Slope Stabilization Work Plan For Poplar River Management Board

Slope Stabilization Work Plan
North American Wetland Engineering, LLC.
January 18, 2007 4444 Centerville Rd, Suite 140
Poplar River Management Board White Bear Lake, MN 55127
Phone: 651-255-5050
Fax: 651-255-5060
5.3 Peak Flow Reduction
Figure 5.2 – J-Hooks on the Rush River
Another method that could potentially reduce sediment transport from the megaslump would be
to reduce peak flows in the river. Because the channel is well armored in the area of the slump
during base flow conditions, normal stream flow does not contribute excessive sediment to the
river. However, streambank conditions above base flow conditions do not have adequate
armoring. When the river rises more than 2 feet, the river contacts bare soils in the area of the
megaslump and sediment is washed from the bank and is carried downstream by the river.
Peak flows occur during spring runoff and also during storm events. Flows can be attenuated by
capturing excessive runoff water in catch basins and stormwater ponds and releasing the water
slowly to the river. This can be accomplished in areas where there are parking lots or other
impervious surfaces. This will only slightly reduce peak flows in this area because much of the
watershed is undeveloped and during spring runoff and storm events, there is no way to capture
runoff water.
5.4 Peak Flow Diversion
Diverting peak flows away from the megaslump would also help reduce sediment transport. Due
to the armoring condition of the bank, peak flows in which the river level rises, appear to
contribute more sediment to the river than base flow conditions. There is a small channel south
of the river adjacent to the megaslump that could be used for peak flow diversion. This channel
would have to be widened so more of the peak flow would be diverted during peak flow events.
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