The proportion of land in given slope classes has been estimated for Iowa counties from a randomly selected sample. The sample, approximately 2 percent of the land area of the state, consists of about 4,500 individual tracts, each about 160 acres in size. A detailed soil map was made of each tract, using a 4-inch-to-the-mile aerial photograph as a base map, thus providing the basic information for a physical land-condition inventory. The data from the soil maps were projected to give estimates of physical land conditions by counties and for the state as a whole. On a state basis, nearly 60 percent of the state has slopes of less than 5 percent gradient, and almost 75 percent of the state has slopes of less than about 9 percent gradient. Summarized estimates of percent land in the 0-1, 2-4, 5-8, 9-13, 14-17, 18-24, and 24 plus percent slope classes are given for all counties of the state, and for the state.
Proceedings of the Iowa Academy of Science
©1960 Iowa Academy of Science, Inc.
Arnold, R. W.; Tyler, L. E.; and Riecken, F. F.
"Estimate of Slope Classes by Counties in Iowa,"
Proceedings of the Iowa Academy of Science, 67(1), 260-267.
Available at: https://scholarworks.uni.edu/pias/vol67/iss1/38