Guidance to Inform Marine Mammal Site Characterisation Requirements at Wave and Tidal Stream Energy Sites in Wales


Title: Guidance to Inform Marine Mammal Site Characterisation Requirements at Wave and Tidal Stream Energy Sites in Wales
Publication Date:
July 17, 2015
Document Number: SMRUC-NRW-2015-012
Pages: 88
Technology Type:

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Website: External Link
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Sparling, C.; Smith, K.; Benjamins, S.; Wilson, B.; Gordon, J.; Stringell, T.; Morris, C.; Hastie, G.; Thompson, D.; Pomeroy, P. (2015). Guidance to Inform Marine Mammal Site Characterisation Requirements at Wave and Tidal Stream Energy Sites in Wales. Report by Sea Mammal Research Unit (SMRU). pp 88.

There is a growing consensus amongst regulators, statutory nature conservation advisors and developers and their environmental consultants that a 'one size fits all' approach to marine mammal site characterisation survey to inform consenting processes for wave and tidal stream projects is not fit for purpose. Furthermore, it is generally recognised that they may not always provide useful information for underpinning environmental assessments. There is a need to tailor pre-application surveys to a) provide specific information in relation to the particular types of impacts posed by the project, and b) to the likely degree of risk of significant impacts to marine mammals posed by the project. This report provides a mechanism for assessing b) and provides guidance on a) how to tailor survey effort to better provide information to inform specific impact assessment predictions. Section 2 of the report provides an introduction and section 3 provides a summary of the legislative background to the requirement for pre-application data gathering.


Section 4 provides an overview of the information requirements for wave and tidal stream energy projects across a number of identified main impact pathways. A number of general requirements for informing all potential impacts of projects were identified, such as a basic understanding of which species are present at a site and an understanding of the functional use of a site. A number of specific impact pathways were identified for wave and tidal energy projects, such as collision (mainly tidal) and disturbance (wave and tidal). For each impact pathway a set of individual information requirements were identified. For collision impacts the key information requirements were those which would enable a robust, quantitative prediction of collision rates. Specifically these are metrics which will help to predict the potential rate of encounter between marine mammals and the moving parts of devices such as information on animal flux through the project area and how this varies over time. It is accepted that there are important pieces of information that have a large bearing on the prediction of the magnitude and consequence of collision impacts, such as evasion and avoidance, which cannot be informed by pre-application surveys and the uncertainty in collision predictions as a result should be borne in mind.


For disturbance related impacts the important metrics are likely to be a measure of the density of animals at the site to allow an estimate of the number of animals likely to be affected and an understanding of why animals are present at a site, to allow a prediction of the nature and consequences of any disturbance. Disturbance can result in displacement of animals away from areas but it can also result in disruption to behaviours which may result in a reduction in breeding success or survival without any displacement.


A number of other impact pathways were also explored although it is noted that these impacts are unlikely to drive survey requirements in isolation from those considered above. The third impact pathway considered was indirect impacts mediated through a change in prey availability. The information requirements are similar to the impact of disturbance; how many animals are using the site and their behaviour and whether they are feeding (and what they are feeding on) in particular.


Entanglement with mooring lines was also considered and information requirements are similar to those for collision risk. An assessment of the risk of this impact occurring requires information on the likely rate of encounter between marine mammals and the device which presents the risk. For entanglement with mooring lines, a prediction of the rate at which marine mammals are likely to come into contact with the hazard will be important but pre-application survey can inform very little about the likelihood of entanglement happening, other than highlighting whether species which may be particularly vulnerable to entanglement are present (e.g. larger baleen w hales).


A number of other issues influencing pre-application data requirements were considered and discussed. This included consideration of how much reliance could be placed on existing data, how to assess whether survey methodologies are likely to be fit for purpose and issues involved in setting thresholds against which to assess potential population consequences of predicted impacts.


Section 5 then provides a detailed step by step process for an initial assessment of risk of wave and tidal stream energy projects to assist in determining pre-application survey requirements. The process is intended to be similar in principle to Marine Scotland’s draft Survey, Deploy and Monitor policy but is adapted and developed more specifically for a more detailed consideration of marine mammals and extends to provide guidance on the type of survey that may be useful to inform the EIA and HRA in each case. This assessment should take account of a variety of features, e.g.:

  • The type of device and its physical and mechanical features and the resulting likely impact pathways – for example a horizontal axis-rotor tidal stream turbine with large, fast moving parts that could cause injury and mortality to marine mammals poses a different level of risk of impact than a surface floating wave energy structure with no such apparent pathway for injury. This would involve a review of the evidence base, including research and knowledge of impacts for a given device or similar types of device. This assessment would need to be carried out for each specific impact pathway identified.
  • The scale of the project – for example, a single demonstrator device is likely to pose a much smaller risk of impacts than a large array of devices;
  • Site sensitivity – the extent to which the proposed project site is used by marine mammals, the importance of the site for those animals and the degree of legislative protection afforded those animals (either as EPS and/or as part of an SAC population) will affect the degree of risk of impacts.
  • The duration of project-clearly the risk of significant impacts will be higher for projects of longer duration.


It is intended that this process would be followed by developers and their consultants at the scoping stage of projects, as part of the evidence plan development. This will allow developers to take responsibility for decisions on pre-application data gathering and to understand the rationale behind any proposed data collection and to understand the costs and benefits of survey work.


A staged, matrix based approach is proposed to classify these various predictors of risk and combine the assessment of biological features and technology related features. Each stage is as follows (note that further guidance on these classifications is given in the main report):


Stage 1: The sensitivity of marine mammal populations = classified as low, medium or high. A predetermined classification has been applied to each of the main Welsh marine mammal populations (harbour porpoise, grey seal, bottlenose dolphins and common dolphins).


Stage 2: The importance of project location to marine mammals based on existing knowledge = classified as low medium or high.


Stage 3: An overall sensitivity matrix combining the results from Stages 1 and 2 to assign a classification of low, medium or high.


Stage 4: Technology risk assessment, which is an assessment of the likelihood that a device associated with a project will result in impacts on marine mammals based on the current evidence base. An assignment of low, medium or high is given. Guiding principles for applying this assessment across the main impact pathways is provided.


Stage 5: Project risk assessment. This combines the technology risk from Stage 4 with the overall project duration to assign a risk of low, medium or high.


Stage 6: Overall risk assessment which combines in a matrix the outcome of Stage 3 (sensitivity) with the outcome of Stage 5 (project risk) to provide an overall classification of low, medium or high.


Stage 7: Determining survey requirements. The final stage in the process determines the survey needs based on the overall assignment of risk. For example, if for a given impact pathway, say for the risk of collision, a low risk is assigned, it is likely that a qualitative impact assessment detailing the justification of lo w risk will be sufficient based on existing information. If a high risk were assigned, this would require a quantitative collision risk assessment which may require the collection of site specific data to inform. The question of how much data are sufficient to inform a risk assessment is a difficult one and is best answered on a project and site specific basis. However the spatial and temporal resolution of previous surveys, the overall area of coverage, and the methods used to collect and analyse the data and how long ago the data were collected will be material considerations. General rules of thumb can be applied (e.g. data should be from within the last five years, though there may be exceptions to this).


A number of worked hypothetical examples are provided to illustrate this process.


Section 6 of the report details the range of survey methodologies likely to provide the information required to evaluate the main impact pathways as detailed in section 4. For collision risk the options for understanding animal flux rate through the swept area of devices which pose a collision risk are explored. These include site specific surveys measuring density and how it varies across the tidal cycle, or individual tagging studies for species where this is possible. The options for understanding animal depth distribution are also discussed. For disturbance related impacts, a quantification of animal abundance and surveys which are focused on understanding animal behaviour at a site are important. Across all impact pathways understanding the potential connectivity with protected sites will be important and techniques like telemetry and photo id may be useful. For all surveys it is important to consider the degree of precision that can be achieved. This may be particularly pertinent to small sites where even intensive effort would result in small sample sizes. Extended details of all survey methodologies discussed are provided in Appendix 1.


Section 7 provides a summary of the report and presents a series of recommendations. In summary, developers of wave and tidal stream energy projects should follow the initial risk assessment process outlined in this report to determine the survey needs for a project. This process will allow the developer to identify which impact pathways might result in potentially significant impacts and which impacts and species should be the focus of any pre-application survey. Alongside careful consideration of available data and the likelihood of site specific investigations providing data of sufficient quality, a specific and appropriate data gathering approach can then be devised and implemented. This process will ensure that developers take responsibility for making informed decisions about survey and the need for data to inform assessments, understanding the risks of potential operational restrictions that may result from poor or inadequate baseline data.

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