Study Update
Coastal Partners have recently completed a year-long tracer study on behalf of Chichester District Council (CDC) along a 2 km stretch of coastline between Selsey Bill and West Sands Holiday Park.
The study involved the deployment of 400 Radio Frequency Identification (RFID) tagged tracer pebbles across 4 different sites to help track the movement of sediment along the frontage. The tracer pebbles were tracked over 10 surveys spaced throughout the year.
The study was carried out as part of the Selsey and Wittering Beach Management Plan (BMP) 2021-2026. Results gathered from this study will help to further the understanding of sediment transport pathways along this section of the coastline, informing the next phase of the Selsey and Wittering BMP 2021-2026, alongside the options appraisal and outline design stages for the Selsey Flood and Coastal Erosion Risk Management (FCERM) Scheme plus future updates of the SCOPAC Sediment Transport Study.
• Tracer results from deployment site 1, the most western deployment site, showed strong westwards alongshore movement by the later surveys.
• Tracer results from deployment site 4, the most eastern deployment site, showed dominant eastwards alongshore movement away from the deployment site towards Selsey Bill throughout the study period.
• Minimal alongshore movement was shown at deployment sites 2 and 3.
• The average sediment transport rate calculated for deployment site 4 was over an order of magnitude greater than the average sediment transport rate calculated for deployment site 1.
• The tracer results suggest either an apparent westward shift in the position of the littoral drift divide, previously understood to have been positioned near Hillfield Road, or the presence of a further littoral drift divide along the West Beach frontage.
Coastal Partners are currently investigating the use of acoustic tags to assist with the monitoring of onshore and offshore movements of material within the nearshore zone. This method will allow for monitoring to be carried out in the sub-sea zone. A pilot study at Hayling Island, Hampshire, is planned for 2025 and if successful, this technique could be implemented at Selsey to help understand the potential onshore/offshore interactions with Kirk Arrow Spit and the wider nearshore zone along West Beach.
A second tracer study will be starting in July 2025 to help establish whether a littoral drift divide is still present near Selsey Bill and identify any onshore sediment transport pathway from Kirk Arrow Spit to the Bill.