Investigating Barrier Island Migration
and Storm Overwash on Wallops Island, VA, Through Vibracoring
Wink, E.R.,Oakley, A.,
Cornell, S.R., &Bollinger,
A.,
2013, Investigating Barrier Island Migration and Storm Overwash
on Wallops Island, VA, Through Vibracoring: Geological Society
of America Abstracts with Programs, Northeastern Section - 49th
Annual Meeting Lancaster, PA, (23–25 March), v. 46, no. 2.
Wallops Island (WI) is a rapidly eroding barrier island located on
the Eastern Shore of VA. Barrier islands migrate toward the
mainland, or rollover, as a natural part of development. They are
important coastline features because of the amount of protection
they offer the mainland and estuarine environments. These islands
are strongly affected by sea level rise (SLR) and are constantly
being reshaped by currents and storm surge. Erosion and flooding
related to SLR and storms cause difficulties for communities and
facilities built on barrier islands. In light of recent and
predicted future acceleration in SLR, it is important to understand
the natural migration of barrier islands. Here we use core data
collected by vibracore to investigate storm overwash and barrier
island migration on WI.
We collected 4 cores, up to 2.5 meters in length, along a transect
across WI from the modern dunes to the back bay salt marsh. We have
extracted 8 samples of organic matter (e.g. shells, roots) for
radiocarbon dating. Once we receive dates for these samples we can
correlate the core data and aerial photographs to historic storm
data. Cores from the seaward side of WI, extracted from modern and
historic dunes, consist entirely of siliceous sands with evidence
for frequent high water events (e.g. heavy mineral layers, organic
detritus), cross-bedding, bioturbation, and stabilization by dune
grasses. Cores taken from the back side of the island (phragmites
stand-VC2, back bay salt marsh-VC1) show distinct changes in
composition and lithology, ranging from back bay muds, to coarse
sand, to organic-rich soils. Loss on Ignition (LOI) data for VC1
show layers with ≥75% organics at core depths of 0-5cm and 45cm
which demonstrate periods of soil maturation and stabilization. LOI
data also show silicate content >90% at depths 7-22cm and
51-95cm. We correlate massive sand layers without cross-bedding in
VC2 and VC1 which we interpret to be evidence of storm overwash fans
that transected the N portion of WI. Overall grain size is coarser
in VC2 and the layer contains numerous shell fragments. Historical
aerial photographs from NASA show evidence for large overwash
deposits occurring pre-1938. Ultimately we hope to use these data,
and deeper cores, to be able to calculate sedimentation and
migration rates for WI.
Investigating Barrier Island Migration
and Storm Overwash on Wallops Island, VA, Through Vibracoring