Irrigation occurs along the Missouri River. Compiled by Rocky Mountain Region. Gently sloping loess-mantled narrow ridgetops are separated by steep slopes bordering drainage ways. Some stream valleys with nearly level flood plains and large stream terraces exist. Dissected plains with broad rolling ridgetops and moderately steep valley sides occur.
Valleys are usually narrow with broad flood plains and terraces, and hilly dissected plains.
There are rivers with wide flood plains and terraces, and small streams with narrow bottomlands. Rolling plains have a deep mantle of windblown sand and sandy outwash. This Section is within Fenneman and Johnson's Great Plains geomorphic physical division. Lithology and Stratigraphy. Most of Section is Cretaceous marine shales, with some sandstones in the extreme northwest.