Development of flood damage curves for Cotonou City, Benin

Blandine Ouikotan, Berry Gersonius, Hans van der Kwast, Abel Afouda, Arthur Mynett

Wednesday 1 july 2015

9:15 - 9:30h at South America (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Flood risk assessment

Parallel session: 8J. Floodrisk - Assessment

With a population of about one million, Cotonou is the main urbanized city and the economic capital of Benin (West Africa). Like most of the coastal cities in West Africa, Cotonou has been facing frequent floods since some decades. In 2010, 20000 people were affected, 9325 were displaced and 3108 homeless. The ongoing urban development in flood-prone areas, the parcelling of wetlands zones and the lack of long term planning of prevention measures are increasing the risk of perpetual flooding. Flood damage curves are essential tool for flood risk assessment to support the choice of mitigation and adaptation measures. This paper presents the methodology used for flood-damage curves construction in a context of little historical flood data records. It gives some results by focusing on the direct and tangible damages on residential dwellings, roads and loss during evacuation process. For the flood characteristics, depth and duration are taking into account. Data was mainly collected from households, municipality and the national institute of statistics and economic analyses (INSAE). People living in the flood prone areas were interviewed. The results were stored in a data base. This includes the socio-economic profile of residents, the type of residential dwelling, their characteristics and contents, the economical value of the exposed items, the characteristics of past flood events. The INSAE data base gives aggregated socio economic information about Cotonou. The costs of evacuation and rescue measures and reparation of roads by the municipality were also integrated in the model. Regression analysis was used to establish the flood damage functions for different types of houses and roads. At this stage of our research and for the different obtained flood damage functions, the study reveals the type of damage that is most costly during flood events in Cotonou.