Shoal Destruction at Mancil Rock, Conecuh River, Alabama

Abstract

Shoal Destruction at Mancil Rock, Conecuh River, Alabama Joann Mossa (bio) Lumber was an important component of the economy of the rural southeastern US in the late 1800s and early 1900s, and rivers provided less expensive routes than rail for floating either timber rafts or loose logs to major ports on the coast. However, obstacles and insufficient river depths throughout much of the year limited the use of rivers for this purpose. Army engineers documented conditions in these rivers and received appropriations from Congress to fund crews to clear out obstacles such as snags, rafts, wood jams, and overhanging trees in rivers across the United States (Wohl 2014). The annual reports of the Chief of Engineers describe the quantity of wood removed, but limited records exist for the rock, marl, clay shoals, islands, and boulders destroyed or modified to allow river transportation. One of many sites where Army engineers proposed work was the Escambia-Conecuh river system in Florida and Alabama (Chief of Engineers 1879). The Chief of Engineers (1879) described the Conecuh River as “impassable for boats, and even the transportation of timber and saw-logs during high-water is difficult.” Regrettably, the maps that accompanied this report could not be located. This issue’s cover photograph depicts the Conecuh River at Mancil Rock (spelled “Mansell” and “Mancell” in some reports), an altered calcareous shoal in Escambia County, southern Alabama (31.136856 °N,-86.836702 °W) (Figures 1 and 2). According to Clarke et al. (1966), the lithology of Mancil Rock is dolomite, composed of ~57.54 percent calcium carbonate, ~34.31 percent magnesium carbonate, and ~4.8 percent iron oxides and aluminum. The shoal remnants in the foreground connect to the right or north bank, water flows through the destroyed middle section, and the distant portion on the left or south bank lies under the shadows (Figure 2). According to Hiram Haines, Assistant Engineer, “the rocks belonging to the Eocene division of the Tertiary formation are exposed and form obstructions in the shape of shoals and heavy bowlders (sic)” (Chief of Engineers 1879). For a full improvement at Mancil Rock (section 15, township 2, range 12), Haines recommended removing 11,300 cubic yards of loose rock and 1000 cubic yards of solid rock totaling $7,650 (Chief of Engineers 1879). For partial improvement, he advised removing 750 cubic yards of loose rock and 100 cubic yards of solid rock totaling $575 (Chief of Engineers 1879). After several years of work on the Escambia, moving upstream annually, in 1887 Army engineers sent two parties totaling eleven men to work on the Conecuh River near Mancil Rock for several months (Chief of Engineers 1888). One crew removed ~3000 [End Page 127] Click for larger view View full resolution Figure 1. Maps of the Escambia and Conecuh rivers and study area, showing A) the location of the watershed within the region, B) the topography and drainage basin of the Escambia-Conecuh with some of its major tributaries, and C) a close-up of the topography of the Conecuh River near Mancil Rock with an arrow pointing to the location of the photograph. snags and logs from the channel and 275 overhanging trees from the banks and the other worked to excavate a channel through the “Mancell Rocks” and remove all rocks visible in the channel at low water. Despite this effort, later reports suggest that the changes at Mancil Rock were incomplete. As Cavanaugh (1906) described: “Mansell rock is a rock reef extending from the right bank toward the left bank so as to almost close the entire river” and “a cut of 600’ to 1000’ should be made.” Referring to 1887 efforts: “some work has been done toward cutting through this reef, but nothing has been accomplished so far.” Soon afterward, Congress appropriated $31,000 for the Conecuh River through the River and Harbor Act of March 2, 1907, small in proportion to the annual commerce reported on the Escambia-Conecuh of $2,500,000 (Chief of Engineers 1907). That year, the Corps staged two barges, a derrick barge and one for the storage of dynamite. Next, the Corps removed 1658 and 1563 cubic yards of rock and marl (Chief...