Abstract
Flood risk maps for the built environment can be obtained by integrating geo-spatial information on hazard, vulnerability and exposure. They provide precious support for strategic urban planning and decision-making. These maps, generated in a probabilistic framework, can consider various sources of uncertainty in the flood risk assessment such as the occurrence of extreme flooding events, future land use and land cover, characteristics of the buildings, and exposure to flooding. This paper investigates how these maps can be used in complicated urban context such as developing countries, where engineers are forced to work with scarce or little data. Specifically, a detailed investigation on the city of Addis Ababa, Ethiopia, has been conducted. Although the city of Addis Ababa is undergoing extensive formal housing development, it is most likely that the informal settlements will continue to constitute a significant portion of urban housing landscape in the years to come. Recent research findings and field work from a large project (FP7-CLUVA) are employed in order to provide a quantified basis for decision-making between alternative adaptation strategies for informal buildings in Addis Ababa. Risk maps, obtained by up-scaling more accurate risk assessment results at neighborhood level, are adopted for risk zoning of the urban residential texture within the city. This provides risk-based criteria for both identifying suitable flood adaptation strategies and prioritizing between viable risk mitigation measures.
Highlights
Despite the rapid progress of scientific knowledge and the increasing awareness of disaster risk and management, the social and economic impact of natural disasters is increasing
This can be attributed to two factors: (a) the collapse fragility curves in Fig. 11a, b indicate that the upgrading strategies are effective only for flood depths less than 1.0 m, and Villas are subjected to relatively more modest flood depths since they are generally located farther away from the river with respect to Mud and Wood buildings Fig. 8c; (b) it can be observed from Fig. 11a, b that the upgrading strategies are more effective for the villas compared to the Mud and Wood buildings
This can be attributed to two reasons: (a) the dimension of the storage is limited by the dense urban built environment in the case study area; and (b) only the northwest streamline B1 seems to benefit from the presence of the storage
Summary
Despite the rapid progress of scientific knowledge and the increasing awareness of disaster risk and management, the social and economic impact of natural disasters is increasing. Floods in particular, are responsible for around 60% of the total population affected, and for almost 10% of the total economic losses due to natural disasters (CRED 2012). Being less resilient to natural disasters (due to several factors such as, fragile economy, poverty, lack of risk awareness, and lack of coping capacity), the urban areas in sub-Saharan Africa are vulnerable to weather-related phenomena. Considering that somewhere between 60 and 70% of the urban population in sub-Saharan Africa lives in existing informal settlements, the urban decision makers need to pay specific attention to their exposure to risk
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