Quantifying Nearshore Morphological Recovery Time Scales Using Argus Video Imaging: Palm Beach, Sydney and Duck, North Carolina

Abstract

Time scales of post-storm nearshore morphological recovery and physical processes governing these time scales are poorly understood at present. The ability to predict nearshore morphological recovery time scales based on pre-, during-or post-resetting storm conditions is an essential requirement for building and validating scale aggregated models that operate at macro-and higher spatio-temporal scales. In this study, quality controlled ARGUS video derived beach states at Palm Beach, Sydney (4 years) and Duck, NC (2 years) and concurrent wave data are analysed to quantify the nearshore morphological recovery time scales (T mr ) and to determine the physical processes that may govern T mr . The results show that T mr is of the order of 5-10 days at these two beaches. T mr is moderately positively correlated with the averaged longshore current over the 3 days immediately after the resetting storm, indicating that it might be possible to develop a predictor for T mr based on wave conditions immediately after the resetting storm. Weak correlations are present between T mr and several pre-storm, during-storm and post-storm parameters at the two sites. However, these correlations are inconsistent between the two sites. A thorough analysis employing long-term beach state and wave data at several different study sites is required to fully understand this phenomenon.

Beach Response to Wave Forcing from Event to Inter-Annual Time Scales at Grand Popo, Benin (Gulf of Guinea)

“…In particular, the shoreline-detection methods are sensitive to waves, lighting conditions, and water levels, which can scale the effects of both the setup and run-up, and reduce the colour signal strength [32]. Previous works on video error detection [18,23,36] compared shorelines measured by video to topographic surveys, and the results suggested a reasonable error (about 0.23 m at Grand Popo, Benin, following [18]). In this work, tidal heights were estimated using the WXTide2 model, to compute the shoreline location.…”

Shoreline Response to a Sequence of Typhoon and Monsoon Events

“…This is confirmed here using the ShoreFor model that presents good skills at predicting intra-seasonal and seasonal scales but poorly describes short-term typhoon-induced dynamics (see Figure 2b, October to November). Recurrence of typhoons is more than 10 days so that they can be considered isolated and without cumulative effect [5]. Winter monsoon events have impacts of similar magnitude to typhoons but with longer recovery, which is close to their observed recurrence period.…”

“…Beach recovery to extreme events is also still debated as there is not even agreement on their transient or persistent impacts [4,5]. For isolated events, departure from equilibrium is related to the event's intensity and duration [2,6,7].…”

Contribution of Wave Setup to Projected Coastal Sea Level Changes

“…conditions is most likely longer, on the order of 1-10 days (Angnuureng et al, 2017;Madsen & Plant, 2001;Ranasinghe et al, 2012). Finally, the formulation was developed for hypothetical steady state conditions; it is not clear whether it can be used to predict the short-term temporal variation of the beach slope.…”