43 Current Research in Coastal and Marine Processes (Posters)

Monday, 19 March 2018
1:30 PM - 5:30 PM
Lake Champlain Exhibition Hall

RECENT LANDFORM DEVELOPMENT AND VEGETATION SUCCESSION ALONG GULL POINT, PRESQUE ISLE, PA, THE DISTAL TERMINUS OF A COMPOUND BARRIER-SPIT SYSTEM ALONG THE SOUTHEASTERN LAKE ERIE MARGIN

Paper number: 43-4
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

The Presque Isle peninsula is a compound barrier-spit system perched atop a recessional moraine along the southeastern Lake Erie coast. Gull Point, the system’s distal terminus, has grown to an extent of ~0.6 km2 since the early 1900s. A shift in local littoral hydrodynamic regime accompanied the upstream installation of breakwaters, inducing lengthening of the point at the expense of the rest of its shoreline. The general evolutionary model for spit development is one of punctuated landform growth to the east by lateral accretion interspersed with erosional events and the recurving of ridges toward the backbarrier. Historic aerial photographs bracket episodes of growth and modification, offering a chronological framework of landform development and subsequent vegetation-succession patterns. Vegetational communities are delineated into four temporal phases, roughly defined by pronounced erosional demarcations of topographic prominence. The youngest (distal) phase east of a 1993 shoreline is herbaceous, with eastern cottonwood and shrub willow species ~1 m in height in the nascent tree stratum, suggesting woody vegetation may take ~15 years to recruit. Extending west to a 1983 shoreline, discrete cohorts of cottonwood ~10 m in height follow ridges with a patchy willow, bayberry, and invasive Morrow’s honeysuckle understory. Extending further west to a pre-1969 ridge 15 to 20 m-tall cottonwoods are underlain by dense bayberry/honeysuckle thickets. Scattered European birch trees are found here, but not in younger distal stands. A maturing cottonwood overstory and a generally intact native bayberry shrub community occur at the proximal and oldest end of Gull Point. In contrast, bayberry is severely invaded by honeysuckle in the younger phases. The arcuate ridge-and-swale topography of the former recurved backbarrier is now prominently exposed along much of the shoreline, where erosion of forested, shore-perpendicular ridges and emplacement of washover fans within interstitial swales is commonplace. Vegetative colonization of newly emplaced landforms at the shoreline appears transient at best, given shoreline retreat rates up to ~10 m/yr, which threaten to breach the spit entirely in select locations.

Geological Society of America Abstracts with Programs. Vol. 50, No. 2

doi: 10.1130/abs/2018NE-310499

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