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Scientific Studies from around the world on the erosion resulting from offshore sand and gravel dredging

Based mainly upon computerised assumptive 'research' made by those selected, appointed and paid for by the dredgers themselves, the British Government continues to claim that they are unaware of any evidence linking offshore sand and aggregate dredging with the rapidly increasing loss of our shoreline. But well founded evidence of the impact exists from researched empirical findings carried out by independent investigators with a more enlightened understanding.

Here follows a few of those papers published that are ignored by those wishing to see the activity continue.

Nearshore Impacts of Dredging for Beach Nourishment by J. Wtrwy., Port, Coast., and Oc. Engrg., Volume 130, Issue 6, pp. 303-311 (November/December 2004).

This paper provides a methodology for predicting the impacts of nearshore dredging on shoreline change by using numerical models for waves, currents, and shoreline change. In this study wave model results were used to estimate longshore sediment transport and shoreline change due to longshore gradients of the longshore sediment transport rate. The results reproduced observed trends of erosion and accretion along approximately 90% of the shoreline.

A new concept for sea defence walls

Much thought has been given over the past twenty years as to the best design for coastal and sea defence walls. Now we have a new concept called 'The TBLOCK System' recently developed by Alan Thompson MIMechE. It consists of a mass concrete structure which interlocks with adjoining TBLOCKs by a cut out down opposite vertical corners. It has been developed to offer an alternative engineering solution for sea defence and coast protection problems at a time when global warming and climate change, not to mention sad and gravel seizure,offers new challenges to Engineers.

Details are to be found at www.tblocks.co.uk/intro.html

History of the Marine Aggregate Industry

Through the auspices of their Marine Stewardship Fund, The Crown Estate recently commissioned a review of the history of the marine aggregate industry, which was written by Dr Sue Gubbay.

The revue looks back over the last 30 years of marine dredging. It describes the historical activity, this followed by improvements made in the industry, some of these undoubtedly provoked by critical environmental pressure groups such as MARINET. It goes on the give the situation as it exists today and then points to the challenges that the dredging industry is likely to have to face in the future.

The report can now be seen by visiting www.thecrownestate.co.uk/1401_sue_gubbay_report.pdf

Mutual co-operation but different fact marketing?

Jerry Berne of Sustainable Coastlines (USA) sends us information that you may wish to peruse, followed by his comments.

www.mms.gov/international/uk.htm demonstrates a link in the US to UK dredging programs. Whilst is does not say that much, here is an extract of the main information within it.

"The UK is participating with the Marine Technology Directorate and the Petroleum Science and Technology Institute on offshore safety research. These research groups are industry-funded and based in the UK.

"The UK participates with MMS, Australia, and Canada in the International Regulators Forum.

"The International Activities Program is participating in a multi-year study of the fate and effects of sediment plumes from sand and gravel dredging in the English Channel. The study is being done by Coastline Surveys, Ltd., a UK marine consultant, along with Hydraulics Research, another consultant, and three major UK dredging firms - ARC Marine, United Marine Aggregates, and South Coast shipping."

Jerry Berne adds his comment: -
"I think it somewhat special that the good old environmentally sensitive UK government's Environment Agency is actually covering up the damage that Offshore Aggregate Dredging is doing while here in the US, our own mining agency MMS (Minerals Management Service) is admitting to it. This seems to be a reversal in what one might have imagined, given the Iraq war intelligence cover-up." Here is a listing site of MMS studies as compiled by Barry Drucker.

Another report of interest not on the above page can be found here.

North Norfolk Dredging Induced Erosion in Eurosion Report - 4th December 2005

The following is an extract from 'Living with Coastal Erosion' - Eurosion Policy Recommendations - December 2003. To see the report in its entirity go to www.eurosion.org/reports-online/reports.html

EXAMPLE OF COASTAL CLIFF EROSION

The municipality of Happisburg is a located in the county of North Norfolk (UK). Sediments are removed from the cliffs under the action of the waves and are transported southwards where they supply the beach of Sea Palling with "fresh" sediments. The two aerial photographs below depict the situation of the area of Beach Road in Happisburg, in 1992 and 1999 respectively. Coastal erosion mainly affected the south-east part of Beach Road, and coincides with the destruction of the wooden defences originally located upfront the cliff.

2.2.2. Human structures and activities have exacerbated coastal erosion

To a lesser extent, coastal erosion is also exacerbated by human activities which are implemented in some cases hundreds of kilometres away from their zone of impact. This has proved to be particularly the case for:

(ii) Aggregate extraction. Dredging of river and seabed for navigational purposes (i.e. deepening navigation channels) or constructional purposes (e.g. sand and gravel mining) removes an important amount of sediments. This creates a sediment starvation which is in certain circumstances compensated by (re)activation erosion processes along the shore areas. This has proved to be the case in a significant number of cases including Cove do Vapor (Portugal), the Western Scheldt estuary (Netherlands and Belgium), Donegal (Ireland), Cavado (Portugal), and North Norfolk (UK). In some cases, dredging activities, by modifying the water depth in the near-shore area, induce wave refraction which in turn modify the long-shore and cross-shore sediment transport patterns.

Addendum 22nd December 2005

Since the Eurosion report was written two years ago, following further dredging in The Wash and off Great Yarmouth, it has been found that the original sediment flow coming down the North Sea has all but ceased. See Southern North Sea Sediment Transfer Study.

Consequently Sea Palling has (up to now) had to receive regular beach renourishment by having sand pumped onto the receding beach. Thus that stated in the report is outdated by this new evidence. The sediment is no longer arriving at Sea Palling by sediment drift, but it is arriving there by being removed by the dredgers and then pumped ashore.

And this too is now outdated, as in September 2005 DEFRA refused the Environment Agency the vitally needed grant of £2,000,000 to pump 150,000 cubic metres of sand onto Sea Palling beach to maintain the defences. (See 'Funding withdrawn from Sea Defences' under our Press Comments section.) This refusal undermines the tens of millions already spent and means the demise the essential defences there, with consequential sea entry at that point followed by the eventual loss of the inland villages and The Broads.

CEFAS (Centre for Environment, Fisheries & Aquaculture Science) find no recovery of eco-system damage after offshore dredging - 18th November 2005

Once BMAPA and their apologists claimed there was no long term impact on the seabed and its inhabitants from offshore aggregate dredging, stating that the seabed and the ecosystem dependant on it rapidly recovered from marine aggregate dredging. They are on record (on our MARINET video) for having claimed recovery and rehabilitation to come about "within a year".

This myth has long been disputed by many fisherman, who have discovered from first hand knowledge and practical experience that dredged out areas do not recover even after sixteen years. (See the findings by Rodney and Graham Burns of the Aldeburgh Fishing Guild under 'The Losses Account' in our Briefing Paper No.1 on this website).

Since then CEFAS and HR Wallingford have produced a very thorough and comprehensive study of the long term impact upon the sea bed following Offshore Aggregate Dredging, albeit they only studied the effect after a period of three years on one site and four on another. The change in strata was noted, that little or no sign of recovery was discovered in the ecosystem of the dredged area stripped of seabed life or the area smothered by the plume from adjacent dredging in that time.

Numerous photographs and charts are included to support the findings.

The paper by Boyd S.E. et al is Paper No.121 in the CEFAS listing. It is in Acrobat Format, entitled "Assessment of the rehabilitation of the seabed following marine aggregate dredging" and is to be found on Internet by going to: - www.cefas.co.uk/publications/techrep/tech121.pdf

Flawed Environmental Impact Assessment (EIA) studies on dredging impact - 6th November 2005

In addition to that we already have within Briefing Paper No.1 and in the listing of scientific papers from around the world on this page, a new paper further evidences that we have long found, that much of the research on the damage resulting from offshore aggregate dredging (or, as these reports usually show, the non-effects) are produced by those profiting from this practice.

The situation we have in the UK appears the same in the USA as shown by the paper 'Flawed studies assess dredge-and-fill programs to protect coastlines' published in the October 2005 issue of BioScience, the monthly journal of the American Institute of Biological Sciences, appears to show.

Marine scientists Charles H. Peterson of the University of North Carolina and Melanie J. Bishop, now of the University of Technology in Sydney, Australia, have reported that, despite expensive, multidecadal monitoring, the majority of studies of the ecological impacts of beach nourishment are scientifically inadequate and suffer from critical flaws, improper analyses, and unjustified interpretations.

Peterson and Bishop point out how the activity can bury shallow reefs and degrade other beach habitats, depressing nesting in sea turtles and reducing the densities of prey for shorebirds, fishes, and crabs, and that the US Army Corps of Engineers and state permitting agencies, which oversee most of the monitoring studies, do not have expertise adequate to assess them.

Peterson and Bishop conclude that reform of agency practices is urgently needed as evidence of the cumulative risk of severe ecological impacts grows. Their survey discovered that monitoring is typically conducted by project promoters with no independent peer review. See also www.aibs.org

Whilst dredging for beach restoration in the USA is seen to have such adverse impact, this must be quite small when compared to the far greater effect in the UK where massive commercial quantities of aggregate have been dredged over many years.

Pat Gowen, 6th November 2005

UK study on seabed smothering from dredging - 31st October 2005

A paper giving insight into the damage created by dredging, specifically the smothering settlement of suspended 'wash off' sediments over the seabed, impacting the animals and plants that live on and within it, can be read in full by going to: www.ukmarinesac.org.uk/activities/ports/ph5_2_6.htm

It stresses how animals with delicate feeding or breathing apparatus, e.g. bivalve shellfish, can be intolerant to increased siltation, so giving reduced growth or fatality. Maerl beds (calcified seaweed) are reported to be particularly sensitive to smothering emanating from channel dredging. It describes how important spawning and/or nursery areas are for fish and other marine animals, and how dredging can result in smothering their eggs and larvae. Shellfish are said to be particularly susceptible during spring when spatfall occurs, and when smothering of intertidal areas occurs, there may be subsequent effects on the availability of animals and plants in bird/fish feeding areas.

The treatise further points out how the blanketing or smothering of benthic animals and plants may also cause stress and reduced rates of growth or reproduction, relating to how sediments are distributed more widely within the estuary or coastal area and may settle over adjacent subtidal or intertidal habitats some distance from the dredged area.

More information on the marine and seabed species impacted may be found on UK Marine SACs Project www.ukmarinesac.org.uk/index.htm

Europe - EUROSION Project - 29th October 2005

EUROSION www.eurosion.org is "a project contracted by the European Commission to a consortium led by the Dutch National Institute for Coastal and Marine Management (RIKZ) for the period 2002-2004."

They are probably the world topmost authority on the problems of coastal erosion and have produced "Living with Coastal Erosion - EUROSION Policy - Recommendations December 2003" which "provides a revised draft outline of the policy recommendations for coastal erosion and coastal flood risk management."

The full report can be downloaded from the eurosion website. www.eurosion.org/reports-online/reports.html
The following from it are direct quotations:

2.2.2. Human structures and activities have exacerbated coastal erosion

To a lesser extent, coastal erosion is also exacerbated by human activities which are implemented in some cases hundreds of kilometres away from their zone of impact. This has proved to be particularly the case for:

(ii) Aggregate extraction. Dredging of river and seabed for navigational purposes (i.e. deepening navigation channels) or constructional purposes (e.g. sand and gravel mining) removes an important amount of sediments. This creates a sediment starvation which is in certain circumstances compensated by (re)activation erosion processes along the shore areas. This has proved to be the case in a significant number of cases including Cove do Vapor (Portugal), the Western Scheldt estuary (Netherlands and Belgium), Donegal (Ireland), Cavado (Portugal), and North Norfolk (UK). In some cases, dredging activities, by modifying the water depth in the near-shore area, induce wave refraction which in turn modify the long-shore and cross-shore sediment transport patterns.

USA - Dredging damage in Alabama - October 2005

Scott Douglas, eminent coastal engineer with the University of Alabama, leaves no doubt as to erosion brought about by dredging. Where this was carried out by the U.S. Army Corps of Engineers, it has dramatically harmed Alabama beaches and necessitated ongoing restoration projects costing the public about $28 million. He maintains that such practices caused hundreds of millions of dollars of losses in a recent hurricane, saying "Hurricane Ivan came ashore on a beach that offered vastly diminished protection from such a storm." Incredibly, in the same article, Corps of Engineers officials actually acknowledged that the dredging and dumping practices may have caused long-term problems.

The Corps of Engineers' prevailing failure on Alabama's shoreline, Douglas contends, is the Mobile Ship Channel. Douglas points out that since 1939, the corps has maintained a 45-foot-deep ship channel cut right through the sandy slope that supports Dauphin Island and the Fort Morgan Peninsula. He says that sand, moving in from the east on the wave-driven conveyor belt, falls into the ship channel, where it collects until the corps dredges it up. Until recent years, the corps dumped the sand several miles offshore, far from the shoal that supports Dauphin Island's beaches and the littoral zone where tides would take the sand ashore.

Five years ago, Dauphin Island property owners sued the corps, claiming that the channel had caused the dramatic erosion on the island's west end. The case is ongoing. Meanwhile, the Federal Emergency Management Agency erected a $1 million protective sand wall, or berm, but it washed away. Then Ivan came along, destroying 33 island homes and sucking away tons of sand.

Germany - 'In deep with marine environmental surveys - Exploiting sandbanks' 24th May 2004

Innovations Report

An application tested by SUMARE, relates to government-sanctioned offshore exploitation of sand on the Belgian continental shelf. However, there is concern that growing exploitation could lead to a reduction in size - or even disappearance - of the banks. In turn this could affect water currents and erosion/sedimentation characteristics of the area, and lead to undesirable impacts on the nearby beaches.

As such the Flemish sandbanks have been subject to monitoring for several years. Traditionally, depth measurements are done by ships equipped with hydrographical instruments. But that is time-consuming, expensive (at a cost of €10,000 per day per ship) and at low tide, navigating the banks can be difficult. Mini-autonomous underwater vehicles, as demonstrated by SUMARE, offer a practical, more efficient and cheaper alternative.

SUMARE's intensive data collection and analysis has shown that human activity on the sandbank could have had an impact on the shape and size of the sandbanks over previous years. However without further detailed analysis, the question of sustainability of the activity remains unanswered. Norro adds: "What is certain is that further investigation supported by intensified monitoring by AUVs, based on the SUMARE design, will form a key contribution," since it enables a faster and more cost-effective answer to be reached.

Netherlands - Assessment by Delft University

Dutch researchers from Delft University produced a paper assessing the impact of Offshore Aggregate Dredging on the shoreline given at the 20th-21st February 2003 European marine sand and gravel Conference (EMSAGG). It shows by graphical and mathematical models the mechanism that brings about draw down and shoreline loss by dredging offshore.

However, it does not appear to do more than call for caution and more studies. Whilst these are ongoing no doubt the dredging will continue to destroy our coastline.
Link to paper

USA - March 1993

Although several years old, the following produces some good information: www.mms.gov/sandandgravel/PDF/REF-NEW.PDF
It in part tells of the 2000 studies off Pea Island, North Carolina, USA, and how the North Carolina Geological Survey and University of Arkansas researchers found that shoals even three miles offshore caused wave fronts to refract. This then "focused" the wave energy causing erosion "hot spots" on shore. Models developed accurately predicted the location of these. Such conclusively explodes the continuing UK claim that dredging so far from the shoreline cannot produce coastal erosion.

Studies from the USA Minerals Management Service (MMS) offer some information, but be aware that the MMS is involved in the extraction of minerals, and not in environmental protection. Barry Drucker, one of its project managers, is basically a dredging advocate. You can go to its environmental studies site for some additional information

The MMS are working with/colluding with the UK's International Regulators Forum (Canada and Australia) on the effects of sediment plumes from sand and gravel dredging in the English Channel. But the studies almost always minimize dredging's negative effects even when the original abstract strongly indicates the opposite. The website to see is www.mms.gov/international/uk.htm

A supposed review of the literature is currently ongoing to list the available information on the environmental effects of dredging. Its executive summary is to be found at www.mms.gov/sandandgravel/PDF/MMS%2093-0005.PDF

Also from the United States Minerals Management Service providing a programme for the assessment for the cumulative effects of offshore dredging, although sadly it avoids any realistic practical evidence for such. It is unfortunate that this has never been put into practice in UK Environmental Impact Assessments. This is found at: - www.mms.gov/itd/pubs/2001/2001-089.pdf

USA - Navigation study for Canaveral Harbor, Florida - August 1990

FINAL FEASIBILITY REPORT AND ENVIRONMENTAL IMPACT STATEMENT - 81240. US Army Corps of Engineers, Jacksonville District South Atlantic Division. CANAVERAL HARBOR FEASIBILITY STUDY - APPENDIX E - COASTAL ENGINEERING ANALYSIS. IMPACTS OF IMPROVEMENTS ON LITTORAL PROCESSES.

Abstract: (from a very long paper)

The US Army Corps of Engineers dredged an initial 27 foot deep channel almost 14 miles offshore to keep the shipping channel clear, but in fact created a massive, hydraulically self-sustaining open pit mine offshore serving to denude the onshore supply and coastline.

Initially, in 1951, 325,000 cubic yards of sand was removed, from 1963 to 1979 the average yearly take was 675,000 cubic yards, and from 1979 to 1990 when the study was made the average was 925,000 cubic yards.

The constant dredging to keep the channel clear and further deepening the original channel continued to promote the loss of both the offshore and onshore material. Studies show the creation of the original channel caused the previously accreting shorelines to begin eroding at incredible rates over forty miles south of the channel dredging. Prior to the dredging, the shoreline was accreting tens of feet per year, so for the visible shorelines to erode in some areas hundreds of feet the offshore had to experience enormous losses in its seabed sediment resources. The effect of the channel dredging was to bring about a steepened and deepened offshore profile, allowing greater storm energies to strike onshore, while at the same time creating a replacement demand resulting in an erosive profile for the nearshore.

The report is thorough, quite comprehensive and detailed, and offers an excellent example of the lack of understanding of coastal physics by the Corps and coastal engineering consultants, and how man can effect massive shoreline changes even with a relatively small project, with far less sediment removal than is taking place off our United Kingdom east coast.

That the dredging took place 14 miles from the coast and brought about so much erosion of the coast is highly significant.