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Navigating Morlais

Menter Mon's plan is for 240 MW generation capacity in tidal energy convertors (TEC = turbines) to be insatlled by six different tidal energy developers in the area of the Morlais Demonstration Zone (MDZ). At their closest the TEC will be 500 m from the tip of South Stack with the nearest major infrastructure above-the-water a further 500 m out. The image above from the seascape report indicates the different types of TEC - each will be in a berth in the MDZ which will take the form of a patchwork of different daughter arrays. Morlais are asking for general permission for the MDZ under what is termed the 'Rochdale envelope' and no detail on deployment layout or plans have been provided.

Each TEC would extract energy from the tide which means changes to flow rates accompanied by wake effects at various scales and depths. Arranging large numbers of TEC into arrays will therefore block and divert tidal streams. HR Wallingford were commissioned by Morlais to model the hydrodynamic effects of the array. Although the model used is not ideal for estimating changes relevant to sea kayaking it is the best we have for now. On the 20th October Morlais released a set of hourly images of tide flows with and without the array which give an indication of what might be expected. The Planning Inspectorate have opened up a window for consultation on this new document which closes on the 30th November (see notice below).

The figures provided by HR Wallingford and the consultation give us a chance to more fully consider the potential impact of the MDZ on sea kayak navigation and use of the area between the MDZ and the coast. We are therefore seeking comments from those who are familiar with the area and use it regularly. To help with the large amount of background material we have organised this around a few key questions which relate to the treatment of kayaks in Morlais' Navigational Risk Assessment (NRA). This is not the risk assessment you make when planning a trip or on the beach before launching but an assessment of risks to the public of introducing new hazards into an area already heavily used for recreational boating. We also have problems with the way Morlais have treated the calculation of these risks - please contact us if you have experience with numerical risk assessment!

Key documents from Morlais and the SCC respose to them are given after each question in case you want to know more - but you don't need to get this deep into it if you don't want to and basic answers to the questions will be very welcome and useful.

This representation of kayak tracks taken from Strava is being used as basis for their interactive boundary assessment and NRA

Question 1: Is this an acceptable representation of kayak routes?

Note the Blue and Purple areas are for sub-surface TEC while Gold and Green are for surface mounted devices. Note: only indicative locations for surface piercing devices in Green zone are shown on figure.

Details of the TECs are:

Morlais website page on navigation:

Additional reading: Interactive boundary assessment

MMC184 20UK1619_RN_MM_VTS02-02_Interacti
Download • 7.67MB

Changes to hydrodynamics

MMC350 MOR-HRW-DOC-0002 Further informat
Download • 4.99MB

Download the hourly data

Question 2: Do the figures showing existing flows agree with your experience of paddling the area or are there things that look wrong & what seems wrong?

Question 3: Looking at the scheme flows, what in your view is the significance of flow changes (speed and direction) for paddling in the area?

Additional reading:hydrodynamic modelling

06_MOR-HRW-DOC-0001 HR Wallingford Coast
Download • 35.65MB
Hydrodynamic effects of Morlais Developm
Download • 1.15MB

Considering risks posed by array to those playing in races

Question 4: For playing in the races, which sections of the race do you use (i.e. starting point)?

Question 5: In a capsize, what route do swimmers/kayaks follow & where might they end up?

Question 6: How long do rescues typically take?

Question 7: How far offshore do you end up before you have completed a rescue?

Additional reading: Navigational Risk Assessment

MMC196 MOR-MCO-DOC-001 Navigation Risk A
Download • 9.64MB
Review of risk assessment in NRA Addendu
Download • 193KB

Additional reading: Shipping and navigation chapter in Environmental Statement

MMC194 MOR-MSP-DOC-002 Replacement ES Vo
Download • 1.69MB
Review of the Morlais Project Shipping &
Download • 552KB

Any other comments?

Please send your response to

Notice of public consultation on hourly hydrodynanic data

Morlais TWAO Notice of FEI_bilingual2
Download PD • 91KB


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