|
|
|
|
|
Issue: 46 | February 2017
|
|
Welcome!
This is our last newsletter from Phase III of the Southeast Regional Coastal Monitoring Programme, as we move seamlessly into Phase IV on 01 April. A glance at the articles below illustrates how far things have progressed since the start in 2002 - 10mm accuracy laser scans, seamless nearshore 3D mapping, radar tide gauges - and yet also how much coastal processes can still surprise us, as demonstrated in this month's Feature Article, kindly contributed by Ian Thomas, Pevensey Coastal Defence Ltd.
Travis Mason – Regional Co-ordinator
|
|
IOC Manual for radar tide gauges
A new volume for the IOC manual on sea level measurement has been issued for radar tide gauges. These instruments have been used by the Southeast and Southwest Regional Coastal Monitoring Programmes for a number of years, and are increasingly being deployed all around the globe. We were invited to include information about our experience with WaveRadar REX instruments, which has been included in the Manual Supplement.
The Manual on Sea Level Measurement and Interpretation Volume V: Radar Gauges (IOC Manuals and Guides 14; JCOMM Technical Report No 89) is published by the Intergovernmental Oceanographic Commission, UNESCO. The Manual and Practical Experiences Supplement can be obtained at:
http://unesdoc.unesco.org/images/0024/002469/246981E.pdf
|
|
|
Surveying on designated sites
We are in the final throes of achieving region-wide approval from Natural England for the timing and method of topographic surveying on beaches in the Southeast Region. The project involved identifying designated sites within each survey unit and liaising closely with Natural England to understand the best practice for surveying environmentally sensitive sites. We have also documented which areas require annual assents from NE. Dr Angela Marlow of Natural England kindly agreed to oversee this project in the Southeast, and to liaise with local Natural England offices to agree and document suitable survey practises. Dr Marlow also gave a presentation at our last annual partners meeting to raise awareness about what features or species may be impacted by surveying and what we can do to minimise those impacts.
|
|
|
Hayling Island frontage during early February storm
Between Thursday 2nd and Friday 3rd February 2017, an area of low pressure tracked eastwards along the south coast, causing high winds and large swell waves along the Hayling Island frontage. This storm event resulted in a high volume of shingle material being pushed up onto the promenade and displaced beach huts. Localised flooding of the promenade restricted public access around Eastoke.
Within 24 hours, the Eastern Solent Coastal Partnership had mobilised excavators to the site to reinstate the beach and clear the promenade. Bulldozers were used to build the beach back to a design profile. The beach was successfully restored within a few days with no flooding to residential properties reported.
|
|
New onshore-offshore geology map
Programme partners will recall our “DORIS” survey – the innovative collaboration between the Maritime and Coastguard Agency’s Civil Hydrography Programme, Dorset Wildlife Trust, the Royal Navy and the Channel Coastal Observatory to undertake an extensive swath bathymetry survey off the Dorset coast in 2009, supported by a financial contribution from Viridor Credits.
British Geological Survey and the University of Southampton have subsequently integrated the survey results with the coastal monitoring programmes’ aerial photography and lidar, together with re-interpretation of existing geological maps, and the results have been published as a seamless onshore-offshore bedrock geology map of the eastern half of the Jurassic Coast World Heritage Site. The map is freely available online at:
http://jurassiccoast.org/jurassic-coast-map-drains-sea-reveal-geology/
BGS commented that this new research highlights the paucity of knowledge about the nearshore sub-tidal zone. From a coastal management point of view, information from this map can highlight sediment-starved areas and is likely to play a pivotal role in future research into region-wide sediment budgets. The superb visual clarity and inter-active nature of the seamless mapping will also provide a powerful tool for coastal managers for public engagement. We very much hope that further collaboration with BGS will follow to roll out similar mapping along other areas of the coastline.
|
|
Lymington Seawall Monitoring
Over the past eight months CCO have been laser scanning a seawall located on the west bank of the Lymington River, adjacent to the Bath Road car park slipway and the Royal Lymington Yacht Club. In the spring of 2016, it was noticed that large cracks had appeared in the wall and an area of paving slabs behind the wall had started to subside. New Forest DC coastal engineers asked CCO if monitoring of the wall could be undertaken using laser scanning, to establish whether or not movement was still progressing. CCO have since been scanning the site every six weeks or so and surveys have revealed very small movements in the wall and paved area behind. Due to the very small amount of movement, surveys have to be carried out to an accuracy capable of detecting movement as small as 10mm. This has been achieved by using a Leica Scanstation C10 and scans have been coordinated using four survey targets fixed to parts of the wall believed to be stable.
|
|
|
|
Cross section showing 0.024m change in height of top of wall June 2016 to December 2016. Note also elevation change of paving and park bench
|
|
|
Metadata updates to MEDIN
The Marine Environmental Data Information Network, MEDIN, is a partnership of UK organisations committed to improving access to marine data, and reports directly to the UK’s Marine Science Coordination Committee (MSCC). Several years ago, arrangements were made to send MEDIN information about the data held on Channel Coastal Observatory’s data archive; not the data themselves but metadata about the what, where and when, together with the website address for users to obtain the data. This fulfils our INSPIRE responsibilities. MEDIN subsequently updates the United Kingdom Directory of Marine Observing Systems (UKDMOS), which is an internet-based searchable database of marine monitoring.
As part of the website refresh, the system of sending metadata to MEDIN has been revised and updated so that, henceforth, metadata updates will be forwarded to MEDIN automatically in January, April, July and October.
|
|
FEATURE ARTICLE
Unusual beach features at Pevensey
Storm Angus, in the early hours of 20th November 2016, recorded the highest waves to date at the Pevensey Bay wave buoy. From a sea defence point of view, the south coast was lucky in that the storm arrived four days after high spring tides. Additionally, peak waves coincided with low water at Pevensey so the defences were largely spared. Despite there being no threat of flooding, there was significant cross-shore transport, with sediment eroded from the front of the beach crest being drawn down to the toe of the embankment. Weather in the week after the event was largely benign and dominated by constructive wave conditions. Sediment drawn down by the storm immediately started to be pushed back up the beach profile, particularly from 24th November onwards as the second spring tide approached at the end of the month.
The process whereby sediment moves up and down the beach profile is happening all the time in response to normal coastal processes. Typically, on falling tides a series of small berms will form, and it is only when conditions remain constant through the neap tide and on to the next spring tide that these small berms are pushed increasingly upwards into a more significant beach feature. Such a feature formed at Normans Bay, Pevensey, by 30th November, where in places the berm rose at least 2m above surrounding beach level (Figure 1).
|
|
|
|
Figure 1: Berm feature at Low Water
|
|
|
Berms of this size do appear periodically, but often become eroded themselves by subsequent wave action. This was one was particularly interesting for several reasons:
- Because it was a low spring tide, the berm formed well seaward of the beach crest
- It was formed purely of gravel and was entirely sand-free and therefore was porous
- At High Water on the largest of the spring tides, winds dropped completely, so water percolating through the berm was mirror-flat, whilst the sea beyond was lightly rippled
- Although porous, the berm structure prevented most of the fines suspended in the sea from getting through, so the water behind the berm was clear, unlike the main body of the Channel, which remained turbid
The “water feature” (Figure 2) appeared for 45 minutes or so either side of High Water before disappearing as the tide receded. It survived for the first three weeks or so of December, but was finally flattened and pushed up to join the front of crest by stronger winds over Christmas.
|
|
|
|
Figure 2: Ponded water in berm feature. This image also demonstrates the extensive length of shoreline along which the feature formed
|
|
Southeast Regional Coastal Monitoring Programme
Area Representatives
Isle of Grain to Beachy Head
Claire Milburn, Canterbury City Council, Strategic.Monitoring@Canterbury.gov.uk
01227 862 537
Beachy Head to Selsey Bill
Dan Amos, Adur & Worthing Councils, Strategic.Monitoring@Adur-Worthing.gov.uk
01903 221376
Selsey Bill to Portland Bill
Stuart McVey, New Forest District Council, Stuart.McVey@noc.soton.ac.uk
02380 598641
Channel Coastal Observatory
CCO@channelcoast.org
02380 598467
|
|
Social Media
Please follow us on Twitter to keep right date with all things coastal. We also have numerous and growing number of informative videos on YouTube!
Please click on the links below to follow and subscribe.
|
|
|
|
|
