South Dakota: basement moisture and foundation risk by county
66 counties, ranked by our combined index. Highest combined risk is Brown County (62), lowest is Custer County (31). The worst soil for foundation cracks specifically is in Harding County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Brown County | 62 | 54 | 69 | 66 | Dakota prairie till plain |
| Bon Homme County | 60 | 52 | 66 | 66 | Dakota prairie till plain |
| Deuel County | 60 | 54 | 63 | 66 | Dakota prairie till plain |
| Hamlin County | 60 | 51 | 67 | 66 | Dakota prairie till plain |
| Faulk County | 59 | 53 | 61 | 66 | Dakota prairie till plain |
| Brule County | 58 | 54 | 58 | 66 | Dakota prairie till plain |
| Harding County | 58 | 42 | 100 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Grant County | 57 | 54 | 68 | 46 | Dakota prairie till plain |
| Stanley County | 57 | 41 | 100 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Tripp County | 57 | 41 | 98 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Douglas County | 56 | 49 | 72 | 46 | Dakota prairie till plain |
| Edmunds County | 56 | 51 | 57 | 66 | Dakota prairie till plain |
| Hyde County | 56 | 40 | 96 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Lincoln County | 56 | 53 | 52 | 66 | Dakota prairie till plain |
| Minnehaha County | 56 | 50 | 71 | 46 | Dakota prairie till plain |
| Davison County | 55 | 52 | 52 | 66 | Dakota prairie till plain |
| Lyman County | 55 | 41 | 93 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Walworth County | 55 | 41 | 93 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Campbell County | 54 | 39 | 91 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Corson County | 54 | 41 | 91 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Day County | 54 | 55 | 43 | 66 | Dakota prairie till plain |
| Beadle County | 53 | 54 | 42 | 66 | Dakota prairie till plain |
| Lake County | 53 | 51 | 48 | 66 | Dakota prairie till plain |
| Meade County | 53 | 39 | 89 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Sanborn County | 53 | 50 | 61 | 46 | Dakota prairie till plain |
| Sully County | 53 | 41 | 87 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Yankton County | 53 | 50 | 47 | 66 | Dakota prairie till plain |
| Bennett County | 52 | 40 | 84 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Charles Mix County | 52 | 53 | 56 | 46 | Dakota prairie till plain |
| Codington County | 52 | 51 | 43 | 66 | Dakota prairie till plain |
| Fall River County | 52 | 40 | 94 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Gregory County | 52 | 50 | 70 | 30 | Dakota prairie till plain |
| McPherson County | 52 | 50 | 60 | 46 | Dakota prairie till plain |
| Potter County | 52 | 41 | 84 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Turner County | 52 | 50 | 59 | 46 | Dakota prairie till plain |
| Union County | 52 | 55 | 52 | 46 | Dakota prairie till plain |
| Haakon County | 51 | 41 | 80 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Spink County | 51 | 50 | 66 | 30 | Dakota prairie till plain |
| Kingsbury County | 50 | 52 | 50 | 46 | Dakota prairie till plain |
| Roberts County | 50 | 52 | 62 | 30 | Dakota prairie till plain |
| Clark County | 49 | 53 | 45 | 46 | Dakota prairie till plain |
| Hand County | 49 | 50 | 49 | 46 | Dakota prairie till plain |
| Marshall County | 49 | 52 | 46 | 46 | Dakota prairie till plain |
| McCook County | 49 | 55 | 53 | 30 | Dakota prairie till plain |
| Miner County | 49 | 51 | 48 | 46 | Dakota prairie till plain |
| Buffalo County | 48 | 52 | 44 | 46 | Dakota prairie till plain |
| Hanson County | 48 | 51 | 57 | 30 | Dakota prairie till plain |
| Jones County | 47 | 42 | 66 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Moody County | 47 | 51 | 43 | 46 | Dakota prairie till plain |
| Pennington County | 47 | 39 | 80 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Hughes County | 46 | 42 | 63 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Oglala Lakota County | 46 | 38 | 80 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Perkins County | 46 | 39 | 68 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Todd County | 46 | 39 | 68 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Aurora County | 45 | 53 | 43 | 30 | Dakota prairie till plain |
| Clay County | 45 | 52 | 47 | 30 | Dakota prairie till plain |
| Hutchinson County | 44 | 52 | 44 | 30 | Dakota prairie till plain |
| Jerauld County | 44 | 53 | 41 | 30 | Dakota prairie till plain |
| Mellette County | 44 | 37 | 65 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Ziebach County | 44 | 39 | 61 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Brookings County | 43 | 50 | 42 | 30 | Dakota prairie till plain |
| Jackson County | 43 | 39 | 67 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Dewey County | 42 | 37 | 59 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Butte County | 33 | 31 | 38 | 30 | Rocky Mountains |
| Custer County | 31 | 29 | 34 | 30 | Rocky Mountains |
| Lawrence County | 31 | 29 | 34 | 30 | Rocky Mountains |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside South Dakota
State lines are political; soil follows geology. These are the distinct ground types inside South Dakota and why each behaves the way it does.
Dakota prairie till plain
The dry climate hides the mechanism: the profile shrinks through dry years, swells after a wet one, and the footing moves. A cycle, not permanent damp.
39 counties: Aurora County, Beadle County, Bon Homme County, Brookings County, Brown County, Brule County, Buffalo County, Charles Mix County, Clark County, Clay County, Codington County, Davison County, Day County, Deuel County, Douglas County, Edmunds County, Faulk County, Grant County, Gregory County, Hamlin County, Hand County, Hanson County, Hutchinson County, Jerauld County, Kingsbury County, Lake County, Lincoln County, Marshall County, McCook County, McPherson County, Miner County, Minnehaha County, Moody County, Roberts County, Sanborn County, Spink County, Turner County, Union County, Yankton County
Missouri Plateau (unglaciated Great Plains)
The water table is deep, so basements rarely flood — but Pierre Shale is one of the most expansive substrates in North America. The risk here is mechanical, not hydraulic.
24 counties: Bennett County, Campbell County, Corson County, Dewey County, Fall River County, Haakon County, Harding County, Hughes County, Hyde County, Jackson County, Jones County, Lyman County, Meade County, Mellette County, Oglala Lakota County, Pennington County, Perkins County, Potter County, Stanley County, Sully County, Todd County, Tripp County, Walworth County, Ziebach County
Rocky Mountains
Shallow bedrock and coarse material. Basements are shallow or absent, and the problem is spring meltwater rather than a water table.
3 counties: Butte County, Custer County, Lawrence County
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