RAPID-RESPONSE BIOGEOMORPHOLOGY: ASSESSMENT OF PERTURBATIONS RESULTING FROM RECORD FLOODING AND TORNADOES IN SE PENNSYLVANIA (IDA, 2021)

During 1-3 September 2021, remnants of hurricane Ida caused damaging flooding and tornadoes, resulting in loss of life and structural damage along the Mid-Atlantic Coast. At Abler Campus (Temple University), a series of intense tornadoes (EF2/EF3) felled large tracts of the forest, including >500 old-growth trees. Drone images collected two weeks after the event allow rapid visualization of treethrow direction, consistent with a rotational component of the near-surface wind shear. Field visits focused on the treefall and root-plate/pit typology, with sediment sampling planned to assess the magnitude and chronology of root-plate decay. High-frequency (800-2300 MHz) ground-penetrating radar (GPR) images of downed trees will provide valuable information about internal anomalies. The damage re-routed an active white-tailed deer (Odocoileus virginianus) population, resulting in new patterns of activity and initiation of post-disturbance biogeomorphic cascades. Along many creek banks in Bucks and Montgomery Counties, the recently resurgent activity (2019-2021) by the North American beaver (Castor canadensis) has rendered numerous streambank sections vulnerable to erosion. At a number of research sites, large bank burrows have been partially infilled with legacy mud, with surrounding vegetation cleared by the flood. GPR surveys of bank burrow sites three months prior to Ida form a reference dataset for further investigation. Along shallow streams, changes to channel bottom and steep cutbanks, along with accompanying biogenic structures (turtle, fish, and crayfish burrows) have been photographed and mapped rapidly and effectively using paddlecraft (kayaks, SUPs). Vast deposits of legacy mud over stream terraces during the 5-6-m-high flood stage formed new tracking surfaces, with numerous traces of white-tailed deer as the dominant and most effective zoogeomorphic impact through edge loading and bank slides. Our pre- and post-event investigations provide a valuable dataset for subsequent research, especially where biogenic structures resulted in hot spots of erosion and bank collapse.