Modeling the Evolution of Coupled Barrier-Marsh-Lagoon Systems: Insight from LBI NJ

Barrier islands and their associated backbarriers provide not only socio-economic value (e.g., beach recreation, coastal protection), but also ecosystem services such as blue carbon storage and support for habitat biodiversity. Despite their importance, it is unclear how coupled barrier-marsh-lagoon systems will respond to sea-level rise in the future. To better understand the dynamics of these coupled systems, we modify and apply an existing cross-shore numerical model to assess coastal change on a range of time periods based on Long Beach Island (LBI), New Jersey. Geographic data on LBI goes from 1840 to present day and changes in barrier dynamics occurs in 1934 where the island transitions from natural to developed. The model accounts for overwash fluxes, which drive barrier migration, as well as marsh-accretion/erosion, which is controlled by the wave regime associated with lagoon geometry. We also consider beach nourishment practices through sediment fluxes to the shoreface. Preliminary model testing suggests that, despite its simplicity, the model can describe the average dynamics of different phases in LBI’s history over the past few decades, which we obtain from a combination of historical maps and more recent LIDAR imagery. Moreover, it supports prior work, which suggests that changes in the overwash flux and initial lagoon geometry are important factors in determining the evolution of these coupled environments. This modeling framework can also be used to better understand the future evolution of barrier-marsh-lagoon systems and identify unexplored feedbacks between barrier and backbarrier environments that could play an important role in future management decisions.