Crowd Sourced Mapping for Flood Risk Assessment

The flood assessment in Accra, Ghana was based on data collected via social surveys and stakeholder consultation.

Floods in Accra are caused by a combination of factors, including the poor construction of the drainage system and waste disposals in the drainage canals.

This was the outcome of a flood risk assessment conducted as part of a project funded by the Via Water programme.

The study was a co-operation between students from the universities of Delft University of technology (the Netherlands) and Kwame Nkrumah University of science and technology (KNUST, Ghana) and Dutch consultants HKV Lijn in Water, Witteveen+Bos, Berenschot and Colan. 

Insufficient drainage capacity
The flood risk assessment suggested that the main influence on flooding of Ghana's capital city comes from imposed downstream water levels and not from the rainfall in the pilot area itself.

The high heterogeneity in drain types creates hindrances and makes it difficult to predict the water behavior. At specific bottlenecks such as culverts and erosion paths, the capacity of the system is insufficient.

Blockage by waste disposal
On top of this limited capacity, waste disposal and accumulation in the drains causes blockages and decreases the capacity especially in low-lying areas.

Siltation occurs along the entire drainage network, especially in the major drains and flat areas.

Based on the hydrodynamic model, however no clear conclusions could be drawn on the effects of waste and silt accumulation, given the misrepresentations of the storage capacity of the water system.

All these factors, within a scenario of increasing climate variability and more intense rainfall, have been considered in this study to analyze the flood risk and assess the causes of urban flooding in a pilot area in Accra. 

Stakeholder consultation
The flood assessment method includes different activities, such as stakeholder consultation, technical and social fieldwork in a neighborhood scale pilot area, flood assessment modeling, awareness creation, and social media experiments to collect relevant data.

An additional aim of the project was to develop a methodology for urban flood risk assessment that can be applied in other African cities facing similar issues.

Source: Duch Water Sector 

Media

Taxonomy

• Water
• Flood Modeling
• Flood damage
• Flood prediction
• Flood

1 Comment

1. After this assessment, Accra is still facing the same problem and even worse. Anytime there is rainfall regardless of the intensity, the chances of flooding is high. So my question is: Why are we still facing such problems? What are the authorities doing about it? The decision makers, what is their role? The citizens, what are they doing to help? Has there been any initiative to curb this situation? It is heartbreaking for the Country capital, after 60+ years of independence to be experiencing flood after every rainfall. 

   My Request: 

   I am a master student (Water Engineering) at the Pan African University Institute of Water and Energy Sciences (PAUWES) and I am interested in working on a Flood risk management in the Capital,Accra. I would appreciate it,if you can provide me with any information or document that will help me. 

   Thank you