HumBioEnvLogy: Flooding: an Environmental Challenge of the Coastal Cities and Low Land areas Like Lagos, Port Harcourt and Warri

We are at it again, the season of continuous rain; it is high time residents of low lands and coastal areas became more vigilant and cautious of their activities that lead to flood. Nature ordinarily will take its course, no matter how hard we try with the mind set of creating more luxurious settings for human satisfaction.

Flooding is simply described as the phenomenon by which water overflows or rises above its normal level to submerge or cover lands that are not usually covered by water. This normally happens during heavy rains, high turbulence or ocean waves that hit the shores, melting of ice in a very fast rate, rivers overflowing its banks and when dams breaks. Flooding naturally occurs as mentioned, and has significant role to play in the balancing of the ecosystem as it helps in the dispersal of foods to organisms, dispersal of plants and animals, dispersal of organisms for reproduction/mating, reduction of population explosion, reviving of lives of hibernating organisms, etc.

Flood most time occur due to unnatural causes, which may also be tagged as artificial causes of flooding. Human activities and technological advancement has contributed so much in the increase in flooding more especially in the low lands and coastal arrears. Our environments are tampered and are exposed to flooding through the following activities:-

Climatic change – the Earth’s temperature is continuously on the rise thus leading to global warming. This is primarily due to the use of fossil fuels that releases Carbon dioxide and other green gasses into the air which traps heat within the atmosphere and has lots of effects on the ecosystem which includes rising sea level due to the melting of the ice. Water increases in its volume when it dissolve from ice state to liquid and this accounts to why the atmospheric conditions (heat) increases the water level in the ocean and as such leads to coastal flooding.

Poor infrastructural planning and development – it has been noticed that there seem not to be a synergy between the engineers, planners, developers, environmentalists, and municipal authorities in the setting up of infrastructures and development of an area with prior consideration to flood. This is mostly the evident in coastal arrears. Emphasis ought to be laid on the tidal chat or inflow of sea water into the channels and how the flow may affect the draining of surface run off during and after rain and percolation. Drainages should be properly designed in sloppy form to restrict the inflow of sea water as the sea water is denser than the precipitating water, and such will push back on it causing more water to be retained and cover the land. Buildings and roads should be raised to a certain level and tilted towards the water ways to reduce flooding.

Infrastructural failures – during the construction of infrastructures like roads in coastal/flood prone areas, drainage systems are designed to be underground and when they get blocked, water does not drain through them again. This can be caused by the use of substandard construction materials, lack of maintenance, attitude of the authorities, etc. This is why a well-planned low land/coastal roads are always flooded.

Indiscipline – our unpatriotic and irrational attitudes as human contributes greatly in the blockage of drainage channels/systems. This is usually notoriously attributed to developing nations where drainage channels have been converted to refuse bin for all manner of solid waste. Sometimes, the street sweepers who are paid for the services have been spotted sweeping sands and other wastes into the drainage system, all in an attempt to cover a certain area within a given period of time. This accounts to why some of our drainage are filled with non-biodegradable wastes, sands, faeces, etc. the channel stenches, harbor organisms than can cause diseases/and infections. The nepotism exercised by the administrators in the award of contracts for the cleaning of the drainage to vendors who do little or no job like hipping of the packed solid objects beside the drainage and on the road without evacuation only for the rain to wash it off into same drainage does not help the situation.

Bridge construction – during the construction of roads to by-pass or cross water ways, bridges are put in places to enable both the road and water to have its way. This at times constrains the flow of water through it. The bridges also obstruct the free flow of water, making floating solid objects to hook within the columns and the base cap of the columns thus stocking sands that eventually block the passage of the water. When situation like this happens, the aim of the bridge construction is completely defeated as the blocked bridges will cause floods.

Deforestation – unsustainable lumbering, uncontrolled agricultural activities, building/acquisition of land for developmental and housing infrastructure has undoubtedly affected our forests – rain water, mangrove and swamps of the delta are either under serious threats or are completely destroyed by the activities of man. The forest trees have natural adaptive features to reduce the fast flow of surface water which minimises the concentration that covers land. Every plant in the forest irrespective of the size plays significant role in the reduction of the water level. They do this by absorbing the water through the roots and are stored/transported the leaves and released to the atmosphere by means of transpiration. Destruction of the trees that has the potentials in holding good volume of water has led to the increase of water in the soil, free flowing water, thus increases chances for flood.

Flood embankment – this traditional way of using earth walls to shore up flood waters has gone advanced as concretes and metal plates are now used for same purpose instead of the earth wall. This is done to create more lands and wage the flood for facilities like beach houses, factories, ports, depots, etc. This tends to push the water away from its natural settings and creates no openings by which the saturated soils can discharge its water content into the nearby water ways. This makes the soils to be supercharged and unable to absorb more water during and after rain as such will lead to flooding.

Impermeable surfaces – urban development has led to the coverage of large areas of land with bitumen/coal tar and concrete for roads, run ways, industries, ports, factories, storage facilities, big organisations, houses, etc., that if collected together covers thousands of hectares of land surfaces that are permanently impermeable. These are surfaces that should percolate water droppings or accumulated water into the underground aquifer and then to the water ways, by so doing, reduces flooding. Other ways by which soil surfaces are turned impermeable without being sealed are through soil pollution with petrochemicals as always seen in the mechanic workshops in developing world. The area is usually covered by the oily dark surface that seals pores /openings on the soil. Any droplet of water on it cannot be absorbed but will flow through the surface to the nearest permeable surface to percolate. This contributes immensely to the causes of flooding as experienced in our environment.

Flood prevention – floods that occur as a result of unnatural causes mostly can be controlled through the following ways:-

• Restoration of natural ecosystem like the swamps, mangrove, and rain forest that has been destroyed by man due to want for more land and creation of artificial island, etc. These individual vegetation have their own natural ways of helping the environment in flood control.

• Tree planting and/reforestation will help the control of flood as the roots of the trees not only create pores through which water percolates, they store water, and transfer some into the atmosphere, thereby reducing free flow of water and flood control.

• Land scape restoration will help to restore the floral distribution that blends well with the topography of every area and has its way of controlling the rise of water in the environment. Its importance cannot be overemphasised as it plays significant role in capturing of carbon dioxide that causes global warming.

• The infrastructural facilities within the riverine and river banks need to be revaluated and restructured to allow easy passage or flow of surface run off during rain as it will help in reducing flood. Some structures are situated exactly at the major exit channel of water and has always caused back log of flood in the area. If such facilities are restructured or removed, flow of water out of the covered land will be freely guaranteed.

• Alternative use of other sources of energy e.g. solar, electricity, other than dependent on fossil fuel will help create a sustainable future and reduce the greenhouse gas emission that causes global warming that indirectly dissolve ice which increases the water level thus causing fluid.

• There should be a very strict review of the activities of man towards the destruction of natural ecosystem like the swamps, mangrove and rain forests to create artificial lands for reasons that are not very justifying when compared with the advanced effect. This continuous abuse or working beyond the limits of nature has resulted to flood as they are no more places hold the volumes of water as reservoir.

• Control measures should be enacted against greenhouse gas and carbon emission through industrial pollution, vehicular emission, exploration, etc., as this will reduce environmental degradation and global warming which affect the water cycle.

• Campaigns and promotion of tree planting and establishment of parks in urban areas more especially the coastal cities and low land zones should be encouraged. This will help redevelop natural ecosystem that has the ability to retain and take up rain water and other precipitation.

• More approval and support should be given to developmental projects that incorporate permeable surfaces that allow water to recharge underground water supplies instead of allowing precipitation to run off and flood vulnerable areas.

• Regular cleaning of the drainage system and evacuation of the accumulated solid waste found and packed from the drainage channels.

Effects of flooding – the devastating and negative effects of flooding can be enumerated as follows:-

 Decay/failure of infrastructures

 Spread of diseases

 Loss of properties and life

 Loss of businesses

 Economic breakdown

 Loss of agricultural products and arable lands

 Dispersal of organisms