Nourishment design and evaluation: Applicability of model concepts

Models can play a fundamental role while moving from nourishment projects to nourishment plans, i.e., when nourishment becomes an integral component of a coastal management strategy. Planning nourishment in the context of a multi-years management strategy requires more significant prediction skills than available in the past and an awareness of dealing with uncertainty. The present paper introduces model classes and modelling situations and describes those elements that are the main sources of such uncertainty. Equilibrium Profile (EP) and Depth of Closure (DoC) are discussed with their time-scale related aspects; granulometry changes are discussed with their effects on the dynamics of a nourished coast; estimation of erosion rate is introduced with its implications on the definition of the “basic state” or the “basic trend” of the coastal system; lateral spreading and beach fill transition are discussed with their economic implications; and calibration and verification are introduced with the additional degrees of freedom that might be added to model development and with reference to risk issues in decision-making. These sources of uncertainty are examined in relation with implications for nourishment and modelling. The main conclusion is that, while there have been significant advances in modelling morphodynamics and morphodynamics applied to nourishment design, advances in defining procedures for quality control of the modelling activity are now required.