Stream Flow: The Importance of Reducing Excessive River Flows
The Rouge Project recognizes that stream flow is a critical element
in the health of the Rouge River. Research has shown that flow is
an important factor in meeting water quality standards. A stable
stream flow is usually an indicator of a healthy river. Erratic
stream flow as measured by velocity and volume of water that travels
in a stream can lead to a multitude of problems. At one end of the
spectrum of erratic stream flow is when there is too much water
in the river which results in flooding. Flooding causes obvious
problems such as the physical destruction of property in the flood
plain, severe water quality problem that result from the flooding
of sewers and the pollutants carried off from the flooded land,
severe erosion of the stream banks, etc. High river flows that fall
short of floods also cause major problems associated with scouring
the stream bed which destroys streambed habitat and stream bank
erosion. Stream bank erosion results in two major problems.
The first is the physical destruction of the banks which destroys
property, causes log jams from the trees that fall into the river,
and is an aesthetic problem. The second problem is the resulting
sediment that enters the river. This sediment alters the fragile
aquatic habitat by "smothering" the bottom of the stream by filling
in the pockets between the rocks and gravel of the stream bed that
aquatic species depend upon. The sediment also carries pollutants
such as phosphorus into the river which can cause insult to the
aquatic species by various impacts such as decreasing oxygen levels.
At the other end of the spectrum of erratic flow is when the flow
in the stream is reduced to extremely low or zero flows, which results
in the degradation and/or destruction/loss of habitat.
USGS and the Rouge Project monitor flow at various stations across
the Rouge River watershed. An analysis of USGS data confirmed that there is a high degree of fluctuation
in the flows in the Rouge River. This fluctuation in flow is a direct
result of increased urbanization development and loss of permeable
soils and wetland storage in the watershed. The gauging station
data on the Rouge River has shown a four-fold increase in the average
number of annual flood events over the last twenty-five years, based
on a five-year running average.
Based on the recognition of flow as a pollutant source and due
to the fact that many communities within the Rouge River watershed
have been experiencing an increasing amount of stream bank erosion
and flooding along the river, the Rouge Project encouraged local
communities to address this issue as part of the subwatershed management
plans and storm water pollution prevention initiatives, as part
of the Michigan General Storm
Several subwatersheds in the Rouge ranked flow as a second highest
priority in their subwatershed management plans, only behind the
protection of public health. The more urban subwatersheds noted
that the management of storm water flows in existing developed areas
is one of the greatest challenges in restoring the river. Even with
total control of pollution sources, the biological and physical
attributes of the river cannot be fully restored without significant
reduction in the impacts caused by the increased frequency, duration,
and size of flows following storm events.
The Rouge subwatersheds are also addressing the issue of flow through
their Storm Water Pollution Prevention
Initiative (SWPPI). The SWPPI includes evaluation and implementation
of pollution prevention best management practices to minimize the
impacts of new development and redevelopment.
Both the subwatershed plans and the SWPPI call for implementation
of best management practices (BMPs). Below is a list of some of
the BMPs being addressed in the Rouge planning process, including
several that can be implemented to address river flow issues. The
alternatives listed below may apply to one community but not to
another, so it is important to note that each of the alternatives
is a unique solution to a specific pollution source or problem.
Storm Water and Water Resource
In undeveloped areas, or in an area where redevelopment may occur,
it is important to have regulations in place that can guide land
development with regard to protecting water quality, quantity, and
the biological integrity of the receiving surface water. This regulation
can use existing data to determine the development impact that can
be tolerated by the surface waters before the system becomes degraded.
Future development or redevelopment can be guided to control runoff
so that local streams and water resources are not negatively impacted.
Land Use Planning and Management
This involves a comprehensive planning process to control or prevent
runoff from certain developed land uses where receiving waters are
sensitive to development. The overall planning process involves
the following steps: 1) determine water quality and quantity goals
with respect to human health, aquatic life, and recreation; 2) identify
the planning area and gather hydrological, chemical, and biological
data; 3) determine and prioritize water quality needs as they relate
to land use and proposed development; 4) develop recommendations
for low impact development to address the problems and needs that
have been previously determined; 5) implement recommendations.
Reduce Directly Connected Impervious Surfaces
Development plans can be created to combine a hydrologically functional
site design with pollution prevention measures to compensate for
land development impacts on hydrology and water quality. The result
will be a reduction in storm water peak discharge, a reduction in
runoff volume and the removal of storm water pollutants. This can
apply to new residential, commercial, and industrial developments.
In urban communities, especially older areas, there may be opportunities
to disconnect impervious areas through downspout disconnection and
the disconnection of sump pumps to driveways and sewer systems.
Slow Storm Water Runoff (Storage Facilities) in Urban Areas
In older urban areas where storm water detention systems do not
exist, storm water storage facilities may be considered. These facilities
are underground control devices that are designed to retard flow
sufficiently to reduce sewer overflows, prevent downstream flooding
and/or reduce velocities. These facilities consist of storage tanks
connected to the existing drainage system, street storage, and parking
Install/Maintain Storm Water Retention Basins and other Infiltration
Storm water infiltration basins are any storm water device or system,
that causes the majority of runoff from small storms to infiltrate
into the ground rather than being discharged to a stream. Most infiltration
devices also remove waterborne pollutants by filtering the water
through the soil. Storm water infiltration can provide a means of
maintaining the hydrologic balance by reducing impervious areas.
Infiltration devices could include the following: basins, trenches,
permeable pavement, and other systems that collect runoff and discharge
it into the ground.
Construct and Maintain Wet Detention Ponds and Constructed Wetlands
Wet detention ponds, or constructed wetlands, are small man-made
ponds or shallower areas with wetland vegetation around the banks
designed to capture and remove particulate and dissolved matter.
Wet ponds and wetlands are ideal for large, regional tributary areas
where there is a need to achieve high levels of particulate and
dissolved nutrient removal. The pond or wetland should be sized
to treat runoff, accumulate sediment, and route floods. The pond
should be configured for aesthetics, safety, and maintenance. Landscaping
design requirements should include a natural vegetated buffer around
the pond/wetland to reduce pollutants entering the area as well
as decrease goose habitat and increase aesthetics. Proper monitoring
and maintenance is necessary for five to ten years after construction.
Construct and Maintain Dry Retention/Detention Ponds
A detention basin is usually dry between storms. It is designed
to capture runoff and release it slowly to allow most of the polluted
sediments to settle. Dry retention/detention basins are used for
tributary watersheds 10 acres and larger in size to attenuate peak
flow and remove particulate matter. The basin should be designed
to treat runoff, accumulate sediments and route floods. It should
be designed for aesthetics, safety and maintenance.
Learn more about BMPs, their applicability, pollutant removal ability, and costs in a detailed BMP report.
Interactive Stream Flow Data Map
Stream Flow: The Importance of Reducing Excessive River Flows