Dissected Till Plains Section of the Central Lowland Province of the Interior Plains.
This landform region is locally called the Southern Iowa Drift Plain.
Area includes portions of the following states:
65% in Missouri
35% in Iowa
Total Land Area 15,895 square miles (41,185 square kilometers).
Bethany, Chillicothe, Memphis, and Plattsburg, Missouri.
Ottumwa, Fairfield, Mt. Pleasant, and Centerville, Iowa.
Mississippian shale and limestone bedrock lies beneath the glacial and alluvial deposits.
Loess covers the surface of almost all of the uplands in this area. Glacial drift that is high in content of clay underlies the loess. Alluvial clay, silt, sand, and gravel deposits are in all of the stream and river valleys. They can be extensive in the major river valleys.
The northeastern part of the area consists of flat, tablelike uplands with steep or hilly land occurring only near the margins of stream valleys. Other parts of the area are more dissected, have less extensive upland divides, and consist mostly of hillslopes. Nearly level, broad valley floors are along a few large rivers.Topography -
Elevation ranges from 660 feet (200 meters) in the lowest valleys to 980 feet (300 meters) on the highest ridges. Local relief is mainly 10 to 20 feet (3 to 6 meters).
Valley floors can be 80 to 160 feet (25 to 50 meters) below the adjacent uplands.
The average annual precipitation in most of this area is 34 to 41 inches (865 to 1,040 millimeters).
Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season.
The average annual temperature is 49 to 54 degrees F (9 to 12 degrees C).
The freeze-free period averages 190 days and ranges from 175 to 210 days.
* this is the percent of area drained by each named hydrologic unit
The Grand, Thompson, and Chariton Rivers, which are tributaries of the Missouri River, begin in the part of this area in Iowa and flow south into Missouri.
The Whitebreast and Des Moines Rivers also occur in the northern part of the area. The Locust River, in the southern part of the area, is another major tributary of the Missouri River.
|Public supply||surface water||10.8%||ground water||5.9%|
|Livestock||surface water||3.9%||ground water||4.3%|
|Irrigation||surface water||0%||ground water||1.5%|
|Other||surface water||71%||ground water||2.7%|
Total daily withdrawls average 220 million gallons per day (835 million liters).
14% Ground water sources
86% Surface water sources
Since the ground water is highly mineralized, many communities in the area rely on surface water for their supply of drinking water. The streamflow fluctuates widely and frequently, so storage is required to maintain any public supplies.
Ground water supplies from glacial drift are small, undependable, and of poor quality. This water is naturally high in total dissolved solids, commonly exceeding the national drinking water standard of 1,000 parts per million (milligrams per liter). Some ground water is pumped for irrigation from alluvial deposits along the larger rivers in the area.
The soils are generally very deep, well drained to poorly drained, and silty, loamy, or clayey.
|Hapludalfs||Armster, Armstrong, and Keswick series||formed in loess and/or pedisediment over till|
|Weller series||formed in loess|
|Gara and Lindley series||formed in till on uplands.|
|Epiaqualfs||Pershing series||formed in loess on uplands and benches.|
|Argialbolls||Edina series||formed in loess on uplands and benches.|
|Argiaquolls||Clarinda series||formed in till on uplands.|
|Argiudolls||Grundy series||formed in loess|
|Lamoni and Shelby series||formed in till|
|Lagonda series||formed in loess and/or pedisediment over till on uplands.|
|Endoaquolls||Zook series||formed in alluvium on flood plains and stream terraces.|
This area supports grassland vegetation. Big bluestem, Indiangrass, little bluestem, and switchgrass are the major species. The natural drainageways and the lowlands interspersed throughout the area support forest vegetation, mainly oaks and hickories. Most of the native grasses have been removed by cultivation and overgrazing.
Some of the major wildlife species include whitetailed deer, raccoon, skunk, opossum, muskrat, cottontail, mink, squirrel, and quail.
|53% -||Cropland||- private|
|26% -||Grassland||- private|
|14% -||Forest||- private|
|3% -||Urban development||- private|
|2% -||Water||- private|
|2% -||Other||- private|
Corn, soybeans, other feed grains, and hay are the principal crops. About one-fourth of the area supports introduced and native grasses. Beef cattle and swine are important sources of income on many farms.
The major resource concerns include water erosion, depletion of the organic matter in the soils, and poor water quality.
Conservation practices generally include systems of crop residue management (especially no-till, strip-till, and mulch-till systems), cover crops, nutrient and pest management, grassed waterways, terraces, manure management, pasture and hayland planting, and grade-stabilization structures. These practices help to control erosion, flooding, and sedimentation.