An Automated Model to Classify Barrier Island Geomorphology Using Lidar Data

Joanne N Halls,Maria A Frishman,Andrea D Hawkes

doi:10.3390/ecrs-2-05149

Abstract

Limited research has studied the use of Lidar in mapping coastal geomorphology. The purpose of this project was to build on existing research and develop an automated modeling approach to classify the coastal geomorphology of barrier islands and test this at four sites in North Carolina. Barrier islands are shaped by natural coastal processes, such as storms and longshore sediment transport, as well as by human influences, such as beach nourishment and urban development. An automated geomorphic classification model was developed to classify Lidar data into 10 geomorphic types over four time-steps from 1998 to 2014. Tropical storms and hurricanes had the most influence on change and movement. On the developed islands, there was less influence of storms, owing to the inability of features to move because of coastal infrastructure. Beach nourishment was the dominant influence on developed beaches, because this activity ameliorated the natural tendency of an island to erode. Understanding how natural and anthropogenic processes influence barrier island geomorphology is critical to predicting an island’s future response to changing environmental factors such as sea-level rise. The development of an automated model equips policy makers and coastal managers with information to make development and conservation decisions, and the model can be implemented at other barrier islands.

Highlights

Beautiful beaches and expensive properties are found on barrier islands, which are features that parallel the coastline and protect the mainland from waves and storms
The following geomorphic feature types were studied: (1) Intertidal: region that is inundated daily because of tides; (2) Supratidal: region that is inundated occasionally because of astronomically high tides or severe weather events; (3) Dunes: linear features that run parallel to the shoreface and have the highest elevation; (4) Hummock: relic dune located behind the primary dune, at a lower elevation than dunes but at a higher elevation than other surrounding features, having a round shape; (5) Overwash: slightly elevated and flat areas located in the back barrier; (6) Swale: low depressions located between dunes and upland areas; (7) Channel: low depressions, cut by water, located adjacent to the supratidal region; (8) Upland: flat portions of the barrier island, behind the primary dune
The fieldwork ground control points (GCPs) were comparable to the Lidar data and could be used to assess the geomorphology classification results

Summary

Introduction

Beautiful beaches and expensive properties are found on barrier islands, which are features that parallel the coastline and protect the mainland from waves and storms. Their location and sandy composition make barrier islands both economically valuable and physically vulnerable. Over 5 years, a barrier island can migrate over 100 m and experience a 50% change in volume [1,2]. Understanding the evolution of barrier island geomorphology can assist policy makers and coastal managers with decisions regarding future land-use development. The entire coastline is fronted by a chain of barrier islands. A typical barrier island system is composed of a gently sloping continental shelf, a sandy island, and a back-barrier marsh that extends into an estuary; individual barrier islands are separated by tidal inlets [3]

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