Ghana’s Perennial Flooding from an Engineering Perspective

A Voice of Reason in the Midst of Chaos and Wailing – Ghana’s Perennial Flooding from an Engineering Perspective

Part 1

The losses due to perennial flooding up and down the country are tremendous in terms of life, land, agricultural production, housing, infrastructure and outbreak of diseases. Flood causes not only enormous physical damage to life and property, but also psychological and emotional devastation. People, particularly the poor lose their belongings which are difficult to replace due to their economic situation.

The economic loss to individuals, the state, corporate organisations and human misery are epic. Sadly, we have lost a number of lives in this year’s flooding, may their souls rest in peace. I think every life lost on such occasions is one too many and must not be allowed to continue. We have failed woefully as a nation to find a comprehensive solution to what has become a perennial nightmare plaguing our nation.

Do not let us for once take solace in the fact that it happens to some developed countries as the sort of weather conditions these countries face are more severe and unforgiving, and will not be in the mess we find ourselves if it was the other way round.

Last year, the government did set up a task force to ascertain the causes and make recommendations to control or mitigate the perennial severe flooding. I think this findings and recommendations should be made public so that practicing engineers can offer their expert advice to help control or mitigate the problem.

As someone who has lived in close proximity to the Odor River in Christian Village, I have witnessed it overflow its bank on several occasions in the past two decades. In the absence of any report pinpointing the exact cause(s) of the flooding, I believe I am well placed to invoke my conservative Engineering judgement on the cause(s) of this flooding menace; and make some recommendations which I hope relevant authorities will take onboard to help mitigate or control flooding across the country.

Some of the possible causes of the flooding are that during times of rain, some water is retained in ponds or soil, some absorbed by grass and vegetation, some evaporates, and the rest travels over the land as surface runoff.

Theoretically, floods occur when ponds, lakes, riverbeds, soil, and vegetation cannot absorb all the water. Water then runs off the land surface in quantities that cannot be carried within stream channels or retained in natural ponds, lakes etc. It is estimated that about 30 percent of all precipitation is in the form of runoff. River flooding is often caused by heavy rain. A flood that rises rapidly, with little or no advance warning, is called a flash flood. Flash floods usually result from intense rainfall over a relatively small area, or if the area was already saturated from previous precipitation or is largely covered by hard standings (buildings and pavements).

The increase in population and unplanned growth of towns and cities, encroachment of settlements/habitations blocking natural drainage channels of waters over the past decade have greatly reduced the natural land surface area available to readily absorb rain water. These have significantly increased the percentage of surface runoff in the event of heavy down pour. Coupled with streams, rivers and ponds not having the capacity to accommodate the increased surface runoffs, they overflow their banks, finding their natural channels blocked, flood waters ruthlessly wreak havoc on these settlements.

Other reasons are indiscriminate dumping of waste into drains and clogging them up, improper drainage systems accompanying our road networks, developments within flood plains, unnecessary bends along our water courses restricting the free flow of water and worst of all a chronic lack of engineering solutions (technical knowhow) on the part of state engineers, even though one would expect these solutions to be blindingly obvious to any trained Geotechnical/civil engineer.

I have watched in frustration on a couple of occasions when contractors came to dredge the Odor River, dumped the dredged material right on the river bank only for it to be washed back into the river at the first sign of rain.

When it came to the construction of the bridge connecting Christian village to Domi over the Odor River, the approach embankments were badly designed and constructed, as the levels of the approach embankments were almost at the level as the surrounding flood plains.

I am afraid, throwing colossal amounts of money at the construction of storm drains as being proposed by the mayor of Accra is not going to be the panacea of the perennial flooding problem.

This will be a complete and utter waste of the tax payers’ money and a kneejerk reaction, merely designed to paper over the cracks and to tell Ghanaians that authorities are doing something to solve the problem. In the cold light of day, we must develop a comprehensive sustainable drainage policy to deal with the problem.

In part two of this article, I shall be discussing the solutions to these challenges stated above and recommendations that I hope the policy makers will take on board.

David Klutse Geotechnical Engineering d_klutse@yahoo.co.uk .............................................................. ..............................................................