost importance as it yields floods of varied amounts. Such floods result in loss of lives and properties worth billions of Ghana Cedis (BGH₵). Accra, the capital city of Ghana, has experienced various levels of floods with the July 1995 incidence recorded as the highest floods over the basin. This research work seeks to investigate the impacts of floods over Accra basin as the future experiences changes in the climate system. Aptitude to predict future precipitations depends on established climate scenarios. Landuse characteristics and atmospheric parameters define the changes in the hydrologic cycle hence the resultant precipitations. This affects the variations in the precipitation pattern as the years proceed. Known precipitation values are used to develop flood vulnerability maps and their impacts due to changes in the precipitations assessed under each of the scenarios in an ARCGIS model for this work. Six main scenarios are developed based on the landuse characteristics of the basin. These are HISTORICAL_1995, SDAN_2020, SDOK_2040, SDIK_2060, SDIOL_2080 and SDIOK_2100 yielding precipitation values of 249.30mm, 234.09mm, 149.58mm, 24.93mm, 124.65mm and 398.88mm respectively. These precipitation values are integrated into the HYDROCAD software to generate runoff depths or flood levels, flood volumes and hydrographs for each of the sub basins within GAMA. Vulnerability assessment depends on known precipitation data; hence the historical_1995 precipitation used to develop the flood vulnerability map of Accra as the reference point for impact assessment. Climate change impacts on floods are then assessed based on the obtained precipitation values under each of the generated scenarios. Therefore, the developed climate scenarios helped to forecast precipitation values over the GAMA basin and assess their future impacts on floods. This will serve as an urban planning tool for the Government of Ghana (GoG) and other flood disaster management agencies.
A Thesis submitted to the School of Graduate studies, Kwame Nkrumah University of Science and Technology in Partial fulfillment of the requirement for the degree of Master of Science in Water Resources Engineering and Management, September-2013