As in many African cities, urban floods are an increasing problem since urban drainage systems are not in line with the strong increase of the population. In the last few years, severe floods hit Ghana’s capital Accra. On June 3rd 2015, heavy rains created flooding that impacted many parts of the Greater Accra Region. Over 200 people lost their lives and many more were displaced and lost their property and livelihoods. Adding to these are the costs of disrupted traffic and economic activities. Besides the impact of the generated flood wave, heavy rain result into pockets of heavily contaminated and bacteria loaded standing water, affecting the health of the communities that reside in low-lying, vulnerable areas.
Accra serves as an example for other African cities with similar development patterns. The rapid urban expansion of Accra has transformed the surface of the basin into a nearly impervious area. There is hardly any infiltration of rainwater and retention capacity for flood water is limited. This leads to larger run-off flows that need to drain out of the neighborhoods. Currently, Accra’s urban drainage system is not capable of coping with the generated flows of extreme rainfall events. This could be due to the layout and dimensioning of the network. Also, the accumulation of solid waste in the drains could have a negative impact on water safety and quality. In some parts the run-off might even be blocked by high sea water levels.
In order to reduce disaster risk and losses in lives, livelihoods and health globally, priorities have been set-up under the Sendai Framework for Disaster Risk Reduction 2015-2030. The first priority for action is ‘understanding disaster risk’ and explains how “disaster risk management needs to be based on an understanding of disaster risk in all its dimensions of vulnerability, capacity, exposure of persons and assets, hazard characteristics and the environment” . In an environment with little available field data of the urban drainage system, such as Accra and other African cities, it remains a challenge to evaluate the flood risk of the city.
The study of the current solid waste handling is essential to come up with solutions for the flooding problems. Accra’s official waste disposal sites are small and overloaded[JS1] , encouraging illegal disposal in drains or the ocean. The effect of waste disposal in the drains and increase of urban flood risk seems apparent. However, the relation between solid waste management and discharge capacity of the urban drainage network has not been quantified in a scientific framework. A systematical assessment of the accumulation of litter in the drains and the origin of the waste is needed in order to get an insight into the effect of solid waste on flood risk.
A cooperation is set-up between TU Delft University, Ghanaian universities KNUST , University of Cape Coast, University for Developments Studies and consultants (HKV Lijn in Water, Witteveen+Bos, Berenschot Consultant and Colan Consult) to analyze the flood risk and assess the causes of urban flooding to ultimately propose sustainable measures in order to reduce the flood risk in the capital city of Ghana.
This project brings together relevant stakeholders in urban drainage from the City Council AMA & various governmental departments (HSD, URD, WMD), NADMO, Ministries (MLGRD, MWRWH), universities, consultants, institutions (IWMI, WRI), World Bank to inhabitants in order to find solutions for the regular flooding problems in Accra. This project helps them to better understand the flooding problems and identify solutions to secure the people of Accra.
A preliminary time-line and summarized list of activities can be seen above. A period of preparation in the Netherlands precedes the fieldwork in which literature research is conducted, a fieldwork plan is designed, workshops are planned and all the necessary contacts are established. In addition a hydrodynamic model of the city of Accra is set up to be completed with field data.
From April 23-May 29, the TU Delft student team will travel to Accra for 5 weeks of fieldwork and together with Ghanaian students will take measurements throughout the pilot study area on the dimensions and capacities of the drains. The students will be assisted by experts of HKV and Witteveen+Bos in their field work. Two workshops are organized during the fieldwork in which the approach and preliminary results will be presented and ideas shared and discussed with stakeholders. Surveys and interviews with inhabitants are carried out during the fieldwork.
Garbage removal in Ghana is done every first Saturday of the month, known as ‘National Sanitation Day’. Our project joins this city council campaign on the 7th of May to raise awareness about the effects of waste disposal on the flood risk level of the city.
Upon return to the Netherlands, analysis of the data will be completed and the deliverables prepared. Experiences and lessons learned during the fieldwork and project will be bundled to set-up the methodology
The current drainage situation in Accra is not sustainable. In our initiative, we see the following aspects that will help to improve this.
· Our innovative and integrated approach to assess the flood risk of the city include multiple fields of expertise: drainage, waste, institutional and social aspects. Using our experiences in the field and input from experts, a methodology for urban flood risk assessment is developed that can be applied throughout the city of Accra and other African cities facing similar issues.
· We experiment with different ways of data collection. In addition to using remote sensing data and smart field surveys, we include social media and open mapping initiatives . Integrating these data sources allows for innovation in urban risk assessment and planning studies.
· Our project focuses on involving all stakeholders to understand and contribute to solve the flooding problems in Accra. Working together with local students on mapping flood risk and finding solutions to help the city of Accra enables sharing of technical knowledge between universities and ensures continuation of the research. Moreover, increased knowledge on these topics is beneficial for future projects and business opportunities for the participating partners.
 Sendai Framework for Disaster Risk Reduction, UNISDR, http://www.unisdr.org/we/coordinate/sendai-framework
 Akvo FLOW, Akvo, http://akvo.org/products/akvoflow/
 OSM, Code for Ghana, http://www.codeforghana.org/2015/06/30/openstreet.html
 Mapping Drainage in Dar es Salaam, Humanitarian Open Street Map Team (HOT), https://hotosm.org/updates/2015-11-19_mapping_drainage_in_dar_es_salaam