A wave-competence approach to distinguish between boulder and megaclast deposits due to storm waves versus tsunamis

Size and mass of boulders and megaclast deposited from intense wave events of the past coupled with measures of depositional elevation, and transport distance are useful metrics to distinguish between tsunami or storm wave period. This outcome provides for a wave-competence scaling approach to better help distinguish between large storms and tsunamis because wave period for tsunamis and wind driven storm waves differ by an order of magnitude. However, wave-competence equations are simple linear approximations of a complex non-linear processes, hence interpretations of the results need to be taken carefully. At best they may help approximate wave forcing based on size of material transported coupled with other pieces of information gained from stratigraphy. imbrications and morphology of boulder and megaclast deposits, as well as aging techniques for temporal correlation with known storms and/or tsunamis. The focus here is to present a conceptual example of how to apply a wave-competence approach to a beach exposed to both tsunamis and major storm waves and how variance in backshore topography (hills and valleys) and source material (sea cliff erosion and scree slope development) may play into interpreting the mathematical results. (C) 2010 Elsevier B.V. All rights reserved.