Why is Boxley Valley so Wide?

Have you noticed how wide the valley is at Boxley Valley? In 'How Rivers Work 101' (intro fluvial geomorphology), we learn that channel and valley width increase downstream along with discharge. A look at a topo map, like the clip from the Boxley map below, or a drive along Boxley Valley to the low water bridge at Ponca where the valley starts to pinch down shows that the Buffalo River is an exception to the rule. For our research team, one of the central scientific research questions is: how does rock type affect river processes? To learn more about valley width, we made measurements of valley width at regular intervals using geographic information systems (GIS) along the river and then partitioned the measurements by lithology to test whether our observation of valley width changing with rock type was statistically relevant. We found that it is. In the limestone reaches (like the reach from Boxley Valley where the Buffalo River begins to the the low water bridge at Ponca) the valley is 70% wider on average than in reaches that are more sandstone dominated (like the reach from Ponca to just upstream of Carver). While it is evident that lithology and valley width are related in the Buffalo River, we're still working to discover how rock type effects the erosion processes that control and produce the variations in valley width.  You can download the full version of the maps shown below from our Maps Page and check back for more research results from our team!   

The geology map at Boxley Valley shows the wide valley where the channel is incised into the Boone Formation limestone. Excerpt from Hudson, M.R., and Turner, K.J., 2007, Geologic map of the Boxley Quadrangle, Newton and Madison Counties, Arkansas: U.S. Geological Survey Scientific Investigations Map 2991, 1:24,000 scale.

The geology map at Boxley Valley shows the wide valley where the channel is incised into the Boone Formation limestone. Excerpt from Hudson, M.R., and Turner, K.J., 2007, Geologic map of the Boxley Quadrangle, Newton and Madison Counties, Arkansas: U.S. Geological Survey Scientific Investigations Map 2991, 1:24,000 scale.

The geology map from Ponca low water bridge to Steel Creek shows that where the channel cuts into the Everton Formation, the valley becomes narrower. Excerpt from Hudson, M.R., and Murray, K.E., 2003, Geologic map of the Ponca Quadrangle, Newton, Boone, and Carroll Counties, Arkansas: U.S. Geological Survey Miscellaneous Field Studies Map 2412, 1:24,000 scale.

The geology map from Ponca low water bridge to Steel Creek shows that where the channel cuts into the Everton Formation, the valley becomes narrower. Excerpt from Hudson, M.R., and Murray, K.E., 2003, Geologic map of the Ponca Quadrangle, Newton, Boone, and Carroll Counties, Arkansas: U.S. Geological Survey Miscellaneous Field Studies Map 2412, 1:24,000 scale.