site and hydrographic survey report€¦ · the hydrographic survey site is located on the west...

Site and Hydrographic Survey Report

Aird, Loch Shieldaig

April 2018

Written by: Reviewed by: Approved by: Status:

Date:

Brian Robertson

Penny HawdonMarc Browne

FINAL

30th April 2018

The Scottish Salmon Company8 Melville Crescent

Edinburgh

EH3 7JA

1 Introduction

2 Site description

3 Survey programme3. 1 Current meter set up

3. 2 Weather station set up

3.3 Current meter configuration file

3. 4 Mooring system4 Bathymetry and site survey5 Data processing

5. 1 ADCP data

5. 2 Magnetic heading corrections

5. 3 Hydrographic survey results

5. 4 Summary statistics5. 5 Meterological results

6 Discussion

Annex 1. HG7 analysis summaries

2. ADCP Specification

3. Site map

2

The Scottish Salmon Company 2018

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INTRODUCTION

This report describes the methods used to collect current speed and direction data

and spot depths at the Aird salmon farm site, and presents the outcomes of the survey.

This deployment was carried out using a Teledyne RD Instruments Acoustic DopplerCurrent Profiler (Sentinel V50 ADCP) mounted in a weighted seabed frame.

Analyses were carried out in accordance with SEPA guidelines ( Regulation andmonitoring of marine cage fish farming in Scotland - a procedures manual. AttachmentVIII Site and Hydrographic Survey Requirements. Version 2. 7, 315' October 2008).

2 SITE DESCRIPTION

The hydrographic survey site is located on the west side of Loch Shieldaig, within LochTorridon at the north side of the existing Scottish Salmon Company ( SSC) Aird farmsite. There were 10 cages on site at the time of survey. Within the survey area theseabed slopes eastwards to water depths > 50m. There is an area of very shallowwater (' Dora Rock') in the southern part of the survey area.

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Figure 1: Location of Aird, Loch Shieldaig


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3 SURVEY PROGRAMME

3.1 Current meter setup

The ADCP deployment position was ( WGS84) 57132. 585' N 005a41. 740' W ( NG 78934

56351) which is 170m from the new proposed site centre for Aird. Detailed

specifications for the ADCP are located in the Annex 2.

The hydrographic data collection period was from 10th July 2017 to 10th August 2017. A half -lunar 15 -day period of data was analysed for this report; from 19th July 2017 to3`d August 2017. Positioning forthe survey was provided by GPS and compatible chartplotter as installed on the SSC landing craft and was backed up using a Garminhandheld GPS with minimum 8 satellite coverage.

3. 2 Weather station set up

Meteorological data was obtained from the Gairloch weather station at ( WGS84)

57043. 867' N 005041. 933' W ( NG 79884 77276), approximately 20km due north of thesite. The data was provided via the website www.wunderoround. com

3. 3 Current meter configuration file

Table 1: Sentinel V50 ADCP configuration files

ADCP model Sentinel V50

ADCP serial number 24476

Number of cells 37

Cell size m 1. 2

First cell centre range m 2. 47

Start date and time UTC 10/ 07/ 2017 16: 00

Time between ensembles minutes 20

Ping interval seconds 1

Number of pings 300

Transducer orientation U

Magnetic variation 0

Cell Standard Deviation cm/s 0. 33

Instrument std.dev [for 1. 2m cells] (cm/s) 5. 716

The ADCP was configured at the time of deployment having established the waterdepth and expected tidal range on site. This was carried out on the instrument settings

using a laptop with wireless connectivity.


3.4 Mooring system

The ADCP was fixed in a gimballed, weighted sea bed frame. The head of the ADCPwas 0. 5m from the seabed throughout the deployment. Internal parameters for pitch,

roll and heading were checked post -deployment to ensure a stable position wasmaintained throughout.

4 BATHYMETRY AND SITE SURVEY

A full bathymetric survey was carried out using a Garmin portable chart plotter withacoustic sounder on 18th October 2017. Boat GPS was used at the start of the surveyto verify accuracy to return positional information ( WGS84). Both devices received aminimum of 8 satellite coverage throughout the survey. Recorded depths werecorrected to Chart Datum ( CD) using Admiralty Total Tide software and referencedagainst tide predictions for the secondary port Shieldaig. The bathymetric surveyconcluded that chart data was reliable throughout the development area.

The bathymetry plot and selected depth soundings are provided below:

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Figure 3: Bathymetric plot

s " The Scottish Salmon Company 2018

Table 2: Bathymetric data

Sounding

GPS Position Time

UTC)

Measured

depth ( m)

Tide

height ( m)

Corrected

depth ( m) Latitude ( N) Longitude ( W) Eastings Northings

A 57- 32. 700 005- 41. 714 178972 856564 1232 46. 58 1. 31 45.27

B 57° 32. 621 005- 41. 867 178811 856425 0928 9.84 2. 90 6. 94

C 67- 32. 624 005- 41. 789 178889 856426 1231 28. 32 1. 31 27. 01

D 57° 32. 629 005° 41. 657 179022 856429 0954 55.64 2. 40 53.24

E 57° 32. 636 005° 41. 538 179141 856434 0953 80. 50 2. 40 78. 10

F 57- 32. 527 005- 41. 828 178840 856249 0956 32. 33 2. 40 29.93

G 57° 32. 538 005° 41. 712 j 178957 856263 1203 39.66 1. 19 38.47

H 57- 32. 547 005- 41. 659 179011 856277 1203 49. 95 1. 19 48. 76

I 57° 32. 435 005° 41. 826 178833 856076 0957 34. 20 2. 40 31. 80

J 57° 32. 438 005° 41. 653 179006 856075 1141 39.77 1. 20 38. 57

K 57° 32. 495 005- 41. 440 179224 856169 1143 59. 49 1. 20 58. 28

L 57° 32. 335 005° 41. 834 178815 855893 0912 16. 77 3. 07 13. 69

M 57° 32. 334 005° 41. 776 1178873 855887 0958 13. 87 2. 40 11. 47

N 57° 32. 322 005- 41. 652 178995 855858 0959 24.36 2. 40 21. 96

O 57° 32. 331 005° 41. 397 179251 855862 1000 70. 85 2. 24 68. 61

P 57° 32. 221 005- 41. 738 178900 855675 1119 3. 46 1. 36 2. 10

DATA PROCESSING

5.1 ADCP data

Data was extracted from the ADCP by downloading to laptop wirelessly. From therethe data was extracted to a bespoke programme ' Velocity' for processing, then laterto Excel.

SEPA specifies that data should be presented for specific depths, therefore the data

was selected against the following requirements;

Sub -surface - from a depth 5m below the lowest predicted spring tide during thedeployment period

Cage -bottom - at a depth corresponding to the bottom of the cages at mean sealevel t 1 m

Near -bottom - as close to the bed as practicable

Mean tidal height recorded by the ADCP during the deployment was 31. 55m from theseabed, with a minimum tidal height for the deployment of 28. 76m. Cage depth wasassumed to be 10m.

Near -bottom, cage -bottom and sub -surface depths were taken at distances of 2. 97m,

19. 77m and 24. 57m respectively from the sea bed.


Table 3: Deployment depth details

Hydrographic data were analysed using the SEPA tool HGdata_ analysis_ v7, runningin Excel. HG7 data summaries can be found in the Annex.

Pre- and post - deployment values were rejected from the dataset, restricting thedataset to 1081 records.

Data quality was confirmed by calculation of the standard deviation ( std. dev) at eachof the chosen depths cells using the exported ' Percent Good' data from Velocity. Thecalculated std. dev was then compared against the expected cell std. dev ( in this case0. 33 cm/ s) and confirmed to fall within the SEPA guideline of 2 cm/ s.

Percent Good' is the percentage of valid pings used to calculate the std. dev. In thiscase, the exported data used is PG1 ( percent of good data computed from 3 beams)

and PG4 ( percentage of good data from 4 beams) from the meter to calculate thestd. dev as follows:

Cell std. dev = Instrument std. dev / q [ no. of pings x { ( PG1 + PG4) / 100 ) ]

The Cell std. dev for surface, mid and bed cells all calculated out as 0. 33 cm/ s,

indicating the data set was of an extremely high quality.


A Grid Magnetic Angle of 0. 5580W ( from http:// www. geomag. bgs. ac. uk/

The Scottish Salmon Company 2018 H

Measured depth at deployment 31. 11 m

Predicted tidal height at deployment

from Admira ty tide tables2. 70m

Corrected depth at deployment (CD) 28. 41 m

Lowest predicted tide during deployment 0. 40m

Charted mean sea level ( range) 5. 40m

Average tidal height 3. 10m

Mean sea level height above bed ( MSL) 31. 51 m

Assumed cage depth 10. 00M

ADCP mooring height 0. 50m

Mean ADCP recorded pressure incl. height 31. 55m

Mean cell height above seabed

Surfacecell

Mid cell

Bed cell

24. 57m

19. 77m

2. 97m

Mean cell depth below Chart Datum depth

Surface cell

Mid cell

Bed cell

3.84m

8. 64m

25. 44m

Hydrographic data were analysed using the SEPA tool HGdata_ analysis_ v7, runningin Excel. HG7 data summaries can be found in the Annex.

Pre- and post - deployment values were rejected from the dataset, restricting thedataset to 1081 records.

Data quality was confirmed by calculation of the standard deviation ( std. dev) at eachof the chosen depths cells using the exported ' Percent Good' data from Velocity. The

calculated std. dev was then compared against the expected cell std. dev ( in this case0. 33 cm/ s) and confirmed to fall within the SEPA guideline of 2 cm/ s.

Percent Good' is the percentage of valid pings used to calculate the std. dev. In thiscase, the exported data used is PG1 ( percent of good data computed from 3 beams)

and PG4 ( percentage of good data from 4 beams) from the meter to calculate thestd. dev as follows:

Cell std. dev = Instrument std. dev / q [ no. of pings x { ( PG1 + PG4) / 100 ) ]

The Cell std. dev for surface, mid and bed cells all calculated out as 0. 33 cm/ s,

indicating the data set was of an extremely high quality.


A Grid Magnetic Angle of 0. 5580W ( from http:// www. geomag. bgs. ac. uk/

The Scottish Salmon Company 2018 H

dataservice/ charts_ navig/ gma_ calc. html) was applied and grid convergence ( fromHGd_ata_ analysis_ v7) was 3. 120°W to give an overall declination of - 3.6780.

Table 4: Magnetic heading corrections

Date I Lat

I Long I NGR_X NGR_Y mag. dec I grid conv. I GMA19/ 07/ 2017 55°42. 931N 005042. 577W 1 178934 856351 3. 678%N 3. 120° W 0. 558- W

N otes:

positions recorded to WGS84, and converted to OSGB36 using OSTN97

magnetic declination from US- NOAA Geomagnetism website

grid convergence from OS corrections tool

grid magnetic angle = magnetic declination - grid convergence

5. 3 Hydrographic survey results

Pitch, roll and heading exhibited very slight variations during the deployment from - 2. 15° to - 1. 640, 2. 520 to 2. 630 and 47. 010 to 48. 900 respectively. These results arewithin acceptable limits for the instrument and indicate a stable deployment.

The data quality calculation is described in section 5. 1, and verifies that data isof goodquality.

Data cells representative to bed, cage depth and sub -surface were extracted from the

data set using Velocity. A summary of processed statistical data is provided in Table5.

8

The Scottish Salmon Company 2018 9

5.4 Summary statistics

Table 5: Summary statistic table


Bed Mid SurfaceNo. of records 1081 1081 1081

Start date / time UTC 19/ 07/ 1711: 00 19/ 07/ 1711: 00 19/07/ 17 11: 00End date/ time 03/ 08/ 1711: 00 03/ 08/ 1711: 00 03/ 08/ 17 11: 00

Mean velocity m/s 0. 062 0. 107 0. 111

Minimum velocity m/ s 0. 000 0. 001 0. 002

Maximum velocity( m/ s 0. 451 0. 480 0.499

Ranked % of mean velocity 71 64 64

Ranked % of 3 cm/ s 46 19 15

Ranked % of 4. 5 cm/ s 60 29 26

Ranked % of 9. 5 cm/ s 81 58 58

Residual velocity m/ s 0.040 0. 067 0. 072

Residual direction OT 003 344 343

Major axis OT 355 345 355

Residual parallel m/s 0. 039 0. 067 0.070

Residual normal m/ s 0.005 0. 001 0.015Amplitude parallel m/ s 0. 113 0. 147 0. 144

Amplitude normal m/ s 0. 050 0. 092 1 0. 105

Amplitude anisotropy 2. 26 1. 60 1 1. 37


5. 5 Meteorological results

The data from the weather station deployed at Gairloch was analysed using the SEPAtool HGdata_ analysis_ v7. HG7 data summaries can be found in Annex 1.

The data from this weather station exhibits no recorded wind speeds in excess of10m/ s.

Mean wind speed over the whole deployment was 2.5m/s. The deployment period

therefore met the requirement of mean daily wind speed < 10m/ s.

DISCUSSION

Observed depth data sets were shown to be consistent with charted depths.

Pressure and altitude records showed no evidence of problems with the deployment

such as mooring dragging or excessive movement of the seabed mooring frame. Thetidal height range and time series are consistent with predicted tidal heights.

In general, the site was characterised by moderate/ strong tidal energy. Surfacevelocity was found to be almost double the bed velocity. Surface, cage depth and bedcell current directions were all observed to dominate in a north to north- north- west

direction. Velocities were moderate/ strong, with a maximum recorded velocity of 0.499m/ s.

The re -suspension threshold of 9.5cm/ s was exceeded 19% of the time for the near -

bed data. The site is therefore likely to experience re -suspension and may result inmoderate export of released solids in AutoDepomod modelling. Velocity and directionshowed clear 12. 5h periodicity at all depths; and velocity showed clear spring neapvariation.

Current directions were parallel to bathymetric contours and would correspond with

prospective cage layout running parallel to the shoreline. Residual current vectorswere orientated north at bed cell and towards north- north-west for the cage depth andsurface cells.

Meteorological data shows no major effect on the surface current.

Overall, the recorded data are indicative of a moderately flushed site and is consideredsuitable for development in terms of hydrography and bathymetry.

This dataset is considered to provide a good basis for AutoDepomod modelling.

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ANNEX 2 ADCP Specification

Depth Cell Sim'

Depth Ceti Sim'

0. 25m

0. 3m0. 5m

Loin20m4. Om6.OmCommvmunmm and Rerwding WirelessInternal memoryRoble paramrtert Velocity accuracy

Fara hrcensnY Profile

Transdowr and Nirdware

Standard Sensors

power

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Velocity resolutionVelocityrarge

ping rate

Vertnat resolution

Dynamic range

Recision

Beam angleCanfiguationDepth ratingMaterials

V20( 100DFIh) V50( SODIdtr) VI00( 300k1tr)

Ragelmyr Std Dev( crNsy' Range( my' Std Deviantsµ' Range ( my I Std Dev( erNsy' Wide/ Hanov, Wide/ Narrov Wide/ Nanow Wide/ Namwv, wde/Naraw Wide/ Narrow

18.0/ 12.6 19. 2/ 36. 5

193/ 140 11./ 208201/ 24.9 71/ 13. 4 44. 1/ 576 19.2/ 36. 512. V26. 9 36/ 6. 7 50. 5/ 64. 6 71/ 13. 5 94. 51120. 6 109/ 20. 624. 5/ 29.4 17/ 3. 2 56.07106 3. 6/6. 7 1035/ 130.4 5. 5/ 10. 3269/ 320 0. 8/ 16 63. 1/ 78. 1 17/ 31 114. 6' 142. 3 27/ 5. 2

674/818 1. 112. 1 121, 7/ 151. 5 1. 8/ 3. 3

Temperature pmweed on trmea seqCOWS lmgOerPIOOICIhR SeInIXITilt tmEmsar Naomatm)

Pressure senior (mounted on transducer)

External DC inert

Imemalbatteryvaltage

Battery caps ty; over- the- counter @O' CBattery pack @5° C

Teledyne RDI' s new software included

01. 11b/ gyn

One 1606 Micm SD Card included

V201V50: 0 5% of the water velocity relative to the ADCP = 0. 3crrys11100: 05% of the water velocity relative to the ADCP 10 Santis

O. lcmVsSnVs ( defau1t512( hMs (maxim iiiUp is 4112

Depth tell size

8OdB1 Still25•

4beancomex; Sth beam vertical

200MTransducer, hauvng, and end cap: plasticConnector metal sbe0

Range - 5° to 45° C, praisisn * A- C, resolution 0. 1 -

Accuracy 2' AMS. resolution 0 V, maxdip angle 85' Pitch range 190'. roll range 1180°, acuraq 2' RMSpredskm DOS' RMS, resolution O V

Range 300nc accuracy Ol%FS

12- 20VDC181/0( new100 wan hours pypltnl)

SIO wart hours

Ready/ - Pre - deployment Oesting. planning, and data recovery) ` Velocity - Poor processing ( data handing. display. and export)"

Eonmiuremal Standard depth rating 200m

Operating temperature . 5* m 45- CStorage temperature 04irMm Mnnes) - So' to 60'( Weight in air 7Skg - 16.OkgWeight in water 1. 6kg- 6Okg

Available Optiom External battery cameAC/ DC power convener • Rh beam ( at time of order only) • Waves pmcessirg • Straight or right angle metal shell connettpr

Daemion, Special configuration drawing available upon request

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