6787 DECEMBER 2013 Great Ouse 100FT Drain Report · PDF fileGREAT OUSE AND 100 FT DRAIN...

GREAT OUSE AND 100 FT DRAIN QUARTERLY BATHYMETRIC SURVEY DECEMBER 2013 SITE SURVEY REPORT

H6787 1 Measured Excellence

ENVIRONMENT AGENCY

GREAT OUSE AND 100FT DRAIN

QUARTERLY BATHYMETRIC SURVEY

DECEMBER 2013

SITE SURVEY REPORT

NO. H6787

LONGDIN & BROWNING (SURVEYS) LIMITED

CHERRY TREE HOUSE

CARMARTHEN ROAD

SWANSEA

SA1 1HE



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.



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

3.2.1 Hydrographic Survey Operations

3.2.2 Tidal Observations

3.3 Processing/Presentation

3.3.1 Post Processing

3.3.2 Data Presentation

4. SURVEY DATA AND FIELD VARIABLES

4.1 Survey Datum

4.1.1 Horizontal Datum

4.1.2 Vertical Datum

5. SURVEY PERSONNEL

5.1 Project Personnel

6. DISCUSSION OF RESULTS

APPENDIX A Existing Tide Boards. Great Ouse

APPENDIX B Existing Tide Boards. 100Ft. Drain



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 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.

Equipment 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.

Riverbed Conditions The riverbed is assumed to be composed of mud, soft silt, sand and

gravel.



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

2013.

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.



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) + 100 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.



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 + 0.25% 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

3.2.1 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 11th

December and the Great Ouse on the 12th December.

3.2.2 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.



3.3 Processing/Presentation

3.3.1 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.

3.3.2 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.

.



4.0 SURVEY DATA AND FIELD VARIABLES

4.1 Survey Datum

4.1.1 Horizontal Datum

Datum - Transverse Mercator - O0 - 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 6377563.00

Semi - Minor Axis b 6356257.00

Eccentricity e2 0.006670540000

Compression f 1/297

Projection

Central Meridian 020 West

Origin 490 North

False Easting 400000 metres West

False Northing 100000 metres North

Scale factor on Central Meridian 0.999601272

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

4.1.2 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.



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



6.0 DISCUSSION OF RESULTS

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 11.2.

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.



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.



APPENDIX A Existing Tide Boards

Great Ouse

Downham Market. Reasonable condition. Needs cleaning.

Tail Sluice. Very poor condition. Needs replacing.



Ferry Crossing. King’s Lynn. Reasonable condition. Markings starting to flake. Needs cleaning.

West Bank. King’s Lynn. Reasonable condition. Needs cleaning.



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.



Gault Bridge - Upstream Face. Good condition. Needs cleaning at lower levels.

Gault Bridge - Downstream Face. Good condition. Needs cleaning at lower levels.



Mepal Road Bridge - Upstream Face. Good condition. Needs cleaning at lower levels.

Mepal Road Bridge - Downstream Face. Good condition. Needs cleaning at lower levels.



Railway Bridge - Upstream Face. Good condition. Needs cleaning at lower levels.

Railway Bridge - Downstream Face. Good condition. Needs cleaning at lower levels.



Welney Suspension Bridge. Good condition. Needs cleaning at lower levels.

Wellmore Lake Sluice. Good condition. Needs cleaning at lower levels.



Denver Eyes Sluice. Good condition. Needs cleaning at mid to lower levels.

6787 DECEMBER 2013 Great Ouse 100FT Drain Report · PDF fileGREAT OUSE AND 100 FT DRAIN...

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