Geology and Geomorphology
Physiographic Region and Geology
The Moreau basin lies in the physiographic province of the United States known as the Interior Highlands. It is part of the northern Salem Plateau, a subdivision of the Ozark Plateau (Figure Ge01). This landform is characterized by rolling upland topography with local relief of 100-200 feet along major drainage divides (MDNR 1986). Gently sloping praire is evident near Tipton, Latham and High Point (USDA 1964). In areas, rugged hills with deeply carved river valleys can be found. The highest elevation (1100 feet) in the watershed is located along the western border of the basin near Versailles. Water flows toward the east and empties into the Missouri River at an elevation of 523 feet. At one time geologists believe the Moreau River may have emptied into the Osage River near Osage City rather than flowing directly into the Missouri River. The theory is that the Moreau shortened itself by meandering too close to the Missouri River where it became captured (Beveridge 1978).
The predominant rock type includes Ordovician age cherty dolomite, thin beds of shale, and minor deposits of sandstone (Figure Ge02). The surface contains a stony red clay residuum of the Jefferson City-Cotter formation and some pockets of loess on the tops of high ground (Figure Ge03) (MDNR 1984). Penetration of water to the subsurface is poor so most water runs off to streams and stream base flows are poorly sustained (MDNR 1984). Minor deposits of lead, iron, germanium, zinc, coal and barite are found in basin counties (USFS 2001). Mining was especially active in Moniteau county near California, Tipton, and High Point in the early 1870?s (Campbell?s Gazetteer of Missouri 1874). These mines are now closed and current mining efforts are directed at sand and gravel, and limestone.
There are two springs, Steenbargen (SE SW 25, R14W, T43N) and Strobel (SW SW 35, R14W, T44N), located near Russellville in Cole county. Neither spring has significant discharge (Vineyard and Feder 1974).
The soils of the basin are classified as Ozark Border. The upland plateau is characterized by narrow ridgetops and valleys. Thin loess deposits occur on the ridgetops. Some soils contain fragipans, a loamy or sandy subsurface horizon of low organic content that can form a cement-like layer that impedes water and the growth of roots. Steep slopes contain deep cherty clayey reddish colored soils over dolomite or limestone. Sandy, loamy and gravelly alluvial soils are in the bottom lands. The predominant soil series are Seymour-Glensted-Creldon-Eldon
These soils support cultivation of corn, soybeans, grain sorghum and hay crops (Allgood and Persinger 1979).
In the 1997 National Resource Inventory, soil erosion losses for lands in the larger 8-digit hydrologic unit (10300102), which includes the Moreau subbasin, were estimated for cropland, pastureland, and non-cultivated cropland. These erosion rates were estimated at 5.619, 1.322, and 0.651 tons of soil per acre annually, respectively, for each land type (Barney 2002, personal communication).
The watershed or drainage area of the Moreau River is 584 square miles. It is located in the southern portion of the Missouri River mainstem-Glasgow to Hermann 8-digit hydrologic unit (10300102) (Figure Ge04). This watershed is further divided into three hydrologic units: the North Moreau (10300102200), the South Moreau (10300102210), and the mainstem Moreau (10300102220) (Figure Ge04). Interestingly, the North Moreau hydrologic unit only includes the North Moreau watershed upstream from Burris Fork. The lower portion is included in the Moreau hydrologic unit. Therefore the watershed areas of these two hydrologic units do not equal the watershed areas for these subbasins (Table Ge01).
The watershed areas of the three major subbasins are: South Moreau Creek 174 square miles, North Moreau Creek 347 square miles, and mainstem Moreau River 63 square miles (Table Ge01). The largest proportion of the watershed (59%) lies in the North Moreau subbasin.
Stream ordination is a method used to describe the branching geomorphologic nature of streams. A 1st order stream is unbranched. A 2nd order stream is formed when two 1storder streams join. A higher ordination can only be formed when two streams of the same order join. In this manner, 71 streams, 3rd order or greater, were identified, ordered, and measured using USGS 7.5 minute topographic maps (Table Ge02). They provide a total of 424 miles of stream frontage. The highest order streams are: mainstem Moreau river and South Moreau Creek, 6th order; and North Moreau Creek, Brush Creek and Burris Fork, 5th order.
On the mainstem Moreau, the river drops an average 1.6 feet per mile. The 5th order and larger reaches of North (first 47 miles) and South Moreau (first 29 miles) creeks drop 3.6 ft/mi and 6.6 ft/mi, respectively (Figure Ge05). Additional gradient information for other streams in this basin can be obtained from the Missouri Department of Conservation Central Region office in Columbia (Address: 1907 Hillcrest Drive, Columbia, MO 65201; phone: (573) 884-6861).