Geology and Geomorphology
The Eleven Point Watershed lies within the Salem Plateau Subdivision of the Ozark Plateau. The Salem Plateau is a heavily dissected plateau with upland elevations of between 1,000 and 1,400 feet (MDNR 1986). Local relief on the uplands is between 100 to 200 feet. In areas of deeply intrenched valleys, local relief ranges between 200 to 500 feet (MDNR 1986). Elevations within the Eleven Point Watershed range between 1,500 feet above mean sea level (msl) in the uplands to less than 340 feet above msl in the lower portions of the watershed within Missouri, specifically the Eleven Point River near the state line. Karst features are prominent throughout this area (MDNR 1986 and Fenneman 1938).
Geologically, most of the Eleven Point Watershed is underlain by Ordovician age dolomites and sandstone/dolomites (Figure Ge01) (MSDIS 1998). Isolated areas of Mississippian age limestone and limestone/sandstone are also present. Most of the prominent bluffs and steep rugged hillsides along the Eleven Point River were formed in the predominantly light brownish-gray, cherty dolomite of the Gasconade Formation (Nigh 1988). These are capped by a thick layer of Roubidoux Sandstone on the ridges and upper slopes (MDC 1997). The Jefferson City-Cotter Formation, a cherty dolomite occurring along ridge tops, is a common Ordovician age formation in the uplands of the watershed (Nigh 1988 and MDC 1997).
The Eleven Point Watershed occurs within the Ozark Soils Region. Allgood and Persinger (1979) describe the Ozark Soils Region as "cherty limestone ridges that break sharply to steep side slopes of narrow valleys. Loess occurs in a thin mantle or is absent. Soils formed in the residuum from cherty limestone or dolomite range from deep to shallow and contain a high percentage of chert in most places. Some of the soils formed in a thin mantle of loess are on the ridges and have fragipans, which restrict root penetration. Soil mostly formed under forest vegetation with native, mid-tall and tall grasses common in open or glade area."
The following is a list of soil associations found in the Eleven Point Watershed in Missouri:
- (Allgood and Persinger 1979)
Stream Mileage, Order and Permanency, Springs
Using United States Geological Survey (USGS) 7.5 minute topographic maps, a total of 139 third order and larger streams were identified. Of the 139 third order and larger tributaries to the Eleven Point River, 106 are third order, 27 are fourth order, 4 are fifth order, and 1 is sixth order. The Eleven Point River is seventh order when it reaches the Arkansas state line (Table Ge01 and Figures Ge02, 03, and 04).
The Eleven Point Watershed is exceptional for the number and length of losing streams in the upper and middle portions of the watershed (Table Ge02)(MDNR 1994). Nearly all streams, with the exception of the lower two miles of Hurricane Creek and the Eleven Point River below Thomasville, lose substantial amounts of surface flow to the groundwater system (MDNR 1994). The losing streams, sink holes, and other karst features recharge many springs within the watershed as well as others outside the watershed (MDNR 1996; Vineyard and Feder 1974). Based on the United States Geological Survey Geographic Names Information System Data as well as Vineyard and Feder (1974), it has been determined that there are a total of 64 named springs within the watershed. Seventeen springs with records of discharge are listed by Vineyard and Feder (1974) (Table Ge03 and Figure Ge05). All the major springs in the watershed emerge on, or near, the Eleven Point River. Twelve of the major springs, including Greer Spring, emerge from the Gasconade Formation (Vineyard and Feder 1974; MDNR 1994). Greer Spring is the second largest spring in the state with an average flow of 289 cubic feet per second (cfs). Four other springs emerge from the Roubidoux Formation near the confluence of Frederick Creek and the Eleven Point River (also known as the Narrows) and have a combined flow of 110 cfs (MDNR 1994). These springs assist in maintaining base flows in the middle and lower portions of the Eleven Point River, while streams in the headwaters of the watershed, which lack significant spring input, are frequently dry (MDNR 1994).
Dye tracings have indicated that some surface water recharges Greer Spring and other springs within the Eleven Point Watershed, however, much of the flow from the Upper Eleven Point, Spring Creek, and Hurricane Creek is lost to ground water system which travels in an East-Northeast direction and emerges at Big Spring on the Current River (MDNR 1994; Adamski, Peterson, Freiwald, and Davis 1995; MDNR 1995, 1996). A positive dye trace indicated at least 2/3 of the watershed of Hurricane Creek is in the recharge area of Big Spring. This provides an excellent demonstration that ground water divisions must be determined before water management plans are made in karst topographies. Figure Ge06 displays the results of successful dye traces completed by various state and federal natural resource agencies (USDA-FS 1997 and MDNR 1995,1996).
"Greer Spring-Upper Outlet"
Using United States Geographical Survey (USGS) 7.5 minute topographical maps permanence of stream flow was determined for third order and larger streams. The USGS identifies streams having water 12 months of the year during years of normal precipitation with a solid blue line. Intermittent streams were identified by a broken blue line and were defined as streams carrying water less than 12 months of a year. Approximately 9% (92.2miles) of the fourth order and larger streams have permanent flow (Table Ge04 and Figures Ge02, 03, and 04). This includes 53% (51.5 miles) of the Eleven Point River; 34% (12.0miles) of Frederick Creek; 16% (5.2 miles) of Spring Creek; and 14% (4.5miles) Hurricane Creek.
Drainage areas were determined from digital raster graphic (drg) versions of USGS 1:100,000 and 1:24,000 scale topographic maps. The drainage area of the Eleven Point Watershed in Missouri is 655,802 acres or 1024.7 square miles. The Eleven Point Watershed was divided into six subwatersheds (not to be confused with the 14 digit hydrologic units or the drainage sections which are used in this document for analysis and display purposes) based on drainage areas accounting for > 5% of the total drainage area of the Eleven Point Watershed (Figure GE 07 and Table Ge04). In karst regions such as the Eleven Point River Watershed, it is of equal importance to understand the ground water divisions. As discussed earlier, much of the water produced by the Eleven Point Watershed emerges from springs within other watersheds. It is likely that springs within the Eleven Point Watershed contain ground water from other watersheds.
Gradient information for fourth-order-and-larger streams was obtained from USGS 1:24,000 scale topographical maps. Composite gradient plots were prepared for fifth order and larger stream channels. The Eleven Point River is a high gradient stream, averaging 11.2 feet per mile. The gradient of the Eleven Point River ranges from 5.8 feet per mile at Missouri/Arkansas State line to 98.0 feet per mile at its headwaters (Table Ge05).In general, gradients of the major tributaries to the South and West of the Eleven Point River (Middle Fork; Barren Fork, Fredrick Creek) are lower than those tributaries to the North (Spring Creek; Hurricane Creek). Drainages South and West of the Eleven Point River are characterized by high, relatively flat plains with local relief of 100 to 150 feet occurring near drainages. Long gentle slopes are separated by broad, rounded ridges and wide, flat valleys. Drainages north of the Eleven Point River are characterized by highly dissected hills with narrow ridges and steep side slopes. Local relief ranges from 250 to 500 feet.