Benefits of the Management
of Storm Water Runoff
Flood Control
 Stormwater
volume, timing and intensity varies depending on rainfall amounts, drainage
patterns, soil conditions and land use within the watershed. Traditionally,
the main purpose of stormwater management was to control flooding. Now
flood control benefits must be balanced with water quality benefits. By
temporarily detaining a large portion of the runoff volume and releasing
it at a slow rate, peak discharge control is accomplished and flooding
is limited.
Improved Water Quality
Many stormwater BMPs can remove significant levels of soluble and particulate
pollutants from the water. Some of the water quality benefits are reduced
soil erosion and sedimentation, lower contaminant loadings and cleaner
bottom sediments. As a result, many of the problems associated with stormwater
runoff can be prevented and costly cleanup efforts can be avoided.
Environmental Amenities
Certain BMPs provide attractive environmental features. For example,
infiltration BMPs provide groundwater recharge that can help maintain
flow levels in stream channels during dry summer months. Shallow marshes
and wet ponds can be designed to create wetland habitat or open water
areas ideal for use by waterfowl, marsh birds and other wildlife. Terrestrial
wildlife habitat can be improved if generous buffer areas around basins
and filter strips are created. By planting trees, shrubs and grasses in
these areas, many types of plant and animal habitats can be enhanced.
Some large wet ponds can provide fishing, swimming or skating recreation
sites. Pond BMPs can also provide pleasant areas for walking, bird watching
or nature hikes.
Which BMP should be used?
The advantages and disadvantages of each BMP must be weighed against
physical site constraints, management goals (flood control and/or water
quality improvements) and costs to determine the optimum approach. The
physical characteristics of the drainage area make some BMPs more beneficial
than others. In fully developed areas or on small sites, the use of BMPs
that require a lot of land, such as ponds and basins, may not be practical.
Vegetative BMPs may not be suitable for some sites due to space limitations
and economic restrictions. In these areas, source controls become even
more attractive. Download the Applicability
of BMPs report (APMATRIX.PDF) here.
How do you ensure BMP effectiveness?
The keys to ensuring BMP effectiveness start with selecting the appropriate
BMP and continue with long-term maintenance. A comprehensive post-construction
program identifies the agency responsible for the BMP, as well as financing
for operation and maintenance functions. The program includes specifying
the personnel, equipment and material elements necessary to accomplish
operation and maintenance functions and performance levels that should
be attained. Further, the program should include a schedule identifying
when and where operation and maintenance functions will be accomplished
over a one-year period. Clearly defined operation and maintenance procedures,
directed at those elements that affect the water quality of stormwater
runoff, should also be included.
Who is responsible for BMPs?
BMP sites can be owned by counties, local governments, homeowner associations
or the private sector. There also can be watershed districts that incorporate
much larger areas and can be known by several names. Under this type of
ownership, a drainage district is under the control of a governing body
which has responsibility for maintaining, operating and improving the
drainage capacity and water quality of the district. The most common method
to control the operation of stormwater systems, and to establish how the
controls will be administered, is through local ordinances. These ordinances
are adopted by governing bodies and, because they are part of the local
law, have the impact of being able to provide enforcement of rules. More
importantly, ordinances can generate methods of collecting funds to construct,
maintain, operate and expand stormwater systems.
To learn more about BMP costs and applicability download Cost Estimating
Guidelines: BMPs and Engineered Controls (BMPMAN.PDF **30 MB**). Download
this report here.
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