Gravel

Walton Lane Environment Agency flood meeting

Residents of Walton Lane, Weybridge, have gained new insights into the Thames Scheme flood plans by talking directly with people working for the Environment Agency on modelling river flows and levels.

A very informative meeting in Walton Lane on 25 April was attended by local residents, including PPDRA committee members Doug Myers and Miles Macleod. In the course of the meeting it was agreed that flows of specific alternatives to widening Desborough Cut would also be modelled.

Headline learnings from the meeting include:

The 2014 floods were a ‘1 in 15 year’ event, based on historic evidence
Flooding has been unusually light in the Thames Valley for the past 40 years, so public expectations of flood risk are low compared with historic reality (and possible extreme events from climate change add more risk)
Flood Relief Channel 3 which discharges at Weybridge would carry its full design flow of 150 cumecs (cubic metres per second) at much lower total river flow volumes than reached in 2014 (which was 500 cumecs)
The flood relief channels would INCREASE the projected risk of Weybridge flooding unless something is done to increase flow downstream of Weybridge
The criterion of acceptability is that the works must NOT increase the predicted river levels for projected flood flows at any point (so downstream works are essential)
Widening the Desborough Cut on its south bank is the cheapest option to increase flow downstream (requiring driving in new vertical sheet piling to define the new bank and excavation of the current bank)
Widening on the northern bank of the Desborough Cut would be more expensive, as it has developed into a more natural kind of shelving bank with many trees limiting flow
Cost is a critical factor
Modelling predicts that Desborough Cut does not need to be widened much along its lower half: widening the upper half and dredging at the first bridge would increase flow sufficiently
Widening the bridges would be expensive (and has not been budgeted for)
The 2014 floods scoured the river bed at the first Desborough bridge, significantly increasing the depth at that point
The Environment Agency are looking into potential alternatives to widening Desborough Channel (but the indications were not particularly positive)
Cutting ‘Doug’s Channel’ through Point Meadow (the north-west horn of Desborough Island) would also require widening or dredging of the remainder of the northern old river loop, which would be costly
The modelling team agreed to model the effect of this northern alternative approach on local levels and flows

Modelling of levels and flows is a highly complicated process, and not a precise science

1D modelling is relatively quick, but only considers the flow within the confines of the river
2D modelling includes flow in the adjacent flood plain, when levels are high, but is slow and very complex
Peer reviewing is a hands-on process, involving CH2M (formerly Halcrow) peer reviewing the JDA model and the design works, in “a process of questions and answers that get to an agreed design”
The overall margin of error in modelling appears to be higher than some of the predicted local changes in level which modelling suggests the scheme will produce, though the calculation of possible modelling error is far from straightforward
(Editor Comment: A truly robust approach would demand that the projected effects must be greater than the margin of error. However, logically the estimated margin of error of modelling can only be based on experience of disparity between modelled flows and actual measured flows.)

Future action timescale

Currently the River Thames Scheme has Treasury approval for the outline case (as previously reported)
Modelling with the latest data is in progress, 1D now, 2D in the coming months
A definitive outline design is planned by the end of 2016, following workshops
Scheme detailed design will follow that
Works timetable is for weirs work in 2018, relief channels in 2020

LATEST NEWS: UPDATE FROM ENVIRONMENT AGENCY 26 MAY 2016 SHOWS FUNDING SHORTFALL

Survey 2015: What do you want for Weybridge?

PPDRA is conducting a survey of local residents’ concerns and wishes for Weybridge, to help us continue to reflect local views.

Our Survey 2015 covers:

Weybridge Town Centre – how to make it more attractive to visit.
Parking – on-street and off-street provision.
Traffic through residential areas – volume and speed, and how to manage it.
Public riversides, green spaces and footpaths – appreciation, concerns and wishes.
Other local concerns.

Survey forms are being distributed with our October 2015 PPDRA Newsletter.
You can also download copy of PPDRA Survey 2015 here.

Portmore Park & District Annual Residents Meeting – 3 Nov 2015

Residents of north Weybridge are invited to share views at our
Portmore Park & District Residents Annual Meeting
Meet other residents and local councillors
Tuesday 3 November, 7:30 for 8:00 pm
St Charles Borromeo School Hall, Christ The Prince Of Peace (Portmore Way)
7:30 – Chat and light refreshments
8:00 – Hear about and discuss local matters which affect our community
We will also briefly conduct the formal business of the PPDRA AGM

Elmbridge Borough Councillors for Weybridge North, Andrew Davis and Ramon Gray, plan to be at our meeting to listen to and speak with residents. This year Ramon Gray was also elected as Surrey County Councillor for Weybridge (his predecessor Christian Mahne was at last year’s meeting).
We hope also to have a guest to speak about the parking review.
Note that PPDRA and our AGM are always careful not to be party political.

Download our October 2015 PPDRA Newsletter (pdf, 1334KB) here.

You can also download copy of PPDRA Survey 2015 (pdf, 508KB) here.

School buys local Green Belt land

Aerial photo of St Georges Junior Land Purchase

St George’s Junior land purchase (in red)

St George’s Junior School has completed the purchase of the adjacent Green Belt land at Greenlands Farm — part of the remaining riverside farmland between Weybridge and Walton — which had been offered for sale as a ‘strategic development opportunity‘.

Ownership by the school looks to be a significantly better outcome, in terms of impact on our local community, than the land being sold to a property developer or to someone interested in extracting the underlying mineral aggregate.

For the immediate future, the land will remain as grazing land.

St George’s has provided information about their new acquisition, and an informative set of answers to frequently asked questions. Download the details of the land purchase here. While the extra land adds substantially to the estate of the school, the land purchase “is not expected to increase pupil numbers”.

The purchase includes the road leading to the Weybridge Health Club, and the lane linking to the school. This opens up possibilities for an additional access route to the school. The purchase also includes the source of the Engine River and a length of Broadwater, adjacent to the gardens of houses in Greenlands Road.

Local Green Belt landscape at risk

Land for sale: green belt floodplain Feb 2014

Development Land? Local Green Belt floodplain for sale

Land at Greenlands Farm has been offered for sale as a ‘strategic development opportunity’, despite being Green Belt, working floodplain, a potential mineral zone, and an important element of Thames riverside landscape.

This is part of the remaining farmland which separates Weybridge from Walton — a significant piece of local countryside, with traditional hedgerows and field pattern. The farmland helps define the local landscape, and is included in the Strategic View from historic Oatlands Park, and the Thames Landscape Strategy.

This farmland also serves an essential function as a working floodplain. The underlying gravel, linked to the Thames by underground aquifers, helps absorb floodwater , which rises in the fields when the Thames is flowing high, as the attached picture shows.

PP&DRA first raised local concerns about development ambitions for this land back in 2005, on the front page of our newsletter.

As Green Belt with exceptional landscape value, and working floodplain, this land should be safe from development. There would be an outcry in the local community if serious plans for developing this land were ever to be put forward.

Gravel pit threat persists

Millions of tons of gravel and aggregate sit below our local Green Belt, and Surrey County Council have parts of north Weybridge earmaked as Potential Mineral Zones, labelled PMZ22 and PMZ23.

Quite rightly, these sites have been rejected at successive reviews of which PMZs to excavate, for access and landscape reasons. But Surrey has to meet targets for gravel extraction, and has regular PMZ reviews, so residents of Weybridge are wise to be vigilant in safeguarding our local landscape.

When we reported on this topic eight years ago, Surrey’s latest PMZ review said access for HGVs getting onto Walton Bridge was one of two major issues preventing gravel extraction in PMZ23. Would it be sceptical to wonder at Surrey’s motives for proposing a huge cloverleaf junction with Walton Lane in their replacement Walton Bridge plans at the time (very handy for gravel lorries)?

Happily, after pressure from local groups, prominently PP&DRA, a Public Inquiry roundly rejected Surrey’s plans for covering the riverside with a big junction, and demanded that the riverside amenities at Cowey Sale be retained and enhanced. The resulting redesigned smaller new bridge and excellent riveside amenities are things the whole community can be proud of — great work by the bridge team.

Surrey’s subsequent 2009 PMZ review said the new bridge (with its improved T-juntion) would make bridge access from PMZ23 easier, but the increased significance of the riverside amenity now made thousands of gravel lorry journeys along the riverside Walton Lane at Cowey Sale an unacceptable issue. So access for gravel removal could only be possible via the river.

The other — highly important — reason for rejection is the landscape value of the current Green Belt. Surrey recognise that there would be a medium term significant adverse effect on local landscape character and the setting of Weybridge.

One matter of some concern is how up-to-date the information which Surrey use in their reviews is. The 2009 update made no mention that the land earmarked for PMZ23 is designated a Strategic View from historic Oatland Park. No mention that there is a Health Club and Riding School on the land potentially to be dug up (SCC only recognise one dwelling). No mention that part of PMZ23 is Exchange Land, given over to public use as part of the Walton Bridge post-Public Inquiry planning consent.

SCC image of PMZ23