A process-geometric visualization of bluff erosion hazards on the Pennsylvania coast of Lake Erie, United States

The Lake Erie coast of Pennsylvania on the North American Great Lakes is dominated by unconsolidated, erosional, Quaternary-age bluffs. This paper describes generation of a non-regulatory, process-geometric Bluff Erosion Potential (BEP) visualization of physical erosion hazards. Four relative lakefront hazard zones were mapped at sub-watershed scales, landward of which the erosion hazard is insignificant over property lifetimes. The Very High Erosion Potential (VHEP) zone is the present-day active hazard zone, located between the bluff toe and crest and experiences ongoing and episodic bluff failure. The High Erosion Potential (HEP) zone extends inland from the landward edge of the VHEP zone, with its landward edge lying on average ~ 12 m from the bluff crest and locally as much as 72 m. The Moderate Erosion Potential (MEP) zone extends inland from the HEP zone, with its landward limit on average ~ 28 m from the bluff crest and locally as much as 144 m. Inland from the MEP zone, the landward limit of the Low Erosion Potential (LEP) zone is on average ~ 60 m from the bluff crest and locally as much as 272 m. Landward of the LEP zone, erosion hazards are expected to be non-existent for at least a century. The BEP hazard map builds upon recent bluff best-management practices by including geometric stable-slope criteria along with process-driven bluff retreat rates to map erosion hazard. It can help coastal stakeholders better understand hazards over century-plus building lifetimes and is an initial step toward a future comprehensive physical/socioeconomic vulnerability assessment.