Stabilizing High, Steep Stream Banks: A Natural Approach
Schuyler County Soil and Water Conservation District
Basin Program Funds:
According to the 1999 publication, "Setting a Course for Seneca Lake," streambank erosion is a primary source of sediment loading in Seneca Lake. The Schuyler County Water Quality Strategy and the New York Department of Environmental Conservation (DEC) Priority Waterbodies List also indicate that streambank erosion in Seneca Lake tributaries is a major contributor of sediment and pollution to the lake. The destruction of a dam on Tug Hollow Creek several years ago has resulted in destabilization and erosion of its streambanks as well as the redirection of flow in the creek.
Approximately 60% of Schuyler County’s 221,000 acres are in the Seneca Lake watershed. Seneca Lake provides ‘AA’ quality drinking water to 70,000 residents and 2,000 lakeshore residents have direct water intakes from the lake. Tug Hollow Creek is a DEC classified trout stream. It is rural in character, approximately 60% forested and 30% agricultural. In the 1890’s a dam was built on Tug Hollow Creek as a reservoir for use by steam engines on the nearby railroad. The dam was washed out in the 1935 flood but was rebuilt with two spillways rather than one. During the 1972 flood, the dam cracked, eventually broke apart and was not rebuilt. Without the flood regulation of the dam, the subsequent floods in 1996 may have caused the destabilization and erosion of streambanks as well as the redirection of flow in the creek. Downstream from the dam site there is a large, eroding cut bank. The bank is approximately 25 feet high and 200 feet long.
Another significant area of concern in Schuyler County is the presence of Ochrepts and Orthents along some county streams. The Soil Survey of Schuyler County New York describes the Ochrept-Orthent complex as, "consisting of deep, somewhat excessively drained, unconsolidated soil material in areas dissected by deep, steep-sided streams. Slopes are commonly near 100 percent but range from 35 to 100 percent. The soil has a tendency to slip or slump downslope, especially where the stream undercuts the soil deposit."
A remediation project using fluvial geomorphic techniques such as J-hooks and/or cross-vanes and bankfull benches were designed and implemented on a large cut bank in Tug Hollow Creek. The landowners have agreed to the use of this site. The project will serve as a demonstration area and the morphology techniques can be taught to others as the preferred method of stream reclamation. The implementation of a reclamation project using fluvial geomorphic techniques will have a positive effect on water quality by reducing erosion, sedimentation, and nutrient loading within the Great Lakes Basin as well as creating an awareness of alternative, cost effective, environmentally sensitive methods.
The focus of the bank stabilization effort in this project was a 20 foot high eroding cut bank on Tug Hollow Creek. At this site workers installed one cross-vane, three grade control structures, four rock barbs, and a bankfull bench 225 feet long along an unstable section of the creek. The total length of affect area along the creek was about 1200 feet. After construction, disturbed areas were seeded and planted with willows. Prevented sediment loss is estimated at 239 tons/year, phosphorus 2390 lbs/year, and nitrogen 478 lbs/year.
An educational/site visit to the project area was conducted to introduce fluvial geomorphic techniques and their effectiveness as erosion control measures for high, steep stream banks., with 10 people in attendance. Monitoring and evaluation of the site is ongoing. The bank is stable, gravel is building up behind the stream barbs, there is pool establishment behind the cross vane, and head cutting in the streambed near the site is not occurring. No further erosion of the pasture above the escarpment or slumping of the escarpment into the stream has occurred. Sixteen glacial escarpments were sampled for soil particle analysis and the Cornell Nutrient Analysis Labs analyzed 40 samples.
Contact: Ms. Elaine Dalrymple, 607-535-9650