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National Rivers AuthorityI

SUMMARY OF MONITORING ACTIVITIES ON THE BLACKWATER ESTUARY

June 1996

National Rivers Authority

SUMMARY OF MONITORING ACTIVITIES ON THE BLACKWATER ESTUARY

e n v ir o n m e n t a g e n c y

SOUTH WEST REGION

LIBRARY

6 1 4 . 77 / NA TNATIONAL RIVERS A UT HORI TY Summary o f m o n i t o r i n g

a c t i v i t i e s on t h eAKNF c . 1 so «00

© Sir W illiam Halcrow & Partners Ltd 1996

Sir Wiliam Halcrow & Partners Ltd has prepared this report in accordance w ith the instructions of National Rivers Authority for the ir sole and specific use. Any other persons who use any information contained herein do so at their ow n risk.

Sir William Halcrow & Partners Ltd Burderop Park Swindon Wiltshire SN4 OQD Tel 01793 812479 Telex 44844 Halwil G Fax 01793 812089

ENVIRONMENT AGENCY

NATIONAL RIVERS AUTHORITY

SUMMARY OF MONITORING ACTIVITIES ON THE BLACKWATER ESTUARY

JUNE 1996

DOCUMENT REFERENCE NO WD/ERD/009

CONTENTS

1 INTRODUCTION 1

2 NATIONAL RIVERS AUTHORITY2.1 NRA Surveys2.2 NRA R&D Commissioned Surveys

2.2.1 NRA R&D Project No. 591:Sedimentation Processes of Managed Retreat 3

2.2.2 NRA R&D Project No. 592: Set Back of Saltings:Pollution of Managed Retreat Sites 3

3 MINISTRY OF AGRICULTURE, FISHERIES AND FOOD 4

4 ENGLISH NATURE 6

5 INSTITUTE OF TERRESTRIAL ECOLOGY 7

6 ROYAL SOCIETY FOR THE PROTECTION OF BIRDS 8

APPENDIX A - LIST OF CONTACTS 9

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1 INTRODUCTION

The Blackwater Estuary, in Essex, is the focus of a number of saltmarsh research initiatives. The most notable of these is the National Rivers Authority (NRA) operational managed retreat scheme at Orplands and the Ministry of Agriculture, Fisheries and Food (MAFF) experimental managed retreat, for habitat creation, at Toilesbury. As a result of these initiatives extensive monitoring has been conducted in the Blackwater by a range of organisations, including the NRA, MAFF, HR Wallingford Ltd, Institute of Terrestrial Ecology (ITE), English Nature (EN) and Royal Society for the Protection of Birds (RSPB). A location plan of the area is shown in Figure 1.

The purpose of this report is to provide a summary of all known monitoring activities in the Blackwater, and it has been prepared in response to a request from the NRA Steering Group for the R&D programme 'Saltmarsh Management for Flood Defence*. This report will enable both current and future researchers to benefit from currently available data. Furthermore, it is intended that future monitoring programmes can be designed so that unnecessary duplication is avoided.

At the end of this report is a list of organisations who are responsible for maintaining the data sets identified within this report. These organisations should be contacted directly for further information. It is anticipated that data can be made available to individuals with legitimate research objectives at zero or minimal cost. An existing agreement already exists between some of the organisations listed which enables data to be exchanged on a reciprocal basis.

WD/art/ERDA/R4S4/6.96 1

2 NATIONAL RIVERS AUTHORITY

2.1 NRA Surveys

The NRA have collected data from a range of surveys in the Blackwater, details of which are summarised below. At present the data are used for assessment of specific sites and no overview interpretative reports have been written.

• Bathymetric/Beach Surveys

Two surveys of the estuary were undertaken during November 1993.and November 1994 using the transects shown on Figure 2.

• Wave/Tide Monitoring

Data were collected, over the period January 1994 to December 1994, at five sites within the estuary. The locations of the data recorders are shown on Figure 3.

The wave measurements were recorded for 20 minutes every 3 hours, and the data consisted o f

date/time still water levelsignificant, maximum and minimum wave heights zero crossing period spectral peak period

The tide measurements were recorded for 1 minute every 15 minutes over blocks of time not less than a fortnightly tidal cycle. Two such periods of tidal measurement were taken at least 6 months apart. The data consisted of:

date/time still water levelstandard error of still water level

Acoustic Doppler Current Profile Monitoring (ADCP)

Three ADCP surveys were carried out during December 1993, June 1994 and November 1994. The transects, along which data were collected, are shown in Figure 3. The processed data gives current vectors (velocity and direction) through the water column.

• Aerial Photographs

Black and white stereoscopic photographs have been obtained from surveys in July 1993 and July 1994, at a nominal scale of 1:5000. Figure 4 shows the run map and extent of the photographic coverage.

WD/art/E RD A/R454/6.96 2

2.2 NRA R&D Commissioned Surveys

2.2.1 NRA R&D Project No. 591:Sedimentation Processes of Managed Retreat

Contractor Institute of Estuaries and Coastal Studies, Hull University (IECS), and, subsequently, Cambridge Coastal Research Unit, Cambridge University

This project commenced in February 1995 and involves a 3 year programme of detailed measurement of hydrodynamic and morphological changes around the managed retreat sites at Tollesbury and Orplands. In addition, there will be similar measurements over a wider area, but at a reduced temporal and spatial resolution. Field experiments are to be repeated during the three year duration of the project. The data to be collected include measurements of water surface elevation, tidal currents, suspended sediment concentrations and morphological changes.

At Orplands, a number of water level recorders were deployed on the mudflats outside the managed retreat site immediately before, during and after the breach of the sea defences. Future biannual monitoring of the site will include measurement of topography, tidal levels, current velocities and the volume and concentrations of suspended sediment entering the set back area.

At Tollesbury, monitoring will take place adjacent to the breach location and at far-field sites. Figure 5 shows the locations of various instruments.

2.2.2 NRA R&D Project No. 592: Set Back of Saltings:Pollution of Managed Retreat Sites

Contractor: Imperial College of Science,Technology and Medicine

This project commenced in March 1995 and will study the potential pollution effects of saline inundation of agricultural soil.

Within the set back areas at Orplands and Tollesbury, soil and sediment, groundwater and surface water samples are being taken before and after inundation for analysis of:

physical and chemical properties of the soilheavy metalsnutrientsorganic micro-pollutants including herbicides and insecticides

Plant cover and health around the sampling stations are being noted and analyses of plant tissue are being carried out for selected pollutants.

WD/art/E RDA/R454/6.96 3

3 MINISTRY OF AGRICULTURE, FISHERIES AND FOOD

The Ministry, in association with English Nature, are funding a full scale experiment in the management of set back of sea defences within the Blackwater Estuary. The key participants in this study and their specific monitoring roles are outlined below. The set-back site is at Tollesbury and breaching took place in August/September 1995.

• Silsoe College

Soil monitoring is being undertaken within the site, with sampling carried out before and following inundation. Parameters to be examined include:

particle size distribution micro morphologyshear strength and penetration resistance hydraulic conductivity pore water pressurescomparative analysis of samples from adjacent saltmarsh

Results from the above will be analysed for changes and trends as a function of time and/or number of inundations.

HR Wallingford Ltd

Detailed bathymetric surveys of existing creeks have been undertaken along with some hydrodynamic modelling.

• Institute of Terrestrial Ecology

ITE are conducting topographical and botanical surveys of the site and adjacent saltmarsh and mud flat areas. The whole site has been surveyed with an infra-red theodolite to an accuracy of +/-10 mm. A network of 28 temporary bench marks have been installed and levelled. The vegetation of the surrounding estuary has been sampled.

For the botanical monitoring, a block layout of 50 plots (2m x 2m) within the site has been established, with each subject to a variety of treatments which can be compared with an untreated control plot. The first recording of the botanical experimental procedures is scheduled for June 1996 with the main recording in September 1996 and each September thereafter.

Mapping of the general distribution of vegetation and the major plant communities of the Tollesbury/Old Hall part of the estuary will be done using aerial photography with ground verification. A vegetation map will be prepared at a scale of 1:2500.

institute of Estuarine and Coastal Studies, Hull University and, subsequently, the Cambridge Coastal Research Unit, Cambridge University.

To complement the NRA commission to study hydrodynamic and morphological outside the Tollesbury managed retreat site, IECS/CCRU are measuring waves, currents and sediment movements within the site post breaching, initially from April 1995 to September 1996.

WD/art/E RDA/R4S4/6.96 4

IECS also prepared an outline environmental assessment of the scheme for planning purposes.

All monitoring activities at the Tollesbury site will be reviewed in 1996 and proposals considered for the nature and extent of continued measurements based on initial results.

WD/art/E ROA/R4 54/6.96 5

4 ENGLISH NATURE

English Nature (EN) undertake monitoring of the Northey Island set back site. This involves an annual biological survey and biannual geomorphological surveys - ie accretion/erosion. The monitoring is largely confined to the site itself with a few monitoring points on the foreshore.

EN also contribute to the NRA's wider physical monitoring activities on the Blackwater, such as bathymetry measurement.

WD/art/ERDA/R454/6.96 6

5 INSTITUTE OF TERRESTRIAL ECOLOGY

Since 1991, ITE have conducted various monitoring activities at Old Hall Marshes (see figure 1) either at or near the Mobile Laboratory on the RSPB Reserve.

• Weather Data

Automatic recording of weather data has been carried out since 1991, and is ongoing. Data include total and net solar radiation, wet and dry bulb temperature, rainfall, wind speed and direction and barometric pressure.

• Tide Data

Automatic recording of tide data has been carried out since 1991 and is ongoing.

• Marsh Surface Level

Between January 1991 and April 1993 monthly measurements of marsh surface level were taken at 80 points. From May 1993 until the present time the number of points was increased to 240.

• Saltmarsh Productivity

This was monitored monthly in 1990, 1991 and 1993.

WD/art/E R DA/R454K5.96 7

As part of the Tollesbury managed retreat experiment, the RSPB undertook counts of waders and wildfowl at the site from October 1995 to March 1996 inclusive. The birds were counted four times each month, at high and low water, on a spring and neap tide. The activity of the birds was also noted during each count, eg roosting, feeding, etc.

6 ROYAL SOCIETY FOR THE PROTECTION OF BIRDS

WD/art/E R DA/R454/6.96 8

APPENDIX A

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HALCROW

APPENDIX A - LIST OF CONTACTS

Fiona BurdInstitute of Estuarine and Coastal Studies Hull University HULL, HU6 7RX

Tel: 01482 465667 Fax: 01482 465001

Professor John Pethick Jeremy Lowe University of Cambridge Down in Street CAMBRIDGE, CB2 3EQ

Tel: 01223 339775 Fax: 01223 333450

Dr Alan Brampton Dr Peter Hawkes Dr Kathryn Carpenter Prof NWH Allsop HR Wallingford Ltd Howbery Park WallingfordOxfordshire, 0X10 8BA

Tel: 01491 835381 Fax: 01491 832233

Mr Tony PoisonFlood and Coastal Defence DivisionMinistry of Agriculture, Fisheries and FoodRoom 407Eastbury House30-34 Albert EmbankmentLondon, SE1 7TL

Tel: 0171 238 6649 Fax: 0171 238 6665

WD/art/£R 0 A/R454/8.96

Mr Richard Leafe Dr Geoff Radley English Nature Northminster House Peterborough, PE1 1UA

Tel: 01733 340345 or direct (RL) 318315 Fax: 01733 68834

Professor John N LesterDr Cecilia MacLeodDepartment of Civil EngineeringImperial College of Science, Technology and MedicineImperial College RoadLondon, SW7 2BU

Tel: 0171 589 5111 Fax: 0171 594 6053

Dr Ken NorrisRoyal Society for the Protection of BirdsThe LodgeSandyBedfordshire, SG19 2DL

Tel: 01767 680551 Fax: 01767 692365

Judith Dunderdale Research Officer Silsoe College Cranfield University SilsoeBedfordshire, MK45 4DT

Tel: 01525 863000 Fax: 01525 863001

Gareth Llewllyn NRA HQ Rivers House Waterside Drive Aztec West Almondsbury Bristol, BS12 4UD

Tel: 0117 9624400 Fax: 0117 9624409

WD/art/ERDA/R454/6 9610

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