Physiographic Regions

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The Glaciated Plain or Drift Plain

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The glaciated plain includes most of Dickey and LaMoure Counties. It is nearly level to undulating with generally less than 20 feet of relief. The most common surface material is glacial sediment (till) deposited by meltwater (Bluemle, 1979). The prairie that formed on the Drift represents a transitional area between the tall grass prairie of the east and the short grass prairie of the west. It is normally referred to as Mixed Grass Prairie.

Prior to settlement of the area by Europeans the area had a very high density of shallow wetlands. As cultivation of the rich prairie soils became the principal use of the land, these wetlands were easily drained into small creeks and streams which generally run east to the James River. Some wetlands persist and are extremely valuable to breeding waterfowl and other marsh related birds.

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The Missouri Coteau

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An escarpment extending from north to south in western Dickey and LaMoure Counties separates the Drift Plain from an area of thicker glacial sediment called the Missouri Coteau. The elevation of the Missouri Coteau is generally 300 to 500 feet higher than the Drift Plain. The Missouri Coteau is characterized by end moraine hills, non-integrated drainage, numerous sloughs, and lakes (Bluemle, 1979). Many poorly drained depressions receive runoff water from nearby higher areas.

The high density of wetlands, the lack of natural drainage and the rocky character of the soil have slowed the transition of the area to cultivated land. Many large remnants of native grasslands still exist in the Missouri Coteau where cattle ranching competes with cultivation as the predominant use of the land. The high density of wetlands and mixed grass prairie which developed on the glacial sediments of the Missouri Coteau support an abundance of waterfowl and other marsh dependent birds.

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The Coteau Slope

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The Coteau Slope is differentiated from the Missouri Coteau by nearly complete, integrated drainage that flows westward toward the Missouri River (Clayton, 1962). Roughly the western 1/3 of Logan and McIntosh Counties are included in the Coteau Slope. Generally, the glacial sediment is thinner in the Coteau Slope. Thinner glacial sediment and less rocky character in many areas of the Coteau slope allow for increased cultivation.

Grasslands remaining in the area represent mixed grass prairie with many plant species in common with the short grass prairie to the west. Wetland density is much lower than in the Missouri Coteau; however, some wetlands are not associated with natural drainage and are extremely valuable to waterfowl and marsh related birds.

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