A root cause of flooding in Accra: developers clogging up the city’s wetlands
Ghana has six designated Ramsar sites. These are wetlands designated under the criteria of the Ramsar Convention on Wetlands, an international treaty that seeks to protect them. In Ghana, these sites are mainly along the coast and are meant to be protected as set out in the convention. But the sites have become targets for property developers whose activities are leading to a decline in the flood resilience of many parts of the capital, Accra. Environmental scientist Chris Gordon explains the functions of wetlands and why more needs to be done to protect them.
What is a wetland?
Wetlands are considered under the Ramsar Convention “areas of marsh, fen, peatlands or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres.” Ghana is a signatory to the convention and the first wetland designated was the Owabi Wildlife Sanctuary Ramsar Site. Wetland areas in Ghana cover all the country’s beaches, mangrove areas, river buffer zones and low-lying land that is flooded by water, at times to a depth of about six metres.
What is its importance to the environment?
Wetlands are important in many ways and are relevant to almost every aspect of human life. They serve as a buffer for floods as they absorb water. They also help reduce the impact of drought as they replenish groundwater by releasing that trapped water slowly into aquifers (the rocks that hold water underground).
The holding capacity of wetlands helps control floods and prevents water logging of crops. Mangroves also reduce the impact of storm surges, and protect the coast from erosion.
Wetlands serve as breeding and nursery grounds for several species of marine fish, which are a source of people’s livelihood (both as fisher-folk and in the downstream fish value chain). They also provide medicinal plants and building materials as well as household items such as mats.
Several species of animals and plants need wetland conditions to survive. All of these animals and plants have intrinsic value too, in that they give people pleasure. Wetlands are very peaceful places.
Why are they under threat in Ghana?
Wetlands are targeted for commercial and residential development in urban areas where there is a shortage of land or in areas where the wetland are seen as prime land for tourist development along the coast.
In the urban setting, wetlands are usually the last places to be developed.
So in a place like Accra, wetlands in low lying flooded areas are being targeted because almost every space has been encroached as a result of ill considered developments (sometimes with the indiscriminate allocation of building permits by local authorities).
Wetlands aren’t suitable to build on. Wetlands soil is waterlogged, often acidic or saline and has a high clay content. It is therefore unstable. Building on this soil is not the wisest thing to do: the buildings are never strong. Even after adding chemicals to the cement and concrete, you find that groundwater in the wetlands erodes the foundations. Filling up the wetland by piling materiel on it does not help, as this material act like a wick bringing corrosive chemicals to the surface.
Landowners know this, but continue with their developments.
What has the impact of the developments been?
The major impact – especially in urban areas – is tied to fact that the wetlands lose their function of acting as a sponge. Wetlands soak up the excess runoff and then release it slowly. This stops high water levels rising, and flooding. The loss of the greenbelt and urban wetlands in Accra has reduced the ability of wetlands to retain water when there is unusually heavy rain.
To build in a wetland you usually need to fill it. You have to add material to build it up. The water that would have previously occupied that space is displaced and needs to go somewhere else. So you may have built years ago and feel your building is safe. However, the water that’s been displaced will result in flooding. The result is that infrastructure such as roads which were previously never flooded now become flooded.
What can be done?
To restore a wetland after it has been encroached on doesn’t just involve removing a building. You have to take away the material that has been put there, in some cases illegally, then you have to try to seed the wetland with the correct types of plants and hope that the animals will come to reestablish it.
It is a long, expensive process. Probably the simplest wetlands to restore are the mangroves along the coast. But even then, the problems caused by erosion, sea level rise and plastic pollution and increased sedimentation because of the runoff are difficult to turn around.
Wetlands are being restored in parts of Europe and North America, because authorities realised that the value of having a wetland was greater than the development that was there.
But this action is rooted in behavioural and attitudinal change. Ghanaian needs to have to get people to stop doing the damage. Then we can see how to remove some of those buildings which are in waterways, how to open culverts, how to plant trees to increase infiltration (the flow of water from above ground into the subsurface). And how to get people to stop paving their entire compounds with tiles which increase water runoff.
It’s everyone’s problem. And everyone can benefit from solving it.