Discussions around the severity of the October 2011 flooding in slum urban communities in Accra, particularly around the area called Sodom and Gomorrah, are controversial. Majority of the media coverage blamed poor drainage and solid waste management systems in the capital as the culprit, while others linked the intensity of the rains to climate change. While these attributions can't be dismissed outright; they are also incomplete. It is dangerous to downplay the socio-economic factors that make poor urban communities vulnerable to flooding in the first place. A look at the interplay between climate, development, and society will help us understand that it is not purely incidental that the flooding happened in the poorest parts of Accra.
Rainfall over Accra – similar to that in most of the semi-arid climate zones of the globe –
is subject to extreme variations. The seasonal cycle of rainfall in Accra is considered bimodal, i.e. it shows two peaking periods (see figure 1) and a gradual increase from March, which peaks during May and June. Thereafter, the rainfall decreases during July-August, and then increases again during September to October. The bimodal nature of Accra's rainfall is modulated by the passing of the rainfall band, linked to the Inter-tropical Convergence Zone (ITCZ). The Accra airport weather station, recorded 156 mm of rain in just two days on 24-25 October 2011. This is as much rain as what is normally experienced during the entire wettest month of the year (June). In other words, while the amount of rainfall was well within the range of what Accra normally receives during the peak rainy season (June), it is the distribution of the rainfall that was highly problematic and triggered the flooding disaster.
Although such singular rainfall episodes cannot be directly linked to climate change, the contribution of global warming cannot be ruled out. However, the role of sea surface temperatures, both in the adjacent Atlantic and the Indian Oceans are also important factors, as were perhaps the prevailing La Niña conditions in the Pacific.
Intense rain spells, such as what occurred recently, can trigger massive water flows at hazardous levels. But as we have witnessed, what transforms a natural hazard into a disaster has more to do with reasons that are not natural and in this event, the inability of urban infrastructure (particularly drainage and sewage systems) to cope with rapid urbanization. Whatever drainage is available was blocked by solid waste. A 2007 Ghana Country Environmental Assessment report by the World Bank estimated that only 40 percent of urban residents in Accra were served by solid waste collection services in 2004.
A long-term solution to Accra flooding, therefore, involves improving the solid waste management system, constructing more and improved drains, and planning infrastructure/settlement development in a way that do not block the natural waterways. Furthermore, since we are likely to experience more and more intense rainfall events over a short duration in a warming world, investment in developing a credible early warning system, embedded within a flood management system from national to local levels, is both urgent and critical more than ever. Rainfall spells events, such as the ones that cause the October flooding over Accra, can be predicted 3-5 days in advance. With the aid of robust monitoring systems, the skill in estimates of the intensity of rainfall can also be improved to provide reasonably accurate rainfall forecasts to enable early warning. Institutions like the National Disaster Management Organization and Accra Metropolitan Assembly need warning information about abnormally high or untimely rainfall to enable them to mobilize in advance. If communicated and understood properly, early warning system could help make contingency planning and evacuation more precise and lives saved.
However these technical solutions will not be enough. It is important to address flooding and other climate risks within a broader development context by linking efforts to considerations of poverty reduction and rural development.
The settlement history of Accra shows that slum communities that are highly exposed to flooding events are created by economic migrants who had to find accommodation in the informal housing sector in the fringes of the city where rent is less expensive and construction of houses is poorly regulated. While the reasons for migration are complex, climate is one of the strong push factors, as demonstrated during the Sahelian drought of 1995. To identify the populations at risk to flooding in Accra, a recent study commissioned by UN HABITAT (2011) tried to predict which drainage channels would overflow given a certain amount of rainfall. The findings indicate that a large portion of the population that are most exposed to flooding tend to be those living in areas with high slum index. The poor state of housing and infrastructure in these areas, as well as the encroachment of dwellings into the waterways, all contribute to increasing the risk of flooding.
The development choices of a country can either enhance or diminish its capacity to adapt to adverse climate impacts, such as flooding. Having registered impressive economic growth in recent years, Ghana is at a significant crossroad of economic development and has an enormous opportunity to get things right. While more money will allow it more choices, careful planning and strong political leadership are needed in order to develop in a way that avoids exacerbating exposure and vulnerability to climate change impacts. Addressing the vulnerability of places like Sodom and Gomorrah means addressing the root causes that create these blighted places in the first place. A development that does not take into consideration the plight marginalized segments of its population runs the risk of creating massive swaths of communities that have to constantly live through the horrors of disasters.
Figure 1. Accra seasonal rainfall amounts during different months of the year (based on 1971-2010 averages) (Data courtesy of Joseph Portuphy/Ghana Meteorological Service)