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Left is a picture of the dam at Rothrock's Mill from 1984.
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The second darter site sampling site is located at Rothrock’s Mill dam. We studied Rothrocks on three occasions. On September 11th 2001, we measured the depth, velocity, conductivity, and calculated the discharge. The traveling kick net was used to capture qualitative invertebrate samples. We also identified trees and vegetation along one bank. On September 18th, we measured calculated discharge, collected and preserved 3 macroinvertebrate samples for macroinvertebrate bioassessment. The Zippin removal depletion method was used to evaluate riffle fish populations. On September 25th, we collected water samples from this site and two others.
The site is difficult to locate; so directions are included in this section. From IUS, take I-265 west to I-64 west. From I-64 west take the Corydon exit. Continue right on HWY 131, and follow this highway until you have reached HWY 62. Turn right and travel to Harrison Springs Road. Turn right and follow Harrison Springs Road to the next intersection. Turn left onto Rothrocks Mill Road, and then turn left into the gravel parking lot.
Another way to access this site is to take the I-64 west exit at the Georgetown. Travel on HWY 64 west for approximately 25 miles until reaching the Milltown exit. Follow the signs to Cave Country Canoes. After going across the one-lane bridge follow Milltown-Leavenworth Road to Old Mill Road. Turn left and eventually a person will cross an old bridge near Rothrock’s Mill.
The Rothrocks Mill site of the river is located in the Milltown Quadrangle, section 11. The geographical location of the site is at the latitude of 38 degrees North 12’ 43.1” and longitude of 86 degrees West 16’ 15.4” with an elevation of 515 ft. Blue River in this area is located in the Escarpment Section of the Shawnee Hills Natural Region.
Rothrock’s Dam originally was the site of a working mill. The area has changed considerably in the last 15 years. In the late 1980’s, the dam was almost completely removed to facilitate canoe passage. Researchers were forced to sample riffles downstream from the dam because silt and sand from the mill pool had washed down and covered the rocks. Later, erosion removed the sand and silt, and now the dam area is inhabited by several different species of fishes. See photographs for pictures of the old dam.
The Rothrock’s site has the alternating fast water riffles and also slower moving pools characteristic of this river. The swifter riffles located in the old dam area are a preferred habitat for the endangered spotted darter, as well as bluebreast and variegate darters. Below the dam are gravel outwash communities where smartweed, water willow, and sycamores thrive.
On September 11th, the air and water temperatures were 29.5 and 20.2 degrees C. The weather was sunny and warm. The river discharge was high, and the fast moving water created strong rapids. Stream riffle velocity averaged 4.08 ft/sec. The river was approximately 80-100 ft. wide on this day, and the depth was between 27 and 36 inches. The calculated discharge was about 1200 cfs.
The surrounding shore was muddy where the path led down to the old dam. Otherwise the banks were stable with little erosion. In the area were limestone, shale, sandstone and dolomite rocks from the middle and upper Mississippian geological period. The major soil type is Haymond Silt Loam of the Haymond-Huntington Association. The epifaunal substrate was well suited for the colonization. We found submerged logs, cobble somewhat embedded in the sediment.
The water chemistry test results indicated ample dissolved oxygen (8 mg/L), moderate alkalinity and hardness, conductivity 0.26ms/cm, and a pH of 8. The nitrate for upstream was 0.007 and 0.09 downstream. The turbidity was 8.7 upstream and 4.9 downstream.
Qualitative samples yielded damselflies, riffle beetles, caddis flies, stoneflies, aquatic worms, water pennies, clams and mussels. Examples of fish were spotted darters (endangered), rock bass, bluntnose minnows, rainbow darters, stonerollers, northern hogsuckers, and banded sculpins.
The riparian vegetation along the shore was a part of the eastern deciduous forest. Examples of the trees near the river were: white ash, red maple, black walnut, sycamore, and box elder. The sycamore was the most abundant bankside species. Rootwads provide habitat for centrarchids like rockbass and longear sunfish. Other vegetation included wild cucumber, smartweed, water willow, and wingstem (yellow wildflower). Vegetation covered more than 90% of the streambank.
