Stormwater Management in an Urban Context - Essay Example

Storm Water Management Inserts His/ Her Inserts Grade Inserts Inserts Water is the one of fundamental resources for human life and it has managed for a long time. Especially, stormwater has become important source for both human and environment. Groundwater can be recharged by stormwater and it can evaporate into the atmosphere or flow over land to lakes, rivers, and other water elements. In the past, conventional stormwater management only concentrated on transportation and diminution of peak flow, but new strategy has been required because urbanization has changed the quantity and velocity of storm water runoff entering streams and flooding becomes more frequent. As a result of that, Water sensitive urban design (WSUD) has emerged and implemented many places as one of the best trends in practice urban storm water management. The aim of this process is to improve drainage and to control storm water quantity, quality and harvesting for ecological protection Storm water is simply the water that originates during storms and snow melts. The soil has a limited ability to absorb or soak water, so the water that is left on the surface after absorption is carried away by the slopes on roads into the drainage that is the sewers or directly into surface water ways. The water that is left on the surface is called surface runoff. The water from these sources is eventually carried away into the surface waters. Rivers, lakes, oceans and streams are all examples of surface water. This water, if not treated or drained out can cause damage to pavements on roads, electrical supplies and many other utilities. To prevent the pavements on roads engineers provide a slope on roads so that the water runoff process can be controlled and water can be channeled into the surface waters and sewers. To control the flow of this water a system has to be designed to fulfill the needs of a particular area. This system is called as storm water management system. This system should be designed to achieve the basic need that is not to allow water stay on the roads rather it should be properly drained out. The storm water can also become a source of pollution after heavy rainfalls. In many countries such as USA and UK some regulations have been set to prevent such cases. Water runoff is a serious problem in Asian countries like Pakistan, India and Bangladesh where there is unusually great amount of rainfalls during the monsoon period. The conditions of the drainage system in the above mentioned countries are below average. A design for the storm water management in these countries is yet to be produced. The new constructions are also making the situation worst due to the fact that new roads designed are not given the proper slopes to get rid of the storm water runoff problems. There are many factors affecting the storm water runoff one of which is the recent developments in the construction field. With the construction of houses, shopping malls, parking lots, apartments and other structures has severely affected the water runoff in urban areas. It has become quiet difficult to alter the routes of water through the large structures, bridges and underpasses and to control the flow towards the drainage systems and sewers. The runoff of storm water can also create various other problems such as erosion and flooding. The new constructions carried out by deforestation and excavation of vegetated land for land use causes adverse effects to the hydrological cycle as well as to the environment. The contributing drainage region establishes the boundary restrictions for the movement of runoff - from the highest elevations to the lowest point of elevation. Some of the impacts of the development on hydrological cycle include increased peak discharges of runoff compared to pre-development levels, Increased volume of runoff formed by each storm in comparison to the pre-development situation, decreased time in which runoff reaches the stream, chiefly if extensive drainage changes are made. Moreover increased frequency and harshness of offsite downstream flooding, reduced stream flow and lower water table levels during extended periods of dry weather due to reduced infiltration in the watershed loss of wetlands and aquatic habitats due to inferior water table levels during dry weather, greater runoff velocity during storms due to increased impervious areas, which move greater volumes of runoff at a faster rate; and increased frequencies and extended periods of high stream flow velocities that can significantly increase stream channel erosion. For the solution of this storm-water management problem that has become a great issue all over the world many approaches are considered but the two most commonly used approaches are: 1. Conventional approaches 2. Water sensitive approaches. There are limitations in conventional stormwater management system because it is only focused on transportation and reduction of peak flow. The concept of conventional stormwater drainage system is to transport all water draining off impervious surfaces directly to nearest water body through a network of drains and pipes. There are no concepts of water quality and harvesting to help ecosystem to be healthy. The conventional system is related to urbanisation and concrete or steel pipes and drains are frequently used to achieve the aim. So, there occur more paved or impervious areas where the system is conducted. When an area is covered with impervious materials such as concrete, water runs off the surface much faster than when it is in a natural condition. The total amount of discharge is the same, but the discharge happens over a shorter amount of time In other words conventional approach focuses on the removal of storm water as quickly as possible from a site or area to reduce the possibilities of flooding. This goal is achieved by providing curbs, gutters, pipe-line systems that can discharge the water to the nearest surface water source. Although this is an efficient way to remove water quickly and prevent on-site flooding, it has proven to be devastating to downstream waters by increasing the frequency and magnitude of floods, altering stream channel morphology alignment, cross-section geometry, streambed composition) and reducing groundwater recharge, all of which make less water available for drinking water withdrawal and stream base flows.Therefore, it can cause a flooding. It has been shown (Monk & Till, 2006) that the conventional system to urban stormwater management is to: Remove almost all native vegetation. Cut (hill tops) and fill (depressions, usually wetlands). Build large areas of impervious surfaces. Install pipes and constructed / hydraulically efficient channels that drain water away from an area as quickly as possible, by directly discharging stormwater into receiving water bodies. Install large-scale systems/devices (such as large sumps or constructed wetlands) downstream of the source of runoff. Moreover, environmental habitats can be destroyed by conventional approach to remove all native vegetation and to reduce or raise flow into the habitats quickly. Ecosystem needs moderate volumes of water firmly left in or released into rivers, lakes or reservoirs, to maintain ecosystem. Hence, new plan has been designed to cover those problems. Indeed, the potential of roof runoff harvesting system is considering in Australia and the government encourage people to install rainwater tank for residential purpose. This can be used for gravity supply, hot water supply and all-house supply excluding drinking water. Also, water quality and quantity controls take into consideration during the stormwater harvesting process. Storm control measures are divided into two groups: 1. Structural measures 2. Non-structural measures Nonstructural storm water control measures include a wide range of actions that can reduce the volume of runoff and pollutants from a new development. Examples include the use of products that contain less pollutants; improved urban design, for example, New developments that have fewer hard surfaces; the disconnection of downspouts from hard surfaces to instead connect with porous surfaces; the conservation of natural areas; and improved watershed and land use planning. Structural storm water control measures are designed to reduce the volume and pollutants of small storms by the capture and re-use of storm water, the infiltration of storm water into porous surfaces, and the evaporation of storm water. Examples include rainwater harvesting systems that capture runoff seep or is piped; the planting of rain gardens on both public and private lands, and the planting of “swales” along the roadside that capture and treat storm water. There is sense that quantity control can affect to decline of food through retention system and improve quality of stormwater. According to Wong (2000), stormwater quantity control has strong relationship with quality management. Reduction of flow and aquatic habitat interruptions and stormwater recycling can be used by source control for stormwater quality development In conclusion, Stormwater is an excellent alternative to non-portable use, it is easy to capture, manage and store on-site. Conventional urban stormwater management has focused on providing highly efficient drainage systems to rapidly collect and remove stormwater runoff. However, the system does not consider quality and harvesting managements related to aquatic ecosystem. Water sensitive urban design (WSUD) can substitute the conventional method to maintain stormwater efficiently and also can help to improve ecological habitats. I believe that the water sensitive system should be a priority when governments and companies deal with urban design. Bibliography MA Department of Environmental Protection & MA Office of Coastal Zone Management. 1997. Storm Water Management. Viewed October 13, 2011. Watre Wiki. n.d. Stormwater. Viewed October 13, 2011. Contech. n.d. UrbanGreen™ Stormwater Solutions. Viewed October 13, 2011. < http://www.contech-cpi.com/Products/Stormwater-Management.aspx > Monk, E. & Till, B. 2006. ‘Quantity is the road to quality’, in proceedings of the 2006 Public Works Engineering State Conference, Department of Environment, 8-10 March 2006. Natural Resource Management Ministerial Council, Environment Protection and Heritage Council & National Health and Medical Research Council. 2009, Australian Guidelines for Water Recycling Stormwater Harvesting and Reuse, National Water Quality Management Strategy, Document No. 23. Wong, THF 2000, ‘Improving Urban Stormwater Quality – From Theory to Implementation’, Journal of the Australian Water Association, Vol. 27, No.6, p.28-31. Read More