IMPACT MAPPING OF INTENSE MULTI-SPECIES ZOOGEOMORPHIC ACTIVITY ALONG A HEAVILY DEVELOPED STREAM REACH, LANGHORNE, PENNSYLVANIA

The impact of animals and plants on erosion and sediment budget in forested streams is often neglected during geological studies. This research focuses on mapping the distribution and impact of native, re-introduced, and invasive species – North American beaver (Castor canadensis), white-tailed deer (Odocoileus virginianus), Canada geese (Branta canadensis), common carp (Cyprinus carpio), white sucker (Catostomus commersonii), and a number of freshwater turtles – along an intensely engineered left (north) bank of a 300-m-long, 30-m-wide reach of Neshaminy Creek (Langhorne, PA). Geolocated spatial analysis of zoogenic activity along the stream terrace and within the channel was used to assess their impact on vegetation and landforms. A number of these features can only be observed from engineering structures (abandoned bridge) or shallow-draft paddlecraft. Burrows created by beaver, fish (e.g., C. commersonii, density >20/m²), and turtles leave the streambank vulnerable to erosion, and the recent increase in beaver activity has made the bank susceptible to collapse. Intense bark chew by beavers on trees 1.4-28.6 cm in diameter is a recent phenomenon and has substantial impact on old-growth deciduous vegetation (e.g., >50-year-old white oaks). Future research will focus on assessing the impact of record flooding related to the remnants of Hurricane Ida (September 2021), including both erosional and depositional modification of zoogenic features. Although it buried some evidence of biogenic activity, this flood deposited a fresh layer of mud (mainly reworked legacy sediment) providing an extensive tracking surface and a marker horizon. Our study presents one of the first detailed zoogeomorphic maps across a riparian-fluvial ecotone in southeastern Pennsylvania.