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.  Shoreline erosion on Lake Minnetonka is of special concern.

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 Minnetonka subwatershed will focus on promoting shoreline restoration with native vegetation and identifying erosion problems on an ongoing basis and working with LGUs to correct them.

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 Lake Minnetonka and the other lakes within the subwatershed
  • Nutrient loading goals for Halsteds, Jennings, and Stubbs Bays

Goal 15.1 - Lake Minnetonka

Identify and address erosion problems in the subwatershed.

Actions

  1. Identify, inventory, and prioritize gully, channel, shoreline and other erosion problems. 
  2. The HHPLS modeled higher than desirable velocities at several culverts that could lead to inlet or outlet erosion.  Local plans should identify these observed or potential locations and assess whether improvements should be made.  Assist LGUs in determining specific impacts and potential improvements.
  3. Regulate new development and redevelopment and ensure compliance with erosion control standards.