SHINGLE TRACING BY A NEW TECHNIQUE

Abstract

A major drawback of all existing tracer techniques for monitoring shingle movement, except that of labelling with radioactive isotopes, is that tracer recovery rates are invariably low, (commonly less than 15% of the total injected) because recovery is limited to the beach surface. Investigations were made into the possibilities of developing a new tracer that might overcome this problem. The paper describes the results of, and the conclusions drawn from two trial field experiments carried out using metal tracer pebbles. These had specific gravities, size and shape similar to the indigenous beach pebbles, and were recovered both on and beneath the beach surface using metal detectors. By assessing the relative merits and drawbacks of the technique it was concluded that the use of metal pebbles as tracers for shingle beaches is more practical than other methods for most tracing purposes. At present the technique is best suited to investigations ranging in length from a few days to a few months and requiring small to medium-scale injections of 5000 tracer pebbles or less. The considerable scope for the further development and application of the technique is discussed.