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Mr Lyall Cairns, Eastern Solent Coastal Partnership


Mr Matt Hosey, Poole Borough Council

Mr Neil Watson, Environment Agency

Research Chair

Dr Samantha Cope, Havant Borough Council

Current Research

SurgeWatch: a user-friendly database of coastal flooding for the UK

SCOPAC Contaminated Land Study

Scanning of historical aerial photography

Beach response in front of structures in open coast

Reducing regional flood and erosion risk from wave action on the Channel Coast

Maintenance of coastal structures - Phase 1: Timber groynes

Completed Research

Poole Bay Nearshore Replenishment Trial (2014-2017)

Bradbury’s Bursary: Lauren Burt (2016) and Emma Harris (2017)

SCOPAC Sediment Transport Study update 2012

Offshore to onshore transport across distinct landforms at Church Norton Spit

Coastal sediment budget project: Minor Funds Contribution

Seabed Mapping Selsey to Eastoke: Minor Funds Contribution 2013-2015

Sediment Tracer Study Phase II: Minor Funds Contributions 2011-2013

Non-Standard Rock Groynes: Minor Funds Contributions 2011-2013

Sediment Tracer Study Phase I: Minor Funds Contributions 2010-2011

ACCESS Project

Extreme Wave Conditions within the SCOPAC region

Strategic Regional Coastal Monitoring

RESPONSE European Project

SCOPAC Sediment Transport Study 2004

SCOPAC Sediment Transport Bibliographic Database v6, 2012

Evolution of the Solent River animation

Evolution of Lyme Bay animation

Preparing for the Impacts of Climate Change

Offshore to onshore transport across distinct landforms at Church Norton Spit

The aim of the project was to establish whether the orthogonal bars act as transport pathways for pebbles across the intertidal.

2. Project

SCOPAC contributed £4,000 to an undergraduate student project to investigate whether the orthogonal bars are acting as sediment transport corridors. The project used painted and tagged pebbles (using the RFID technology perfected in previous Eastern Solent Coastal Partnership research during 3 deployments (17/18 February, 4/5 March and 18/19 April 2016). Pebbles previously collected from the feature included two sizes (approximately 100g and 300g) and were placed in rows parallel to the shore across the feature and left for two high tides after which all pebbles found were collected again for the next test. Placement and collection positions were collected with dGPS and an example of the layout and movements of pebbles during the first deployment can be seen in Figure 2.

Figure 2: click for enlarged image

Figure 2: Example of pebble placement (yellow) and collection (red) positions from the first deployment. Note that the aerial photography in the left hand panel is from June 2013 (CCO) illustrating some of the shore parallel movement of the orthogonal bar.

3. Results

Wave conditions were different for all three events (Figure 3) with the first deployment being the most energetic followed by deployment 2 and 3.

1. Background and motivation

Church Norton Spit at Pagham Harbour, West Sussex has undergone cycles of accretion and breaching since the harbour’s formation in 1910.

In the last 14 years, the spit has experienced excessive growth, although the source of this material is unknown.

The material for this growth must therefore come from the sub-tidal as there is no other input from land or alongshore. Some of the material will move as part of bedforms (green circled in Figure 1) but some may move using bedforms as a transport path (the orthogonal bar in the red circle). This latter process had been postulated by Julian Orford in a few papers in the 1990s, but remained a general untested hypothesis.

University of Sussex (lead) £4,000

Minor Funds Contribution 2015-16

Figure 1: click for enlarged image

Figure 1: Aerial photography showing location of the more or less stationary orthogonal bar (red) and other intertidal shingle features (green)

This project was instigated by Dr Uwe Dornbusch of the Environment Agency, Arun DC and Chichester DC and was led by Dr Cherith Moses from the University of Sussex with input from Professor David Sear from the University of Southampton. 

The Eastern Solent Coastal Partnership provided the tracer study retrieval equipment.

Figure 3: Wave and tide conditions during deployments taken from Rustington wave buoy and Littlehampton tide gauge.

4. Summary

The measurements on the orthogonal bar at Church Norton Spit show that pebbles move along the bar even under comparatively low energy conditions and support the assumption that these features act as transport corridors.

It is recommended that a future study deploy the tracers for more than one tidal cycle to identify longer term fluctuations in transport.  In addition, further work on quantifying the volume of shingle moving along the orthogonal bars would be of benefit to understand their significance as a transport mechanism in relation to the wider sediment cell.

The project was carried out as part of an undergraduate thesis by Lucy White at the University of Sussex. The thesis is available here (see right).

Uwe Dornbusch, 21-6-2016