HYDROGRAPHIC AND SITE SURVEY REPORT

Transcription

1 HYDROGRAPHIC AND SITE SURVEY REPORT Proposed Pen Site at Dounie, Sound of Jura Prepared for: Kames Fish Farming Ltd Kilmelford Argyll PA34 4XA Tel: +44 (0) TransTech Limited com Caerthann House Grosvenor Crescent Connel Argyll PA37 1PQ Registered in Scotland, No: SC175087

2 Contents 1. Introduction Site Description Survey Details Hydrographic Survey Meteorological Survey Bathymetric Survey Magnetic North to Grid North Conversion GPS and Depth Sounder Calibration Hydrographic Survey Results Meteorological Survey Results Bathymetric Survey Results Discussion and Conclusions List of Figures Figure 1. Schematic diagram of mooring array deployed during the survey....5 Figure 2. Instrument configuration details...5 Figure 3. BGS magnetic north to grid north conversion....7 Figure 4. Summary data for sub-surface bin (25.6 m above seabed) during the 15-day period....9 Figure 5. Summary data for net-bottom bin (15.6 m above seabed) during the 15-day period Figure 6. Summary data for near-bed bin (2.6 m above seabed) during the 15-day period Figure 7. Graph of ADCP pressure sensor readings and Admiralty Total Tide predictions at the Dounie site Figure 8. Graph of ADCP pitch, roll, heading and corrected heading during the 15-day period Figure 9. Summary data for weather during the 15-day period Figure 10. Depth at ADCP, possible pen group grid corners and cardinal points List of Tables Table 1. Set-up and deployment details of the ADCP used during survey Table 2. Tidal data predicted at nearest tidal port to the monitoring site during the 15-day period....8 Table 3. Current speed during the 15-day period Table 4. Summary data for the 3 bins during the 15-day period....8 Table 5. Average wind speed and direction at the Dounie site Table 6. Meteorological data measured for the Dounie site during the 15-day period Table 7. Depth measurements at ADCP deployment location, cardinal and possible grid corner positions. 15 List of Acronyms ADCP ATT BGS CD GMT GPS Acoustic Doppler Current Profiler Admiralty Total Tide British Geological Survey Chart Datum Greenwich Mean Time Global Positioning System LST Lowest Spring Tide MSL Mean Sea Level OS Ordnance Survey OSGB36 Ordnance Survey Great Britain 1936 SEPA Scottish Environment Protection Agency WGS84 World Geodetic System 1984 Dounie Hydrographic Report (2015v1) p2/17

3 uality Assurance The data used in this document and its input and reporting have undergone a quality assurance review which follows established TransTech Ltd procedures. The information and results presented herein constitute an accurate representation of the data collected. TransTech is registered with SEPA ( Scottish Environment Protection Agency) for marine pen site Biomass (Ref: AMMR08v02) and Chemical discharge modelling (Ref: AMMR08v01). Document Details Author: Garret Macfarlane PhD, BSc (hons) Issue Date: 5 November 2015 Issue No: 2015v1 Dounie Hydrographic Report (2015v1) p3/17

4 1. Introduction This report has been produced by TransTech Ltd from hydrographic, meteorological and bathymetric data collected for a proposed pen site at Dounie, Sound of Jura, Argyll. 2. Site Description The proposed site lies off Dounie on the eastern side of the Sound of Jura. It is proposed to locate the centre of the pen group within 150 m of the ADCP position reported in this document. 3. Survey Details 3.1 Hydrographic Survey Surveyed by: Kames Fish Farming Ltd Survey dates: 17 September 2 October 2015 The data are presented here to the current recommendations contained in the SEPA document Attachment VIII, Site and Hydrographic Survey Requirements ( v2.7, 31 October 2008). A 600 khz Teledyne RDI Sentinel Workhorse was deployed at the proposed pen site. This was mounted in a gimballed seabed frame and deployed in a single-point mooring arrangement Figure 1). The mooring was positioned where local topographic features would not cause spurious data collection. The instrument was set-up as described in Table 1 and Figure 2. The transducer head where the pressure sensor is located was 0.50 m from the base of the seabed frame. The position of the ADCP was recorded on meter deployment and on recovery to verify that the meter remained in a fixed position. Dounie Hydrographic Report (2015v1) p4/17

5 Figure 1. Schematic diagram of mooring array deployed during the survey. Figure 2. Instrument configuration details. Dounie Hydrographic Report (2015v1) p5/17

6 The ADCP contained an internal pressure sensor to measure depth at the deployment site. Table 1. Set-up and deployment details of the ADCP used during survey. Position of bins selected for AutoDEPOMOD in m above seabed ADCP Position* Dataset Start Dataset End Measured Depth mcd) Sub-Surface: 25.6 Net-Bottom: 15.6 Near-Bed: 2.6 Sound of Jura E, N) 17/09/15 02/10/ ** Position recorded relative to WGS84 datum using Garmin GPSMap 62. Grid InQuest was used to convert this to OSGB36. Depth measured by pressure sensor. Valid data (1081 records) was obtained for 15 days incorporating both spring and neap tides for the period 17/09/15 11:40:00 hrs GMT to 02/10/15 11:40:00 hrs GMT. Predicted tidal heights during the period of deployment are shown in Table 2. Hydrographic data are presented below Tables 3 & 4 and Figures 3 to 8) in accordance with the recommendations described by SEPA. Admiralty Total Tide mean sea level at the site is chart datum m and the lowest predicted spring tide during the deployment was chart datum m. 3.2 Meteorological Survey Surveyed by: Kames Fish Farming Survey dates: 17 September 2 October 2015 Wind speed and direction data were obtained during the deployment period by a Campbell Scientific BWS-200 weather station positioned on the shore of Shuna Island at NM Although the weather station was located 15.5 km north of the ADCP its measurements are considered acceptable for the assessment of maximum wind speed during the deployment at the Dounie site. Wind speed and direction data for the period 17/09/15 14:00 to 02/10/15 14:00 GMT are presented in Tables 5 & 6 and Figure Bathymetric Survey Surveyed by: Kames Fish Farming Ltd Survey date: 17 September and 2 October 2015 A previous visit to this site indicated that charted depths are inaccurate. Thus, a depth survey was carried out to provide the bathymetric data required by AutoDEPOMOD. Eight hundred and ninety five depths were collected at the potential pen site location. The measured depths were converted to chart datum using Admiralty Total Tide software. The survey included possible grid corners, cardinal points and the ADCP s deployment location. These are provided in Table 7 and Figure Magnetic North to Grid North Conversion Current and wind direction data was collected in degrees magnetic north and is reported in this document relative to grid north. Dounie Hydrographic Report (2015v1) p6/17

7 Magnetic north was 45 ( 0.75º) west of grid north ( obtained from Figure 3). The hydrographic data was corrected from magnetic north to grid north by subtracting 0.75º from the magnetic north direction data using SEPA s HG_data_analysis_v7.xls tool (version 7.11). Figure 3. BGS magnetic north to grid north conversion. 3.5 GPS and Depth Sounder Calibration All positions were recorded relative to WGS84 datum using a Garmin GPSMap 62. Throughout the survey the Garmin indicated an accuracy of ± 3 m. Prior to using the GPS it was checked against a Furuno GPS/WAAS Navigator and a Navnet VX2 Chart Plotter/GPS on the survey vessel. Depth measurements were recorded using a Furuno ECV-1100L depth sounder on the survey vessel. This was checked against a Hawkeye handheld digital sonar which provided similar readings (± 0.2 m for ten measurements at varying depths). Dounie Hydrographic Report (2015v1) p7/17

8 4. Hydrographic Survey Results The following pages contain tabulated and graphic outputs for the selected 25.6 m, 15.6 m and 2.6 m ADCP bins (bins 24, 18 and 1 respectively) during the survey period at Dounie. Table 2. Tidal data predicted at nearest tidal port to the monitoring site during the 15-day period. Nearest tidal port Tidal state High water Date & GMT) Height of high water (m) Low water Date & GMT) Height of low water (m) Carsaig Bay predictions based on Oban) Spring 30/09/15 18: /09/15 12: Neap 22/09/15 23: /09/15 17: Table 3 shows mean speed, ranked percentage of the mean current speed and m/s as a ranked percentage within the current speed record for the selected surface, middle and bottom bins. Table 3. Current speed during the 15-day period. Bin Height above seabed] Mean speed m/s) m/s Major Axis (og) Amplitude anisotropy Residual speed m/s) Residual Direction og) Sub-Surface 25.6 m] 5.56 m below LST Net-Bottom 15.6 m] m below MSL % % Near-Bed 2.6 m] % Table 4 shows the tidal ellipse major axis used derived from 1º bins from current direction frequency analysis; the decomposition of easterly and northerly vector components relative to the tidal ellipse major axis; and the tidal current amplitude relative to the tidal ellipse major axis. Table 4. Summary data for the 3 bins during the 15-day period. Bin Sub-Surface 25.6 m] Net-Bottom 15.6 m] Near-Bed 2.6 m] Tidal ellipse major axis Components of current residual (m/s) Components of tidal current amplitude ( m/s) Bearing (og) Parallel (U) Normal (V) Parallel (U) Normal (V) Dounie Hydrographic Report (2015v1) p8/17

9 Figure 4. Summary data for sub-surface bin (25.6 m above seabed) during the 15-day period. Dounie Hydrographic Report (2015v1) p9/17

10 Figure 5. Summary data for net-bottom bin (15.6 m above seabed) during the 15-day period. Dounie Hydrographic Report (2015v1) p10/17

11 Figure 6. Summary data for near-bed bin (2.6 m above seabed) during the 15-day period. Dounie Hydrographic Report (2015v1) p11/17

12 ADCP Pressure Sensor Depth + Frame Deployment Depth (mcd) + ATT Tidal Prediction / 09/15 18/ 09/ 15 19/09/15 20/ 09/15 21/09/15 22/09/15 23/ 09/ 15 24/09/15 25/ 09/15 26/09/15 27/09/15 28/ 09/ 15 29/09/15 30/ 09/15 01/10/15 02/10/15 Figure 7. Graph of ADCP pressure sensor readings and Admiralty Total Tide predictions at the Dounie site Pitch ( deg) Roll (deg) Heading (deg) Corrected Heading (deg) /09/15 18/09/15 19/09/15 20/09/15 21/09/15 22/09/15 23/09/15 24/09/15 25/09/15 26/09/15 27/09/15 28/09/15 29/09/15 30/09/15 01/10/15 02/10/15 Figure 8. Graph of ADCP pitch, roll, heading and corrected heading during the 15-day period. NB: Heading differed by 6.60 degrees with the three lowest readings ( 11.87, 8.47 and degrees) occurring on 26/09/15 at 16:40 and 17:00 hrs GMT and on 27/09/15 at 05:00 hrs GMT. Excluding these readings heading differed by just 2.80 degrees. A heading correction was applied to the data reported in this document to take account of these fluctuations. Dounie Hydrographic Report (2015v1) p12/17

13 5. Meteorological Survey Results This and the following page contain tabulated and graphic representations of wind speed and direction for the Dounie site during the 15-day period. Table 5 reveals that the daily average wind speed remained below 10 m/s for more than 3 consecutive days in compliance with SEPA guidelines. Table 5. Average wind speed and direction at the Dounie site. Date Average Speed ( m/s) 17/09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /09/ /10/ /10/ Table 6. Meteorological data measured for the Dounie site during the 15-day period. Major Axis og) Max Speed m/s) Mean Speed m/s) Residual Direction og) Residual Speed m/s) Dounie Hydrographic Report (2015v1) p13/17

14 Figure 9. Summary data for weather during the 15-day period. Dounie Hydrographic Report (2015v1) p14/17

15 6. Bathymetric Survey Results Depth measurements for the possible grid corners and cardinal points and at the ADCP deployment location are provided in Table 7. Figure 10 shows the location of these measurements. Table 7. Depth measurements at ADCP deployment location, cardinal and possible grid corner positions. Location Time GMT) Lat & Long WGS84)* Eastings OSG36 m) Northings OSG36 m) Measured Depth (m) ATT Correction m)** Depth mcd) Charted Depth mcd) Cardinal 1 11:25 Cardinal 2 11:27 Possible SE Grid Corner Possible SW Grid Corner 11:28 11:29 Cardinal 5 11:31 Cardinal 6 11:32 Spot Depth 11:34 Possible NW Grid Corner Possible NE Grid Corner 11:35 11:40 Cardinal 4 11:42 Cardinal 3 11: September September & 2 October 2015 ADCP 17/09/15) ADCP 02/10/15) 10: : : : : : Position recorded to WGS84 datum using Garmin GPSMap 62 ( displayed accuracy during depth soundings was ± 3 m). Correction is for Admiralty Total Tide predicted tidal amplitude at Carsaig Bay. Dounie Hydrographic Report (2015v1) p15/17

16 C4 ( 41.1) GC ( 59.3) GC ( 22.4) ADCP ( 31.06) SD ( 29.3) C3 ( 50.3) C5 ( 14.6) C6 ( 5.9) GC ( 28.1) GC ( 18.0) C2 (15.6) C1 ( 11.9) Depths are given in mcd, GC = Possible Grid Corner, C = Cardinal, SD = Spot Depth. Figure 10. Depth at ADCP, possible pen group grid corners and cardinal points. Dounie Hydrographic Report (2015v1) p16/17

17 7. Discussion and Conclusions The pitch and roll of the transducer were stable throughout the deployment ( 1.6o maximum change in pitch, 1.4o maximum change in roll). The heading record showed a maximum change of 6.6o and the direction data has been corrected to take account of the deviation from the initial measurement. The pitch, roll and heading data coupled with the pressure sensor s depth record indicate that the ADCP remained undisturbed. Mean depth, as recorded by the pressure sensor over the reported 15-day deployment, was m. The pressure sensor was 0.5 m above the seabed and MSL according to ATT is 0.91 m above CD. This gives an approximate deployment depth of mcd which complies with the measured depth at the deployment site of 29.9 mcd. Measured tidal heights throughout the deployment also corresponded with ATT predictions. The bin heights reported in this document are 2.6 m, 15.6 m and 25.6 m above the seabed. These heights meet the criteria specified in Attachment VIII of SEPA s Fish Farm Manual i.e. 3 m above the seabed for the near-bed bin, ±1 m from the bottom of the nets at MSL for the midwater bin (net depth is expected to be 16.0 m), and circa 5 m below LST for the near-surface bin. The average depth for the possible pen group corners is mcd. The deployment depth mcd) meets SEPA s desirable target of ±5 m of the mean depth of the corner depths. Wind speed was not greater than 10 m/s for 3 consecutive days. The current speed and direction data are considered representative of the Sound of Jura site. A grid file using measured depths has been created for AutoDEPOMOD modelling as charted depths are inaccurate in this location. The site and hydrographic survey reported in this document is considered to comply with the requirements of Attachment VIII of SEPA s Fish Farm Manual and the current speed and direction data are considered to be representative for the Dounie site. Dounie Hydrographic Report (2015v1) p17/17