Built Environment, flooding regime change, and its effect on adaptation to climate change in the cities of developing countries: Learning a lesson from Addis Ababa City, Ethiopia

Abstract This study presents the challenges of rapid flooding regime change due to the expansion of built environment across the cities of developing countries based on Addis Ababa as a case study. A hydrological study of the city was conducted using three different land use maps of Addis Ababa digitized from the city map of 1984, 1986, and 2002. The study indicated that the average runoff coefficient of the city increased from 28% in 1984 to 45% in 2002. This indicates that the annual generated runoff volume increased by more than 60% in 2002 than that in 1984. The flood peaks increased from insignificant (inner city) to more than 100% (in all directions away from the inner city). Therefore, the change of runoff volume and runoff transformation potential resulted from the expansion of built environment can explain the recurring floods in Addis Ababa city. Given the recent increased history of flooding in Dar es Salaam that occurred almost annually since 2011 and the recurring flood occurrence in Accra, it is evident that expansion of the built environment exasperated the flooding disaster across many cities in Africa. Unlike cities in the developed world where climate change impacts are common concerns, cities of developing countries are confronted with compound impacts of expanding built environment and the impacts of climate change. Effective adaptation to the impacts of built environment, through integrated city best management practices, is a necessary condition and a pathway to climate change adaptation in the future.