Offshore Overfalls MPA


Status: Marine Conservation Zone (MCZ)Farnes East MCZ Boundary


The Offshore Overfalls MCZ is a joint inshore and offshore site located in the eastern English Channel, approximately 18km south-east of the Isle of Wight. The seabed is predominantly coarse sediments with areas of sand, mixed sediments and exposed bedrock. Natural England is the statutory nature conservation body responsible for the site within 12nm.


The site protects 593km2 of seabed, including the English Channel outburst flood geomorphological features which are quaternary fluvio-glacial erosion features. The varieties of habitats found in the site support a diverse range of species. Sponges, hydroids and bryozoans cover the cobbles and boulders where crabs, sea stars and sea urchins abound. Burrowing worms live within the sediment alongside burrowing anemones and bivalves such as scallops


More detailed site information can be found on the Summary tab below

Map displaying the MPA boundary

View and download spatial data for this MPA

on the JNCC UK MPA interactive map.


Legislation behind the designation: Marine and Coastal Access Act (2009)


Protected Features:

EUNIS Code: Protected Features Feature Type General Management Approach
(to achieve conservation objective)
A5.1: Subtidal coarse sediment Broad-Scale Habitat 

Recover to Favourable Condition

A5.4: Subtidal mixed sediments Broad-Scale Habitat 

Recover to Favourable Condition

A5.2: Subtidal sand Broad-Scale Habitat 

Recover to Favourable Condition

English Channel outburst flood features (Quaternary fluvio-glacial erosion features) Geomorphological Feature Maintain in Favourable Condition


Conservation Objectives
The overarching conservation objectives for the designated features of all protected sites in UK offshore waters is to ensure they either remain in, or reach favourable condition. The ability of a designated feature to remain in, or reach favourable condition can be affected by its sensitivity to pressures associated with activities taking place within or in close proximity to a protected site.

Site Timeline

The diagram below is a summary of the key milestones involved in the selection and designation of Offshore Overfalls MCZ.  More detail can be found within the relevant documentation listed below.

Offshore Overfalls MCZ timeline

Relevant documentation

The documents referred to below and any other historical documents relating to Offshore Overfalls MCZ were produced during the selection and designation process and therefore may be out of date.  This Site Information Centre is the most up to date source of information for this MPA, and will reflect any additional information gathered since these documents were produced.

Further information about the Marine Conservation Zone site selection process and historic MCZ advice is available on the JNCC MCZ pages.


Information for this site summary was adapted from JNCC’s scientific advice to Defra on the designation of Offshore Overfalls MCZ and incorporates any further information gathered since this document was produced. Please refer to this document in the relevant documentation section for further details and information sources.

Site overview

The Offshore Overfalls MCZ is located in the Eastern English Channel approximately 18km south-east of the Isle of Wight and just north of the Offshore Brighton MCZ. It includes a mixture of sediment types which create a dynamic seabed environment and host a diverse ecosystem. The site depth ranges from 20m to 70m, the deeper areas coinciding with a valley system running through the site from the south to the north-east. This valley is part of the English Channel Outburst Flood Features (Quaternary fluvio-glacial erosion features) which are protected within the site for their importance to the study of geomorphology.

The English Channel Outburst Flood Features were formed during the Pleistocene Epoch more than 200,000 years ago when sea levels were much lower than they are today and the English Channel was not yet covered by seawater. A large glacial meltwater (freshwater) lake, in part of the area now occupied by the southern North Sea, burst its retaining bank to the south. This created a vast discharge of sediment and water that carved out large-scale longitudinal valleys, the outburst flood features, which were later submerged by seawater in the English Channel when sea levels rose again after the Ice Age. These erosional features have scientific value as they help us to understand the Ice Age history of the area, including sea level change, and how massive-scale flood features develop, which may provide important information about tsunami events. Within the Offshore Overfalls, MCZ these erosional features are evident as deeper valleys within the site which run along the south east corner.

Offshore Overfalls MCZ was originally recommended by the Balanced Seas Regional MCZ Project in 2011. The site was prioritised for additional evidence collection in a verification survey undertaken by JNCC and Cefas in 2012 to improve confidence in the presence and extent of broad-scale habitats and habitat features of conservation importance (FOCI).

The 2012 survey confirmed the presence of the broad-scale habitats (BSH) designated within this MCZ (subtidal coarse sediment, subtidal mixed sediments and subtidal sand sediment), along with moderate energy circalittoral rock which was recorded sporadically across the MCZ.

The BSH subtidal sand is located in two isolated patches that fringe the northern margin of the Northern Palaeovalley and associated with marine bedforms that form a collection of sediment ripples and waves. These marine bedforms are predominantly comprised of sandy sediment although some coarse or mixed sediments may be present in the troughs of the sediment waves. The BSH subtidal mixed sediments is confined to the northeast of the MCZ. Evidence from the 2012 survey shows bedrock structures visible at the seabed in this region, covered with a thin veneer of mixed sediments. Bedrock structures are sporadic along the south east of the site and in an area to the north-west known as the ‘Overfalls’ which is the namesake of Offshore Overfalls MCZ. Subtidal coarse sediment is predominant within the MCZ, covering almost three quarters of the site. It is located on the flanks and terraces of the Northern Palaeovalley and within the valley floor.

Offshore Overfalls MCZ was included in the proposed network because of its contribution to ENG criteria to broad-scale habitats (BSH), and its added ecological importance. The area is incredibly diverse with 278 infauna species and 45 epifauna species identified from the 2012 survey. This data was reviewed by Envision Mapping Ltd for JNCC in 2016 and statistically analysed to reveal the potential biotopes present within the site. The majority of stations (52 out of 59) were assigned to the biotope SS.SCS.CCS.MedLumVen (Mediomastus fragilis, Lumbrineris spp. and venerid bivalves in circalittoral coarse sand or gravel) EUNIS code A5.142. This biotope fits with the broad scale habitats designated within the site and was characterised by comparatively high numbers of the bristle worm Notomastus latericeus, along with the pea urchin (Echinocyamus pusillus).The full report of this analysis will be published shortly.

The infauna biological communities appear to be dominated by a diverse range of burrowing worms (polychaetes). Bivalves such as the Queen scallop (Aequipecten opercularis) occur in smaller numbers along with the Long-clawed porcelain crab (Pisidia longicornis) and the common brittlestar (Ophiothrix fragilis). The epifauna, living on top of the sediment, are dominated by hydroids and bryozonas and also include a range of sponges (Porifera), sea anemones (Actinaria) and sea stars such as the common starfish (Asterias rubens) and the Common Sun Star (Crossaster papposus). Various species of fish are also present including thornback ray (Raja clavata), red gurnard (Chelidonichthys cuculus), Small spotted catshark (Scyliorhinus canicula), and Bib (Trisopterus luscus).

Further detail on the evidence for this MCZ/can be found on the Evidence tab.

Site location:  Coordinates for this MCZ can be found in the Designation Order listed in the Relevant Documentation.

Site area:  593km2, which is similar to the size of the New Forest National Park (566km2).

Site depth range:  20m to 70m. The seabed depth drops significantly in the middle of the site where it overlaps with the northern Paleovalley.

Charting Progress 2 biogeographic region - Eastern Channel

Site boundary description
The northwest corner and limit of the northern boundary of the site are concurrent with the original boundaries proposed by the Balanced Seas Regional Group. The boundaries around the larger offshore part of the MCZ were set to include an area of higher biodiversity and are determined by geographical coordinates alone.



Site specific data
There are a range of data that underpin this MCZ. The full overview of the data used to support site identification, along with information on confidence in feature presence and extent are available in the  Scientific advice on possible offshore Marine Conservation Zones considered for consultation in 2015 and the Scientific advice on offshore Marine Conservation Zones proposed for designation in 2015/16.  JNCC will be adding relevant survey data for this MPA to our MPA interactive map in due course.

Data for this MCZ have been collected primarily through JNCC funded or collaborative surveys and some through other data sourcing.  Data gathered provide direct evidence confirming the presence of the protected features within the site.


Survey and data gathering

  • Offshore Overfalls MCZ MB0120 Survey - 2012
    JNCC collaborated with Cefas on an MCZ site verification survey to Offshore Overfalls MCZ, funded through the MB0120 Defra data collection. Video, images, acoustic data and grab samples were collected across the site.


Data analysis reports
Analyses of data gathered as part of the surveys listed above, as well as other relevant data analysis products, are available via the following reports:

  • British Geological Survey Particle Size Analysis (PSA) Data Points
    Particle Size Analysis of historical British Geological Survey data was collated and used to identify habitat type within the MCZ. PSA  was used to provide habitat type in Modified Folk classification. This has been converted by JNCC to the EUNIS habitat using JNCC's 'Correlation Table showing Relationships between Marine Habitat Classifications (2004 and 2007 versions) and Habitats Listed for Protection' .
  • Marine ALSF Regional Environmental Characterisation Surveys (RECs) South Coast Synthesis (Surveys conducted 2007)
    The South Coast Synthesis Study combines the Eastern English Channel REC habitat map with the South Coast REC habitat map and synthesises the gaps to create coverage across the English Channel. The study proposed some alternative habitat types that are not part of the EUNIS habitats classification system and JNCC translated these into the closest official EUNIS habitat types.
  • MB0102 Task 2A Erosional Fluvio-glacial Features [2009]-
    Habitat map providing a shape file of the English Channel Outburst Flood Feature (Quaternary fluvio-glacial flood features) taken from Gupta et al. 2007.
  • EUSeaMap - Last updated in 2014
    Supporting information on the presence and extent of the Subtidal sands and Subtidal mixed sediments was provided from EUSeaMap, a predictive seabed habitat mapping report for European waters.
  • Offshore Overfalls rMCZ Post-survey Site Report [unpublished]-
    Report detailing the findings of a dedicated seabed survey at Offshore Overfalls MCZ, providing evidence of the presence and extent of broad-scale habitats and habitat FOCI outlined in the original site assessment document. Reporting is underway and will be made available in due course.
  • Community analysis of Offshore Overfalls MCZ data – [2016]
    JNCC contracted Envision Mapping Limited to complete a community analysis of offshore MCZ grab and video data to establish biotopes present. The following European Nature Information System (EUNIS) biotopes were assigned after multivariate analysis of the 2012 survey data. The Marine Habitat Classification for Britain and Ireland (version 15.03, JNCC 2015) has been provided in brackets:

          EUNIS Level 4 habitats:

                      A5.14: Circalittoral coarse sediment (SS.SCS.CCS)

          EUNIS Level 5 biotopes:

                      A5.142: Mediomastus fragilis, Lumbrineries spp. and venerid bivalves in circalittoral coarse sand or gravel (SS.SCS.CCS.MedLumVen)


References for further supporting scientific literature consulted during the identification of this site can be found in the annexes of our advice.


Additional relevant literature
Please be aware that although these sources contain information which is of interest in relation to this MPA, they do not necessarily represent the views of JNCC:


Knowledge gaps
If you are aware of any additional data or relevant scientific papers for this site not listed in the relevant documentation, or the [insert site name] Site Summary Document listed in the relevant documents section, or the annexes of the MCZ advice documents, please contact JNCC.



MPA Conservation Advice

Conservation objectives
Conservation objectives set out the desired state for the protected feature(s) of an MPA.

The conservation objectives for the protected features of an MPA are useful if you are:

  • planning measures to conserve the site and its protected features;
  • monitoring the condition of the protected features; or
  • developing, proposing or assessing an activity, plan or project that may affect the protected features of the site

The Conservation Objectives for the protected features of the MCZ are:

Subject to natural change, the broad-scale habitats Subtidal coarse sediment, Subtidal sand and Subtidal mixed sediments features are to remain in or be brought into favourable condition, such that:

  • its extent is stable or increasing; and
  • its structures and functions, its quality, and the composition of its characteristic biological communities are such as to ensure that it is in a condition which is healthy and not deteriorating.

Subject to natural change, the English Channel Outburst Flood Features (Quaternary fluvio-glacial erosion features ) geomorphological interest feature is to remain in or be brought into favourable condition, such that:

  • its extent, component elements and integrity are maintained;
  • its structure and functioning are unimpaired; and
  • its surface remains sufficiently unobscured for the purposes of determining whether the conditions in the points above are satisfied

More information regarding the conservation objectives for the protected features of the Offshore Overfalls MCZ is available in the site Designation Order, In addition to the conservation objectives above, General Management Approaches (GMAs) have been set by JNCC for each feature which provide a view as to whether a feature needs to be maintained in or be brought into favourable condition i.e. recover, based on our knowledge about its condition. For more information on the General Management Approach for MCZs see Defra’s MCZ Designation Explanatory Note.

The GMAs for the protected features of the MPA are:

Subtidal coarse sediment: Recover to favourable condition
Subtidal mixed sediments: Recover to favourable condition
Subtidal sand: Recover to favourable condition
English Channel Outburst Flood Features (Quaternary fluvio-glacial erosion features): Maintain in favourable condition


More information on the GMA for the features in Offshore Brighton MCZ is provided in  Scientific advice on possible offshore Marine Conservation Zones considered for consultation in 2015  and the Scientific advice on offshore Marine Conservation Zones proposed for designation in 2015/16.


Advice on operations 

Section 127 of the Marine & Coastal Access Act (2009) states that JNCC may provide advice and guidance regarding matters capable of damaging or otherwise affecting the protected features of an MCZ.

JNCC has published the following advice on activities which are capable of damaging or otherwise affecting protected features in MCZs:


JNCC provides a list of activities occurring within the Offshore Overfalls MCZ and information on management within the activities and management tab. JNCC has provided this to aid the cumulative assessment of impacts of human activities within the site.  While every attempt has been made to ensure this information is accurate and kept up-to-date, the list is not to be considered exhaustive or definitive. The list does not, for example, include activities occurring off-site which may also be capable of affecting the protected features.


For the most up-to-date information about the biological communities present within the site and their spatial distribution, please see the evidence tab. Sensitivity information for the protected features within the site can be found in a Technical Report commissioned by Defra to support the MCZ designation process.


The information contained within the evidence tab, the activities and management tab, the above Technical Report and the advice listed above on activities which are capable of damaging or otherwise affecting the protected features in MCZs are useful if you are:

  • Carrying out any activity that may impact the protected features of the site and need to find out how to operate within the law,
  • an authority providing advice on specific proposals,
  • an authority responsible for putting management measures in place.

Our scientific understanding of the ecology of the protected features of the site and how activities can affect them may change over time. Similarly the activities taking place within the site may also change over time. JNCC’s conservation advice will be kept under review and will be periodically updated to reflect this. Further information on JNCC’s conservation advice work is available on the offshore MPA conservation advice webpage.



Activities known to be currently occurring within this MPA
(Activities information correct as of March 2016)


Licensed activities:

  • Oil and gas – There are no current oil and gas activities within the Offshore Overfalls MCZ, however a plugged and abandoned well is located in the east of the site.  
  • Aggregate extraction – There are no aggregate licenses within the site however an aggregate license area borders the north west corner of the site boundary. 


Existing licensed activities that take place within Offshore Overfalls MCZ will continue to be managed in line with relevant legislation and application processes by the competent authorities.  Information on JNCC's role in the provision of advice for licensed activities in the UK offshore area is available on the offshore industries advice webpages



At present there is evidence of fishing activity from UK and non UK registered vessels in Offshore Overfalls MCZ. These include beam trawling, pelagic and demersal trawling, dredging, seine netting and pursers. 

There is currently no fisheries management in place designed specifically to protect the designated features of the site.

In the 6-12nm portion of the site, the Marine Management Organisation (MMO) can introduce measures (e.g. bylaws) where appropriate. Such measures would be developed following individual site assessments and subsequent stakeholder engagement. Where other Member States (OMS) have historic fishing access rights, any management proposals would need to follow processes laid out in Article 18 of the revised Common Fisheries Policy (CFP). The portion of the site which falls outside of 12nm will be exclusively managed under the CFP. In accordance with Article 18, requests for management will be developed jointly between the UK Government and any Member States with a direct management interest in the area affected. Once drafted, there is a requirement to consult the North Sea Advisory Council  prior to submission of any final recommendations to the European Commission. The MMO will be the lead authority regarding implementation and compliance of any measures.

  •  Other activities:
  • Shipping – Due to the site’s proximity to the busy ports of Southampton and Portsmouth and location in the English Channel, shipping activity is moderate to high across the site.

Under international law, ships have a right of passage at sea including in areas designated as MPAs (unless management specifies the restriction of ship transiting as outlined through an International Maritime Organisation measure).  The pressures associated with shipping activity within Offshore Overfalls MCZ are not considered likely to impact the protected features of the site.

  • Ministry of Defence (MoD) activity – The MCZ is located in a military practise area with some restrictions in operation. Activities include acoustic trials with towed sonar equipment.

The MoD has incorporated all designated MPAs into their Environmental Protection Guidelines (Maritime) and wider Marine Environmental and Sustainability Assessment Tool. These guidelines are used to manage MoD activity to minimise the associated risks to the environment.

  • Recreational Activities: Scuba diving and angling (recreational fishing) may occur in the site which is also used by sailing boats and recreational motor boats.

The Defra UKHO records show 31 wrecks located in the vicinity of Offshore Overfalls MCZ and six obstruction points.

Site Management
Management Plan: JNCC is undertaking a review of management plan requirements for offshore MPAs. Further detail will be provided at a later date.

Management Group: MPA Management National Steering Group

Further information on conservation advice in relation to this MPA can be found under the Conservation Advice tab.





MPA Monitoring

JNCC is currently leading on the development of a strategy for biodiversity monitoring across all UK waters, to include MPA monitoring. For MPAs, data and evidence collected from monitoring activities will aim to:

  • Enable assessment of condition of the features within sites;
  • Enable assessment of the degree to which management measures are effective in achieving the conservation objectives for the protected features;
  • Support the identification of priorities for future protection and/or management; and,
  • Enable Government to fulfil its national and international assessment and reporting commitments in relation to MPAs and help identify where further action may be required.

Information on monitoring of this MPA will be provided when it becomes available.




MPA Assessment

Assessments of the condition of designated features in offshore MPAs are required to report against our legal obligations. Ideally these assessments should be based on observed data, and then measured against targets for predefined indicators. However, for MPAs in offshore waters we do not always have the appropriate information to be able to do so. This is particularly true for seabed habitats, which are the main type of feature designated for protection in offshore MPAs. 

To address these challenges, JNCC has been an active partner in the development of new approaches and tools for the assessment of habitats and species for a variety of national and international status reports. They include the second cycle of the Conservation Status Assessment reports under the EU Habitats Directive, Charting Progress 2 (CP2) and the OSPAR Quality Status Report (QSR). JNCC continues to develop and pilot tools for the assessment of marine habitats and species in offshore waters to improve the quality and transparency of our offshore MPA assessments, and contribute to the monitoring of marine biodiversity in UK waters. These tools cover methods for producing interim assessments of site features and their responses to pressures, as well as developing more robust indicators for determining condition of the features.

Under the UK Marine & Coastal Access (2009), JNCC is required to report to Ministers on the degree to which the conservation objectives of the protected features of Marine Conservation Zones (MCZs) have been achieved.  Every 6 years from 2012, the Marine Act requires a report setting out how MCZs have performed against their conservation objectives, as well as the effectiveness of the network as a whole. 

The assessments of features within MPAs will also feed into six yearly reports on the state of the marine environment under the Marine Strategy Framework Directive (MSFD), which aims to achieve Good Environmental Status (GES) by 2020.




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