What is Stormwater?
Stormwater is rainwater or meltwater that travels across rooftops,roads, parking lots and other impervious surfaces.This is where it becomes a problem!
As stormwater passes over these surfaces it
picks up oil, heavy metals, chemicals, road
salt, and nutrients before ending up in local
surface waters.
According to the New Hampshire Department
of Environmental Services:
On undisturbed sites, much of the stormwater
is intercepted by natural ground cover or
is absorbed into the ground. Land clearing
and development reduce the capacity of the
land to absorb rainwater and snowmelt,
which leads to more water flowing over the
land and into surface waters.
What is Stormwater Management?
Stormwater management is the method of directing rainfall toward a treatment area, an appropriate body of water, or an identified outfall.
Traditionally stormwater has been treated as a problem that needs to be exported from the property as quickly as possible. When exported
from a site it runs over many different surfaces and into surface waters.
Unable to handle the increased water volume and pollutants, these waterbodies often experience eroded banks, loss of habitat and aquatic life, and increased flooding and property damage. We now
understand that stormwater needs careful management onsite to avoid flooding, pollution, and water shortages which can negatively
affect the City of Dover and its residents.
Historically, stormwater in Dover was managed
through the use of an underground storm
sewer system and direct outfalls to surface
waters. The existing stormwater infrastructure
is a mix of new structures installed as part of
development during the last 25 years, and
very old structures and pipes that served as a
combined sewer system until the 1970’s.
However, extreme rain events may overwhelm
this type of municipal infrastructure. When this
happens excess stormwater impacts the sanitary
sewer system that conveys wastewater
from residential and commercial structures to
the wastewater treatment plant. According to
the Dover Master Plan, even today the City
experiences significant amounts of infiltration
into the sewerage treatment system during
periods of heavy rain.
Using Low Impact Stormwater Management Practices in Dover
In developed areas roofs, decks, patios, pavement, and other impervious surfaces prevent stormwater from soaking into the ground.
Using low impact stormwater management practices involves retaining as much stormwater as possible on the property rather than letting it run into storm drains. This can help keep harmful volumes of stormwater and pollutants out of our surface waters while recharging Dover’s groundwater supplies. This reduces the impact on natural
resources and contributes to Dover’s future sustainability as a community,
and as part of the Seacoast Region.
This is accomplished by conserving forests and other natural areas, and stormwater controls that retain runoff such as:
Rain Barrels – capture rainwater and store it for use later.
Rain Gardens – landscaped areas designed to capture and filter stormwater.
Dripline Trenches – control erosive runoff from rooftops.
Dry Wells – collect and infiltrate runoff from downspouts.
Infiltration Steps and Trenches – built to slow and infiltrate runoff.
Paths and Walkways – direct foot traffic and prevent soil erosion.
Water bars – intercept runoff to prevent erosion.
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