Tuesday, 3 July 2012

Flooding: Causes and Effects.

Floods in Hereford and Worcester, UK. Source: BBC
Hi guys,
You will agree with me that flood events are one of the greatest environmental disasters of our time. In almost every continent of the world, there is a reported case of flooding and storms and without any doubt it is undesirable as it has led to the loss of many lives and property.

Flooding is primarily caused by natural weather events like rainfall and thunderstorms. Whenever there is heavy rainfall combined with thunderstorms over a short period of time, you can be sure that flooding will occur. Extensive rainfall over a long period of time will also lead to flooding. A flood will also occur when a river overflows its bank and the excess water spills onto the flood plain, which is usually also as a result of heavy rainfall. 

Scientists also say that greenhouse gas emissions have increased the occurrence of extreme weather events, making flooding more likely. In the United Kingdom, research carried out on flood events that occurred in 2000 was attributed to more green house emissions in the atmosphere which led to greenhouse warming and made the floods more likely. Scientists in Oxford University performed a model of the atmosphere as it actually was, and carried out another model of what the atmosphere would have been without the carbon dioxide and other greenhouse gases. Interpolating the two models on a third model, they found that the likelihood of the flood occurring was doubled as a result of humanity's emissions of carbon dioxide and other greenhouse gases.That year, the Hampshire village of Hambledon in the UK was underwater for six weeks and the loss to the country was estimated to be about £1bn.

Some of the factors that may encourage flooding include:
  •  A lack of vegetation and woodland. This is because trees and other forms of vegetation obstruct surface runoffs, while roots of trees take up water from the soil. A lack of vegetation will mean that surface runoffs will be high, and this can lead to flooding.
  • Rivers surrounded by steep channel may also lead to flooding when the river overflows its bank as a result of excessive rainfall which lead to a high surface run off.
  • Drainage basin in urban areas are made of concrete which is impermeable and encourages surface flows. The drainage system takes the water quickly and directly to sewage treatment plants or as in some countries directly to rivers. Heavy rainfall in short periods in instances like this will lead to flooding. Faulty or ill maintained sewer networks and insufficient drainage networks will also encourage flooding.
  • Buildings and other developments like car parks in inappropriate places such that they prevent rainfall from draining away naturally can also lead to flood events. 
  • Canals, reservoirs and other man made structures can fail causing flooding to areas downstream. Industrial activities, water mains and pumping stations can also give rise to flooding due to failure.
The effects of flooding includes damage to homes and properties, potential loss of lives, disruption in livelihood and communications and usually an economic loss to the Government. This is because businesses may lose stock, patronage and productivity. Flooding can also affect vital infrastructure. Tourism, agriculture and transportation can also be affected. Road links, canals, rail links may become damaged. The repair cost of the damaged infrastructure can be very high and the period before reinstatement long. Potable water supply may be lost or contaminated and these can have significant health effects as well. One good thing about flooding though is the deposition of silt on the flood plain making it fertile for agriculture and thereby supporting the livelihood of inhabitants of such areas by the provision of food. People living on or near floodplains may rely upon regular flooding to help support their farming and therefore provide food.

Controlling Flood events includes Dam Construction. 
Kainji Dam in Northwest Nigeria
Dam are built along the course of a river. This helps to control the amount of water available for discharge and excess water is held back in this way and released in a controlled manner. This approach helps to reduce the risk of flooding. The stored water can be used to generate hydroelectric power. The downside of building dams is that they are expensive and need to be properly maintained.
Floods can also be mitigated against by a process referred to as river engineering. This entails widening or deepening the river channels to enable it carry more water and reduce the risk of flood. This in itself is a potential flood risk because the water flows faster and may soon flood downstream.

Proper urban planning entail controlling developments close to a floodplain which helps reduce the chance of flooding. Drainage and sewer systems should be properly planned and well maintained. Clogging the sewer system with litter as is the case in most developing metropolitan states can significantly increase the risk of flooding.
Afforestation or the planting of trees should be practised in flood plains and areas prone to flooding. This is a low cost and environmentally friendly approach to reduce and prevent floods.

Flood management approaches should be economical, environmentally friendly and socially sustainable. Sustainable developments manage the immediate flood situation (prevention and control) without compromising the needs of future generations.


  1. you can add much on above topics and also precautions. otherwise it is a excellent blog.

  2. can give more information about flood management ,otherwise its really good