Human activities and urbanization processes create changes in the environment and interfere in the natural processes and systems. Agricultural development affects land cover and soil, drainage networks cause hydrologic changes in the system, water flow regimes change in urbanized systems, and soil can no longer perform its evaporating functions. As a result, the generation of runoffs changes significantly in the system, and stormwater flows become more intensive and more concentrated. The changing character of stormwater flows, along with high level of pollution following urbanization lead to decrease of water quality and overall degradation of the habitat.
The purpose of stormwater management is to control the quality and quantity of runoffs, and to maintain the balance as close to the natural system as possible, or to maintain a balance in the new system in the most optimal way (Daniels & Daniels, 2003). In the sphere of stormwater runoff management, there exist best management practices which include devices, systems and methods allowing to manage and control runoffs, the presence of pollutants, and the extent to which runoffs are used as a natural resource. The purpose of this paper is to analyze existing types of best management practices for stormwater runoff management, to consider their pros and cons and to discuss to what extent these practices allow accomplishing the fundamental objective of stormwater runoff management ”“ minimization of changes in speed, volume and quality of runoffs compared to the conditions before development.
1. Types of stormwater management
Stormwater runoff best management practices (BMPs) might include maintenance and operating procedures, regulations for practices, scheduled activities, requirements for treatment, and specific methods or devices used to reach the objectives of stormwater runoff management. It is possible to identify two types of BMPs: structural and nonstructural (Daniels & Daniels, 2003). Nonstructural BMPs include the techniques which are based on natural measures, do not involve significant development efforts, and can either help to regulate the processes of stormwater runoff generation, or reduce the level of pollutants in these flows. These practices use economic instruments, educational methods and governmental regulations to reach the objectives of stormwater runoff management.
Structural BMPs include development methods and systems which were specifically engineered for storing or treating stormwater runoffs or for removing pollutants. These BMPs are based on engineering solutions and use physical properties of the natural system to improve stormwater runoff quality, or to control the quantity of the runoffs. While nonstructural BMPs are also referred to as source control BMPs, nonstructural practices can be viewed as small scale treatment BMPs. Both types of BMPs are important for reaching the purpose of stormwater runoff management. Best practices used in both types of BMPs are discussed in the next two sections.
2. Best practices of nonstructural stormwater management
Overall, nonstructural BMPs can be divided into the following categories: public education, management and planning, management of materials, maintenance of streets and storm drains, prevention of spill, control of illegal dumping, control of illicit connections, and reuse of stormwater (Daniels & Daniels, 2003).
Public involvement is highly important for reaching the objectives of stormwater runoff management and normalizing the hydrologic system of urbanized environment. It is important to have a plan of public education and participation before development. This plan should include public education on garden activities, water conservation, management of household and pet wastes, and trash management (Daniels & Daniels, 2003). Moreover, new development areas should be thoroughly planned: site design should be done with consideration of minimal changes to stormwater runoffs: important natural areas should be preserved as possible, vegetation should be controlled, impervious surfaces should be reduced, etc. Installation of green roofs is a highly effective nonstructural BMP, allowing to control stormwater runoffs with minimal costs and reach possible closeness to natural runoff generation processes. There also is a concept of low-impact development, which is very promising for stormwater runoff management: hydrologic landscapes of new developments are designed to be very close to original conditions. This effect is reached using site level changes and natural landscaping combined with more traditional techniques (such as retention ponds). Management and planning BMPs play a leading role in optimization of hydrologic systems.
Management of materials allows to reduce the number of pollutants, and cut down the number of chemicals used for construction. Substitution of hazardous materials with safer products and introduction of efficient housekeeping practices can help minimize the changes brought by human activities in the ecosystem. Maintenance of streets and storm drains BMPs are rather varied: cleaning of streets, catchbasins, maintenance of roadways, flushing of storm drains, cleaning of storm channels and hotspots of stormwater and other post-construction maintenance procedures are essential for keeping the designed balance. These BMPs are necessary, but not sufficient for effective stormwater runoff management.
Prevention of spill and cleanup practices such as control of ground tank spill and control of vehicle spill reduce the risk of pollution. Controls of illegal dumping ”“ governmental regulations, collection of hazardous waste, stenciling of storm drain and recycling of used oil – help in reducing pollution and minimizing runoff changes. Controls of illicit connections also serve these two purposes, and include such methods as prevention and detection using dry weather flows, upgrades for pump stations, construction of storage and treatment facilities for wet weather conditions, and improvement of sewer systems (Daniels & Daniels, 2003). Finally, mechanisms of stormwater reuse also allow to minimize the changes of stormwater runoffs by the use of additional water as a source of non-potable water with the help of tanks for roof runoffs, irrigation and surface detention ponds.