Sand & Gravel extraction on the North Sea Continental Shelfs & UK waters
For each country an overview is given of extraction activities and statistics, if available. Note: The last update of this overview has been in 2001. However DNO is exploring options to get a recent update from national authorities.
- The Netherlands
- The United Kingdom
Extraction on the Continental Shelf of Belgium
Aggregate Extraction Activities
During the last two decades marine sand has been extracted from the Belgian Continental Shelf to supply the construction industry with sand for mortar and concrete.
At first users were not inclined to use these marine aggregates out of fear for the harmful influence seashells and salt might have on the end products. With the years this doubts faded, progressively increasing the demand for marine aggregates from about 400,000 m³ (0.6 million metric tons) in 1979 to over 1,700,000 m³ (2.5 million metric tons) in 1999. Occasionally the production was doubled due to important offshore projects, like in 1997 with the construction of pipelines for the transport of gas. (see also statistics below)
On top of this production comes the dredged sand for public infrastructure works, like harbour construction and coastal protection.
Due to the progressively closing sand and gravel pits on land, the demand for marine aggregates is thought to increase during the coming years.
General statistics on the extraction of marine aggregates (1979 - 1996)
|Production in m3||370,000||440,000||480,000||380,000||580,000|
|Production in m3||490,000||500,000||500,000||640,000||620,000|
|Production in m3||970,000||1,010,
|Production in m3||1,600,
Production statistics per zone (1997 - )
Generalised destination ** statistics (1997 - )
|No data available||0||0||43,095||39,948||12,710|
|click to enlarge||
* Destination: place where the extracted sand or gravel is unloaded
Administration, Legislation and Licensing
The marine sand and gravel exploration on the Belgian Continental Shelf has been authorised by the Law of 13 June 1969 on the exploration and exploitation of the non-living resources of the territorial sea and the continental shelf and by the Royal Decree of 7 October 1974 on the attribution of concessions for exploration and exploitation of mineral and other non-living resources of the continental shelf. The delimitation of the extraction zones was specified in the Royal Decree of 16 May 1977 on the measures for the protection of navigation, marine fisheries, environment and other essential interests during the exploration and exploitation of mineral and other non-living resources of the seabed and subsoil in the territorial sea and on the continental shelf. Due to the agreement between Belgium and the Netherlands on the delimitation of the continental shelf and the territorial sea, Belgium obtained in 1999 three extra exploitation zones, namely R9A, S7A and S7F.
Remark: The titles and linked documents referring to legislative documents were freely translated and have no legal value. Only the texts published in the Official Journal of Belgium (Moniteur Belge - in French; Belgische Staatblad - in Dutch) have legal value.
- 13 June 1969. Act on the exploration and exploitation of the non-living resources of the territorial sea and the continental shelf (as modified by the Law of 20 January 1999 on the protection of the marine environment and by the Law of 22 April 1999 on the exclusive economic zone of Belgium).
- 7 October 1974. Royal Decree on the attribution of concessions for exploration and exploitation of mineral and other non-living resources of the continental shelf of Belgium (as modified by the Royal Decree of 22 April 1983).
- 16 May 1977. Royal Decree on the measures for the protection of navigation, marine fisheries, environment and other essential interests during the exploration and exploitation of mineral and other non-living resources of the seabed and subsoil in the territorial sea and on the continental shelf.
- 10 August 1998. Act on the adoption of the Agreement between the Kingdom of Belgium and the Kingdom of the Netherlands on the delimitation of the Continental Shelf, and Annexes and correspondence; and of the Agreement between the Kingdom of Belgium and the Kingdom of the Netherlands on the delimitation of the Territorial Sea, signed in Brussels on 18 December 1996.
- 12 August 2000. Royal Decree on the installation of the Consultative Commission charged with the co-ordination between the administrations concerned by the management of the exploration and exploitation of the Continental Shelf and the Territorial Sea and to the fixation of the modalities and working costs.
Changes in the Belgian legislation
Two new laws brought significant changes to the Law of 13 June 1969.
These laws are the Law of 20 January 1999 for the protection of the marine environment in the marine territories under jurisdiction of Belgium and the Law of 22 April 1999 on the exclusive economic zone of Belgium in the North Sea.
The Law of 20 January 1999 aims at an increase of the environmental protection of the North Sea and adds 4 new paragraphs to article 3 of the Law of the 13 June 1969.
The first new paragraph (Art.3,§2) specifies that each demand for concession or authorisation must include an environmental assessment report. The regulations concerning the procedures, the countenance and the form to be taken into account while making this environmental assessment study, will be published in a future Royal Decree, established jointly by the Ministers of Economy and Environment.
It also specifies that exploration and exploitation are subject to a continuous study of the impact of these activities on the sediment movement and on the marine environment.
Art.3,§3 implements that concessions or authorisations can only be obtained after a favourable advise of the Minister of Environment. Furthermore, if the continuous study reveals unacceptable negative consequences of the exploration and extraction activities on sediment dynamics or on the marine environment, the concession or authorisation may be revoked or suspended, completely or partially.
Paragraph 4 specifies that all exploration and exploitation activities are subject to royalty fees. These fees are used to fund the continuous study of the influences of the concerned activities on the movement of the sediment and on the marine environment.
The last paragraph of this article (Art.3,§5) implements the creation by royal decree of a consultative commission to ensure the co-ordination between the different administrations concerned by the management of the exploration and exploitation of the continental shelf and the territorial sea.
This commission will have the following specific tasks:
- the co-ordination of the examination of the concession demands and the formulation of an advise on these demands;
- the follow-up of the different studies on the effects of sand and gravel extraction on the continental shelf;
- the examination of a three-years synthetic report with results of the continuous survey;
- the recommendation of corrective measures if negative influences are detected;
- the formulation of advice for a policy on all aspects related to sand and gravel extraction.
This consultative commission was instored by the Royal Decree of 12 August 2000.
The Law of 22 April 1999 mainly changes some definitions and increases the jurisdiction of the Law of 13 June 1969 to artificial islands.
It also defines clearly the boundaries of the continental shelf of Belgium and replaces article 4 of the Law of 13 June 1969, which was out of date, by a new article regulating the installation of cables and pipelines. A Royal Decree on the installation of cables in the Territorial Sea is in preparation.
The Law on the exclusive economic zone also adds a 10 article to the Law of 13 June 1969. This article refers to articles 55 en 56 of the Law of 22 April 1999, which specifies the penalties for infractions on the modified Law of 13 June 1969.
For more information on the Belgian legislation concerning the marine sand and gravel exploitation, contact:Ministry of Economic Affairs
Administration Quality and Safety
Fund for Sand Extraction
To Mr. B. Gonsette
North Gate III
Koning Albert II-laan, 16
or visit our site at mineco.fgov.be/ministry and look under "Inventory of Formalities" for "Continentaal Plat" (on the Dutch pages) or "Plateau Continental" (on the French pages).
Necessary adjustment of the exploitation zones
To comply with the obligation to take over the Dutch concessions in the border area and to obtain a better balance between the different users of the Belgian sea areas, the sand extraction areas need to be adjusted. This however is not easy: the different interests are not parallel, often they are even contradictory. A balance though has to be found between the interests of fisheries, exploitation and shipping, the need to provide space for telecommunication cables and gas pipelines and the protection of the marine environment.
The Fund for Sand Extraction is finishing a study in which an evaluation was made of the possible sand extraction areas. Based on this study, a proposal will be elaborated, which will be submitted to the consultative commission.
For years the extraction of marine aggregates was nearly uncontrolled. The administration had to relay on the honesty of the captain to obtain data on the extraction site and on the number of loads the ship brought in. Regularly, third parties reported that the total sailing time of certain extraction vessels was not sufficient to sail back and forth to the exploitation area. These infractions to the regulations could not be monitored, since Belgium did not dispose of coast guards.
As response to a lack of supervision from the authorities and a demand coming from the scientists charged with the monitoring of the environment in the extraction zones, an automated registration system was developed. The system was based on the registration system of MUMM (Management Unit of the North Sea Mathematical Models), that had been used to monitor the dumping of industrial waste at sea. In collaboration with MUMM and a specialised company, a new system was developed for the specific usage on dredging vessels and DGPS positioning was incorporated.
In 1995, after intensive testing, the technical requirements of the black box were incorporated to several concession decrees, but technical difficulties in the development of software and in the installation on board the dredgers delayed its application to the second half of 1996.
To prevent tempering with the system, the responsible administrations opted for a sealed system. This seal may only be broken by personnel of MUMM, who by order of the Fund of Sand Extraction collects the stored data and carry out (or supervises) the necessary repairs.
The black box registers following data:Parameters to be entered by the ships crew:
- Identification of the concessionary;
- Classification number of the journey.
- Identification of the exploitation vessel;
- Date of recording;
- Hour (GMT) of recording;
- Position of the vessel;
- Speed of the vessel;
- Data about the dredging pumps (on/off);
- Status of the exploitation (yes/no).
- 1 hour, when the exploitation vessel has not been sailing during at least 15 minutes and the dredging pumps are not functioning;
- 15 minutes, when the exploitation vessel is sailing and the dredging pump is not functioning;
- At least once every 60 seconds, depending on the recording space of the time applied by the Fund for Sand Extraction, when the dredging pump is functioning.
Figure showing the processed black box data of a dredging vessel.
green = pumps not active, red = pumps active (other parameters can also be colour coded)
The collected data are retrieved and processed by the MUMM, who reports it to the Fund for Sand Extraction. If infractions are noted, an explanation will be requested by the Fund for Sand Extraction. After an initial phase, where some errors in the system were detected, recordings a very small number of minor violations, which generally can be explained.
Follow up of the exploitations
From the beginning of the exploitations in 1979, the licensees paid a fee to the Department of Sea Fisheries of the Ministry of Agriculture, to the Management Unit of the North Sea Mathematical Models of the Ministry of Environment (transferred in 1997 to the Royal Institute for Natural Sciences of Belgium) and to the Fund for Sand Extraction (FSE) of the Ministry of Economic Affairs.
These departments were respectively charged with the study of the influences of the extraction of marine on the total fish stock, on the marine environment and on the sedimentology and geomorphology of the extraction zones. In 1993 a joint report was published in the Belgian annals of Mines, of which some copies (in Dutch or French) can be obtained at the FSE.
In 1998 the FSE started a multidisciplinary project. The aim of this project is to obtain a better knowledge of the impact of sand extraction on the geomorphology and sedimentology of sandbanks, on the physical and chemical stresses sand extraction is putting on the macrobenthic organisms and on the possible remobilization of heavy metals during sand extraction. To bring this project to a good end 2 geologists, a geographer, a biologist, a chemist and an administrative staff member were hired and collaboration with the Geological Survey of Belgium, the Research Unit for Marine and Coastal Geomorphology of the "Universiteit Gent", the Laboratory of Marine Biology of the "Université de Mons-Hainaut" and the Laboratory of Analytical and Environmental Chemistry of the "Vrije Universiteit Brussel" was established. To unable the scientists to collect enough data, some 15% of BELGICA's* total available time has been appointed to the FSE.
Up to now bathymetric recordings have been made with single beam sounding systems. However, recent developments in the field of multibeam echosounder systems and data treatment, convinced the Ministry of Economic affairs to make the acquisition of such a system. In 1999 a Simrad 1002S multibeam echosounder was installed on board the BELGICA. In areas effectively used for sand exploitation, the multibeam allows the geo-scientists to make more accurate measurements, hereby making it possible to assess more objectively the influence of the exploration.
Aside of making bathymetric, geomorphologic, sedimentologic and depth difference maps, attention is given to the relation between geological, biological and chemical elements of the marine environment.
The results obtained during this and subsequent projects will unable the newly formed consultative commission (see legislation) to propose measures for the sustainable development for the Belgian Territorial Sea and the Continental Shelf.
Contact:Ministry of Economic Affairs
Administration Quality and Safety
Fund for Sand Extraction
To Mr. B. Gonsette
North Gate III
Koning Albert II-laan, 16
* BELGICA: oceanographic research vessel belonging to the Belgian Federal Office for Scientific, Technical and Cultural Affairs and managed by the Management Unit of the Mathematical Model of the North Sea.
Projects in Preparation
At the request of the Ministry of Economic Affairs field recordings are being made in the context of the geomorphological and sedimentological research into the influence of sand exploitation on the stability of the seabed . Since 1984 the oceanographic research vessel BELGICA has been used intensively for that purpose. Some 10 % of BELGICA's total available time is devoted to the sedimentological research into sand exploitation areas.
Up to now bathymetric recordings have used the classic single beam sounding system, already installed aboard when the BELGICA was built in 1984. However, recent developments in the field of multi beam echo sounder systems coupled with signal treatment techniques are much more efficient and productive than the aforementioned single beam appliances. With these multi beam systems, also called padloders, bathymetric recordings can be made much faster and with the same covering degree of recorded area. Recording times can be reduced by a factor from 8 to 10, i.e. a considerable economy in the operation time of the research vessel. The time thus saved can be used for other recordings, so that the study can be extended.
In areas effectively used for sand exploitation a more detailed recording can be made and used to assess more objectively the influence of exploitation and to draw up detailed exploitation charts:
- by improving the recording data a reliable digital field model can be drawn up, thanks to which cross sections of banks can be determined in a flexible way. These cross sections are necessary for the calculation of bank volumes, the drawing of isolines and the development of three-dimensional plots;
- it is also possible to make very precise charts, which enable us to impose exploitation charts in the licence area and to control effectively the imposed exploitation conditions;
- through a better knowledge of the banks and with the use of digital field models it will be possible to carry out quantitative morphological monitoring, so that the final purpose, i.e. the management of sand banks and the protection of the marine environment, can be achieved.
To achieve this important goal much research and study has still to be made though. Consequently the research that the University of Gent has been making has to be completed.
In connection with the research made by the University of Gent three parallel studies are planned in the next few years in coordination with the aforementioned commission for sand extractions. The Université de Mons-Hainaut, the Vrije Universiteit Brussel and the Belgian geological service will carry out these studies. They should lead to a better view of the influence of sand extraction on the ecosystem through a better knowledge of residual streams, the variations of the salinity, the population spreading, water quality and the composition of sediments.
Knowledge is necessary because coastal zones are no static system. They are subject to a continuous evolution under the influence of natural forces such as tidal effects, wind, changes due to seasons such as the temperature and light and dark hours, and human activities such as dredging, hydraulic works and pollution.
These three laboratories have a great and long experience in the marine research field, more precisely in the domain of sediment behaviour (movement) and sediment changes (compound), as well as in the relation between the sediment biotope and the sediment composition and structure. Sediments are no dead system, they contain more or less organic matters and pores, where countless biochemical processes take place. Each element in itself, the assembly of different elements and their mutual relations exert an influence on the sediment.
Each of the laboratories has an experience in one or more of the following research domains: geology, hydrogeochemistry, and biogeochemistry. Together they cover the global research themes. Through the cooperation of these three laboratories, there will be a better notion of the impact of sand and gravel dredging on the sand movement, the changes in the sediment composition and structure and the influence on the ecosystem.
For further details on the studies in hand, would you please refer to the promoters, namely Professor R. Paepe of the Belgian Geological Service, Professor M. Jangoux of the laboratory for marine biology of the Université Mons-Hainaut and Professors W. Baeyens and L. Goeyens of the laboratory for analytical chemistry of the Vrije Universiteit Brussel.
Extraction of Sand and Gravel on the Continental Shelf of Denmark
National Policy on supply of sand and gravel
The Raw Materials Act
The exploitation of raw materials on land and on the seabed is regulated in the Raw Materials Act of 30 June 1997. The Act does not apply to oil and gas.
The purpose of the Act is to ensure that exploitation of raw material deposits is based on the principles of sustainable development. The supply of raw materials to the society shall be ensured in the long term, and the raw materials is to be used according to their quality. Furthermore waste products shall be used to the greatest possible extend as a substitution for natural materials.
Important factors to consider in the administration of the Act are on the one hand the quantity and quality of the resources and ensuring sound exploitation of raw material resources, as well as commercial considerations. On the other hand, the administration shall safeguard nature conservation and the environmental, cultural, and social aspects as well as commercial interests of other sectors.
Exploitation of raw materials on land
The exploitation of raw materials on land is administrated by the regional authorities, the 14 County Councils. Any extraction of raw materials on land for commercial purposes requires a permission from the County Council. Normally a permission can be granted for a period of up to 10 years.
The regional administration of raw materials on land is based on guidelines laid down in the region plans according to the Planning Act after an evaluation of the raw materials deposits and environmental aspects and other interests areas. Areas where exploitation is preferably meant to take place, are designated in the regional plans. The regional plans are revised every 4th year.
Exploitation of raw materials from the seabed
The Ministry of Environment and Energy, the National Forest and Nature Agency is responsible for the administration of marine raw materials, sand, gravel and stone both in the Territorial Waters and on the Continental Shelf.
Exploration and exploitation of raw materials on the sea bed requires a permission and may take place only in delimited areas which have been subject to an environmental assessment. Also beneficial use of dredged materials is included in the regulation. Permissions can be granted for a period of up to 10 years.
Application for exploitation, which can be assumed to have a significant impact on the environment is subjected to a special EIA-procedure in accordance with the EEC- Directive 85/337 as amended by Directive 97/11 during which the general public, public authorities and organizations have the opportunity to state their opinion (Ministerial Order nr. 126 of 4. March 1999).
This EEA-procedure does always apply to dredging of more than 1 million m³ a year or a total of more than 5 million m³.
In general permissions will not be granted in International Nature Protection Areas and in areas with a water depth of less than 6 m.
Dredging vessels working in Danish Waters must have an authorization from the Ministry of Environment and Energy. The total tonnage is limited to 25.000 m³. Authorization may be granted on special conditions, for a limited period of time and for utilisation for a specific task.
Raw materials shall be used in agreement with their quality, i.e. materials of high quality shall not be used where low grade materials are available. To ensure this, the Minister of Environment and Energy can make regulations on quantity and quality of materials used for special purposes and that waste products, substitute products and reused materials shall be used in building and construction works.
In order to reduce the use of natural resources and encourage reuse, a tax of Dkr. 5/m³ is imposed on natural raw materials. Waste products, substitute products and reused materials are exempted from taxation.
Materials from capital and maintenance dredging shall be reused to the greatest possible extent in order to minimize the use of natural resources and to reduce the environmental impact from disposal of the materials. To encourage reuse, dredged materials are also exempted from taxation.
Demand and supply of dredged materials in Denmark
In Denmark 10 - 15 % of the total production of sand and gravel comes from the sea. Over the last 20 years an average of 5 mio. m³ has been dredged from the sea every year. The variations in the amount over the years is mainly caused by demand for large quantities of sand fill for land reclamation in connection with harbour constructions and infrastructure projects such as the fixed links across Storebælt and between Denmark and Sweden.
In the same period, there has been a substantial increase in the demand for sand for beach nourishment from 40.000 m³ in 1980 to 3 mio. m³ in 1997 mainly on the west coast of Jutland.
No detailed forecast for the future extraction has been prepared. In general, it can be noted that the extraction varies in line with the development of the national economy. It is therefore expected, that the total marine extraction will remain on the current level in the next 5 years, perhaps with a slight decrease in the dredging of coarse aggregates due to an expected weak decline in construction industry.
In Århus Bugt 5 mio. m³ of sand fill will be dredged during 1999 and 2000 for the enlargement of the port of Århus. On Zealand a new container terminal is being planned which will require dredging of up to 5 mio. m³ sand fill. However, the initiation of the project has not been decided yet. Creation of a new recreational area including an artificial beach on the island of Amager just outside Copenhagen is in a preliminary planning stage. Feasibility studies are currently being conducted for a fixed link between Denmark and Germany but a decision whether to built the link or not will not be made within the next 1 - 2 years.
It is expected that the dredging of sand for beach nourishment on the west coast of Jutland will remain on the current level in the next few years. A growing interest in soft protection of the coasts in the Inner Danish Waters may in the future increase the demand.
Expiration of a number of licences on land and increasing environmental conflicts may, in some parts of the country increase exploitation of marine sand and gravel at the expense of land materials.
Marine aggregates in Denmark is dredged from appr. 150 areas in the Inner Danish Waters in the Baltic and the North Sea. The total area where dredging is allowed is 1000 km².
Approximately half of the dredging areas are only used periodically for minor quantities to the local markets. Only in 10 areas quantities of more than 100.000 m³ were dredged during 1997. Of these, 6 areas in the North Sea were used for beach nourishment. More than 50 % of the coarse aggregates was dredged in only 2 areas situated in in the North Sea and in in the Baltic.
On an average, 50 % of the dredged aggregates is used for construction and the rest is used as sand fill and for beach nourishment. Most of the material for construction is landed in ports near larger towns and used here and in the local hinterland. Only minor quantities are transported over considerable distances on land. 40 % of of the coarse aggregates is exported.
Aggregate Extraction Activities
The extraction of marine sand and gravel represent 10-13 % of the total production of materials for construction and reclamation. The dredging of sand fill for land reclamation has increased markedly over the last 10 years caused by several large construction works in coastal areas.
From 1989 to 1993 more than 9x106.m3 of sand fill and till have been dredged for the construction of the Great Belt bridge and tunnel project.
During the construction of the fixed link between Denmark and Sweden 1.3x106.m3 has been dredged with a spill of only 2.8 %. In the same period 7x106.m3 dredged materials of glacial till and limestone has been reused for reclamation and as hydraulic fill in ramps for the bridge and tunnel.
A major enlargement of the harbour of Århus is expected to require more than 5x106.m3 of sand fill in the next two years. The construction works started in the autumn of 1998. Until now 1.3x106.m3 has been dredged from 2 areas in Århus Bight. The spill from the dredging operations has been 3.7 %.
The consumption of sand for beach replenishment at the west coast of Jytland has shown a pronounced increase from 40,000 m³ in 1980 to more than 3.5x106.m3 in 1998.
0-2 mm m3
0-20 mm m3
6-300 mm m3
|Sand fill m3||Misc.|
* The figures from 1998 are preliminary.
No detailed forecast for the future extraction has been prepared. In general, it can be noted that the extraction varies in line with the development of the national economy. It is therefore expected, that the total marine extraction will remain at the current level for the next 5 years, perhaps with a slight decrease in the dredging of coarse aggregates due to an expected slight decline in construction industry.
In 1996 the National Forest and Nature Agency commissioned the Geological Survey to accomplish an evaluation of the total reserve volume of sand and gravel in Danish Waters based on all existing data collected since 1979. The results are now available (in Danish). A total of 4,500x106.m3 has been identified so far of which 3,500x106.m3 should be available for dredging. Most of the materials are sand for fill and construction, with only limited resources of coarse aggregates are available.
The calculation of the reserve volume is based on known technical limitations (i.e. overburden) and present environmental restrictions. All identified resources in the Inner Danish Waters have been evaluated. The present knowledge of the resources and the environmental conditions in the North Sea and the Baltic is very incomplete. However, it is expected that there are large resources in unmapped areas.
|TRUE||Coarse Sand||Gravel||Sand fill||Sum||Misc.||Total|
|Sand fill for
Environmental Impact Assessment
Nearly all the dredging works are finished. Only dredging of minor high spot areas in the shipping lanes is still going on. By the end of 1998 the total amount of 14.2 x106.m3 had been dredged with an average over-spill discharge of suspended sediment in the order of 4.1 %.
Until now only minor effects have been demonstrated. The effects are in accordance with the forecasts and within the accepted limits.
A detailed resource assessment and an environmental impact assessment of dredging of sand fill has been carried out on Kriegers Flak in the Baltic by the Øresund Consortium. The assessment has been prepared in accordance with the EC Directive 85/337. Preliminary results indicate, in accordance with the EIA, that there is no environmental impact outside 1000 m from the dredging area.
The Harbour of Århus
A major enlargement of the harbour of Århus requires dredging of more than 5 x106.m3 of sand. Based on prospecting carried out by the Harbour authorities two areas in Århus Bight were selected for dredging. Due to the size of the project the Harbour was requested to carry out an environmental impact assessment in accordance with the EC Directive 85/337 as part of the application procedure. Based on the assessments spill limits were set to 6 % and 7 % respectively. The spill was measured every 10th cargo and a wider monitoring programme was established to document the environmental impact remained within the limits stated in the license condition.
Investigations of the potential impact on bottom fauna and birds is being carried out off Limfjorden prior to commencement of dredging of sand to be used in the construction industry (cement production).
In order to ensure a sustainable extraction of raw materials the National Forest and Nature Agency has initiated a 3 year research project on environmental economics. A study of the energy consumption and emissions from dredging and transport of marine and land based resources will be finished before May 1999.
Later 1999 the Agency will launch a scoping study on the environmental, social and economical aspects of dredging on land and at sea. Based on the findings of this project key aspects will be selected for further studies.
In 1994 The Forest and Nature Agency initiated a 3 research project to investigate the consequences of marine dredging in co-operation with the Geological Survey of Denmark and the National Environmental Research Institute. The project is still running. One of the aims of the project is to establish a decision framework (computer aided Expert System) to evaluate the environmental consequences of existing and future dredging projects based on content of fines in the resource, hydrography, spreading of fines and ecological models.
A detailed study of the ecological consequences of dredging in coarse sediments was started in may 1996. Especially the effects on the benthic flora and fauna on surrounding stone reefs will be evaluated.
The Forest and Nature Agency and the Coastal Protection Agency have initiated monitoring program off the west coast of Jutland to study the effects of dredging of sand for beach protection.
The study is based on a comparison with simultaneous changes in a reference area. The post-nourish temporal development is analysed using the BACI concept (Before/After Comparison Impact). A complete quantitative recovery including the number of species, the abundance and the biomass of the bottom has occurred in less than one year after the sand extraction. However, the predominance of a supposed opportunistic species of polychaete (Spio filicornis) in the borrow area may indicate partially disturbed habitat.
Measurements of Spill from Dredgers on Kriegers Flak
Extensive spill measurements have been carried out during dredging of more than 1 x106.m3 of sand fill for the Øresund Link project.
In the dredging license issued by the National Forest and Nature Agency a condition is stated, that the spill for any cargo must not exceed 5%. For every 10th cargo of dredge material, the outwash (overspill) is measured for suspended solids.
Spill measurements are carried out by taking water samples from the overflow every 10 minutes during dredging. An estimate of the water pumped in conjunction with the concentration of fines enables the quantity of suspended sediment being discharged per cargo to be estimated.
As shown in the figure below.
It is evident from the above figure that there are large variations in the performance of the different dredgers. Dredger 1 and 2 show high spill percentages and large variations between the individual measurements. These dredgers were not allowed to continue after the test period.
Dredgers 3 and 4 were able to remain within the spill limit of 5 %. It can be seen in the figure below that Dredger 3 has a very low spill with minor variations between individual measurements. The slight increase in the overspill suspended solids over time (dredger 3; figure above) is most likely due to an increase in the turbidity of the water at the drag head due to continuous dredging.
It can be concluded that large differences in the spill exist between individual dredgers. Although there are minor variations in the sediment composition in different parts of the dredging area, it is the design of the dredger which has the over-riding influence on the concentration of suspended sediments discharged.
A 'key' difference noted between the design of the dredgers was that the dredgers with large hoppers and with central spillways (i.e. designed for dredging muddy sediments) performed much better than dredgers specifically designed for the extraction of coarse sediment.
Administration, Legislation and Licensing
The Forest and Nature Agency is, according to the Raw Materials Act, responsible for the administration of marine aggregate extraction in territorial waters and on the continental shelf.
A new Raw Materials Act entered into force on 1 January 1999 (Consolidated Act No. 569 of June 30, 1997). From this date all dredging activities will take place in permitted areas. A 10 year transitional period is allowed for dredging in existing areas.
New dredging areas are subject to a Government View procedure including public and private involvement. The applicant is requested to provide sufficient documentation about volume and quality of the resources in the area and to carry out an environmental impact assessment Ministerial Order No. 1167 of 16. December 1996). Permits will be granted for a period of up to 10 years.
Extraction activities which can be assumed to have a significant impact on the environment may be granted licenses only on the basis of an assessment of the environmental consequences in accordance with the EC-directive 85/337. The procedure is laid down in Ministerial Order No. 126 of 4. March 1999. Dredging of more than 1 x 106.m3 for a specific project or in a single area will always be subjected to this procedure.
Besides permits for dredging in specific areas dredgers must have an authorisation to dredge in Danish Waters. In order to maintain a sustainable and environmentally justifiable dredging activity the total tonnage of the dredging fleet will be held at the present level.
The National Forest and Nature Agency is responsible for the mapping of sand and gravel in Danish Waters. Since 1990 the Geological Survey of Denmark and Greenland (GEUS) has carried out the mapping projects.
Extraction of Sand and Gravel on the Continental Shelf of France
Aggregate Extraction Activities
Marine aggregate extraction has been stable over recent years with an annual production of around 3.5 x 106 tonnes.
Administration, Legislation and Licensing
Marine aggregate extraction legislation is presently under revision by the Ministry of Industry which is responsible for legal procedures. Because of the reduction of terrestrial reserves, extraction of marine sediments is an important alternative source. However, the present legislation is not compatible with marine applications and its revision requires further technical and scientific knowledge of the marine ecosystem and of the impact of this activity. A review of the existing international studies on the impact of extraction of marine aggregates on this ecosystem is in progress. This will enable the government to set clear objectives for the management and regulation of this activity, so that the interests of other users of the sea are properly protected.
Five main topics have been identified in this study, namely:
- existing knowledge on littoral sediments, associated macrofauna and fishing interests within the potential extraction areas, to identify sensitive areas.
- the physical and biological impact of dredging activity in various sediment types.
- rehabilitation processes associated with different extraction techniques, local hydrodynamics and sediment types.
- relationships between benthic macrofauna and fish to predict impacts on fish.
- identifying compensating measures and/or rehabilitation of dredging sites.
Environmental Impact Assessment
Compilation of the data contributed to the group over the last few years resulted in a review paper being presented at the annual ICES conference held late October 1998 in Crete, entitled "physical and biological impact of marine aggregate extraction along the French coast of the eastern English Channel; short and long-term post-dredging restoration".
Extraction of Sand and Gravel on the Continental Shelf of Germany
Aggregate Extraction Activities
The greatest amount of sediment extraction is derived from maintenance dredging within estuaries and supporting waterways accounting for between 45 and 55 million tonnes per annum. The extraction of sand for beach nourishment purposes is also undertaken and the total amount of marine aggregate (sand) dredged in 1998 was 11.6 x 106.m3. This figure is broken down as follows:
|Area off Sylt||0.7x106m3|
The situation in Schleswig-Holstein is as previously reported: i.e. no extraction of marine sediments has taken place or is currently planned. In the near future a map will be published by the Federal Agency for Nature Conservation (BfN) on the coastal shelf of Mecklenburg-Vorpommern showing all actual extraction areas. There are 20 extraction sites licensed for coastal defence purposes (Richtlinie marine Sandgewinnung für den Küstenschutz - RL-MSK). These sites are not permanently exploited but are only periodically used for coastal defence projects in the respective regions. A total of 14 extraction sites are licensed for commercial use (concrete, filling material, road construction etc.). The total amount of material extracted in 1998 is not available at present, however, the amount extracted in 1997 was 2.269 x 106.m3
Administration, Legislation and Licensing
On 23 March 1998 the Helsinki Commission adopted the HELCOM Recommendation 19/1 "Marine Sediment Extraction in the Baltic Sea". The recommendation is based on the information on the effects of sand and gravel extraction collected by ICES and takes into account the specific ecological qualities of the Baltic Sea. In addition to the current ICES reports on the topic the value of sensitive areas is emphasised. Two categories are distinguished:
- Areas in which no permits shall be granted, namely;
- Nature reserves
- National parks
- Natura 2000 and EU Bird Sanctuaries
- Areas in which permits shall only be granted if a thorough EIA has established that extraction is not likely to cause significant adverse ecological effects on
- Baltic Sea Protected Areas (BSPA) according to HELCOM Recommendation 15/5
- Ramsar sites
- Areas inhabited by communities of long-living threatened invertebrate species (e.g. the bivalves Arctica islandica, Astarte spp., Macoma calcarea)
- Important fish spawning areas
- Important feeding grounds for migrating or wintering waterfowl within resting and wintering areas of international importance
- Large areas densely covered with macrophytes (especially such as Fucus, Zostera, Furcellaria)
- Submarine boulder fields on lag deposits where they represent a rare or particularly ecologically important habitat type
- Areas of permanent upwelling cold water which provides habitat niches for specialised benthic species
- Submarine sills with significance for water exchange
- Marine areas near to the coast with significance for coastal sediment transport or with protective function for the coastline ( e.g. sand banks, spits and bars).
Environmental Impact Assessment
A 3-year research project was initiated in March 1999 by the Federal Maritime and Hydrographic Agency (BSH). The study will focus on refilling processes of extraction pits and furrows off the islands of Ruegen (Baltic) and Sylt (North Sea) with respect to changes in sediment composition and distribution, seabed morphology as well as possible lowering of the seabed and effects for coastal stability.
Two sites will be investigated near the island of Ruegen where gravelly sands are extracted for industrial use. As gravel is of interest the sandy sediment fraction is put back to the sea by overspill. The sediment is extracted in shallow waters (max. 10 m water depth) and deep pits (6 m below the seabed) are produced. Sand ripples are observed in the extraction site which are assumed to result form the sandy overspill. Sand-grade sediment is extracted for beach nourishment in water depths of 10 to 20 m where extraction furrows are produced. The sedimentological survey will be combined with wave and current measurements for a range of dredge pits to determine at what depth pits can dredged without causing long-term impacts on the environment.
In the North Sea an extraction pit (up to 6 m below seabed in a water depth of 14 m) off the island of Sylt is eroding (in-filling) much more slowly than expected. The material deposited within the pit mainly consists of fine-grained sediment with high organic content giving rise to anoxic conditions. Another study site is located in a tidal inlet of the North Frisian Wadden Sea and has been once used for coastal defence. The extraction pit remained stable over several years (1994-98) despite strong tidal currents. At both study sites bathymetric, seismic and sedimentological surveys should give insight into sedimentation rates as well as into the major sediment transport pathways which are responsible for the refilling. Possible lowering of the surrounding seabed is of special interest in the case of the extraction offshore of Sylt.
The field investigation phase of a research project conducted by the Federal Agency for Nature Conservation (BfN) and the University of Rostock and jointly funded by the Federal Foundation for the Environment (DBU) and BfN has been completed. Presently the results have not been fully analysed, but the following preliminary conclusions can be drawn and will be published within the next month (BfN- Skripten Reihe).
The analysis is based on a case study monitoring the physical and biological changes of the water column and the sediment at an extraction area close to the Darß-Zingst peninsula in the Southern Baltic Sea. A total of 320,261 m³ of sand was extracted in November 1997 for coastal defence purposes.
The effects of extraction were very severe but localised and were found to have a short-lived impact on the macro benthic populations within the area. In the dredged area, the populations were reduced in abundance, diversity and biomass but the area was not totally devastated.
The morphological and topographical changes in the area have been severe. Prior to extraction, the area consisted of a gently sloping sand bank, with medium sand, low in organic content. As a result of dredging, the area was deepened up to a depth of 6m, and within this area, dredged furrows were found to have retained drifting algae and fine organically rich sediments. The sediments observed in the ridges were found to be composed of fine sands.
The following summer these changes led to localised oxygen depletion in the deeper parts of the extraction area and especially in the dredged furrows. To date, a comparable phenomena has not been described for these flat and dynamic coastal regions. As a consequence of the oxygen depletion, there was a second die off of the macrobenthic community and there was a cessation of the recolonisation process. Oxic conditions were re-established in autumn after storm activity which allowed recolonisation of the macro invertebrate communities to continue.
The study also examined the effects of disturbance (change in grain size, sulphur concentration, oxygen depletion and organic content) on several "sensitive" macrobenthic species found in the red data lists. Preliminary data indicates that none of the three red list invertebrates (Travisia forbesii, Cerastoderma lamarckii, Bathyporeia elegans) sampled in the area prior to dredging have recolonised the area.
A literature review is underway on the physical effects of dredging and disposal in marine areas. A total of 720 papers have been collected, but at present only 350 have been reviewed. During the last 50 years there has been a dramatic increase in the number of reported studies eg. between 1950 and 1970 there were less than 1 % of the papers identified in the review where as between 1970 and 1990 there were 54 %.
A preliminary assessment of the literature (350 papers) indicates that suspended sediment concentrations and the overburden of sediment on the bed are among the major factors impacting the benthos.
Investigations are planned to measure the effects of turbidity on the behaviour of the common mussel (Mytilus edulis). Both laboratory base experiments and field surveys will be undertaken with the aim of understanding how suspended solids effects behaviour of the mussels in relation to different factors. In the laboratory the behaviour will be studied by examining the bivalve gape using electrical contacts that register if a single mussel is opened or closed. The registration of 42 individuals in parallel will provide the possibility, to secure the results by statistical analysis. This study is planned to start in 1999 and will last 3 years.
Extraction of Sand and Gravel on the Continental Shelf of The Netherlands
Aggregate Extraction Activities
Sand Extraction 1998
The amount of sand extracted from the Dutch sector of the North Sea in 1998 was as follows:
|Euro-/Maas access-channel to Rotterdam||4.7 x 106m3|
|IJ-access-channel to Amsterdam||6.3 x 106m3|
|Dutch Continental Shelf||10.5 x 106m3|
|Total sand extraction in 1998||21.5 x 106m3|
About 0.073 x 106 m3 has been dredged on the Danish shelf (SIRI field) for a gravity foundation and dumped on the Dutch shelf.
The main applications of the extracted sand are for the beach nourishment programme and for land uses. In 1998 approximately 7.4 x 106m3 was used for beach nourishment and approximately 14.1 x 106 m3 was used mainly for land fill with a small part of this quantity used for the construction industry in Belgium and South-Western part of the Netherlands.
Gravel Extraction 1998
In 1998 no extraction of gravel took place in the Dutch part of the North Sea. Due to the Dutch policy on the extraction of surface minerals as written down in the Structure Plan for Surface Minerals, extraction on the Claever Bank will not be permitted before the termination of gravel extraction carried out in conjunction with the lowering of the winter bed of the River Maas. This policy is influenced by a major Delta plan project planned for the south-east of the Netherlands (Limburg). The effects of this plan will lead to a production of relatively high quantities of gravel over a relatively short period of time due to be completed by 2005. The total available quantities will increase from 35 to 60 million tonnes due to these works.
Shell Extraction 1998
On basis of the National Policy plan and EIA for shell extraction (December 1998) there are maximum permissible amounts defined from 1999 onwards.
The total amount (in m³) of shell extracted from the Wadden Sea, North Sea and Internal Waters from 1992 up to 1998 was as follows:
Wadden Sea and sea-inlets of the North Sea (grey marked)
The south-west part (Zeeland)and the North Sea (grey marked)
Administration, Legislation and Licensing
Due to the new Extraction Law (01-01-1997) the applicant has to pay fees for the administrative costs of the licence procedure. One of the results of this procedure is that the applicants have applied for larger areas under the new scheme.
A new marine boundary has been established between Belgium and the Netherlands with the effect that two extraction areas now fall within the Belgium sea sector. Provision has therefore been made to ensure that they both come under Belgium regulatory procedures within 5 years.
There are fixed amounts for shell extraction in the Waddensea and sea inlets, western Schedlt and Voordelta. By contrast, all other parts of the Dutch sea sector, out to a limit of 50 km, have no fixed limits for quantities of extraction of shell. However, it is understood that in these areas the quantities of shell are naturally much reduced compared to the sites mentioned above.
In June 1997 the Rijkswaterstaat, directorate South-Holland, together with the Rotterdam Municipal Port Management applied for a licence for the extraction of 30 x 106.m3 sand out of 6 borrow pits which will be refilled with relative clean (LC-DMAF guidelines) dredged material coming out of the harbour of Rotterdam. To enlarge the knowledge of borrow pits the execution of the works will be accompanied by morphological and ecological monitoring. Each borrow pit will have a maximum size of 5 x 106 m3. The maximum depth permitted will be 10 meters below seafloor. One pre-extraction survey and a single post extraction survey for a beach nourishment scheme have already been carried out.
Environmental Impact Assessment
Borrow Pits (Punaise Project)
During the fall and winter of 1996/97 a beach nourishment project was executed at the central Dutch coast near Heemskerk/Wijk aan Zee. For the nourishment a pin-point dredge technique was used. The borrow pit was located at a water depth of 7 m and reached a depth of 19 m below the sea floor. After the beach nourishment was completed the pit was filled with sand from deeper water. A morphological monitoring programme of the pit was carried out during the work (Rakhorst, 1997).
The pit was refilled with sand that was coarser than the original sand. Three months after the refill there was no difference in grain size in the upper 5 cm between the sand in the pit and in the reference area.
Before and after the nourishment an ecological monitoring programme of the benthic fauna was carried out. A survey in January 1997, two days after the refill of the pit, showed that the mollusc Spisula subtruncata survived dredging and became established within the pit. The recolonisation of the pit area, especially by the worm Phyllodoce mucosa, was rapid (Van Dalfsen and Storm, 1998a). After three months (May 1997) the biomass in the pit area was comparable to its status immediately following the refill, but a change in the contribution of the different species was noticeable. For example, the contribution by Spisula subtruncata had decreased, although the contribution by worms had increased. There was no recovery found of the molluscs and crustaceans (Van Dalfsen and Storm, 1998b).
A survey in April 1998 showed that 15 months after the refill of the pit the benthic community had for the most part recovered. However, there are still differences in composition and density of the community between the pit and the reference area. In particular, the recovery of amphipods had not occurred. In the pit Spisula subtruncata is still dominant. In the reference area a high density of worms and amphipods were noted. Compared to the period before the extraction the biodiversity at both the pit and the reference area showed reduced values (Van Dalfsen et al., 1999)
A final survey is planned for April 2000.
The final report of the MAST RIACON Project on the ecological effects of subaqueous sand extraction North of the Island of Terschelling has been completed (Essink, 1997; Van Dalfsen and Essink, 1997). The report describes the effects on the benthic fauna of a sand extraction (2.5 Mm3) carried out in 1993 (this paper was included in an Annex in the 1998 WG report). One pre-extraction survey and two post-extraction surveys were carried out. After one year, a change in benthic community structure was observed due to a reduction in long-living species and recolonisation by opportunistic species. After two years the original structure had largely been restored. Nevertheless, adult specimens of longer-living species are rare. The total biomass after two years is still less than that before extraction. Complete recovery is predicted to take a further few years.
To verify this prediction a new project RIACON2 is formulated. In the framework of this project a survey is carried out in September 1997, four years after the extraction.
From 1995 to 1997 no changes were found in total macrofauna abundance. This possibly indicates a stabilisation of the benthic community in terms of abundance. The community structure in the borrow area in 1997 had not returned to its initial structure and composition in 1993, i.e. prior to the extraction. The expected recovery in terms of abundance and population structure of long living species such as molluscs and sea urchins was not found ( Van Dalfsen, 1999).
Overall the surveys show that, although the original community structure had not been re-established, the effects of sand extraction which were still visible after two years, are no longer obvious after a period of 4 years. Natural fluctuations in the benthic community are most likely to explain this departure from the original structure. The changes in the benthic community at the borrow site show concurrence with patterns found in the entire coastal and offshore zone in the Netherlands.
A bathymetric survey of the site four years after the extraction shows that the sand pit, which has a depth of about two meters, has not been in-filled by natural processes. Nevertheless, bedforms seem to cross the area as they did before the extraction.
Large Scale Projects
Several plans for large land reclamation projects are being launched in the Netherlands. In 1997 the government decided to study the enlargement of the Rotterdam harbour area with 1000 ha industrial area and 750 ha nature area. This enlargement is located just off the coast of the present harbour area.
The amount of marine sand needed for this new harbour area will vary between 400 and 700 x 106 m3 depending on the chosen design. This amount is about 25 times the present yearly extraction of marine sands.
Studies are being undertaken to define the morphological and ecological effects of large scale extraction. The effects on the water movement, sand transport and morphology is defined by the location, orientation to the main currents and the design of the extraction area. The extraction depth appears to have a significant bearing on the magnitude of the effects (Hoogewoning, 1999). An overview of ecological effects of large scale sand extraction in this area is given by Van Dalfsen (1998) and Van den Berg (1999).
The behaviour of overflow during sand extraction and investigations into the possibilities of reducing the overflow are presented within the Project Environmental Sound Sand Extraction report (Badloo, 1999; Van der Salm, 1999).
Two other plans, which are much less certain, are the construction of an airport island and a land reclamation project to protect the coast between Hoek van Holland and Scheveningen. for these plans a sand supply of 800 x 106m3 and 400 x 106m3 will be required, respectively.Environmental report(s)
- Title: Long-term recovery of geomorphology and population development of large molluscs after gravel extraction at the KLaverbank (Nort Sea
- Year: 1993
- Source holder: Bureau Waardenburg bv
- Contact person: Dr. G.W.N.M. van Moorsel
- Author: Dr. G.W.N.M. van Moorsel
- Abstract: The report deals with the geomorphology and macrobenthic community of the Klaverbank, a gravel dominated area in the Dutch part of the North Sea, and evaluates the long term effects, two year after an experimental gravel extraction.
Extraction of Sand and Gravel on the Continental Shelf of Norway
Aggregate Extraction Activities
No sand and gravel extraction has taken place on the Norwegian shelf in 1999, which is similar to the latest 5 years.
Carbonate sand has been extracted along the Western coast, mainly in the counties Rogaland, Hordaland. There has been a decrease in volume, from on average 100 - 150 000 tons/year between 1990 to 1995, to 78 000 tons in 1996, 87 000 tons in 1997 and 52 000 tons in 1998 (STIL 1998).
Extraction of Sand and Gravel on the Continental Shelf of The United Kingdom
Administration, Legislation and Licensing
Regulation under the Government View Procedure
There has never been any statutory control of marine dredging in the UK apart from that exercised by Harbour Authorities within their specific areas of jurisdiction and by Coast Protection Authorities within 3 miles of the coast.
The only lawful control on dredging outside these areas has been exercised by a licensing system operated by the Crown Estate which owns nearly all the seabed within the UK 12 mile territorial limits and has ownership rights to all minerals within the rest of the UK share of the European Continental Shelf. Such licenses are issued on a commercial basis and do not take into account environmental criteria.
There are several areas of coastal waters off the UK which are either owned by Harbour Boards or are in individual private ownership. Any dredging within these areas is, therefore, a private matter between dredging operators and the individuals concerned.
A growing awareness of environmental issues led to the introduction of the 'Government View' (GV) procedure in 1968 whereby the Crown Estate would not issue a dredging license unless the Government expressed a favourable view on the environmental implications of the proposed dredging operation. The GV procedure is administered by the Department of the Environment, Transport, and the Regions in English waters and by the Scottish, Welsh and Northern Ireland Offices within their respective territorial waters.
The GV procedure involves wide consultation within Government; with specialist, independent consultees; with local authorities and the general public. If a dredging proposal poses any threat to the coastline, a favourable GV would not be issued. Furthermore, in considering applications for a GV, DETR maintains a presumption against dredging unless the environmental and coastal impact issues are satisfactorily resolved.
In 1989 the GV procedure was amended to reflect the requirements of EC Directive 85/337/EEC and to require Environmental Impact Assessment (EIA) to be undertaken for all applications for a GV. However, the procedure remains a purely informal process with no statutory backup but, nevertheless, Environment Statements have been submitted with every GV application since 1989 due to the co-operation and goodwill of the dredging industry.
The Environmental Impact Assessment and Habitats (Extraction of Minerals by Marine Dredging) Regulations 1999 will come into force within the UK and will transpose into UK legislation the requirements of not only EC Directives 85/337/EEC and 97/11/EC on (EIA) but also EC Directive 92/43/EEC on Habitats as well.
These Regulations will introduce the statutory control of marine dredging for the first time within the UK. They will require the submission of dredging applications to be determined on environmental criteria by the Secretary of State of the Environment, Transport and the Regions. Every dredging application will have to be accompanied by an Environmental Statement and the Secretary of State is required to assess the transfrontier implications of applications where necessary. The new Regulations also provide for public hearings into dredging applications and enable the Secretary of State to adequately monitor all permitted dredging and to enforce dredging control whenever necessary.
Visit the Crown Estate website for more information on the Government View Procedure.
Management by the Crown Estate
Since 1990 the Crown Estate has operated an ArcInfo Geographic Information System (GIS) as the primary source of data relating to the management of offshore marine aggregate extraction licences. The GIS essentially links graphical information on database tables and contains information on dredging licences, admiralty features, seabed geology, prospecting surveys and a wide range of other seabed uses and activities offshore. The UNIX system has been replaced with a PC based Windows NT platform which is considerably cheaper, quicker and easier to use and gives a better product.
The GIS is an essential, management tool which allows data to be accessed and manipulated to create reports, maps, statistics and charts.
Electronic Monitoring system (EMS)
In January 1993 the Crown Estate introduced an electronic monitoring system (EMS) which records the date, time and position of all dredge-like manoeuvres. All vessels dredging on Crown Estate licences must be fitted with the EMS which records time and status of the vessel at 30 minute intervals on standby and 30 second intervals if indicators show the vessel to be dredging. To ensure security information from the various sensors is encrypted on diskettes which are changed every month. The diskette are analysed by the Crown Estate within 20 working days of the month end.
During 1998 thirty eight vessels dredged on 77 licences. There was a total of 31,737 hours of dredging, a 12% decrease from 1997. On average 10,000km of dredge tracks have been recorded, analysed and stored each month, (a total of about 720,000km since 1993). A total of 58 min. 15 seconds (0.003% of total hours dredged) was confirmed as being out of area.
Visit the Crown Estate website for more information.
Environmental Impact Assessment
Regional Seabed Sediment Studies and Assessment of Marine Aggregate Dredging
(Brampton A H & Evans C D R (1998) CIRIA C505.
This report was produced as part of a CIRIA project looking at the character, origins, distribution and movements of seabed sediments, and the potential effects, particularly on the coastline, of dredging sand and gravel from the seabed. The research sought to provide a structured approach to regional studies of sediment mobility over the seabed which can be used in other parts of the UK, identifying the objectives, benefits, scope and methods that can be used. It also provided guidelines for studies needed to assess the impacts on the coastline of proposed dredging operations, with due regard to the requirements of local authorities and other organisations concerned with managing the coastline and the coastal zone.
A regional study of the seabed and its sediments was carried out for a specific area west of the Isle of Wight.
Seabed Sediment Mobility Study - West of the Isle of Wight (Brampton A H, Evans
C D R and Velegrakis A F) 1998 CIRIA project report 65.
This report describes an investigation of the sediments and their mobility over a large area of seabed west of the Isle of Wight. The results of such a study can help planners assess the possible environmental effects of proposed dredging of the seabed for sand and gravel. The study included investigations into:
- the solid geology and coastline of the study area, particularly the erosion of the solid strata and the production of sediments by this process;
- the origins of the existing sediments along the shorelines and on and under the seabed;
- the character and distribution of sediments across the study are, eg. the grain sizes, thickness of deposits, and surface features such as sand waves;
- indications of sediment transport derived from morphology changes, for example erosion of the coastline or changes in the volume of underwater banks of sediment;
- the hydrodynamics of the study are, principally waves and tide, and calculations of long-term transport rates and directions.
From this an explanatory model of the movements of the sediment over the seabed was produced, identifying the origins, direction of movement and destinations of the sand on the seabed in the area. In order to demonstrate one potential use of a regional seabed study, two hypothetical dredging areas were chosen and the potential effects on the coastline of the study area of extracting sand/gravel from them were studied.
Inshore Seabed Characterisation of Selected Sectors of the English Coast
The aim of this project was to provide a computerised overview of the geoscience within sectors of the English coast which would assist with offshore aggregate related planning issues. This was provided as a set of digital files using Microstation Review software. A separate report was provided to complement the data held on the digital files, and to provide a description of the geology of the designated sectors.
Bristol Channel Marine Aggregates Resources and Constraints
Marine aggregates dredged from the Bristol Channel are currently supplying a major proportion of the sand used in the construction industries of South Wales and South West England. The Bristol Channel is renowned for its strong currents and high tidal range and is an extremely complex hydrodynamic environment. As well as aggregate extraction, the area supports active fishing and tourist industries, a number of large ports, industrial centres, and a diverse range of cultural, historical and ecological environments.
Traditional aggregate resources both on land and sea are finite and as resources become exhausted or sterilised due to increasing constraints on the extraction, pressure to use those that remain increases. It is recognised that there is currently limited information available about the true extent and nature of the sand and gravel resources in the Bristol Channel and of the constraints on working them. The complex hydrodynamic nature of the channel make understanding the origins and interactions between different resource deposits and the potential effects of their extraction (i.e. both individual or cumulative) on the other resources/users and the environment within the Channel extremely difficult. The current research project being managed by Posford Duvivier and ABP Research and Consultancy Ltd, is a major initiative by the Welsh Office, the Department of Environment Transport and Regions (DETR) and the Crown Estate designed to overcome some of these uncertainties.
The principal objectives of the study are:
- to further develop our understanding of the sediment transport regime in the Bristol Channel, and the extent to which the sediment deposits are interlinked;
- to define the marine aggregates resources and to evaluate constraints on their extraction in the Bristol Channel; and
- to prepare a report on the above to assist those organisations involved in the Government View procedure (and any subsequent arrangements) in the evaluation of proposals for future dredging.
Work on the project started in September 1996 and was divided into three phases. Phase I involved the definition of the key issues to be addressed and the collection and review of existing data. This review of existing data formed the basis for a programme of primary research and modelling to be undertaken in the subsequent phase. In Phase II of the project, modelling and primary research was undertaken to define the overall sediment transport regime, the interaction between sediment cells and the extent and nature of the resource in the Bristol Channel. The results were analysed with reference to the data collected in Phase I to establish the marine resource and develop a methodology for examining the relationships and linkages between marine aggregate dredging and the physical, biological and cultural environment. The culmination of Phase III is a final report which is in the process of being prepared.