Five relevant African cities (Addis Ababa, Dar es Salaam, Douala, Ouagadougou and Saint Louis) were selected for applying the measures and tools that have been developed within CLUVA (CLimate change and Urban Vulnerability in Africa). The project aims at delivering a reliable analysis of both the climate scenarios and their adverse effects regarding these five urban areas.
Five types of climate related hazards were studied in the frame of the project:
- Floods: the variable related to floods is represented by the annual maximum of rainfall height or the maximum of a discharge for a given duration and for a given return period (or recurrence interval).
- Droughts: a drought is a deficit of precipitation so that it is insufficient to meet water demand. Three types of droughts are considered: meteorological drought (i.e. insufficient amount of precipitations), agricultural droughts (i.e. deficiency in water for crop) and hydrological drought (i.e. deficiency in water surfaces and subsurfaces).
- Desertification: according to UNCCD (United Nations Convention to Combat Desertification), it “is land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities”.
- Heat waves: these are defined by summertime weather conditions that are substantially hotter and/or more humid than average, for a location at that time of the year.
- Sea level rise: due to global warming, a world-wide sea level rise would inundate wetlands and low lands, erode shorelines, exacerbate coastal flooding, increase the salinity of estuaries and aquifers, and change the heights, frequencies and other main characteristics of waves (according to the IPCC working group).
Conclusions with regard to climate induced hazards are summarized below for every selected city.
Addis Ababa is the capital of Ethiopia, with a population that totals up 3 384 569 and has a subtropical climate which is moderated by its high height location. The meteorological station is placed at 2355 m. Floods cause annually huge damages to urban settlements along streams coming from the surrounding mountains. Height droughts occurred between 1964 and 2010 and 20 scorching periods (three consecutive days of hot temperatures) were counted over the 1987-2010 period. Based on this analysis, it is possible to conclude that Addis Ababa is vulnerable to floods, droughts and heat waves.
The city of Dar es Salaam borders the Indian Ocean. It was shown that the capital of Tanzania is vulnerable to climate induced hazard such as floods, sea level rise, soil and coastal erosion, droughts and outbreak of diseases. This vulnerability is worsened by deforestation, loss of biodiversity, high growth rate and poor strategic planning policies.
Douala is the largest city in Cameroon and is located on the Wouri river estuary. Its population is roughly 3 million people. Douala is particularly vulnerable to floods (strong rainfalls take place from June to October) and droughts (7 were listed between 1974 and 2010) and heat waves (many occurred: 374 during the 1985-2010 period).
Ouagadougou is the capital of Burkina Faso. It is located in the west sahelian region and the number of inhabitants is expected to quadruple in the next thirty years. The harmattan (a dry wind) and the monsoon are the two main factors that determine Ouagadougou's climate. The climate consists of a dry period from October to April with an average temperature of 30°C and a wet period from May to September. The cold season runs from December to January, with a minimum temperature of 19°C. The maximum temperature during the hot season, which runs from March to May, can reach 45°C. Ouagadougou is clearly vulnerable to floods, droughts, desertification and heat waves.
Saint Louis is situated in the northwest of Senegal. Its population totals up 176 000 people. The geographic appearance is characterised by (i) the sahelian region, where the city is located, (ii) the marshes that surround the city and (iii) the narrow island on which the heart of the city is built on. Saint Louis is located in a wetland area, 6 drought events were listed from 1974 to 2010. As the city is built on an island between the mouth of the Senegal River and the Atlantic Ocean, it is the most threatened by sea levels rise in Africa. Moreover, data showed particular desertification problems and 206 scorching episodes from 1983 to 2010. The city is strongly vulnerable to floods, droughts, desertification, sea level rise and heat waves.
Climate change and urban vulnerability in Africa - D. 5.2 Report on climate related hazards in the selected cities- submission date: 16 February 2012