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
Section 3 - Poplar River Watershed Study
3.1 Preliminary Watershed Investigation
In order to help quantify the overall and relative contributions of sediment from various land
uses and land cover types within the Lower Poplar River watershed, SE Group conducted a study
of the Lower Poplar River. A complete discussion of the model can be found in the 2006 AUAR
and the report completed by SE Group. This section provides a summary of the findings.
3.2 WEPP Modeling of Sources of Sediment
SE Group utilized the US Department of Agriculture – Agricultural Research Service Water
Erosion Prediction Project (WEPP) model to compute sediment detachment for the various land
cover types within the watershed. The model was used to compute detachment only, and did not
account for routing and buffering (which reduce actual yields to the stream system), in order to
provide an approximate order-of-magnitude estimate of the sediment generation in the lower
watershed. Because the analysis did not account for factors that can result in the removal and
deposition of sediment from water before reaching the river, it represents a conservative analysis
(i.e., it overestimates the contribution of sediment to the Poplar River from the land uses of
interest).
In order to compute total sediment detachment, the following computation was performed: a
cross-multiplication of: (land cover area) versus (slope area) versus (soil texture) versus (erosion
rate) from WEPP. The output of the process provides an estimate of soil detachment, and not
actual delivery to the stream system. The detachment-only analysis is likely over-representing
the amount of sediment produced in the lower watershed. The results of the WEPP analysis are
outlined in Table 3.1.
15