An Integrated, Probabilistic Modeling Approach to Assess the Evolution of Barrier-Island Systems Over the Twenty-First Century

Janaka Bamunawala,Ali Dastgheib,Ad Van Der Spek,A Brad Murray,Roshanka Ranasinghe

doi:10.3389/fmars.2021.755699

Abstract

Barrier-island systems, spanning ∼7% of the world’s coastlines, are of great importance to society because not only they provide attractive, liveable space for coastal communities but also act as the first line of defense from coastal storms. As many of these unique coastal systems are affected by both oceanic and terrestrial processes, it is necessary to consider the holistic behavior of applicable terrestrial and coastal processes when investigating their evolution under plausible future scenarios for climate change, population growth and human activities. Such holistic assessments, also accounting for uncertainties, can readily be achieved via reduced-complexity modeling techniques, owing to their much faster simulation times compared to sophisticated process-based models. Here, we develop and demonstrate a novel probabilistic modeling framework to obtain stochastic projections of barrier-island evolution over the twenty-first century while accounting for relevant oceanic and terrestrial processes under climate change impacts and anthropogenic activities. The model is here demonstrated at the Chandeleur islands (Louisiana, United States) under the four Intergovernmental Panel on Climate Change (IPCC) greenhouse gas emission scenarios (i.e., Representative Concentration Pathways 2.6, 4.5, 6.0, and 8.5) with results indicating that there are significant uncertainties in projected end-century barrier-island migration distance and available barrier freeboard under the high emission scenario RCP 8.5. The range of uncertainties in these projections underscores the value of stochastic projections in supporting the development of effective adaptation strategies for these fragile coastal systems.

Highlights

Barriers are elongated, wave, tide, and wind-built ridges that are composed predominantly of unconsolidated sand and gravel and protect the adjacent mainland from open ocean processes
Results of the model application at the Chandeleur Islands are presented in section “Projected Changes in the Barrier Island System” and the projected barrier island evolution under hypothetical conditions is presented in section “Projected Changes of the Barrier Island Under Hypothetical Initial Conditions.”
The rate of global mean sealevel rise was taken as 2.1 mm/year for the 1986–2005 period, as per the projections presented in Chapter 4 of the Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate [i.e., Oppenheimer et al (2019)]

Summary

Introduction

Wave, tide, and wind-built ridges that are composed predominantly of unconsolidated sand and gravel and protect the adjacent mainland from open ocean processes. Barrier island coasts cover about 7% of the world’s coastlines (Stutz and Pilkey, 2001, 2011) and are often densely populated areas subjected to potentially conflicting interests of economy, coastal safety and ecology. They are generally separated from the mainland by tidal creeks, bays, and lagoons. Beaches and dune systems form on the barrier island facing the ocean, while the side facing the mainland shore often contains marshes, tidal flats, and/or maritime forests These coastal ecosystems areas are important habitats for seabirds, fish, and nesting sea turtles

Results

Discussion

Conclusion