Development and Application of an Empirical Dune Growth Model for Evaluating Barrier Island Recovery from Storms

Abstract

Coastal zone managers require models that predict barrier island change on decadal time scales to estimate coastal vulnerability, and plan habitat restoration and coastal protection projects. To meet these needs, methods must be available for predicting dune recovery as well as dune erosion. In the present study, an empirical dune growth model (EDGR) was developed to predict the evolution of the primary foredune of a barrier island. Within EDGR, an island is represented as a sum of Gaussian shape functions representing dunes, berms, and the underlying island form. The model evolves the foredune based on estimated terminal dune height and location inputs. EDGR was assessed against observed dune evolution along the western end of Dauphin Island, Alabama over the 10 years following Hurricane Katrina (2005). The root mean square error with EDGR (ranging from 0.18 to 0.74 m over the model domain) was reduced compared to an alternate no-change model (0.69–0.96 m). Hindcasting with EDGR also supports the study of dune evolution processes. At Dauphin Island, results suggest that a low-lying portion of the site was dominated by overwash for ~5 years after Katrina, before approaching their terminal height and becoming growth-limited after 2010. EDGR’s computational efficiency allows dune evolution to be rapidly predicted and enables ensemble predictions to constrain the uncertainty that may result if terminal dune characteristics are unknown. In addition, EDGR can be coupled with an external model for estimating dune erosion and/or the long-term evolution of other subaerial features to allow decadal-scale prediction of barrier island evolution.

Influence of Sand Trapping Fences on Dune Toe Growth and Its Relation with Potential Aeolian Sediment Transport

“…HOUSER et al (2015) [77] conducted field measurements at the northern Gulf of Mexico (Santa Rosa Island, Florida and Galveston Island, Texas) and found that for predicting the evolution of a barrier island's foredune height a parameterized sigmoid growth curve can be applied. These results are supported by DALYANDER et al (2020) [12], who developed an empirical dune growth model to predict the evolution of the foredune of a barrier island for the example of the Dauphin Island (Alabama). This could influence the observed variability in sediment accumulation independently of the sand trapping configurations.…”

“…The coastal dunes are already more established at the eastern end than the western end, see Figure 13. This might explain more rapid growth at the western end than at the eastern end, given that dune growth tends to follow a sigmoid growth curve [12,77]. HOUSER et al (2015) [77] conducted field measurements at the northern Gulf of Mexico (Santa Rosa Island, Florida and Galveston Island, Texas) and found that for predicting the evolution of a barrier island's foredune height a parameterized sigmoid growth curve can be applied.…”

“…Long-term coastal dune development results from the sum of erosive processes due to hydrodynamic forces during storm surges and accretive processes due to aeolian sediment transport processes, resulting in growing or eroding coastal dunes [4,7,8]. Additionally, coastal management interventions like beach nourishments, installing sand trapping fences, the presence of vegetation, the sediment grain size, or the beach width can, amongst others, influence the development of the coastal dunes [4,6,[9][10][11][12][13].…”

“…It should, however, be noted that only three measuring points are available. The growing pattern of coastal dunes following a sigmoid growth curve ( [12,77]) may also explain why, for Norderney, the observed volume changes do not correlate to potential aeolian sediment transport since the growth of coastal dunes is a product of both potential transport and sand trapping.…”

Assessing Habitat Change and Migration of Barrier Islands

“…The simulations included a static sea-level change and geomorphologic evolution for various simulated storms with and without a suite of restoration actions. Geomorphologic predictions were made using numerical models that capture long-term alongshore sediment transport (Delft 3D), shortterm storm-induced impacts (XBeach; Roelvink et al 2009), and dune building and recovery (empirical dune growth model; Dalyander et al 2020). The simulations highlighted in this study were the contemporary geomorphology and the future predicted geomorphology with a 0.96-m static sea-level change and subsequent geomorphic evolution over a decade with high storminess (i.e., less than four storms that result in overwash; 29% probability of occurrence based on storm climatology; Mickey et al 2020).…”