Site and Hydrographic Survey Report

Transcription

1 Site and Hydrographic Survey Report Aird, Loch Shieldaig April 208 Written by: Reviewed by: Approved by: Status: Date: Brian Robertson Penny Hawdon Marc Browne FIAL 30th April 208 The Scottish Salmon Company 8 Melville Crescent Edinburgh EH3 7JA

2 Introduction 2 Site description 3 Survey programme 3. Current meter set up 3. 2 Weather station set up 3. 3 Current meter configuration file 3. Mooring system Bathymetry and site survey 5 Data processing 5. ADCP data 5. 2 Magnetic heading corrections 5. 3 Hydrographic survey results 5. Summary statistics 5. 5 Meterological results 6 Discussion Annex. HG7 analysis summaries 2. ADCP Specification 3. Site map The Scottish Salmon Company r s scour s= a' '

3 C2 ITRDUCTI 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 Doppler Current Profiler (Sentinel V50 ADCP) mounted in a weighted seabed frame. Analyses were carried out in accordance with SEPA guidelines ( Regulation and monitoring of marine cage fish farming in Scotland - a procedures manual. Attachment VIII Site and Hydrographic Survey Requirements. Version 2. 7, 35' ctober 2008). 2 SITE DESCRIPTI The hydrographic survey site is located on the west side of Loch Shieldaig, within Loch Torridon at the north side of the existing Scottish Salmon Company ( SSC) Aird farm site. There were 0 cages on site at the time of survey. Within the survey area the seabed slopes eastwards to water depths > 50m. There is an area of very shallow water (' Dora Rock') in the southern part of the survey area. a Loch Torrklon Loch Shieldaig g Aird 00 Q D Skm Figure : Location of Aird, Loch Shieldaig Rafscopis= The Scottish Salmon Company 208 Son. C

4 3 SURVEY PRGRAMME 3. Current meter setup The ADCP deployment position was ( WGS8) ' 005a. 70' W ( G ) which is 70m 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 0th July 207 to 0th August 207. A half -lunar 5 -day period of data was analysed for this report; from 9th July 207 to 3`d August 207. Positioning forthe survey was provided by GPS and compatible chart plotter as installed on the SSC landing craft and was backed up using a Garmin handheld GPS with minimum 8 satellite coverage Weather station set up Meteorological data was obtained from the Gairloch weather station at ( WGS8) ' ' W ( G ), approximately 20km due north of the site. The data was provided via the website com 3. 3 Current meter configuration file Table : Sentinel V50 ADCP configuration files ADCP model Sentinel V50 ADCP serial number 276 umber of cells 37 Cell size m. 2 First cell centre range m 2. 7 Start date and time UTC 0/ 07/ 207 6: 00 Time between ensembles minutes 20 Ping interval seconds umber of pings 300 Transducer orientation U Magnetic variation 0 Cell Standard Deviation cm/s 33 Instrument std.dev [for. 2m cells] (cm/s) The ADCP was configured at the time of deployment having established the water depth and expected tidal range on site. This was carried out on the instrument settings using a laptop with wireless connectivity. The Scottish Salmon Company 208

5 3. Mooring system The ADCP was fixed in a gimballed, weighted sea bed frame. The head of the ADCP was 5m from the seabed throughout the deployment. Internal parameters for pitch, roll and heading were checked post -deployment to ensure a stable position was maintained throughout. BATHYMETRY AD SITE SURVEY A full bathymetric survey was carried out using a Garmin portable chart plotter with acoustic sounder on 8th ctober 207. Boat GPS was used at the start of the survey to verify accuracy to return positional information ( WGS8). Both devices received a minimum of 8 satellite coverage throughout the survey. Recorded depths were corrected to Chart Datum ( CD) using Admiralty Total Tide software and referenced against tide predictions for the secondary port Shieldaig. The bathymetric survey concluded that chart data was reliable throughout the development area. The bathymetry plot and selected depth soundings are provided below: x a YM B I D E Co03 :' I K 09T" alch SHIELD. UG 3} Figure 3: Bathymetric plot The Scottish Salmon Company 208 s "

6 Table 2: Bathymetric data Sounding GPS Position Latitude ( ) Longitude ( W) Eastings orthings Time UTC) Measured depth ( m) Tide height ( m) Corrected depth ( m) A B C D E F G j H I J K L M P DATA PRCESSIG 5. ADCP data Data was extracted from the ADCP by downloading to laptop wirelessly. From there the data was extracted to a bespoke programme ' Velocity' for processing, then later to Excel. SEPA specifies that data should be presented for specific depths, therefore the data was selected Sub -surface - deployment against the following requirements; from a depth 5m below the lowest predicted spring tide during the period Cage -bottom - at a depth corresponding to the bottom of the cages at mean sea level t m ear -bottom - as close to the bed as practicable Mean tidal height recorded by the ADCP during the deployment was 3. 55m from the seabed, with a minimum tidal height for the deployment of m. Cage depth was assumed to be 0m. ear -bottom, cage -bottom and sub -surface depths were taken at distances of 2. 97m, 9. 77m and 2. 57m respectively from the sea bed. The Scottish Salmon Company 208

7 Table 3: Deployment depth details Measured depth at deployment Predicted tidal height at deployment from Admira ty tide tables Corrected depth at deployment (CD) Lowest predicted tide during deployment Charted mean sea level ( range) Average tidal height Mean sea level height above bed ( MSL) Assumed cage depth ADCP mooring height Mean ADCP recorded pressure incl. height 3. m 2. 70m 28. m 0m 5. 0m 3. 0m 3. 5 m 00M 50m 3. 55m Mean cell height above seabed Surfacecell Mid cell Bed cell 2. 57m 9. 77m 2. 97m Mean cell depth below Chart Datum depth Surface cell 3.8m Mid cell 8. 6m Bed cell 25. m Hydrographic Hydrographic data data were were analysed analysed using using the the SEPA SEPA tool tool HGdata_ HGdata_ analysis_ analysis_ v7, v7, running running in in Excel. Excel. HG7 HG7 data data summaries summaries can can be be found found in in the the Annex. Annex. Pre- Pre- and and post post - - deployment deployment values values were were rejected rejected from from the the dataset, dataset, restricting restricting the the dataset dataset to to records. records. Data Data quality quality was was confirmed confirmed by by calculation calculation of of the the standard standard deviation deviation ( ( std. std. dev) dev) at at each each of of the the chosen chosen depths depths cells cells using using the the exported exported ' ' Percent Percent Good' Good' data data from from Velocity. Velocity. The The calculated calculated std. std. dev dev was was then then compared compared against against the the expected expected cell cell std. std. dev dev ( ( in in this this case case cm/ cm/ s) s) and and confirmed confirmed to to fall fall within within the the SEPA SEPA guideline guideline of of 22 cm/ cm/ s. s. Percent Percent Good' Good' is is the the percentage percentage of of valid valid pings pings used used to to calculate calculate the the std. std. dev. dev. In In this this case, case, the the exported exported data data used used is is PG PG ( ( percent percent of of good good data data computed computed from from 33 beams) beams) and and PG PG ( ( percentage percentage of of good good data data from from beams) beams) from from the the meter meter to to calculate calculate the the std. std. dev dev as as follows: follows: Cell Cell std. std. dev dev = = Instrument Instrument std. std. dev dev / / q q [ [ no. no. of of pings pings x x { {( ( PG PG + + PG) PG) / / ) ] ) ] The The Cell Cell std. std. dev dev for for surface, surface, mid mid and and bed bed cells cells all all calculated calculated out out as as cm/ cm/ s, s, indicating indicating the the data data set set was was of of an an extremely extremely high high quality. quality Magnetic Magnetic heading heading corrections corrections AA Grid Grid Magnetic Magnetic Angle Angle of of 5580W 5580W ( ( from from www. www. geomag. geomag. bgs. bgs. ac. ac. uk/ uk/ HH The The Scottish Scottish Salmon Salmon Company Company

8 dataservice/ charts_ navig/ gma_ calc. html) was applied and grid convergence ( from HGd_ata_ analysis_ v7) was W to give an overall declination of Table : Magnetic heading corrections Date I Lat I Long I GR_X GR_Y mag. dec I grid conv. I GMA 9/ 07/ W % W 558- W otes: positions recorded to WGS8, and converted to SGB36 using ST97 magnetic declination from US- AA Geomagnetism website grid convergence from S 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 to -. 60, to and to respectively. These results are within acceptable limits for the instrument and indicate a stable deployment. The data quality calculation is described in section 5., and verifies that data isof good quality. 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 Table The Scottish Salmon Company 208

9 5. Summary statistics Table 5: Summary statistic table Bed Mid Surface o. of records Start date / time UTC 9/ 07/ 7: 00 9/ 07/ 7: 00 9/ 07/ 7 : 00 End date/ time 03/ 08/ 7: 00 03/ 08/ 7: 00 03/ 08/ 7 : 00 Mean velocity m/ s Minimum velocity m/ s Maximum velocity( m/ s Ranked % of mean velocity Ranked % of 3 cm/ s Ranked % of. 5 cm/ s Ranked % of 9. 5 cm/ s Residual velocity m/ s Residual direction T Major axis T Residual parallel m/ s Residual normal m/ s Amplitude parallel m/ s 3 7 Amplitude normal m/ s Amplitude anisotropy The Scottish Salmon Company Company 208

10 5. 5 Meteorological results The data from the weather station deployed at Gairloch was analysed using the SEPA tool HGdata_ analysis_ v7. HG7 data summaries can be found in Annex. The data from this weather station exhibits no recorded wind speeds in excess of 0m/ s. Mean wind speed over the whole deployment was 2. 5m/ s. The deployment period therefore met the requirement of mean daily wind speed < 0m/ s. DISCUSSI bserved 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. The tidal height range and time series are consistent with predicted tidal heights. In general, the site was characterised by moderate/ strong tidal energy. Surface velocity was found to be almost double the bed velocity. Surface, cage depth and bed cell 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 99 m/ s. The re -suspension threshold of 9.5cm/ s was exceeded 9% of the time for the near - bed data. The site is therefore likely to experience re -suspension and may result in moderate export of released solids in AutoDepomod modelling. Velocity and direction showed clear 2. 5h periodicity at all depths; and velocity showed clear spring neap variation. Current directions were parallel to bathymetric contours and would correspond with prospective cage layout running parallel to the shoreline. Residual current vectors were orientated north at bed cell and towards north- north-west for the cage depth and surface cells. Meteorological data shows no major effect on the surface current. verall, the recorded data are indicative of a moderately flushed site and is considered suitable for development in terms of hydrography and bathymetry. This dataset is considered to provide a good basis for AutoDepomod modelling. 0 s The Scottish Salmon Company 208 ''^-.

11 00 pop 5 Lq 2 ] ci i5 m 0 ff- W 0 Ffzz QDW- Le offce nrw LIQPT- SZ 0( wwtz qopwu 0 PW cc V W - Lc 0 & rvw zo Lm STco

12 6 3 F a o Bny so o Bny po 0 Bw co 0 enwo 0 my to o inr Le 0 lnroe 0 MR o In" Z 0Inra 0InroZ 0 mr9z 0 lnr> z 0lnrez 0Inrzz uo Inr z o inroz o lnr6l omr% C C G ono on oo Yom Shoo 6 3 F a o Bny so o Bny po 0 Bw co 0 enwo 0 my to o inr Le 0 lnroe 0 MR o In" Z 0Inra 0InroZ 0 mr9z 0 lnr> z 0lnrez 0Inrzz uo Inr z o inroz o lnr6l omr% C C G

13 06ntl" f0 0 6ntl' 0 3 V 6ntl f0. n: n' V 6ntl- Z n: F n: 06ntl- 0 : 0^ f- lc I 0nf- E rl n' I 0nf- 6Z : 0nfZ 0nf- LZ. 0nf- 6Z L I 0nf9Z 0nf- Z 0^ fyz 0nhZL n 0 tnf- R Il, 0^ f - Z 0 W- 6 00` 6{ c o M H 6 li? o A f T ymo a mem mm o o c 06ntl" f0 0 6ntl' 0 3 V 6ntl f0. n: n' V 6ntl- Z n: F n: 06ntl- 0 : 0^ f- lc I 0nf- E rl n' I 0nf- 6Z : 0nfZ 0nf- LZ. 0nf- 6Z L I 0nf9Z 0nf- Z 0^ fyz 0nhZL n 0 tnf- R Il, 0^ f - Z 0 W- 6 00` 6{ c o M H 6 A f mem mm 5 a h.' 3 C 06ntl" f0 0 6ntl' 0 3 V 6ntl f0 n:. n' V 6ntl- Z n: F n: 06ntl- 0 : 0^ f- lc I 0nf- E rl n' I 0nf- 6Z : 0nfZ 0nf- LZ. 0nf- 6Z L I 0nf9Z 0nf- Z 0^ fyz 0nhZL n 0 tnf- R Il, 0^ f - Z 0 W- 6 00` 6{ c o H M

14 + f^ p. 6 B 0 2 ' 0 A0 0 CI 0 r0 r 0 t0 MM CI r 0 m Zw" 0 0 i S 0

15 AEX 2 ADCP Specification Depth Cell Sim' Commvmunmm and Rerwding Depth Ceti Sim' 25m 3m5m 20m. Loin 6.m Wireless Internal memory Roble paramrtert Velocity accuracy Fara hrcensny Profile Transdowr and irdware Velocity resolution Velocityrarge ping rate Vertnat resolution Dynamic range Recision Beam Canfiguation angle Depth rating Materials V20( 00DFIh) V50( SDIdtr) VI00( 300ktr) Ragelmyr Std Dev( crsy' Range( my' Std Deviantsµ' Range ( my I Std Dev( ersy' Wide/ Hanov, Wide/ arrov Wide/ anow Wide/ amwv, wde/araw Wide/ arrow 8.0/ / / 0./ / 2.9 7/ 3.. / / V / / / / / 29. 7/ / / / 3 269/ 320 8/ / 78. 7/ 3. 6' / / , 7/ / 3. 3 b/ gyn ne 606 Micm SD Card included V20V50: 0 5% of the water velocity relative to the ADCP = 3crrys 00: 05% of the water velocity relative to the ADCP 0 Santis. SnVs lcmvs( defaut52( hms (maxim iii Up is 2 Depth tell size 8dB Still 25 beancomex; Sth beam vertical 200M Transducer, hauvng, and end cap: plastic Connector metal sbe0 Standard Sensors power Temperature pmweed on trmea seq CWS lmgerpiicihr SeInIXI Tilt tmemsar aomatm) Pressure senior ( mounted on transducer) External DC inert Imemalbatteryvaltage Battery caps ty; over- C Battery C Range - 5 to 5 C, praisisn * A- C, resolution - Accuracy 2' AMS. resolution 0 V, maxdip angle 85' Pitch range 90'. roll range 80, acuraq 2' RMS predskm DS' RMS, resolution V Range 300nc accuracy l%fs 8/0( 2-20VDC new 00 wan hours pypltnl) SI wart hours Sofrnare Teledyne RDI' s new software included Eonmiuremal Standard depth rating 200m perating temperature. 5* m 5- C Storage temperature 0irMm Mnnes) - So' to 60'( Weight in air 7Skg - 6.kg Weight in water. 6kg- 6kg Ready/ - Pre - deployment esting. planning, and data recovery) ` Velocity - Poor processing ( data handing. display. and export)" Available ptiom External battery came AC/ 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 I Vwtuwnla9naamm amea' RxaraeSYnaYa 2 aytwrangpuauwra. n sx, a. rrwa ttpawen... pnemme WYkirT} MopY. 5\ evey. 6x cm} e bmehwba6tlenlaemal ranbvgeprgm S wnnaooaewwrreel. w s wesr saarm... emam The Scottish Salmon Company 208 5

16 l LID l i wi 7 - x- SS e R a a LL m t LL Q E J U F rm ma L k s I Z 0 u am C ur W m 00nm ca m «Ua a3 o w ma tm 2 m mc T Em m 9 ca Cl) m 0 CD LID E E