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The Jubilee River story - Closure Report by Atkins (February 2007)

Summary of the Atkins Jubilee River Post 2003 Recommendations Closure Report January 2007 (03-01-07. First Issue) by Ewan Larcombe 2/3/2007

This document is no longer available on the Thames Flood Forum website.

NOTICE

This document has been produced by ATKINS for the Environment Agency Thames, Asset Systems Management solely for the purpose of the Jubilee River Post 2003 Recommendations Closure Report.  It may not be used by any person for any other purpose other than that specified without the express written permission of ATKINS. Any liability arising out of use by a third party of this document for purposes not wholly connected with the above shall be the responsibility of that party who shall indemnify ATKINS against all claims costs damages and losses arising out of such use.

CONTENTS

Includes:

1 Executive Summary

2 Introduction

2.1Background

2.2 Closure Objectives/Brief

2.4 Reports Considered

3 Report Recommendations

4 Summary of Works                  

4.1 Introduction

4.2 Mill Lane Road Bridge, July 2003

4.3 Manor Farm Weir, July 2003

4.4 Myrke Embankment, September 2004

4.5 Chalvey Left and Right Banks, October 2004

4.6 Slough Road Weir, September 2005

4.7 West Town Farm Service Bridge, December 2005

4.8 Mill Lane Road Bridge, March 2006

4.9 Chalvey Rail Bridge, August 2006

4.10 Myrke Footbridge, August 2006

4.11 Eton, August 2006

4.12 Black Potts, August 2006

4.13 A4 Road Bridge, August 2006

4.14 Timeline, Works, Reports, Surveys.

5 Key Considerations

5.1 LFP Design Capacity

5.2 Post Event Understanding

5.3 Modelling of the Lower River Thames

5.4 Accuracy of Topographical Survey

5.5 Embankment Raising Principles

6 Capacity Chronology

7 Conclusions

8 Appendices

Appendix A: Report References

Appendix B: Report Recommendations

Appendix C: Location Plan

 

1 Executive Summary

The purpose of this report and the study work undertaken as part of this report has been to appraise the recommendations made in a series of documents produced after the January 2003 flood event.

The event in January 2003 revealed a number of failures in the design and identified some performance issues of the newly opened Maidenhead Windsor and Eton Flood Alleviation Scheme (MWEFAS) and specifically the Jubilee River element of that scheme.

A number of reports were provided for assessment and evaluation and this report tracks the recommendations made in those various reports through to their conclusion.

 

This report aims to help the reader follow the progression of reporting and recommendations made since 2003 to the present day. Initial reports focussed on the most critical requirements for repair or reconstruction of the damaged areas of the Jubilee River together with aspects requiring further study or data. Later reports concentrated on examining solutions for identified weaknesses

 

Following repair and remedial works and the gathering of data the focus of attention moved to the capacity of the Jubilee River both in relation to its original design and specification and to its interface with the River Thames. There were recommendations made for bank raising works to develop the capacity of the Jubilee River up to its original design however it was recognised during the development process that this was not a straightforwardly achievable objective. Studies concluded that the design capacity originally envisaged was not achievable through construction of the works as designed. This has been made clear by the use of improved modelling techniques and the availability of new hydraulic data which have altered the understanding of the influence the River Thames downstream condition has on predicted water levels in the Jubilee River.

As a consequence of this acknowledgement the project team agreed that the most appropriate way forward to conclude the remedial works to the Jubilee River was to ensure embankment levels were set at the originally modelled LFP 1 in 65 year water level plus 300mm freeboard and within the original planning permission granted for the scheme.

The hydraulic modelling upon which analysis to date is based has not been formally calibrated against a real measured event. Data gathered through future operation of the Jubilee River will be used to further verify and improve the hydraulic model.

Works have now been undertaken to raise all those embankments where the above criterion, within a 50mm tolerance margin, was not met.  The final phase of the remedial works was completed in September 2006.

In addition to the various remedial works, studies and surveys, the Environment Agency has agreed processes for gathering further data to monitor and evaluate the performance of the Jubilee River in the future and also to liaise with stakeholders in a timely manner. These are not addressed in this report.

 

2 Introduction

2.1 Background

Between the 4th and 8th January 2003, the River Thames catchment experienced the largest flood event since 1947. To prevent flooding of Maidenhead, Windsor and Eton approximately 140m3/s were diverted from the River Thames into the Jubilee River, via the Taplow Sluice in accordance with the operation rules.

During passage of this flow, a number of structures and areas of embankment along the Jubilee River suffered significant damage. Since 2003, Jacobs and Atkins have been working with the Environment Agency on studies and remedial works to restore the Jubilee River to its design requirement.

Atkins was commissioned by the Environment Agency to carry out a condition assessment report, which was issued in April 2003. Based on this and subsequent reports as well as both hydraulic and physical modelling results, a series of works has been recommended either in the form of remedial works to repair damage, or raising bank heights to increase the capacity of the Scheme nearer to its original design intent.

 

2.2 Closure Objectives/Brief

The main objectives of this report are listed below:

1. To list the recommendations made by Atkins and others in the reports post 2003.

2. To provide a summary of the works undertaken to implement the recommendations of those reports.

3. To clearly show the logical links between all recommendations, including the decision-making process behind their development.

4. To provide a clear chronological account of the estimates of changes to the capacity of the Jubilee River.

5. To verify that the remedial works have been carried out in accordance with the recommendations made since the 2003 flood event.

The report covers the entire length of the Jubilee River from the River Thames upstream of Boulters weir (Maidenhead) to its confluence with the River Thames downstream of Romney weir (Windsor).

Closure Report by Atkins (link to Thames FF) (This is no longer supported on the Thames FF web site but I do happen to have a copy here - Jubilee River post 2003 Closure Report - Atkins - January 2007 (1mB)