Urbanization increases Essay Example for Free

Urbanization increases Essay Golf courses also use fertilizers and chemicals in watering and maintaining the area which also contribute to the contamination of water. According to 1FAOs estimate of changes of forest area cover in developing countries, the world’s forest area had significantly decreased during the period of 1980 to 1995 largely brought about by development and the demands of urbanization. The developing countries have contributed to the natural forests as much as 25%, an average of 12% in Latin America, 5% in Asia and 8% in Africa (FAO, 1997). It has to be stressed that the figures correspond to only 15 years span. Gornitz and colleagues also found that vegetation clearing accounts for a one percent reduction of annual stream flow and an average of 10% decrease in the annual volume of freshwater used by humans (Gornitz et. al, 1997 page 148). The most direct physical impact of urbanization to the interruption of the water cycle is the general increase in the impervious cover (IC). The increase in IC due to urbanization affects the water cycle in these ways: 1. Urbanization increases impermeable land covers such as sidewalks, roads, roofs and parking lots. These urban structures decrease the amount of water to be absorbed by the soil as infiltration process is hardly possible to occur in these areas. In highly urbanized areas, more half of the volume of rainwater flows as run-off (Center for Watershed Protection, 2003). Studies also reveal that in cases where impervious cover is less than 10%, streams to where run-off flows remain protected. On the other hand, if IC is above 10% run-off that goes to the streams will cause the ecosystem to be degraded (American Society of Civil Engineers, 1996). Center for Watershed Protection said some of the evidences of this damage are bank erosions, sedimentation and the loss of stream bank tree covers. 2. Urbanization significantly increases annual floods. As infiltration and transpiration is reduced much of the surface precipitation is diverted to the drainage system. In a pre-urban setting, precipitation is intercepted by the natural vegetation through the process of absorption. Ground cover and forest canopy naturally absorbs rainfall through their roots. The wider the ground cover and the denser the forest canopy, infiltration and transpiration of precipitation are held in its natural state as more water is stored in the water table. This way water storage deep down into the ground as reservoir. With the clearing of vegetation and deforestation, urbanization becomes directly liable for the increase in annual floods. Because of the increase in the volume of run-off water in highly urbanized areas, the construction of drainage systems have been the nearest possible solution made by the government. Such drainage systems were designed to regulate the flow of run-off directly to the watercourse. However localized flash flooding seemed aggravated the problem with the construction of such sewage systems. The problem with this development projects is that the volume that watercourse and the drainage systems can contain is limited. The speed or velocity of runoff brought about by high peak storm water. Another vital factor is time which is relatively not enough for water to be absorbed and contained by the drainage systems and so flash floods are always possible. With flash floods, water contamination is highly possible because the excess water that runs in the streets catches much of the contaminants in the land surface which will then be carried to the bodies of water as flood find its way to leave the area. Because highly urbanized areas do have little ground cover like trees to absorb storm water, run off will likely stay longer in the surface as infiltration is hardly possible. Because imperviousness is directly related to water dynamics, highly urbanized areas have the high risk of containing high peak storm discharges. In urban areas, collection in combined sewerage systems may impose increased hydraulic and pollutant loads on conventional wastewater treatment facilities (Perry and McIntyre 1986).