|
As soon as a new development starts in our neighborhood, many
of us become concerned. We ask, “What will happen to our
precious stream?” We know that development will dump high-volume
runoff into our stream and put it under stress.
How can we protect our streams from the negative impacts
of increased runoff due to development? For many years,
jurisdictions have used conventional stormwater management systems
to manage the problems associated with runoff.
Conventional stormwater management systems are designed to
remove runoff from the site as fast as possible. A system of
pipes and open channels brings the runoff to a pond, usually
located at the lower end of the site. Creating stormwater management
ponds is a common practice in conventional stormwater management
systems. However, these systems only decrease the rate at which
runoff enters the stream. They do not change runoff volume or
frequency. Therefore, our stream will still be under stress.
One other approach we can take is low-impact development or
LID. The goal of LID is to maintain the condition of the
watershed as it was before development, thereby preserving the
integrity of the receiving waters. To achieve this goal, LID
emphasizes “source control” of runoff. Runoff is controlled
where it is formed rather than being conveyed to ponds.
In LID, runoff is managed in small, cost-effective landscaped
features such as rain gardens, filter strips, vegetated buffers,
grassed swales, and rain barrels located near the source of
impact. With these landscape features, runoff that enters the
unit either will penetrate the soil and recharge the groundwater
or enter a pipe at the base of the unit to be gradually released
to a stream. This approach allows a developed site to be
designed as an integral part of the environment and maintains
the site’s predevelopment watershed conditions. Furthermore,
because LID helps site planners decrease runoff volume in the
first place, it also decreases the dependence on stormwater
management ponds needed to detain or retain the stormwater runoff.
LID also is advantageous to developers. LID practices such
as reducing impervious surfaces, decreasing the use of storm
drain piping and inlet structures, and eliminating or reducing
the size of large stormwater management ponds can significantly
reduce development costs. In some cases, developers can
achieve a greater yield per lot and, therefore, a greater return
on investments.
However, LID as the sole solution to stormwater management
in Virginia has a long way to go. Because the use of LID tools
has not been regulated by many jurisdictions, developers hesitate
to apply them. Furthermore, we must educate the public and
the industry about the environmental benefits of this approach.
A well-planned public outreach program will be a good first
step in this direction.
|
