Lower Thames Flood Strategy - river widening concerns

Elmbridge Borough Council has said it cannot support some of the proposals made in the Environment Agency Lower Thames Flood Strategy. The issue was raised in Council by Weybridge North Councillor Miles Macleod, who expressed concerns which found widespread and wholehearted support.

The Environment Agency proposes to create large-scale new flood diversion channels upstream, bringing extra peak flood flows towards Weybridge and other parts of Elmbridge. The EA further proposes to widen Desborough Cut on the southern bank by 4 metres (that's the right hand bank in our picture) to help the flow move on downstream. The widening would cut into the Thames Path, and have a big impact on the landscape and amenity value of the Thames riverside between Weybridge and Walton.

UPDATE 31 December 2009: Elmbridge Borough Council has now sent its formal response on the EA Flood Strategy proposals to the Environment Agency. 

Key points are that Elmbridge Borough Council:

• does not support the works proposed to the Desborough Cut at the present time, and requires further public consultation

• requires assurance that no works are commenced upstream until downstream works are completed in order to avoid the risk of additional flooding within Elmbridge as a consequence of Flood Management measures being implemented higher up the Thames

• requires assurance of external scientific validation of the EA flood flow modelling

This response follows the EBC Environmental Affairs Overview & Scrutiny Committee considering the EA proposals, in an agenda item requested by Cllr Macleod. The Overview & Scrutiny Committee voted to recommend that the Elmbridge BC response to these proposals states that it cannot indicate its support for the proposed works in their current form.

Cllr Macleod subsequently also spoke on the matter at the 9 December full Council meeting, receiving strong support from fellow councillors.

Concerns about the Strategy

The Lower Thames Flood Risk Management Strategy proposes to accommodate extra peak flow through new upstream flood diversion channels, one of which would discharge by D'Oyly Carte Island.

Your local councillors, along with many residents, are concerned about two aspects of the strategy:

• the prospect of allowing greater peak volumes of flood water to arrive at Weybridge
• the impact on the riverside landscape and amenity of widening the river downstream to take the resulting peak volumes

Pushing the flood problem down the river?

We have a fundamental concern about flood diversion channels bypassing upstream floodplain, carrying extra water faster and discharging the increased peak volume somewhere downstream. In this case they would channel an extra volume of water onto our doorstep in Weybridge.

If new upstream channels are to be created, then downstream changes are essential to manage the flood risk from extra peak flow (although that simply passes the problem even further downstream).

Engineering or Environment?

How can the extra flow be accommodated with minimum damage to the local environment and amenity?

We are concerned that the strategy is an engineering approach, focusing on flood relief for Reach 3, rather than an adequately environmental approach to the flood issues. It is not clear how much the EA have taken into account the very significant amenity value of the Thames Path, and the fact that this is a treasured stretch of publicly accessible countryside right on the doorstep of urban communities. How have the engineering issues been balanced against the overall ecological, landscape and amenity impact?

We understand from the EA that the southern bank of Desborough Cut had been chosen because it has fewer trees and is a concrete / piled bank. The Northern bank has a lot of mature trees, and is a now a more natural riverbank. The banks and trees have environmental value. They also have amenity value as they help define the local landscape. Chopping down the mature trees would change the landscape for the next 30+ years. And this is landscape appreciated the thousands who enjoy the river and the Thames Path. There is a very difficult balance to be struck between flood relief and landscape conservation.

Conserving the Thames Path landscape

When we attended an EA consultation exhibition, the project manager was sympathetic to concerns about safeguarding the amenity value of the Thames Path alongside the Desborough Cut, and the importance of keeping the path separated from the road (Walton Lane) – something we think is very important. He spoke of the possibility of making the Thames Path a boardwalk at the places where the bank/path/road distance is particularly narrow, to maintain the distance of the path from the road as much as possible. But it would still be a huge change to the character of path and the Thames landscape.

We would like to see 'no reduction in the separation of the Thames Path from Walton Lane' adopted as an absolute principle.

If the southern bank is chosen to be cut back for widening, none of this of course addresses the separate issues around path closure during the works. There is no easy & safe diversion route for the walkers and cyclists. But the longer term environmental and amenity issues should be the more significant concerns in getting this right.

Other possibilities?

In conversation at the EA event, we discussed other possibilities for managing increased flow, including:

• dredging the Desborough Cut (apparently not enough impact on peak flow flood reduction unless the river slope to the next weir is increased)
• widening the old river (less effective than widening the cut),  and/or
• opening up further overflow channel(s) into the Engine River: under Walton Lane and through the lower fields of the farmland, where water already wells up slowly at times of flood through aquifers under Walton Lane (allowing greater flow at times of potential flood would be more in line with the approach taken in the proposed upstream works; worth exploring further)

We wonder if the desired results could be achieved with less damage to the environment and landscape by a combination of the above.

Overview & Scrutiny

Councillor Miles Macleod requested that the EA Consultation be added to the Elmbridge BC Environmental Affairs Overview & Scrutiny Committee as an urgent item, and that an appropriate person from the Environment Agency should be invited to come to explain their proposals and answer questions from Committee members and other interested Councillors.  The EA subsequently appeared to speak at a special EBC Planning Committee meeting, with EAO&S members also participating, and the topic was added to the EAO&S agenda of 19 Nov 2009 (as requested by Cllr Macleod).

When the Elmbridge Borough Council EAO&S committee discussed the proposals, while recognising the need to manage peak flood levels, members were opposed to the impact the proposed scheme would have on the local riverside and amenity. The committee voted to recommend that the Elmbridge response to the EA proposals includes the following: "This Council regrets that on the basis of the information and assurances provided to date it cannot indicate its support for the works proposed to the Desborough Cut at the present time, and requests that the Environment Agency commits to work closely with the Council and its residents when drawing up detailed plans in order to preserve the environment and attractiveness of the Thames Path alongside Desborough Cut, together with the amenity and landscape of the Cut generally."