DEPTH OF CLOSURE: IMPROVING UNDERSTANDING AND PREDICTION

Robert J. Nicholls, Magnus Larson, Michele Capobianco, William A. Birkemeier

Abstract


The closure concept is a fundamental cross-shore boundary condition for morphodynamics and other applications such as beach nourishment and sediment budgets. This paper examines closure at a range of scales, particularly from events up to years. At these scales, closure is primarily a function of direct external forcing (cross-shore redistribution of sediment by waves), indirect external forcing (sediment loss/gain by littoral transport and the resulting profile translation) and internal system dynamics (bar dynamics). Therefore, simple wave-based models such as Hallermeier (1981) cannot be expected to predict the actual closure, although they can predict distributional properties such as the limit. A general approach to develop more user orientated estimates of closure over a range of timescales is outlined based on equilibrium theory. This will include a user-defined depth change criterion as a function of timescale.

Keywords


depth of closure; depth of closure prediction

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