is rainwater and melted snow that runs off streets, lawns, and other sites.
When stormwater is absorbed into the ground, it is filtered and ultimately
replenishes aquifers or flows into streams and rivers. In developed areas,
however, impervious surfaces such as pavement and roofs prevent precipitation
from naturally soaking into the ground. Instead, the water runs rapidly into
storm drains, sewer systems, and drainage ditches and can cause:
turbidity (muddiness created by stirred up
sediment) from erosion
in the stream flow hydrograph (a graph that
displays the flow rate of a stream over a period of time)
streams, rivers, and coastal water
Traditional stormwater management design has been focused
on collecting stormwater in piped networks and transporting it off site as
quickly as possible, either directly to a stream or river, to a large
stormwater management facility (basin), or to a combined
flowing to a wastewater treatment plant.
Low impact development (LID) and wet
infrastructure address these concerns through a variety of
techniques, including strategic site design, measures to control the sources of
runoff, and thoughtful landscape planning.
LID aims to restore
natural watershed functions through small-scale treatment
at the source of runoff. The goal is to design a hydrologically functional site
that mimics predevelopment
green infrastructure encompasses
approaches and technologies to infiltrate, evapotranspire, capture,
and reuse stormwater to maintain or restore natural hydrologies.