J. C. Schofield’s scientific contributions

Beach changes in an area where the sea floor is in equilibrium with sea level are not only a function of the local energy input and time, but also of sea-level change. The magnitude of beach change, erosional and progradational, is related to maximum depth of the local sea-floor profile of equilibrium and both are a function of local wind strengths and directions. Removal of sand by man from shallow depths and from beaches within the essentially closed Ocean Beach-Mangatawhiri Sand System exceeds natural input by an average of about 1750 m per kilometre of coast per year. Starvation of the local beaches is tentatively shown by the difference in behaviour of Mangatawhiri Spit and beaches of Great Barrier Island; the latter are part of another system where sand is not being removed by man. Mangatawhiri Spit beach is apparently being starved at a rate of about 4750 m per kilometre per year; this rate may include the continued effect of a more localised removal of sand. Starvation of beaches in the Ocean Beach-Mangatawhiri Sand System may accelerate their erosion now and for some time in the future, particularly during periods of rising sea level.