Conveyance and End-of-Pipe Measures for Stormwater - FCM

2.2.3 Impacts on Stream Habitat
Along with changes in stream hydrology
and morphology, urbanization diminishes
the habitat value of streams due to:
■ degradation of habitat;
■ loss of pool-riffle formation;
■ loss of riparian vegetation;
■ loss of substrate;
■ sedimentation/fouling of the stream bed;
■ reduced base flows; and
■ increased stream temperature and pollution
levels.
2.2.4 Impacts on Biological Community
In addition, stream corridors experience
impacts on biological communities which
include:
■ declines in the terrestrial and bird
populations, and in their abundance
and biodiversity;
■ succession of cold water species
by warm-water species;
■ reduced benthic community diversity
and abundance; and
■ increased representation of pollutiontolerant
species.
2.2.5 Impacts on Water Quality
Polluted stormwater runoff and water quality
impairment come primarily from diffuse
or scattered sources—many of which are the
result of human activities within a watershed.
Urban drainage systems collect and convey
polluted runoff to receiving waters resulting
in point source pollution. The most frequently
occurring pollution impacts include (Marsalek,
2003a):
■ reduced dissolved oxygen levels in streams;
■ increased suspended solids concentration;
■ nutrient enrichment;
■ microbial contamination;
■ pollution by hydrocarbons, toxic materials,
and road salt/deicers;
■ higher water temperatures associated
with runoff heating on impervious surfaces
and in open surface stormwater
management facilities;
■ sedimentation, trash and debris; and
■ reduced recreational use of near-shore
waters.
2.3 Objectives and Goals of
Stormwater Management
Stormwater management involves prevention
and mitigation through a variety of methods
and mechanisms. The primary objectives
include the following:
■ Achieve healthy aquatic and related
terrestrial communities.
■ Reduce erosion/sedimentation impacts.
■ Maintain and re-establish natural
hydrologic processes and encourage
infiltration/replenish soil moisture.
■ Protect, preserve and enhance natural
features of watershed.
■ Enhance water quality in receiving waters.
■ Improve water quality in contact
recreational waters and reduce beach
closures.
■ Minimize aesthetic nuisances (algae
and floatables).
■ Reduce basement flooding.
■ Protect life and property from flooding.
■ Provide recreational, educational, and
aesthetic amenities in the urban landscape.
■ Encourage reuse of stormwater
by considering it as a resource
and not as a nuisance.
Conveyance and End-of-Pipe Measures for Stormwater Control — July 2005 17
2. Rationale
2.2 Impacts of
Urbanization
2.3 Objectives and
Goals of Stormwater
Management
Urban drainage
systems collect
and convey
polluted runoff
to receiving waters
resulting in point
source pollution.