2.5.4 Wetlands

Approximately 51 percent of the land area within the Lake Minnetonka subwatershed is shown on the National Wetland Inventory as wetland (see Table 8). 

Table 8.  National Wetlands Inventory wetlands in the Lake Minnetonka subwatershed.

Circular 39 Type

Area (acres)

Cowardin Class

Area (acres)

Seasonal

4.1

Emergent

1,739.1

Wet Meadow

20.8

Forested

213.2

Shallow Marsh

1677.7

Scrub Shrub

114.0

Deep Marsh

96.2

Unconsolidated Bottom

14,477.3

Open Water

14399.7

Aquatic Bed

2.8

Scrub Shrub

114.0

 

 

Forested

211.0

 

 

Riverine

.3

 

 

Municipal/Industrial

22.6

 

 

TOTAL

16,546.4

 

16,546.4

Source: Minnesota DNR. 

In 2001-2003 the District undertook a Functional Assessment of Wetlands (FAW) on all wetlands greater than one-quarter acre in size.  This assessment used a variant of the Minnesota Routine Assessment Method.  In contrast to Table 8 above, which shows wetland acreage and type from the National Wetlands Inventory completed in the 1980s, Table 9 below shows the acreage and type as assessed in the field.   Using the results of that analysis, individual wetlands were assigned to one of four categories – Preserve, and Manage 1, 2, or 3 (see Figure 12 and Table 10).  Wetlands that were evaluated as Exceptional or High on certain ecological or hydrologic values were assigned to the Preserve category.  The balance of evaluated wetlands were assigned to a category based on this assessment of current functions and values, with Manage 1 wetlands exhibiting higher values and Manage 2 and 3 moderate or lower values.   Refer to the Functional Assessment of Wetlands (2003) for details of methodology, classification, and management recommendations.

Table 9.  Dominant wetland type in the Lake Minnetonka subwatershed as assessed in the Functional Assessment of Wetlands.

Circular 39 Type

Area (acres)

Seasonal

170.7

Wet Meadow

316.0

Shallow Marsh

1,346.3

Deep Marsh

548.4

Open Water

235.0

Scrub Shrub

176.6

Forested

63.5

Bog

2.4

Lake

292.1

Not typed

46.9

TOTAL

3,197.9

Note: Based on field assessment.  Excludes those areas determined in the field not to be wetlands, and stormwater ponds clearly excavated out of upland.   Includes some small areas that were not field assessed.

Source: MCWD 2003 Functional Assessment of Wetlands.  See Figure 11.

Table 10.  Wetland management classifications of wetlands in the Lake Minnetonka subwatershed as determined in the Functional Assessment of Wetlands.

Classification

Number

Area (acres)

% of total

Preserve

278

1,682.1

55.2

Manage 1

141

375.5

12.3

Manage 2

281

625.5

20.5

Manage 3

264

366.4

12.0

TOTAL

964

3,049.5

 

Note:  The FAW excluded large lakes and wetlands less than ¼ acre in size; those areas are included in the NWI, so total will not match Tables 8 or 9.

Source: MCWD 2003 Functional Assessment of Wetlands.  See Figure 12.

The subwatershed has a large number of wetlands of various sizes distributed across the landscape, including several very large wetlands.  Many scored highly on vegetative diversity, fish and wildlife habitat, or aesthetics (see Figure 13).   Some of the wetlands were also evaluated for restoration potential.  Factors considered were the ease with which the wetland could be restored, the number of landowners within the historic basin, the size of the potential restoration area, the potential for establishing buffer areas or water quality ponding, and the extent and type of hydrologic alteration.  Several wetlands of moderate or high restoration potential are located throughout the subwatershed, including a large wetland adjacent to Lake Marion and several wetlands south of Whaletail Lake in the city of Minnetrista (see Figure 14).