ZOOGEOMORPHIC IMPACT OF BEAVERS ON A SUBURBAN CREEK, PENNYPACK ECOLOGICAL RESTORATION TRUST, PENNSYLVANIA

A recent resurgence of beaver activity (2018-2020) along Pennypack Creek (southeastern Pennsylvania) wasinvestigated using georeferenced observations (including a citizen-science component), field measurements, time-lapse photography, and trail-camera video. Zoogeomorphic impact includes a large bank burrow in bedrock-anchored legacy (post-milldam removal) sediments, felling of a range of vegetation (traditional, anomalous, and invasive species), utilization of an abandoned milldam, and construction of huts along culvert-controlled water bodies. Tree-damage assessment (full or partial cutting, bark gnawing) includes trunk metrics and geomorphic context. The majority of impact was within 10 m of the bank, extending into ephemerally flooded wetlands. Juvenile incisor marks on subaerial prop roots within 2 m of the stream represent a new type of castorid-plant interaction, with implications for slope stability. Several erosional hotspots in the vicinity of the dam may be related to heavily used trails and vegetation removal. Geomorphic cascades along the creek likely involve bank erosion and bottom sediment reworking by native and introduced fish species. Our study documents an ichnologically diverse set of structures resulting from a keystone landscape engineer adjusting to an anthropogenically altered riparian landscape.