What is Stormwater and where does it come from?
Stormwater is
any precipitation that collects in a natural or constructed storage or
transport system following a storm event. For example, during
construction of a new building or neighborhood, sites are often cleared
and the soil is firmly compacted, which prevents rainfall or snowfall
from soaking into the soil.
As a result, the rain water and snowmelt
flow along the surface of the ground: this is stormwater runoff. In
addition to construction activities, impervious areas such as roads,
roof tops, parking areas, and sidewalks prevent infiltration of
moisture from rain and snowfall, thus causing stormwater runoff. This
runoff can be too much for the existing natural drainage systems to
handle. As a result, storm sewer drainage systems are designed to
rapidly collect runoff and convey it away (using curb and gutter,
enclosed storm sewers, and lined channels). The stormwater runoff is
then discharged directly to downstream waters such as creeks, streams,
reservoirs, and lakes.
How does Impervious Area affect water quantity?
Impervious area creates a barrier that does not allow water to soak
into the soil and prevents the rainfall or snowfall from recharging
ground water supplies in that area. This reduces the amount of ground
water that is available to well water users and increases the
downstream surface water flow.
Changes in Runoff Patterns
Water that soaks into the soil is naturally filtered and cleaned. Water
flowing on the surface of developed property picks up pollutants such
as sediment, oil, and salts from roads and parking areas, fertilizer
from lawn runoff, and bacteria from property where animals are kept.
The effect of one property on the quality and quantity of stormwater
runoff may seem insignificant. However, the collective impact from all
properties in the City can negatively affect water quality. And keep in
mind: such stormwater runoff, after it enters streams and ponds, or
soaks into the ground, eventually becomes drinking water. This is one
reason protecting water quality is so critical in Federal Heights.
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