Volume IV. L. Minnehaha Creek (PDF)
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MINNEHAHA CREEK MCWD H/H and Pollutant Loading Study – 2003 L-1 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion Minnehaha Creek Table of Contents L. Minnehaha Creek....................................................................................................................... 3 L.1. General Description............................................................................................................ 3 L.2. Physical Features................................................................................................................ 6 L.2.a. Land Cover/Land Use.................................................................................................. 6 L.2.b. Geology ....................................................................................................................... 9 L.2.c. Soils ........................................................................................................................... 10 L.2.d. Groundwater.............................................................................................................. 10 L.3. Water Quantity ................................................................................................................. 17 L.3.a. Watershed Hydrology................................................................................................. 17 L.3.b. Watershed Hydraulics ................................................................................................ 28 L.3.c. Water Quantity Findings and Discussion ................................................................... 30 L.3.d. Watershed Recommendations .................................................................................. 56 L.3.e. Watershed References .............................................................................................. 56 L.4. Scour and Erosion-Prone Areas........................................................................................ 59 L.4.a. Streams ...................................................................................................................... 59 L.4.b. Lakeshore .................................................................................................................. 67 L.5. Water Quality ................................................................................................................... 68 L.5.a. Watershed Pollutant Load Analysis........................................................................... 68 L.5.b. Lake Modeling and Associated Goals....................................................................... 72 L.5.c. MPCA Impaired Waters and Point Source Permits................................................... 80 L.6. Recommendations ............................................................................................................ 84 MCWD H/H and Pollutant Loading Study – 2003 L-2 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion L. Minnehaha Creek L.1. General Description This report segment addresses the portion of the Minnehaha Creek watershed that is located downstream of Grays Bay dam (Figure IV.L.1-1). This area includes Minnehaha Creek (about 22 miles to the Mississippi). It is also referred to as the “lower watershed.” Also discussed in this report section are several subwatersheds that are located within the political boundaries of the MCWD, yet are non-contributing to Minnehaha Creek itself. These subwatersheds are indicated on Figure IV.L.1-1, and the following table lists the all of the subwatersheds that are discussed in this section, along with their acreages: Table IV.L.1-1 List of “Lower Watershed” Subwatersheds and Acreages Watershed Subwatersheds Acres Contributing: Minnehaha Creek MC-1 through MC-184 30,290 Non-Contributing: Wood Lake (Grass Lake) WL-1 through WL-3 1135 Powderhorn Lake MR-3 332 Mississippi River Direct MR-1 through MR-2 950 Figure IV.L.1-2 shows the subwatersheds and their drainage configuration. MCWD H/H and Pollutant Loading Study – 2003 L-3 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion Plymouth g%55 .35 Wayzata RT 3 ,- RT 1 RT 2 Golden Valley 394 ,.- ,.-394 ,.-94 Saint Cedar Lake Lake Louis of the Isles Gray's Park Bay Outlet Lake ,-.35 Calhoun g%55 Minneapolis Hopkins Lake 7 Lake g% Harriet Hiawatha .494 /(169 ,- Edina Lake Minnetonka Nokomis Diamond RT 2 RT 1 Lake Grass Lake g%62 Subwatershed Boundaries ,-.35 Major Watershed Boundary Non-contributing Areas g%100 Major Roads City Boundaries Richfield g%77 Streams Lakes 0.500.5Miles N Figure IV.L.1-1 Minnehaha Creek Political Boundaries H&H Report/Basins/Projects/flow_030331_kl MCWD H/H and Pollutant Loading Study – 2003 L-4 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion 1 < 3 < < 2 21 4 < 108 45 107 < < < 18< 119 < < < < 5 106< From 100 < 44 46 < < < < Grays Bay 7 < < 22 38 104 109< 6 < 19 < 20 33< 47 < Watershed < < 101 121 8 23 < < < 34 48 102 < < < < < To Mississippi 39 < 120 30 < 105 < 118 < 49 103 < < < < 50 < River < 32 < < 41 52 25 < < 122 < 29 31 < < 117 < < 51 < 24 < 37 53 114 < < 123 < 40 < 28 < < < 10 66 < < 110 < < < < < 36 43 < < MR-3 < 17 42 54 55 < 126 16 27 < 115 < 116 < < 35 56 < 57 111 < < 67 < < 14 26 58 < < 113 < 62 < 127 < < < < 112 < < < 69 60 < < 9 < 68 < 170 12 61 < 11 13 59 125 65 171 < 70 76 124 < 176 15 75 128 < 64 < < 177 < 130 172 < < < < < < < 140 < < < 152 173 < 183 < < < 147 < 180 < 80 83< 174 178 < < 71 < 63 72 < 77 153 169 < < 74 84 < < < 182 < < < 175 181 < < 150 < < < 184 131 139 < < < 148 81 < < 154 179 73 < 168 < To < 129 141 165 85 99 < < < < < < 149 < < Miss. < < 138 166 86 < < < 164 < 98 136 137 167 133 < 79 82 132 < < < < < 96 < 151 River 87 < 94< 134 145 146 < 143 < < < MR-2 < 97 < 88 < < 78 < 92 < 93 162 MR-1 89 < 135 163 < 95 < 144 91 161 WL-1 142 < < < < 159 90 160 < < Flow Direction WL-3 < Overland flow for events < 158 < significantly exceeding 156 100-year recurrence To Wood < Lake < 157 Subwatershed Boundaries Major Watershed Boundary Non-contributing Areas 155 Landlocked Subwatersheds Streams Lakes 0.500.5Miles N Figure IV.L.1-2 Minnehaha Creek Flow Direction H&H Report/Basins/Projects/flow_030417_kl MCWD H/H and Pollutant Loading Study – 2003 L-5 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion L.2. Physical Features The following sections detail the MLCCS, geology, soils, and groundwater of the Minnehaha Creek watershed. L.2.a. Land Cover/Land Use For comparison purposes, the various MLCCS land cover classifications have been combined into five impervious surface area categories and six vegetative cover type categories (Figures IV.L.2-1 and IV.L.2-2). Although not shown here, each of the impervious surface area categories was further broken down with respect to type of land use and vegetative cover found on non-impervious surface areas. A more detailed map showing MLCCS cover types to Level 3 for the entire MCWD is included in Appendix 3 (Figure IV.Appendix.3-1). A description of all MLCCS cover types is also included in Appendix 3 and is incorporated into the District's interactive GIS tool. Land use is dominated by single family residential. Blocks of parks and recreational areas are scattered throughout the watershed, in addition to areas with a high concentration of commercial and industrial land uses. Percent imperviousness is, on the average, higher in the eastern portion of the watershed. Currently in the Minnehaha Creek watershed, the “26% to 50% impervious cover” category of land use dominates the landscape (Figure IV.L.2-2), making up 50% of the landscape (Figure IV.L.2-2). Under 2020 land use conditions, “26% to 50% impervious cover” remains the most dominant category, with few changes predicted in the majority of the categories. The biggest percent increase (Table IV.L.2-1) occurs in the “0% to 10% impervious cover” category. The biggest percent decrease was found in the forests and woodlands category. MCWD H/H and Pollutant Loading Study – 2003 L-6 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion MCWD H/H and Pollutant Loading Study – 2003 L-7 Emmons and Olivier Resources, Inc. Volume IV: Watershed Modeling and Discussion 16000 14000 12000 10000 8000 Minnehaha Creek Area [acres] Figure IV.L.2-2 6000 4000 Land Cover 2000 Existing Conditions 2020 Conditions 0 0% to 10% impervious cover MCWD H/H and Pollutant Loading Study – 2003 Emmons and Olivier Resources, Inc. 11% to 25% impervious cover 26% to 50% impervious cover 51% to 75% impervious 76% to 100% impervious cover 50% Agricultural Land 40% Forests & Woodlands Land Cover Category 30% Grasslands Lakes & Open Water Wetlands 20% Maintained Natural Areas 10% Percent Watershed Area Wetlands 0% Volume IV: Watershed Modeling and Discussion L-8 Table IV.L.2-1 Minnehaha Creek Watershed Land Cover Percent Change Percent Change Land Cover Category (from existing to 2020 conditions) 0% to 10% impervious cover 44% 11% to 25% impervious cover 0% 26% to 50% impervious cover 0% 51% to 75% impervious cover 0% 76% to 100% impervious cover 0% Agricultural Land 0% Forests & Woodlands -15% Grasslands 0% Lakes & Open Water Wetlands 0% Maintained Natural Areas 0% Wetlands 0% L.2.b. Geology In contrast to other subwatersheds in the west part of MCWD, the Minnehaha Creek watershed has the full stratigraphic sequence of bedrock units found in the Twin Cities Basin. The Platteville-Glenwood Limestone is the prominent uppermost bedrock unit beneath the Minnehaha Creek watershed.