Abstract
Estimates of the impacts of sea level rise and changing wave climates on shoreline change in the future are an increasing area of interest for many coastal stakeholders, engineers, and scientists. The ability to predict such change requires accurate information on the temporal evolution of key forcing parameters, such as wave height and period. An added complexity in modelling shoreline change is that beaches evolve in time. Higher wave conditions produce more dissipative beaches, resilient to further change, while periods of low waves produce highly dynamic low to intermediate beach states. Here, a simple shoreline model based on an equilibrium principle and forced by wave height and period is used to explore potential shoreline change projections at two different beach types: a highly dynamic storm dominated beach and a more dissipative seasonally dominated coastline. In all cases, the model parameters (which are previously shown to be a function of mean beach state) are assumed to not change after the 7-year calibration period, despite changes in wave energy. At both sites, an increase in average wave energy is predicted to either slightly accrete or stabilize a beach, while increases to storm waves results in severe erosion at the dynamic storm-dominated beach and only mild erosion at the dissipative beach. The paper concludes with a discussion on the validity of constant model parameters and poses the question over what timescales does a beach evolve to changing waves and how can this information be incorporated into simple empirical-based equilibrium shoreline models.
Highlights
Sandy shorelines are dynamic coastal features that are influenced by temporal variability in wave processes as well as sea level (e.g. Bruun 1962)
Does an increase in overall wave conditions really promote an accretionary or stable response at all beaches? It is an interesting concept when we ask ourselves, why and how do beaches exist and know there must be a balance in the constructive and destructive forces over the long term for them to be present today. While this accretionary response potentially can be explained by an increase in sediment transport due to higher wave conditions, one might expect that a beach should evolve to a new equilibrium state as well, such that accretion slows in time
A storm-dominated, intermediate type beach subjected to higher wave conditions should transform to a higher energy beach state in time (e.g. Wright & Short 1984; Wright et al 1985)
Summary
Sandy shorelines are dynamic coastal features that are influenced by temporal variability in wave processes (i.e. wave height, period and direction) as well as sea level (e.g. Bruun 1962). We utilize an existing equilibrium shoreline model to explore how the current trend in wave conditions (namely offshore significant wave height, Hs,o, and wave period, Tp) along 2 distinct stretches of coastline could impact shoreline evolution over the 2 decades under the assumption that model parameters derived from a short-term calibration data set remain valid for long-term simulations.
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