The matter of the perennial flooding of Accra requires detailed investigation.
1. Comprehensive Hydrological Study
A full detailed hydrological study of Accra is required. The topological map of Accra, superimposed with the built, structural and environmental development, road and highways network, rivers and streams. Then a detailed outline of existing gutters and their relative sizes superimposed. This will clearly reveal that small gutters at higher topology should drain into larger drains at lower elevations and even into yet larger drains, ending up at rivers or streams. These follow the natural contours of the earth and ultimately into low-lying areas where rivers and streams run free!!! We often simply see gutter built as jobs for the “ladies”, each built the same size, even when several gutters converge at a point.
2. Aerial Documentation During Heavy Rains
There ought to be drone flights that take videos and pictures at regular intervals during such heavy rains and associated flooding to further document and detail the natural run of the flooding as it drains. These aerial studies will clearly outline and reveal the natural drainage path of the floods. These will aid the critical planning of a full hydrological drainage plan for Accra.
3. Road Infrastructure and Drainage Integration
Several roads including even the motorway have no existing drainage at the lowest slope of the road, they are tanked in by the curb on either side of the road and cannot naturally drain. I hope the new construction of the motorway will address this fundamental. Even the bridges and culverts I see being built appear inadequate for the 2 x4 lanes road being constructed. They simply appear to extend the existing size culverts, without taking into account the wider road and consequentially larger volumes of water that will flow during a heavy downpour. We are already creating new problems of flooding for the many homes and businesses that find that they are now in a valley relative to the new road level. Urgent steps must be taken to engineer better and larger paths for the waters and a more comprehensive drainage plan for the new motorway and other roads under construction. To add, I hope they are making and laying tunnels in the middle and across at regular intervals for the laying of power and fibre optic cable that might be required, along these routes for leverage energy and Telco networks.
4. Holistic Drainage Master Plan
Having done all these studies, now we have to prepare a detailed drainage plan that takes a holistic view of the entire Accra, what will be expanded rivers or streams to take the large flows, clear off natural and manmade barriers and obstacles. We have to be sure what flows into what and design and engineer it as such. Japan diverted a river in order to build a high-speed road and rail on the river bed!!!
5. Tidal Impact Assessment and Mitigation
Lastly, a study of the sea levels, lunar cycles etc is required to be sure that outlets of these rivers and streams that flow into the sea are not compromised by high tides that will naturally block the rate of flow out to the sea and lead to a backwash and exasperated flooding. In which case, we need to engineer some sort of deep dams in the river ways to hold flood waters during such high tide and heavy rains.
6. National Engineering Initiative
This is a critical national high-level engineering project with the best Ghanaian minds around the table!!!
My two pence!!!
Leslie Mensah Tamakloe
