A flood is an overflow or deluge of water that comes from a river or other bodies of water and causes or threatens or damages.
“Floods are one of the most dramatic interactions between man and his environment, emphasising both the sheer force of natural events and mans inadequate efforts to control them. (Ward, R 1978)”
Since the early 20th century we have seen flooding increasing through out the UK. In the last 10 years flooding has become more obvious and dangerous to populations around the UK.
Flooding can be seen to have a number of causes, some natural in origin and some a result of human intervention, the question is how has flooding increased and what factors have caused it to do so.
A natural effect is a cycle or systems reacting to an input and giving feed back.
This can be vegetation taking up more carbon dioxide and growing bigger to cope with CO2 emission or as in this case it is the rivers and seas releasing water to the land to deal with increased quantities of water at any given time.
The main natural effect towards flooding is changes in climate mainly from precipitation.
Looking at studies you would assume this was from increased precipitation but as shown in Figure 1 it is more likely that occurrences of continual precipitation over a short period of time.
This is due to water saturating ground during the first few hours of rainfall so when precipitation is sustained over a day or couple of days the ground can not cope with the excess water and so moves over the saturated ground as run off.
This run off collects in streams and rivers causing serge’s in river flow, to an extent that the rivers can then not cope with the inundation of water so overflow.
Thus causing land and floodplains to flood. During winter months ground is more likely to become frozen which increase run off and is why most flooding has been seen in winter months. But this does not mean it is not possible to have flooding during the summer months.
From news and public concern these days we are seeing more reactions to flooding. Scientist has come to the conclusion that due to climate change flooding will continue and worsen. As we see summers getting dryer and hotter and winters becoming colder and wetter a pattern of increased flooding seems inevitable.
In winter months cold ground decreased infiltration of precipitation but in the summer months dry crumbly soils have the same effect towards the rain.
Other factors that may linked to flooding apart from prolonged rainfall is the melting of ice which increases serge’s of water into rivers and streams. Increased melting is a concern brought about from increased global warming.
With colder winters and hotter summers predicted to be on the increase certain other problems escalate and increase potential flooding.
When winters get very cold precipitation turns to snow fall, this snow settles and builds up. Once it eventually gets warmer there is a sudden increase in water for rivers to deal with.
If this snow stay and it begins to rain the snow is melted and twice as much water enters the ground this runs off into overflowing rivers and streams. If precipitation is extensive flooding is inevitable.
Since the early 1990’s we have seen flooding over the UK more predominate, as we have dealt with the problems ourselves not just watched it on television.
Figure 2 and figure 3 are photos taken from the BBC News website showing sites of flooding in October 2002 and February 2004.
These pictures capture the very real and dramatic effect water can have on an urban area.
Luckily these floods only lasted a couple of days and no more than a week.
Unfortunately they had already caused thousands of pounds worth of damage and put many members of the public in danger.
Figure 4 and 5 show that even in the summer months floods are possible and causes as mush damage as they do in the winter. Figures taken from BBC News website
Global warming resulting in warmer winters and colder summers. Global warming also has a net result that there is more snowmelt, more precipitation and less infiltration. This increases flood risks and occurrences.
Global warming is said to be on the increase as we burn more fossil fuels each day in generation stations. This is to cope with further swelling populations who like there creature comforts a little too much.
Building of Dams in the UK took place before designers knew the effects of internal erosion. Therefore dams in the UK are more susceptible to cracking and collapsing. Higher safety measures have been taken place to keep dams safe. However if there were ever an outburst from a dam it would send serge of water into nearby rivers and streams causing sudden flooding.
Land use is the next big problem in the UK. Deforestation happened so long ago all over the UK that it can not be included to such an extent. Major recent changes in land use such as increase in agriculture and leaving fields without vegetation in them over the winter months decreases chances of infiltration and interception.
Urbanisation changes the land the most dramatically, as it removes vegetation and builds and covers the land with impermeable surfaces. This is not such a problem during summer when there are a few showers but in winter the drainage system installed on roads and streets can not cope with huge amounts of water.
In extreme cases flooding fills drains and pulls waste up with it, which as a result can cause illness.
The most crucial and most idiotic reason that flooding now occurs in urban areas is location.
Governments have been told they need to meet deadlines and build a certain amount of houses to cope with people moving in and out of cites. This has resulted in the use of floodplains for homes, local businesses, schools and other necessary amenities
Flooding has been occurring for hundreds of years. From human development and urbanisation in the UK and other places in the world flooding is becoming more common in everyday life.
Nature uses flooding to help balance the hydrological cycle so it can keep running.
Increased global warming is one of the most probable causes for increased flooding as figure 6 shows that precipitation has been on a constant level for many years.
But saying it is all global warming’s fault brings up another problem. Is human activity causing global warming or is it the way the Earth balances its cycles, when one system increases another decreases. With this type of balancing there is always going to be over flow and that’s what a flood fundamentally is an over flow or excess water that a river, sea or stream can not cope with.
My opinion is that people actually do not realise what is happening to the world and their habitats until it effects their way of life. It has been shown over many a year that flooding of homes and businesses causes evacuation, which unsettles everyone.
With increased building on green field sites, which so happen to be floodplains, it is the Government and housing planners that are being greedy. They should think about changing climates and the problems flooding actually causes before a house is placed some where that is unfit.