Abstract
Ocean‐basin‐scale climate variability produces shifts in wave climates and water levels affecting the coastlines of the basin. Here we present a hybrid shoreline change—foredune erosion model (A COupled CrOss‐shOre, loNg‐shorE, and foreDune evolution model, COCOONED) intended to inform coastal planning and adaptation. COCOONED accounts for coupled longshore and cross‐shore processes at different timescales, including sequencing and clustering of storm events, seasonal, interannual, and decadal oscillations by incorporating the effects of integrated varying wave action and water levels for coastal hazard assessment. COCOONED is able to adapt shoreline change rates in response to interactions between longshore transport, cross‐shore transport, water level variations, and foredune erosion. COCOONED allows for the spatial and temporal extension of survey data using global data sets of waves and water levels for assessing the behavior of the shoreline at multiple time and spatial scales. As a case study, we train the model in the period 2004–2014 (11 years) with seasonal topographic beach profile surveys from the North Beach Sub‐cell (NBSC) of the Columbia River Littoral Cell (Washington, USA). We explore the shoreline response and foredune erosion along 40 km of beach at several timescales during the period 1979–2014 (35 years), revealing an accretional trend producing reorientation of the beach, cross‐shore accretional, and erosional periods through time (breathing) and alternating beach rotations that are correlated with climate indices.
Highlights
Coastlines are among the most dynamic environments on Earth
We model the influence of foredune erosion (FDE) on shoreline erosion rates as well as the influence of sediment supply, which can be the major driver in prograding beach morphodynamics
We have developed an efficient coastal response model (COCOONED) providing a framework that combines a fast delivery hybrid nearshore propagation of offshore waves using SWAN, data mining, and statistical methods, and a process-driven coastal evolution model
Summary
Coastlines are among the most dynamic environments on Earth. The natural processes that shape these environments are driven by both episodic high-intensity events (e.g., storm surge flooding and storm waves) and daily modal wind, wave, and tidal conditions, which operate over longer timescales and drive chronic shoreline erosion/accretion. Earth's climate exhibits cycles, including sequencing and clustering of storm events, and seasonal, interannual, and decadal oscillations of various sorts These cycles are superimposed on an accelerating background climate change arising from human activities (IPCC, 2013). Each of these climate signals—the cycles and the trends—will tend to cause shifts in coastline position and planview shape (e.g., Antolínez et al, 2018; Coco et al, 2014; Davidson et al, 2010; Moore et al, 2013; Ruggiero, Buijsman, et al, 2010; Ruggiero et al, 2016; Vitousek, Barnard, & Limber, 2017). Accelerated sea level rise (SLR) is occurring and the associated change in sediment transport patterns can lead to long-term shoreline erosion (e.g., Bruun, 1962; Cowell, Stive, Niedoroda, Swift, et al, 2003; Cowell, Stive, Niedoroda, Vriend, et al, 2003; Moore et al, 2010; Ranasinghe & Stive, 2009; Wolinsky & Murray, 2009)
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