Earth Geology Topography Overview
At the places where erosion has cut through the Roubidoux sandstone layer, the valleys of the Bryant and its tributaries begin to look different. Where the streams cut through it, the sandstone layer forms stairstep rapids, waterfalls, and "box canyons."
As you continue down from this point, you will usually see sandstone bluffs along and above the stream level. The harder sandstone forms a cap rock that protects the softer underlying rock layers. This allows the stream walls to be very steep, forming the bluffs commonly seen along the streams. These bluffs are always most prominent on the outside of a meander curve.
The Roubidoux formation is a major water-bearing layer (aquifer) and springs are common where the stream valleys cut through it.
Northern Headwaters of the Bryant
The northern headwaters of the Bryant and its tributaries begin along the southern edge of Wright County, south of Mansfield and Norwood, and in extreme southeastern Webster County, south of Cedar Gap. Here the Bryant headwaters are actively eroding into the southern margin of the Springfield-Salem plateau. This produces a distinct irregular "rim" or break in topography between the relatively flat Springfield-Salem plateau and the very rugged topography of the Bryant watershed. The Bryant's share of this rim extends eastward from Cedar Gap, past the southern edge of Mansfield and Norwood, to the southern edge of Mountain Grove. The rim continues on to the east past Cabool, marking the head of the North Fork watershed, Bryant's sister stream. This rim also extends westward from Cedar Gap to Dogwood and beyond. Here it is at the head of the Bryant's neighbor to the west, the Beaver watershed.
Stream Gradients - How the Bryant Drops From its Beginning at Cedar Gap Down to Where it Joins the North Fork
Lead Hill, in the area of Cedar Gap on the northwest edge of the Bryant watershed, is 1,744 feet high, the second-highest point in the state. (The only higher point is Taum Sauk Mountain of the St. Francis Mountains of eastern Missouri, which is about twenty feet higher.) The elevation of the surface of Norfork Lake, just below the junction of the Bryant and the North Fork at Tecumseh, is at 546 feet. The difference in elevation is approximately 1,200 feet --- a considerable drop if you measure it "as the crow flies," which gives a linear (straight-line) distance of 39.5 miles.
If you divide the 1,200 foot drop by this linear distance of 39.5 miles, you get a stream gradient of just over 30 feet/mile. Of course the Bryant does not flow "as the crow flies", but does a lot of of meandering (winding), which probably just about doubles the distance. The actual distance that a drop of water flows as it travels from the top of Lead Hill to where the Bryant joins the North Fork is 70 miles. This gives an average stream gradient of 17 ft/mi. (1,200 feet divided by 70 miles.)
However, for its first five miles of headwaters, the Bryant is an "intermittent stream," appearing and then disappearing underground. Over this first five miles the elevation drops by 624 feet. This gives it the very steep stream gradient of 125 ft/mi! Over the remaining 65 miles the elevation drops by just 560 feet for an average gradient of 8.7 ft/mi. This great difference in gradient between the headwaters of Bryant and the main channel of its lower 65 miles shows up in the way stream erosion has shaped the land over the first 5 miles and the lower 65.
It is interesting to note that water that flows off the north side of Lead Hill goes into the Gasconade watershed, the Bryant's neighbor watershed to the north. This water ends up at the Missouri River after traveling 260 miles downstream. Over this 260 miles the elevation drops by about the same amount as the Bryant, 1,200 feet. This gives the Gasconade an overall stream gradient of about 4.5 ft/mi. As you might expect, this gradual drop creates a less rapid flow and produces a considerably less rugged topography than the Bryant does.
Caves And Sinkholes
Another important feature in the Bryant watershed is the common occurrence of caves and sinkholes. The dominant rock type in the area is carbonate rock. Carbonate rocks are subject to solution or dissolving by groundwater. This produces cavities or caverns in the rock, which may be seen as caves in hillsides or a collapsed caves or "sinkholes" in relatively flat areas.