4.15 Erosion Control

Goal 15 - Erosion Control

Control temporary sources of sediment resulting from land disturbance and identify, minimize and correct the effects of sedimentation from erosion-prone and sediment source areas.

Discussion

Erosion within the subwatershed can result in sediment being transported to lakes, wetlands, and streams, where it can degrade water quality and habitat.  Sediment accumulating in channels, culverts, and other facilities can reduce their ability to convey stormwater, while erosion can undermine their stability.

The key areas identified in this plan for conservation activities include buffer zones adjacent to streams and channels.  In some cases these buffer zones are riparian or flow-through wetlands, and those wetlands have been identified as key conservation areas.  Where streams and channels flow through upland areas, conservation of native vegetation within these zones would also increase or maintain infiltration rates; decrease or maintain runoff rates and pollutant conveyance to water resources; and help minimize erosion.   Restoration of lakeshore would have the same benefits.  Identifying, addressing, and preventing erosion is necessary to meet District goals as well as to meet state and federal nondegradation, water quality and biological integrity requirements and to prevent the need for future TMDLs. 

Requiring new development and redevelopment to infiltrate some of the new stormwater generated would reduce post-development volumes downstream and help reduce future erosion in streams and channels; minimize new pollutant loading that would have been conveyed by that stormwater; and help maintain groundwater levels, preserving wetlands.  Limiting discharges from subwatersheds and basins that are currently landlocked is necessary to prevent further degradation of downstream water quality as well as to limit new volumes discharged to channels that are already experiencing erosion.

Strategies in the Lake Virginia subwatershed will focus on identifying erosion problems on an ongoing basis and working with LGUs to correct them, as well as considering potential downstream impacts of new volumes discharged from development.

Desired Outcomes: Reduction in pollutant loading of temporary and permanent nature from erosion to supplement other goals.

Metrics:

  • In-lake nutrient concentrations/Trophic State Index Scores (TSI) for Lakes Minnewashta and Virginia, and in-lake nutrient concentration in Tamarack and St. Joe
  • Nutrient loading goals for Lakes Minnewashta and Virginia

Goal 15.1 - Lake Virginia

Identify and address erosion problems in the subwatershed.

Actions

  1. Identify, inventory, and prioritize erosion problems in the subwatershed.
  2. Work cooperatively with LGUs to address identified erosion problems.
  3. Regulate new development and redevelopment and ensure compliance with erosion control standards.

Goal 15.2 - Lake Virginia

Manage water volumes in Minnewashta Creek to prevent erosion.

Actions

  1. Implement the regulatory and management activities identified in this plan.
  2. Inspect this channel periodically to assess its condition.
  3. Work cooperatively with the Cities of Chanhassen and Victoria to reduce volumes as necessary.