Barrier islands face a gradual path toward drowning under most sea level
rise scenarios
Abstract
The expected increase in rates of sea level rise during the 21st century
and beyond may cause tidal inlets to expand and barrier islands to
drown. However, many aspects remain unclear, e.g., the timescales
involved in the drowning process have received little attention. To gain
insight into the morphodynamics of barrier systems subject to sea level
rise, we here present results obtained with a novel barrier island
model, BRIE-D. This new model allows for changes in the alongshore
extent of the barrier lying below sea level. These concern reductions in
barrier width, barrier height, as well as lateral expansion of tidal
inlets. Model results show that the evolution of barrier islands is
susceptible to the wave height and the rate of sea level rise that they
experience. It takes hundreds of years for barrier islands to drown in
response to high rates of sea level rise (more than 15 mm/yr).
Furthermore, increasing rates of sea level rise cause an earlier and
more severe barrier drowning in environments with low waves. Barrier
systems that face higher waves can undergo more frequent inlet closures
(due to a larger amount of sediment imported into the inlets), but also
the degree of barrier drowning might increase (due to a deepening of the
toe of the shoreface). The latter process dominates over the former when
rates of sea level rise are higher than 5 mm/yr.