Permeable Surfaces and Storm Water Management in Urban Areas
Due to the ever growing rate of population, urban areas are becoming more and more a requirement, this being possible only through the loss of rural areas which have extremely important functions of their own, especially when it comes to storm water management.
The soil in the rural areas play a very important role as it lets the storm water seep through from the surface down to the water table in the rocks. This is considered as the natural water reservoir. Because of such a role, the contrary happens in urban areas. Water does not find a way to infiltrate as the concrete is not permeable and, therefore, it ends up as runoff. Along its way, it picks up pollutants including harmful chemicals, metals, and trash along with other contaminants. As the water finds its way in the ocean, so do the contaminants and, thus, they end up polluting it causing harm to the aquatic life. This type of pollution is called “nonpoint source” pollution. Apart from this, impermeable surface have a number of other consequences such as the risk of flooding when a storm hits, and also the fact that potable and irrigation water becomes scarce.
Storm water management can be carried out in many different forms, the most common one being storing and cleaning runoff in open ponds, man-made tanks, and sewers. Such systems are referred to as ‘above-surface storage’. They are usually specifically designed in such a way in order to be capable of filtering out common pollutants such as waste and other pieces of debris at the inlet. If not, they are left to settle at the bottom and are removed later. Such systems are preferred in undeveloped areas as there is the requirement of a piece of land since it is above the surface, therefore, it can be put into use in sub-urban areas.
Unfortunately, they also have their disadvantages, the main one being that the quality of the water is not maintained. Water that is left to stand still in open tanks for long periods of time can cause mosquitoes and other insects, and bacteria, to multiply. Wild animals may also come here and all of this clearly reduces the water quality. Maintenance is another down side as it takes a lot of time and is quite expensive as well to remove the sediment when there are the pollutants already. The removal of the sediment which has accumulated is a process which requires skilled workers along with their specialised equipment. Furthermore, if there would be the need to repair critical structural features, engineers may be required.