The soils formed in sandy alluvium. Slopes are 1 to 9 percent. Albaton and Wabash soils are clayey and occupy nearly level parts of the flood plain. These soils are more gently sloping, less undulating positions of the flood plain. Grable and Percival soils are finer textured in the upper part, and Onawa soils are finer textured throughout.
Grable soils occur on flood plains but are less undulating and occur further back from the river.
Percival and Onawa soils occur on nearly level flood plains. Modale and Waubonsie soils are clayey below a depth of about 2 feet and occur on nearly level flood plains. Runoff is low. Permeability is rapid or very rapid. The soil floods unless protected by levees or dams.