The cross-shore profile response of shingle barrier beaches to storm waves are investigated with the aid of: random wave studies in a 3-dimensional mobile bed physical model; and by full-scale field measurements of shingle beaches to storm action. The investigations focus upon crest evolution of barrier beach profiles and conditions giving rise to overwashing and overtopping of the unconfined beach crest. The influence of a wide range of hydraulic variables and beach geometry are examined, in a dimensionless framework, on the development of the dynamic equilibrium profiles of shingle barriers. A dimensionless barrier inertia parameter is presented and a parametric threshold equation is proposed, to describe the onset of barrier beach overwashing; this is combined with a list of governing variables and their range of validity. Hypotheses postulated previously for profile response of shingle beaches are examined. Such studies define the limits of the validity of the empirical framework, developed by Powell (1990); they suggest modifications to the predictive formulae for the crest elevation parameter. Overtopping and crest elevation build-up can be described by these predictive formulae, within the limits of the barrier inertia parameter overwashing threshold. Process studies attribute both overtopping, by run-up and foreshore widening by undermining the barrier crest, to overwashing. Physical model data are validated and predictive methods verified for a limited range of conditions, using field measurements made during and following extreme events on Hurst Spit. Model studies are used, to provide the basis of design of a large-scale beach recharge scheme for Hurst Spit, this was implemented in 1996. An extensive regional field monitoring programme and SANDS database has been established, comprising measurement of water levels, barrier response, wind and wave conditions.