Abstract: There are clear indications that in the planning and implementation of an expensive new flood defence project the Environment Agency is at risk of repeating the mistakes of the past. The Jubilee River extension proposal – now known as The River Thames Scheme (Datchet to Teddington) - is currently in the development phase. Recently re-costed from £309m to £588m the partnership funding shortfall is significant – the project is at risk and there is no ‘Plan B’.

Factors influencing the increasing stage and reducing discharge over time of the River Thames are considered. In addition sub-standard design and construction of the Jubilee River flood channel led directly to significant structural failures, limited discharge and an out-of-court settlement. The original Jubilee River channel failed to achieve the projected cost/benefit ratio and resulted in an assortment of unintended consequences. Experience has shown that professional assertions given in evidence at the 1992 Maidenhead, Windsor and Eton Flood Alleviation Scheme Planning Inquiry have not been achieved and furthermore the Inspector’s concerns about hydraulic model limitations went unheeded.

An ever changing hierarchy, defective strategy, inadequate scrutiny and insufficient knowledge combined with a lack of honesty/openness and a reluctance to accept responsibility for mistakes due to consequential reputational harm leads directly to an inability to learn and thus improve future performance. Are we at risk of history repeating itself?

The Thames side towns of Windsor, Eton and Maidenhead flooded often simply because they were located on flood plain. In the mid 1980’s the Maidenhead, Windsor and Eton Flood Alleviation Scheme (MWEFAS) was conceived. Without going into detail the National Rivers Authority (having considered many options) submitted a plan for a parallel channel approximately 50m wide x 12km long that took flood water out of the Thames up-stream of Maidenhead and returned it into the Thames down-stream of Windsor. This proposal was properly considered at a Planning Inquiry commencing in October 1992. Below is the expert view of the Assessor: P Ackers - M Sc(Eng) FCGI FICE MIWEM MASCE - on the hydraulic models used to justify the scheme.

Some three years elapsed between the 1992 Inquiry and Ministerial Approval in 1995 and it appears that Mr Ackers concerns about hydraulic model limitations went unheeded or forgotten by the scheme designers and the Environment Agency who were now in charge of the project. The project commenced in about 1996 and was inaugurated in mid-2002. With the arrival of the January 2003 flood event Maidenhead, Windsor and Eton were protected by the new channel but the undefended villages downstream were inundated for the first time since 1947. Manual operation of the new channel control flow structure at only 2/3rds capacity allowed flood water to bypass the attenuating characteristics of the natural upstream flood plains. Thus flood flows arrived downstream earlier, rose more quickly and finished at a higher level. Furthermore the new channel suffered significant structural damage during the 2003 flood event. In particular the Taplow Flow Control Structure lacked a stilling basin and consequently suffered severe erosion. Marsh Lane Structure embankments suffered severe erosion, Manor Farm Weir was curved downstream in the middle, Slough Weir downstream face protection was swept away and the Myrke Embankment in Datchet almost collapsed. Repair and rebuild costs totalling millions of pounds were offset by an out-of-court settlement of £2.75m received from the designers for sub-standard design and construction. The recommendations from Clive Onion’s 2004 Mechanisms of Flooding Report have not been adopted. These referred to Main River dredging and also arrangements for the disposal of dredged materials. The 2007 Summer Floods could be categorised as a ‘near miss event’ in the Windsor area and were far worse elsewhere. This incident preceded firstly the ‘Pitt Review’ and ultimately to the Flood and Water Management Act 2010 which created the ‘lead local flood authorities’ and clarified responsibility for different types of flooding. The FWMA 2010 (s19) introduced a requirement for the llfa to investigate and publish a report on flood events within its area. I do think we need a Royal Commission on Land Drainage and we would also benefit from legislation requiring Parish and Town Councils to report regularly on the state of their land drainage infrastructure.

I would like to acknowledge the contribution of the late Sq. Ldr. Mike Reade (BHS member - of Munich, Germany) in particular with reference to River Thames blocked flood arches, rising bed levels and the Royal Commission on Land Drainage.

END