DISTRIBUTION AND CHARACTERISTICS OF BEAVER IMPACT ALONG NESHAMINY CREEK, PA: COMPARISON WITH HISTORIC SIGNS OF ACTIVITY

The impact of beaver populations on streambank geomorphology has been underappreciated and zoogeomorphological research is rarely included in traditional ecological or geological studies. Data collected during the summer and fall of 2019 along middle Neshaminy Creek (Bucks County, Pennsylvania) include both historic (n=10) and new (n=33) cut stumps. The mapped distribution shows that 91.3% of beaver activity took place on the left (east) bank of the creek over a total distance of 16 km. The average distance between the stumps and the riverbank ranged from the edge up to 8.3 m (mean: 3.45 m), with 81.8% of the stumps located within 5 m from the cutbank. Stump diameter ranged from 4.12-21.01 cm (mean: 9.17 cm), with ~70% of the stumps <10 cm in diameter suggesting preference for smaller trees close to the creek. The treefall azimuth based on observed remnants and cut angles, ranged from 000-353° with a mean of 187.13° (mean stream azimuth: 249°). Comparisons of the two directional indicators at teach site suggests preference for felling downslope and toward the stream, initiating a geomorphic cascade. This project utilizes a statistical approach to analyzing zoogeomorphic activity, with implications for managing near-stream ecosystems. When applied to historic stumps, it provides important information no only on the age of previous activity phases, but also can aid in locating former drainage patterns.