ENVIRONMENT AGENCY GREAT OUSE AND 100 FT DRAIN QUARTERLY BATHYMETRIC SURVEY DECEMBER 2013 SITE SURVEY REPORT NO. H6787

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1 ENVIRONMENT AGENCY GREAT OUSE AND 100FT DRAIN QUARTERLY BATHYMETRIC SURVEY DECEMBER 2013 NO. H6787 LONGDIN & BROWNING (SURVEYS) LIMITED CHERRY TREE HOUSE CARMARTHEN ROAD SWANSEA SA1 1HE H Measured Excellence

2 ARCHIVE RECORDS Please note that all field and original information relating to the enclosed report, unless otherwise requested by the client, shall remain in the Archive Library of Longdin and Browning (Surveys) Limited for a minimum period of FIVE (5) years. It is the client s responsibility to inform Longdin and Browning (Surveys) Limited before cessation of this period, if original analogue or digital information is required to be passed on for completeness of their own records and archive register. H Measured Excellence

3 CONTENTS SITE SUMMARY 1. INTRODUCTION 1.1 Introduction and Scope of Work 2. SUMMARY OF RESULTS 2.1 Bathymetry 3. SURVEY SYSTEMS/EQUIPMENT/OPERATIONS 3.1 Positioning and Echo Sounding Equipment 3.2 Field Operations Hydrographic Survey Operations Tidal Observations 3.3 Processing/Presentation Post Processing Data Presentation 4. SURVEY DATA AND FIELD VARIABLES 4.1 Survey Datum Horizontal Datum Vertical Datum 5. SURVEY PERSONNEL 5.1 Project Personnel 6. DISCUSSION OF RESULTS APPENDIX A APPENDIX B Existing Tide Boards. Great Ouse Existing Tide Boards. 100Ft. Drain H Measured Excellence

4 SITE SUMMARY Survey Area Great Ouse and 100 Ft Drain between Earith and King s Lynn. The 100 Ft Drain Survey has now been extended from Earith to Brownshill Staunch. Requirements Equipment Riverbed Conditions Single beam bathymetric survey along the centre line of the tidal Great Ouse (25.2 Km in length from the Wash to Denver Sluice) and 100 Ft Drain (35.2 Km from Denver Sluice to Earith Lock and 3.4 Km from Earith to Brownshill Staunch). Record the existence, location and condition of tide gauge boards along the 57 Km channel. 4.5M Survey Vessel with 30Hp outboard engine. Leica 1200 RTK DGPS Positioning System PC Computer. Coastal Hypack Hydrographic Software. Navisound 415 Echo Sounder with 210 Khz transducer. The riverbed is assumed to be composed of mud, soft silt, sand and gravel. H Measured Excellence

5 1.0 INTRODUCTION 1.1 Introduction and Scope of Work This report details the sixth bathymetric site survey carried out for the Environment Agency of the Great Ouse and 100Ft Drain. The survey was carried out in accordance with the specifications by Longdin & Browning (Surveys) Limited during December This was the third survey of the new contract to be carried out by Longdin and Browning to gather data for comparison purposes against previous and future surveys. The last four surveys were carried out by Longdin and Browning and the results are shown in the overlay comparisons. The existence, location and condition of tide boards along the entire 57 Km are also included in this report. H Measured Excellence

6 2.0 SUMMARY OF RESULTS 2.1 Bathymetry The soundings of the 100Ft Drain and Great Ouse have all been reduced to SLD. This is Ordnance Survey Datum (Newlyn) m. This datum was supplied by the client and the Horizontal grid was O.S. National grid. The same survey line was followed from the previous survey carried out by Longdin & Browning on both the 100Ft and Great Ouse as best as possible. This was not always possible on the Great Ouse due to the sand banks and can be seen on the track plots. The same survey line was followed from the last survey for the extended stretch between Earith and Brownshill Staunch as accurately as possible. H Measured Excellence

7 3.0 SURVEY SYSTEMS/EQUIPMENT/OPERATIONS 3.1 Positioning and Echo Sounding Equipment The navigation system was the Leica 1200 DGPS. This system uses a base unit on a known coordinated point transmitting corrections to the rover unit on board the boat. This will give a 3D positional accuracy of better than 2 cm. The raw DGPS positions, in WGS84, were converted internally to OSGB36 using a dedicated software loop and the resulting grid positions were logged. Corrections were made to the raw data for equipment latency by the online software. The Echo Sounder used was a Navisound 415 echo sounder operating with a 210 khz transducer. The prevailing conditions and use of the RTK heighting meant that there was no need to employ a heave motion sensor. The resolution of the soundings is 1cm in depth and an accuracy of 5cm % of indicated depth. The echoes were recorded in analogue form on thermal paper and also digitally to the logging computer. The analogue record displays raw depth. The echo sounder was calibrated using the standard bar-check method to set the draft and speed of sound in water. 3.2 Field Operations Hydrographic Operations The vessel Lobrow was used for the duration of the survey, operating out of Denver Lock. Hydrographic observations were performed on the 100Ft Drain on the 11 th December and the Great Ouse on the 12 th December Tidal Observations The tide observations were taken directly from the RTK heighting of the GPS system. This was calibrated against existing tide boards along the 57Km length where possible. Most of the tide boards are in good condition but need cleaning at lower levels. H Measured Excellence

8 3.3 Processing/Presentation Post Processing The observed data was edited for erroneous spikes and then reduced to local datum using the observed tides. The resulting data was then processed to an ASCII X, Y, Z file and sampled at various spacing for use in the charting Data Presentation The results of the hydrographic survey are plotted on bathymetric charts at a scale of 1:20,000. Separate charts have been produced for The Great Ouse and 100 Ft Drain showing a plan view of vessel track. 2 Km marker locations and bridges have been labelled. A Bathymetric profile has been produced showing the depth relative to SLD(m) at 20m intervals. 1Km marker location and bridges have been labelled. This data has been overlaid with previous surveys for comparison and analysis.. H Measured Excellence

9 4.0 SURVEY DATA AND FIELD VARIABLES 4.1 Survey Datum Horizontal Datum Datum - Transverse Mercator - O 0 - AIRY Geodetic Parameters of System Calibration. The whole of the project was conducted on the Transverse Mercator (TM) Projection, Airy (UK) Spheroid, horizontal datum; U.K. National Grid. (OSGB 36). Airy's Spheroid Semi - Major Axis a Semi - Minor Axis b Eccentricity e Compression f 1/297 Projection Central Meridian 02 0 West Origin 49 0 North False Easting metres West False Northing metres North Scale factor on Central Meridian Units Expressed International metres Datum Shift Parameters The transformation used is the OSTN 02 transformation using the OSGM 02 geoidal model. These are both supplied by the Ordnance Survey and are the definitive parameters for UK Survey work Vertical Datum The Vertical Datum is based on Ordnance Datum Newlyn. 100 metres has been added to all values so that negative levels are avoided. H Measured Excellence

10 5.0 SURVEY PERSONNEL 5.1 Project Personnel Name Assignment Duties M. Thomas Site Supervisor & Hydrographic Survey Senior Hydro Surveyor M. Jones Hydro Assistant Hydrographic Survey R. Evans Land Surveyor Control and Shore Support H Measured Excellence

11 6.0 DISCUSSION OF RESULTS GREAT OUSE AND 100 FT DRAIN QUARTERLY BATHYMETRIC SURVEY DECEMBER 2013 Great Ouse: Denver Sluice - The Wash The recent survey shows an increase in material at KP 1.5 of up to approximately 1.0m. The area between Downham bridge and Stowbridge show a build up of material, filling in previous holes, but these areas always appear very mobile. Downstream of Stowbridge there appears to be slight decreasing changes in levels of between 0.3m and 0.5m between KP 7.3 and KP 8.9. Bed levels between KP 9 and Magdalen Bridge at KP 11.2 show an increase of varying values up to 1.0m. A decrease in bed levels can be seen between KP 11 and KP Looking downstream from Magdalen Bridge, bed levels between KP12 and KP 13 show both increase and decrease of material of approximately 0.3m. The deep area near KP 13.6 shows a shoaling of bed levels by up to 1.5m. The deep holes at Pipeline (KP 15.9) and Pipeline (KP 17.3) both show a decrease in bed levels. Levels from KP 18 to the A47 Bridge show a general increase of material of approximately 0.3m. The deep area around the A47 Bridge and Free Bridge shows an increase in levels which again could be due to mobile material. A build up of material can be seen between KP 20.4 and KP 21. Once again the area around Ferry (KP 21.6) shows very mobile material. This can also be seen through to the downstream survey limit. It must again be noted that prior to this survey, the strong gale force winds and very high spring tides experienced have affected these level changes. H Measured Excellence

12 100Ft Drain: Denver Sluice - Earith Road Bridge The bathymetric data from this survey shows a good general correlation with the previous survey carried out in October this year. The bed levels between KP 0 and KP 4 shows an increase in material of approximately 0.5m and 0.7m. Levels around Welmore Sluice Outfall and Denver Lock show a higher increase and possible movement of material. Between KP 4 and KP 9.5 levels show little change apart from a bed level decrease between KP 7.6 and KP 8 of approximately 1.2m maximum. At Wash Road Suspension Bridge (KP 9.7) levels have decreased by an average of 0.6m. Upstream of KP 10 shows little change in bed levels as far as the Viaduct at KP 15 apart from possible movement of material. An increase of material can be seen between KP 15 and KP 15.7 of up to 0.7m. Moving upstream from KP 16, there shows little change in levels as far as KP 20. An increase in levels can be seen at KP 20.5 of up to 0.5m. Levels from KP 21 through the bridges at Mepal and Gault show minimal changes in bed levels. The bed levels upstream of Gault Bridge show little change up to Earith Bridge. The stretch between KP 28.3 and KP 29 is still very uneven giving varying comparisons, but in general show little change. The extension upstream of Earith to Brownshill Staunch show very little change in bed levels from the last survey. It must be noted that prior to the December survey, gale force winds and very high spring tides were experienced which would affect level changes. H Measured Excellence

13 APPENDIX A Existing Tide Boards Great Ouse Downham Market. Reasonable condition. Needs cleaning. Tail Sluice. Very poor condition. Needs replacing. H Measured Excellence

14 Ferry Crossing. King s Lynn. Reasonable condition. Markings starting to flake. Needs cleaning. West Bank. King s Lynn. Reasonable condition. Needs cleaning. H Measured Excellence

15 APPENDIX B Existing Tide Boards 100 Ft Drain Earith Bridge - Upstream Face. Good condition. Needs cleaning at lower levels. Earith Bridge - Downstream Face. Good condition. Needs cleaning at lower levels. H Measured Excellence

16 Gault Bridge - Upstream Face. Good condition. Needs cleaning at lower levels. Gault Bridge - Downstream Face. Good condition. Needs cleaning at lower levels. H Measured Excellence

17 Mepal Road Bridge - Upstream Face. Good condition. Needs cleaning at lower levels. Mepal Road Bridge - Downstream Face. Good condition. Needs cleaning at lower levels. H Measured Excellence

18 Railway Bridge - Upstream Face. Good condition. Needs cleaning at lower levels. Railway Bridge - Downstream Face. Good condition. Needs cleaning at lower levels. H Measured Excellence

19 Welney Suspension Bridge. Good condition. Needs cleaning at lower levels. Wellmore Lake Sluice. Good condition. Needs cleaning at lower levels. H Measured Excellence

20 Denver Eyes Sluice. Good condition. Needs cleaning at mid to lower levels. H Measured Excellence