2.5 Hydrologic Systems

The Department of Natural Resources’ Public Waters Inventory identifies 86 basins and three watercourses within the Minnehaha Creek subwatershed as under the jurisdiction of the DNR (see Figure 10).  These include the Chain of Lakes; other named lakes, ponds, and marshes; and numerous unnamed basins, listed in Table 4.

Table 4.  Public Waters in the Minnehaha Creek subwatershed.

Name and DNR ID#

Name and DNR ID#

Name and DNR ID#

Name and DNR ID#

Bass (27-15 P)

Mother (27-23 P)

Unnamed (27-717 W)

Unnamed (27-755 W)

Brownie (27-38 P)

Nokomis (27-19 P)

Unnamed (27-718 P)

Unnamed (27-756 P)

Calhoun (27-31 P)

Norby's Pond (27-685 W)

Unnamed (27-719 P)

Unnamed (27-757 W)

Cargill Pond (27-754 W)

Pamela Pond (27-675 P)

Unnamed (27-720 W)

Unnamed (27-758 W)

Cedar (27-39 P)

Sanctuary Marsh (27-665 P)

Unnamed (27-721 P)

Unnamed (27-759 W)

Cemetery (27-17 P)

Taft (27-683 P)

Unnamed (27-722 W)

Unnamed (27-762 W)

Diamond (27-22 P)

Twin (27-656 P)

Unnamed (27-723 W)

Unnamed (27-763 W)

Duck (27-25 P)

U.S. Lock & Dam #1 (27-3 P)

Unnamed (27-724 W)

Unnamed (27-771 W)

Edina Mill Pond (27-41 P)

Unnamed (27-1087 W)

Unnamed (27-725 W)

Unnamed (27-772 W)

Grays Bay Outlet (27-761 W)

Unnamed (27-657 P)

Unnamed (27-726 W)

Unnamed (27-773 W)

Hannan (27-52 P)

Unnamed (27-658 W)

Unnamed (27-728 W)

Unnamed (27-774 W)

Harriet (27-16 P)

Unnamed (27-659 W)

Unnamed (27-736 W)

Unnamed (27-779 W)

Harvey (27-670 W)

Unnamed (27-660 P)

Unnamed (27-737 W)

Unnamed (27-780 W)

Hiawatha (27-18 P)

Unnamed (27-661 W)

Unnamed (27-739 W)

Unnamed (27-83 W)

Lake of the Isles (27-40 P)

Unnamed (27-662 W)

Unnamed (27-740 W)

Unnamed (Cedar Manor) (27-713 W)

Lamplighter Park (27-710 P)

Unnamed (27-663 W)

Unnamed (27-741 W)

Unnamed (Cobblecrest) (27-53 P)

Legion (27-24 P)

Unnamed (27-666 W)

Unnamed (27-748 W)

Unnamed (Westling Pond) (27-714 W)

Meadowbrook (27-54 P)

Unnamed (27-667 W)

Unnamed (27-749 W)

Victoria (27-51 P)

Melody (27-669 W)

Unnamed (27-682 W)

Unnamed (27-750 W)

Windsor (27-82 P)

Milner Pond (27-684 W)

Unnamed (27-712 W)

Unnamed (27-751 W)

Wolfe Park (27-664 P)

Minnehaha Marsh (27-84 P)

Unnamed (27-715 W)

Unnamed (27-752 W)

Minnehaha Creek

Minnetonka (27-133 P)

Unnamed (27-716 W)

Unnamed (27-753 W)

Unnamed from Brownie to Calhoun

 

 

 

Unnamed from Harriet to Minnehaha Creek

Source: Minnesota DNR.  See Figure 10.

The HHPLS included detailed modeling of the current and 2020 hydraulic and hydrologic conditions in the subwatershed.  That modeling includes the following results for modeled locations (lakes, ponds, channels, and crossings) within the subwatershed (see Table 5):

  • Existing Normal Water Level;
  • Existing High Water Level, peak discharge, and peak velocity for the 1.5 year, 24-hour and 100-year, 24-hour events;
  • 2020 predicted HWL, peak discharge, and peak velocity for the 100-year, 24-hour event; and the
  • Existing High Water Level for the 100-year, 10-day snowmelt event.

Those detailed results are not reproduced here, but are incorporated by reference.  The HHPLS model predicted that land use changes would not significantly impact high water levels in the subwatershed.   However, it was noted that overtopping of the creek banks can occur.   Numerous land locked subwatershed units or small basins occur in the subwatershed, and management of discharge from those landlocked basins as well as from land use change is important to minimizing or preventing further streambank erosion

Table 5.  Modeled peak discharge from the Minnehaha Creek subwatershed (cfs).

Event

Existing

2020

Snowmelt

1.5 year, 24 hour

219.7

-

-

100 year, 24 hour

676.2

677.9

-

100-year, 10-day

-

-

618.5

Source:  2003 MCWD Hydrologic, Hydraulic, and Pollutant Loading Study (HHPLS)

The HHPLS scour analysis identified nearly 120 locations along the creek as having high erosion potential based on soils and modeled velocity.  The Stream Assessment included a geomorphologic analysis of creek stability as well as a detailed survey of the creek for sites actually experiencing erosion and streambank failure (see Section 2.5.2 below).