Strom: Storm Water Management Questions And Answers
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Course
Storm Water Drainage
Institution
Storm Water Drainage
Strom: Storm Water Management Questions
And Answers
What are the environmental impacts from changes in storm water drainage patterns? -
increased flood potential due to increases in peak flow rates
- decreased groundwater supply caused by reduced infiltration
- increased soil erosion and sedi...
Strom: Storm Water Management Questions
And Answers
What are the environmental impacts from changes in storm water drainage patterns? -
increased flood potential due to increases in peak flow rates
- decreased groundwater supply caused by reduced infiltration
- increased soil erosion and sedimentation brought about by greater runoff volumes and
velocities
- increased petrochemical pollution from street and highway runoff
- contamination of winter runoff by salt and sand in colder regions
What changes in stream hydrology can result from development? - peak discharges, which
can be as much as two to five times the predevelopment rate, generally increase the frequency
and severity of flooding
- higher velocities coupled with increased imperviousness may also result in reduced stream flow
during extended dry periods caused by reduced infiltration. Groundwater that would normally be
recharged during wet periods and released slowly from soil during dry periods is lost as surface
runoff
- stream geometry also changes. Streams are widened due to increased volume and velocity,
which results in increased stream bank erosion.
, Strom: Storm Water Management Questions
And Answers
- Usually the stream bank is undercut, destabilizing vegetation and, in turn, exacerbating the
erosion problem. Eroded material is deposited in stream channels as sediment, which reduces
stream flow capacity.
- Flood elevations are raised; as noted, this phenomenon increases the extent of the area at risk of
flood damage
Where do contaminants come from? - pollutants are accumulated on paved surfaces and
are flushed from these surfaces during a rainstorm
- contaminants may be released through corrosion, decay, oil and fuel leaks, leaching or wearing
away of construction materials and coatings, brake linings, tires, and catalytic converters.
- developed areas, as well as agricultural areas, contribute herbicides, pesticides, fertilizers,
which stimulate algal growth and reduce the availability of oxygen in water
- fallen leaves and animal poops that would normally decompose in underdeveloped or low-
density settings are more easily washed from paved surfaces, further increasing nutrient and
bacteria levels in streams, ponds, and lakes
Changes in stream hydrology and geometry, combined with reduced water quality, decrease the
value of what? aquatic, stream bank, and floodplain habitats. Not only are stream channels
and flows altered and pollution levels raised, but these conditions are further exacerbated by low
summer flows and higher water temperatures.
, Strom: Storm Water Management Questions
And Answers
How was storm water managed in the past and how is it different now? - Historically, the
primary concern in dealing with storm water runoff was to remove it as quickly as possible.
Traditionally, this was accomplished by conveying runoff by storm sewers, swales, gutters, and
channels to the nearest water body, usually a stream or river.
- more recently storm water management practices have recognized the need for controlling off-
site impacts caused by increased runoff. The objectives of these revised practices are twofold:
1. to reduce downstream flooding through the use of detention facilities that store and release
runoff at a controlled rate.
2. to reduce flooding damage by restricting floodplain development. Most legislation at either
the state or local level states that the peak rate of runoff after development cannot exceed the rate
prior to development.
In the most recent philosophy, in addition to the volume and rate of runoff. One primary
management objective is what? deal with runoff on-site rather than transporting the
problem off-site!
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