One of the most complicating aspects of research is the constant flow of our “knowledge”between fact and fiction. There is an ever present need to re-examine and re-evaluate the scattered bits of evidence with which we try to analyse the activities of mankind’s in the modern world as it affect the environment. It is not uncommon to find that yesterday’s “fact” is one of today’s discarded theories or that what is merely a calculated guess today maybe a verified historical maxim tomorrow.
We will be discussing how "Man kind" actions has drastically induced flooding.
Floods are one of the most common hazards in the World, however not all floods are alike. Some floods develop slowly, while others such as flash floods, can develop in just a few minutes and without visible signs of rain. Additionally, floods can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states. Flash floods can occur within a few minutes or hours of excessive rainfall, a dam or levee failure,or a sudden release of water held by an ice jam. Flash floods often have a dangerous wall of roaring water carrying rocks, mud and other debris.
Overland flooding is the most common type of flooding, it typically occurs when waterways such as rivers or streams overflow their banks as a result of rainwater or a possible levee breach and cause flooding in surrounding areas. It can also occur when rainfall or snowmelt exceeds the capacity of underground pipes, or the capacity of streets and drains designed to carry flood water away from urban areas.
You have to be aware of flood hazards no matter where you live or work, but especially if you are in low-lying areas, near water, behind a levee or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds or low-lying ground that appear harmless in dry weather can flood.
What would you do if your property were flooded? Are you prepared?Even if you feel you live in a community with a low risk of flooding, remember that anywhere it rains, it can flood. Just because you haven't experienced a flood in the past, doesn't mean you won't in the future. Flood risk isn't just based on history; it's also based on a number of factors including rainfall , topography, flood-control measures, river-flow and tidal-surge data, and changes due to new construction and development.
The Impact of Human Activities on Flooding
More people are living in towns and cities, population growth and urbanisation has led to demand for land to build on - floodplains are flat and are food for housing, concrete and tarmac, used for roads and pavements as they are impermeable, precipitation cannot infiltrate so gets into the river much more quickly, interception is reduced as trees and plant matter is removed so precipitation gets into the river much more quicker and easier. Often surface water is channelled directly into drains and sewers. Construction of bridges over rivers constrict rivers, slow discharge and reduce the carrying capacity of the river.
Rapid deforestation has taken place. Land is now used for framing, settlement and mining etc. With no trees there is a greater risk of soil erosion as the precipitation is not intercepted. Flood damage is greatest near the mouth of a river because wide,flat floodplains are most susceptible to damage. The volume of water is greatest here because many tributaries have joined the river.
Global warming has been blamed for what some claim is an increasing frequency of flooding. There is evidence that average sea temperatures have risen and this rise has been blamed for the increasing frequency and severity of tropical revolving storms in the Caribbean. Such storm bring heavy rainfall and storm surges along the coastlines of countries lying in their path. In spring 2005, scientist reported that average sea temperatures were 3 degrees Celsius above normal and predicted that the 2005 hurricane season in the Caribbean and southern states of the USA would be particularly savage. This proved to be the case. notable hurricanes included Katrina, which led to the flooding of New Orleans.It is predicted that global warming will result in reduced rainfall in some areas, but in other, such as western Europem rainfall totals might increase. higher temperatures will result in increased evaporation over the seas and oceans, leading to greater precipitation. Such an increase will inevitably cause more rivers to flood, particularly since most floodplains have become heavily urbanised over the last two centuries.
Global warming has lead to the melting of the polar ice caps. One major consequence of this would be a rise in sea level, so floodplains lying close to the present sea levels would be at risk from flooding. The major deltas of the world, such as those of the Nile, the Mississippi and the Ganges-Brahmaptura, would be at particular risk.
What step have you taken to stop or at least reduce Flooding in your area?
SAVE THE EARTH
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