Evaluation of stream bank erosion along Lycoming Creek (Summer 2002)
Lycoming College Clean Water Institute Interns, Theresa Black and Amy Curry, under direction of Dr. Mel Zimmerman
During the summer 2002, Lycoming college interns walked or floated the entire stretch of Lycoming Creek between Roaring Branch (N 41° 34,294, W 76° 57.891) and lower Heshbon Road (N 41° 16.127, W 77° 03.036). This stretch covers a distance of 28 miles. Attached is the stream bank erosion form used. A ¼ mile section around Ralston was not assessed due to Penn DOT Bridge construction. Lycoming Creek above Roaring Branch was not done due to the nature of the area with the stream braded, marsh and/or dried. The area of the creek below Heshbon Road to the mouth of the creek in Williamsport (" 2 miles) was not completed due to the residential nature of the area.
A total of 245 observations were noted along Lycoming Creek from Roaring Branch to lower Heshbon Road. These observations are summarized in Table 1. Of these, 16 were bridges, making up 6.53% of the total. There were 28 midchannel bars, or 11.42%. Deposition bars made up 13.06% of the stations, or 32 of the 245 sites. There were 18 areas of Rip rap (or 7.35% of the observations). Eight tributaries along the creek were noted (adding up to 3.27% of the total). 17 concrete walls (many from old bridges that have been destroyed) made up 6.94%. An area of dried creek bed accounted for 0.41% of sites. This location was south of Roaring Branch and the creek started again " ¼ mile down stream, fed by a tributary. Observations of erosion were documented on 108 sites (making up 44.08%). 58 of the 108 eroded banks, (or 53.70%) occurred on the right banks, and 50 (or 46.30%) occurred on the left banks (right and left banks are determined as you face downstream).
Bank erosion potential is based on an analysis of bank height, bank angle, density of roots, and particle size. Assessments of the characteristics of each bank are in terms of erosion potential of HIGH, MODERATE, or LOW. These are summarized below:
Table 2. Summarizes the bank erosion potential based on bank heights. A LOW height was determined to be between 0 to 6 feet, a MODERATE was between 6 to 9 feet, and a HIGH potential was anything greater than 9 feet. 36 banks were determined to be LOW, consisting of 33.33% of the total. There were 44 banks rated MODERATE in height, consisting of 40.74% of the total. 28 banks were rated HIGH, making up 25.93%. For right banks, 26 were LOW (44.83%), 23 banks were MODERATE (39.66%), 9 banks were HIGH (15.52%). For left banks, 10 were LOW (20.00%), 21 were MODERATE (42.00%), and 19 were HIGH (38.00%).
A summary of bank erosion potential based on bank angles can be found in Table 3. The angle of banks was also assessed. LOW potential would be a bank with an angle of 45 degrees. MODERATE potential would be closer to 90 degrees, and HIGH potential would be greater than 90 degrees. Of the total banks, 17 were rated LOW (15.74%), 67 were rated MODERATE (62.04%), and 24 were rated HIGH (22.22%). Of the 58 right banks, 12 were LOW (20.69%), 32 were MODERATE (55.17%), and 14 were HIGH (24.14%). For left banks, 5 were LOW (10%), 35 were MODERATE (70%), and 10 were HIGH (20%).
A summary of bank erosion potential based on root density can be found in Table 4. The root density of the vegetation on the banks was assessed. LOW erosion potential would be a well vegetated bank with greater than 60% cover. MODERATE would be a root depth of about 30 to 60% of the bank. HIGH potential would be sparse root coverage of less than 30%. For the total banks, there were 11 LOW potential banks (10.19%), 67 MODERATE banks (62.04%), and 30 HIGH banks (27.78). Of the right banks, 5 were LOW potential (8.62%), 39 were MODERATE potential (67.24%), and 14 were HIGH potential (24.14%). Of the left banks, 6 were LOW potential (12.00%), 28 were MODERATE potential (56.00%), and 16 were HIGH potential (32.00%).
A summary of bank erosion potential based on particle size can be found in Table 5. Particle sizes were also assessed with a LOW erosion potential being a bank made up mostly of bedrock and boulders, a MODERATE erosion potential being a bank of fist-sized rocks, and a HIGH potential being a bank made up of sand or clay. For the total banks, there were 7 LOW potential banks (6.48%), 72 MODERATE banks (66.67%), and 29 HIGH potential banks (26.85%). Of the right banks, 3 were LOW potential (5.17%), 35 were MODERATE (60.34%), and 20 were HIGH (34.48%). Of the left banks, 4 were LOW (8.00%), 37 were MODERATE (74.00%), and 9 were HIGH (18.00%).
A summary of bank erosion potential based on length of site compared to bank height can be found in Table 6. The approximate length of each erosion site, using categories of 0 to 50 feet, 51 to 100 feet, 101 to 250 feet, 251 to 500 feet, and 501 to 1000 feet, was also determined. If a site appeared to be longer than 1000 feet, we would start a new erosion analysis. Out of the total sites, 11 (10.12%) were 0 to 50 feet in length, 27 (25.00%) were 51 to 100 feet, 34 (31.48%) were 101 to 250 feet, 34 (31.48%) were 251 to 500 feet, and 2 (1.85%) were 501 to 1000 feet. Of the right bank sites, 3 (5.17%) were 0 to 50 feet in length, 14 (24.14%) were 51 to 100 feet, 27 (46.55%) were 101 to 250 feet, 13 (22.41%) were 251 to 500 feet, and 1 (1.72%) was 501 to 1000 feet. Of the left bank sites, 8 (16.00%) were 0 to 50 feet in length, 13 (26.00%) were 51 to 100 feet, 7 (14.00%) were 101 to 250 feet, 21 (42.00%) were 251 to 500 feet, and 1 (2.00%) was 501 to 1000 feet.