Storm Dynamics Control Sedimentation and Shelf-Bay-Marsh Sediment
Exchange along the Louisiana Coast
Abstract
Hurricanes benefit wetland accretion by augmenting the delivery of
mineral sediment, an essential process allowing marshes to offset
submergence due to rising sea levels. Using Hurricane Gustav as a
control, we examined eight synthetic storms with varying characteristics
(track, speed, intensity, size) to evaluate sediment exchange between
the inner shelf and the bay and bay-to-marsh interfaces. All storms
showed net landward sediment transport from the inner shelf to the bay
to the marsh—storms with closer proximity, higher intensity, and
slower forward speed positively correlated with net sediment exchange;
storm size had little impact. Except for very slow-moving storms, most
scenarios cause net bay erosion as more sediment is conveyed to landward
wetlands than is replenished from erosion of the inner shelf. This
sediment deficit suggests a future deepening of the bay, which will
worsen due to accelerating sea-level rise.