|
|
The Fredricksburg site is located along Highway 150. The riffle studied is located directly below where the 150 bridge crosses the Blue River at Fredricksburg. This site is apparently the northern-most outpost for the spotted darter along the Blue River. Dr. Claude Baker, et al. had collected two spotted darters here in a previous study in 1984. With the sewage problems associated with Salem, which is only several miles upstream from this point, it was determined that this would be a good study location. It was evaluated on September 23, 1999 at 1:30 PM EDT. The weather was sunny and warm with an outside air temperature of 80 degrees.
The general area included dense forest and bankside vegetation with farmland and a small town nearby. The bridge and riparian canopy cover of silver maple trees Provided partial shade to the riffle. Bank vegetation was abundant and dense. Understory vegetation was substantial and provided excellent bank stability.
Upstream the banks were naturally channelized. The right bank here was much steeper than the left. The right bank consisted of fields, while the left bank consisted of dense vegetation.
Downstream, the banks were again naturally channelized. The right bank had some tree cover with farmland in the distance. The left bank was again covered with dense vegetation.
The physiographic region of this site is the Shawnee Hills Natural Region, Escarpment Section. The bankside soils are classified as Haymond Silt Loam.
The riffle at Fredricksburg was approximately 37 feet wide with an average depth of 5.9 inches and a maximum depth of 10 inches. The average velocity was only 1.5 feet per second and the diccharge was 27.31 cubic feet per second. This riffle was partially clogged by fallen leaves which were trapped because of the relative shallowness of the riffle. On the upstream and downstream sides the riffle was bordered by glides that then gave way to extended deep pools.
The substrate in the riffle itself was made up of small to medium sized rocks, gravel and silt. the river beds of the pools on either end of the riffle appeared to consist of maily fine silt or mud with few rocks and boulders.
This site had some distubances. The most obvious of these was the presence of the pillars from the highway overpass on either side of the riffle. There also was a large concrete boulder in the riffle left over from the noe defunct mill that was located on this site.