Abstract. Barrier island transgression is influenced by the alongshore variation in
beach and dune morphology, which determines the amount of sediment moved
landward through wash-over. While several studies have demonstrated how
variations in dune morphology affect island response to storms, the reasons
for that variation and the implications for island management remain unclear.
This paper builds on previous research by demonstrating that paleo-channels
in the irregular framework geology can have a directional influence on
alongshore beach and dune morphology. The influence of relict paleo-channels
on beach and dune morphology on Padre Island National Seashore, Texas, was
quantified by isolating the long-range dependence (LRD) parameter in
autoregressive fractionally integrated moving average (ARFIMA) models,
originally developed for stock market economic forecasting. ARFIMA models
were fit across ∼250 unique spatial scales and a moving window
approach was used to examine how LRD varied with computational scale and
location along the island. The resulting LRD matrices were plotted by
latitude to place the results in the context of previously identified variations
in the framework geology. Results indicate that the LRD is not constant
alongshore for all surface morphometrics. Many flares in the LRD plots
correlate to relict infilled paleo-channels, indicating that the framework
geology has a significant influence on the morphology of Padre Island National Seashore (PAIS). Barrier island
surface morphology LRD is strongest at large paleo-channels and decreases to
the north. The spatial patterns in LRD surface morphometrics and framework
geology variations demonstrate that the influence of paleo-channels can be
asymmetric (i.e., affecting beach–dune morphology preferentially in one
direction alongshore) where the alongshore sediment transport gradient was
unidirectional during island development. The asymmetric influence of
framework geology on coastal morphology has long-term implications for
coastal management activities because it dictates the long-term behavior of a
barrier island. Coastal management projects should first seek to assess the
framework geology and understand how it influences coastal processes in order to
more effectively balance long-term natural variability with short-term
societal pressure.