Structural BMPs include various technology options used to modify hydrologic system as close to the natural as possible. Key types of structural BMPs are ponds, stormwater wetlands, practices of infiltration, vegetative filters, organic and sand filters, and different technology options (Daniels & Daniels, 2003).
Commonly used structural BMPs are stormwater ponds, where approximately 90% of runoff water can be captured. Dry detention basins, extended detention ponds with special retention outlets, and wet ponds form a set of solutions for different development conditions (Daniels & Daniels, 2003). Each of these methods has own pros and cons. Dry ponds are helpful only for runoff control and cannot be used to remove pollutants, wet ponds require large surfaces and need an external flow to maintain the level of water, extended detention ponds are optimal for control of runoff peak discharges, but their use for areas with warm water is limited.
A widely used method of controlling runoffs are vegetated systems which act as biofilters. Such techniques as wet and dry grass swales, vegetative strips (buffer areas), and systems of bioretention fulfill filtration and control of runoffs (Daniels & Daniels, 2003). Constructed wetlands are commonly used to reduce runoff pollution. Other techniques used to store runoff waters are infiltration trenches ”“ underground water reservoirs, and porous pavement systems allowing water permeate into the ground.
Pollution control functions are most often performed by filtration systems ”“ surface sand filters, filters located in the underground, vault sand filters located around parking lots and compound filtering systems. Technology development have also added to BMPs: the systems of underground water retention referred to as water quality inlets, multiple treatment systems with several chambers and vortex separators perform the functions of storing and filtering stormwater runoffs, thus reducing the external flows and balancing the system to resemble the natural one.
Urbanization is a rapidly development process, and thus best practices of stormwater runoff management are rapidly evolving. Many of new BMPs have the properties of both structural and nonstructural BMPs, thus combining the advantages of both approaches. Treatment technologies for stormwater as well as methods of controlling pollutants and preventing pollution are being continuously improved. Significant impact can be expected from the use of environmentally safe materials in construction and use of new advanced technologies such as green roofs. Regarding structural BMPs, the systems of bioretention which recreate the natural balance in urbanized environment should be noted, along with advanced filtering systems and pollution control techniques.
It is hardly possible to invent one best management practice allowing to reach the purpose of stormwater runoff management. In order to minimize the effect of urbanization on stormwater runoffs, complex measures are required, where engineering solutions and technologies would be aligned with governmental regulations, educative arrangements and economic reforms in order to cause minimal runoff changes compared with the predevelopment conditions.