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Thursday, April 27, 2006

 

surface permiablity and flooding in urban areas

Urbanization poses a very unique problem to the inhabitants of the area. As an area becomes more urbanized it loses natural surfaces of soils and vegetation to the impermeable surfaces of cement and buildings. The problem here is that as water accumulates in the urban area it flows off the impermeable surfaces along old streambeds or into oversaturated natural ground cover.
The problem of impermeable surfaces is that water is not the only substance that is not absorbed. Other fluids, including toxins like engine oil or gasoline, also stay on the surface. In the event of precipitation, all the chemicals that were on top of the soil now flow with the water run-off into stream channels and the natural ground cover and end up in the water supply.
As urbanization spreads, surface permeability decreases. The decrease in available soils for water absorption leads to increased run-off. As the run-off increases, so to does flooding and water contamination. This also prevents water from getting into the ground to become part of the water supply as it normally would, which can decrease the amount of water available to the people of the newly urbanized areas, as well as lead to fires and other natural hazards.
As cities grow, so to do the demands for water. What is often overlooked is that the city is generating its own loss of water in more ways than one. Some cities have devised ways of containing the run-off created by urbanization, but this does not really address the problem. Also, most cities that find themselves short of water do not devise ways to ensure that they will not run out.
In Colorado Springs, we have two different ways of dealing with water supply. The county water districts allow new building permits for whole communities, gulf courses and all, whether or not there is enough water to support it. The water sanitation districts have put on watering limitations in recent years, but these will probably go away when the drought goes away. On the Air Force Academy, the water sanitation has come up with a way to reuse water. All the grass medians have signs warning you that the very funky smelling water is non-potable.
A good way for cities to deal with both the water run-off caused by urbanization and an impending shortage in the water supply, also caused by urbanization, is to learn to not just store storm run-off, but to reuse as much water as possible. Raising water rates will not curb the cities issue of new building permits. However, the issues created by increased urbanization might also hold the solutions.

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