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Fig. 8.14 Inlet formed during Hurricane Isabelle, September 2003, Outer Banks North Carolina. The inlet was closed artificially
within a few weeks in order to facilitate road access. (Photograph courtesy of the Program for the Study of Developed Shorelines,
Duke University, NC.)
Case study 8.1 Impact of storms on sediment movement: Texas Coast, USA
Measurements of sediment movement along coasts can be made at various time-scales. Short-term
studies use instruments to provide information on the relationship between sediment transport
and coastal dynamics. Longer-term studies involve comparison of beach profiles, maps, charts
and air photographs in order to quantify change, which then may be related to records of wave
activity, sea-level and climatic variables. In either approach, identifying the role of storms in the
total sediment budget can be difficult because of their infrequency (which makes them difficult
to capture on record) and their high magnitude (which destroys instruments).
Working on part of the barrier island coast of Texas (Case Fig. 8.1a), Morton et al. (1995)
monitored beach sand volumes on two barrier islands separated by an inlet (Case Fig. 8.1b).
The barrier islands are experiencing long-term sea-level rise and limited sediment supply and
hence have been migrating landward over the past 100 years (Case Fig. 8.1b). The inner shelf is
muddy and all sand movements in the nearshore can be clearly identified and volumes of sand
calculated. Measurements over a 10 year period showed that volumes of sand lost from one
barrier island (Galveston Island) did not match the volume gained by the adjacent, down-drift
barrier island (Follets Island). Instead, sand eroded from the up-drift island was transported
across the tidal inlet on the shoreface and deposited there. Subsequently it was transported by
waves onto the down-drift island.
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