Tracer Pebbles

Technology for changing oceans

To design and build fit-for-purpose sea defences, we are always looking to improve our understanding of coastal processes. To help us do this we have developed an innovative method to track the movement of sediment along our beaches.

A simple idea that delivers amazing results

By fitting a locally sourced beach pebble with a unique Radio Frequency Identification tag we receive very valuable information. The ‘Tracer Pebble’ broadcasts a unique ID number which is detected using Global Positioning System equipment and from this our engineers analyse trends in beach behaviour.

By deploying and tracking these pebbles, we collect the patterns of drift which helps to inform local coastal management decisions, aids coastal defence scheme design and guides beach maintenance activities.

Hurst Spit Study with New Forest District Council

In a recent study 1,300 tracer pebbles were deployed at Hurst Spit to help understand sediment transport pathways. The study highlighted information that had not been revealed in other surveys - the pebbles bypass groynes and rock revetments. It also showed that the offshore breakwater was successful in slowing transport rates of the beach material which in turn, helps to stabilise the beach.

Additionally, no tracer pebbles were found to bypass Hurst Castle over the duration of the study, indicating they may well be taken offshore. Those deployed immediately east of Hurst Castle were shown to rapidly move off north before accumulating on a new mini cuspate foreland feature.

The study provided a wealth of useful insights. The information is being used by New Forest District Council and Environment Agency to inform the Hurst Spit Beach Management Plan and the Lymington to Hurst Spit options development.

New Horizons

Our most recent tracer study is at West Bay in Dorset. 1200 native pebbles were deployed in 2022 and they are now being tracked to understand sediment transport pathways around the harbour and adjoining beaches below the cliffs. This information, combined with analysis of data from the National Network of Regional Monitoring Programmes (https:// coastalmonitoring.org/) and additional topographic and bathymetric data collected through the study, will inform the Beach Management Plans for West Beach and East Beach. “I am really pleased with what the team have produced. It is an extremely interesting and detailed study, which will be tremendously valuable to us as Hurst is progressed. I am impressed, and surprised, with the distance some pebbles appear to have travelled, very useful information.”

Peter Ferguson

Coastal Project Engineer, New Forest District Council