Flooding Mitigation Project - update spring 2020
Wallington Flood Alleviation Scheme. (FAS)
As at March 2020 a small amount of property level resilience work and some wall strengthening at the footbridge is still to be completed under this scheme.
The Raised Road Flood Defence on Wallington Shore Road incorporating remedial work on faults identified as long ago as 2014 was finally completed on Friday 7th February 2020. Two days later a Flood Warning and a Flood Alert were issued by the Environment Agency for the Monday Midday tide. The weather conditions increased the forecast tide by 0.6 metres to a predicted 5.44 metres. A successful test for the new defence which prevented a flood that would probably have reached as far as the Cob & Pen PH, threatening some properties.
[Historical Note: The “Bund on the Bend” was a locally conceived plan to help to prevent tidal floodwater flowing up Wallington Shore Road. Support from the Environment Agency was not, at that time, forthcoming so with planning permission granted and with WVCA funding, a team of volunteers completed the first earth bund in March 2011 (18 tons of soil in Phase 1 and 10 tons of topsoil in Phase 2). A subsequent application to extend the bund downstream was approved by FBC and the Environment Agency and the work was completed in August 2017. The supporting, auxiliary work (by Hampshire Highways) required the construction of a road hump, expected to be between 6 and 8 metres in length and centred on the high point of the S-bend. Consent from the Environment Agency had now been secured and we were hopeful that the Highways Agency would progress the repairs to the riverbank gabions in the same area.]
As a result of the Gabion Replacement work adjacent to ‘Lowlands’ a flap valve into the river, partially covered with soil and vegetation, was exposed. Three nearby road gullies which often backed up into Wallington Shore Road on high tides are connected to this outfall and leakage has been much improved. Deficiencies in the flood wall have been remedied under the FAS and a major section adjacent to Wallington Bridge was rebuilt, which required separate funding. Funding limitations meant that leakage under the foundations of the wall could not be addressed at this time. One resident has built a brick sump at the lowest point of the back gardens and the WVCA funded the purchase of an automatic submersible pump. The pump has already worked on many occasions and helps to drain water from four adjacent properties and beyond. Rated at 22,000 litres per hour the pump copes with most of the influxes, but it is estimated that a 2nd pump of similar capacity is needed to cope with the largest tides. The North Wallington Flood Wall received much attention to strengthen, level and replace sections and to install flood gates at the bottom of gardens.
Raising of the White Horse footbridge no longer believed to be necessary.
Update spring 2019
There are two ongoing projects:
The Wallington Flood Alleviation Scheme. [FAS]
This project is now in its sixth year.
The rebuild of the ﬂood defence wall adjacent to the 5-arch bridge has been completed and the extensive repair works to the ﬂood wall along the gardens of Wallington Shore Road are complete. The work on repairs, new walls, garden ﬂoodgates and levelling to a standard height of existing walls has now been completed.
Note: The Environment Agency has not yet called down the £10,000 pledged by WVCA to the scheme.
The redesign and restructuring of the Road Hump at Lowlands. There is now an embarrassingly long-standing requirement for Hampshire Highways to fulﬁl their promise. Detailed design work was under way last November and the job was due to be completed by this spring.
This work is the essential ﬁnal component in the Wallington FAS and an update has been requested from the project leader.
Other than the above, the Environment Agency finished any further planned action in Wallington in the medium term. My understanding is that refers to a period of approximately ten years.
The River Wallington Natural Flood Management Scheme [NFM]
After a slow start I am delighted that, at last, this vital upstream catchment area project is now an oﬃcially registered Environment Agency project with a newly appointed project leader. He was good enough to invite me to the EA headquarters in Chichester on 19th. March to discuss the scheme.
Some expenditures of approximately £5,000 have now been confirmed through WVCA for an initial survey of the Potwell stream, a tributary of the Wallington which runs from Purbrook Heath nearly as far as Southwick Lake, and which is thought to be a promising area of study.
Arcadia is the business arm of the Hampshire & Isle of Wight Wildlife Trust and they are tasked with carrying out the survey to identify suitable areas where river ﬂow may be slowed. They will prepare drawings of proposed works at the various sites.
I have accompanied Arcadia on two full days of surveys and the EA project leader was with us on one of the days. Much of the ground covered was in the company of the relevant tenant farmers, and the manager of a nature reserve and SSSI. The survey to date has been very thorough and we have covered in detail over 15 miles of streams, ditches, brooks. The lead lady for Arcadia is extremely knowledgeable and is Arcadia’s Farm Advisor.
It has been a privilege to walk these private lands with the tenant farmers and I am impressed by their interest in environmental improvement and their readiness to engage with us. Unfortunately, I am less optimistic about the current local planning applications within Wallington Village; if successful they could so easily cancel out any of the potential advantages to be won through the project in the upper catchment.
Flooding Mitigation Project - update summer 2018
The Environment Agency staged a Public Drop in session in the Village Hall on 9th May to show details of the scheme and to provide an opportunity for residents to ask questions about the construction work due to take place from later in that month.
Basic aim – the scheme has been developed by the Environment Agency in partnership with Hampshire County Council and Wallington Village Community Association and is intended to deliver improvements by undertaking repairs to existing flood walls and, where necessary, raise them to provide a consistent level of defence. In addition, the road hump at ‘Lowlands’ will be raised to reduce the risk of incursion of tidal flooding. Taken together these steps are intended to reduce the risk of flooding to more than 60 of the most vulnerable properties in the village.
Phasing of the work - The work will be carried out in separate ‘reaches’ of the river and beginning in May. There are seven designated reaches:
- Reach 1 covers the stretch in the vicinity of ‘Lowlands’
- Reach 2a covers most of the bank behind the gardens of Wallington Shore Road from ‘Lowlands’ to just below the bridge. Reach 2b is the short section to the bridge.
- Reach 3 extends to close by where the Clapgate stream joins the river.
- Reaches 4a and 4b extend wall protection of the properties in North Wallington up to the ramp (slipway).
- Reach 5 comprises work in the vicinity of the FBC Depot and included raising of the White Horse footbridge by a specialist contractor.
- Reaches 6 and 7 go as far as the Cattle Bridge.
The order of construction is planned to be 4a followed by 2a, 4b and completing 3 by the end of this summer. Reach 1 (road hump) and Reach 5 (raising of footbridge) will be subject to HCC timings.
Flooding Mitigation Project - update June 2017
Having identified the preferred Option which is costed at £1.15M and established that Central Government would only provide £480K, the challenge set to the Environment Agency (EA) and ourselves is to address the funding shortfall, some £672K.
The EA are mandated to follow a “Partnership Funding” approach when addressing such funding shortfalls and have in recent months submitted funding applications to a wide range of different Organisations, the result(s) of which will be known in the next 6 months or so. As it is clearly to the benefit of our Members, WVCA have agreed to contribute £10K towards the project, which has the additional benefit of providing “leverage” and demonstrates to a wider audience that we are contributing ourselves.
HCC (Highways) have recently agreed to (but have yet to implement) the fitting of an additional Drain to the Flood Defence Hump on the SBend@Lowlands, which will restore the integrity of the Hump and in late April, work began to repair the damaged riverbank wall immediately downstream of the 5 Arch Bridge.
Flooding Matters - winter 2016 update from the Environment Agency
In July 2016, we held a public exhibition at the Village Hall to present our preferred option for potential work through the village that aims to reduce the risk of flooding from the river and sea to 63 properties. We also explained that central government funding is unlikely to cover the full costs of the preferred option, and that partnership funding would be required to enable any scheme to be implemented.
Since then, based on your feedback, we have been:
- Allocating staff to the key roles that will be needed to deliver the next phase of the project.
- Trying to maximise the benefits of the scheme by investigating the potential to manage flows upstream. Key locations have been identified and we are liaising with landowners to determine what measures are possible and then working to determine what benefit they may offer to Wallington Village and the wider area.
- Working with partners and community representatives to seek potential partnership funding from a wide range of sources. A funding strategy has been developed and negotiations are underway.
For further information please contact the project team by using the following contact details:
- Email: Wallington@environment-agency.gov.uk
- Write: Wallington Flood Defence Improvements, Environment Agency, Canal Walk, Romsey, SO51 7LP
- Call: 020 847 45901
Flooding Matters updates - 2015 to 2016
On 22ndJanuary 2015 the Environment Agency staged the first of the planned Exhibition/Drop In Workshops at the Village Hall to outline the short list of three 'schemes' that could be implemented as part of the Wallington Flood Defence Improvements project. A good number of villagers took the opportunity to study the displays and to ask questions of the Agency staff in attendance. The accompanying WVCA display input had been very professionally prepared by Richard Boswell and was well received. The Cost/benefit analysis results had to be held over due to the run-up to the General Election.
By the time of the 2015 AGM in June of that year the Agency's follow up work could be summarised and an information note was distributed, the text of which is below:
Wallington Village is at risk of flooding from the river, the sea and surface water. In 2006 the Environment Agency looked at options to reduce the risk of river flooding. However, we were unable to identify an option that could be developed for a reasonable cost.
In 2012 the government introduced the Partnership Funding approach. This links the amount of funding available for a project to the benefits it can deliver. It may not cover the full cost of the project, but it allows funding to be 'topped up' through alternative sources e.g. working in partnership with other organisations, financial contributions, sponsorship, allowing free access over private land or offering the use of land for construction site offices.
We are now working with the local community and the Eastern Solent Coastal Partnership in an attempt to develop an approach for managing flooding risk in Wallington from all sources.
Progress to date
We reviewed the flood history of the area and studied existing reports to identify all potential ways of improving the level of protection in Wallington. These are some of the options we considered:
- Upstream water management.
- A flood storage pond at the Water Meadow in North Wallington.
- Improve the capacity of road drainage at Drift Rd/White Horse Pub and Wallington Shore Rd.
- Connect the surface water drains on Broadcut to the Broadcut pump.
- Sustainable Urban Drainage System (SUDS) storage for surface water in the industrial estate.
- Targeted dredging of the channel to improve water movement in key locations e.g. Broadcut Shoal.
- Targeted improvements to flood walls e.g. strengthening/raising/constructing new ones.
- Increase the capacity of water movement at key bottleneck locations.
- A road hump along Wallington Shore Rd to tie in with an extension to the existing flood bund.
- Replace/install non-return flaps on drains in key locations e.g. along Wallington Shore Rd.
- Dredge the Millpond to provide a flood reservoir.
- A new structure at the Delme Roundabout culvert to regulate flood tides.
We used a computer model to check how well each option would reduce flood risk. Unfortunately, our modelling revealed that many of the options would not provide a significant reduction in flood risk and the list has been narrowed down to the following 3 options:
Make the most of the existing river walls - The River Wallington has a series of walls along its banks and a number of pipes running into the river. The aim of this option is to maximise the protection from the walls by repairing, strengthening or building them up to a consistent level. Fitting non-return flaps to the pipes will ensure river water does not flow back up the pipes and cause flooding
Property level measures - Some properties in Wallington have been fitted with protective devices to reduce the damage caused during flood events. Other properties might also benefit from these devices. There are many types of doors, barriers and gates designed to limit water getting into your property. Raising electric sockets and the use of waterproof plaster can also help your home be more resilient to flooding.
Change how the river catchment is managed - Managing the river above Wallington (including how water enters the river) could slow the flow of water through parts of the catchment. This could change the way flood flows develop, reducing peak flood levels and spreading them more evenly across the tidal cycle.
We will continue using the computer model to test and develop these 3 options. We will also look at the cost, benefits and risks of each option and what funding is available. Once we understand how each option will reduce flood risk and how much it costs, we can choose the preferred one. Once the preferred option has been chosen, we will identify the likely environmental risks, prepare outline designs and carry out further consultation with the local community and other interested parties. We will then prepare a business case for building the preferred option. This will be submitted for approval in winter 2015. If the Environment Agency budget holders approve the business case and we secure funding for the project, we hope to start work on site in 2016, but this is not guaranteed.
To help us understand the cost and risks of each option, we need to look at the ground conditions along the river and beneath the river walls. During the course of the summer 2015 we will be installing 3 boreholes at different locations across the village between the Water Meadow in North Wallington and the flood bund along Wallington Shore Road. We will also be digging a series of small trenches along the riverward side of the river walls. We may require access through some gardens during this time. We will write to you in the next month with more details.
Notice was also given that a second public exhibition and update would be held in January 2016. Regrettably this had to be postponed pending local elections and the EU Referendum and it did not actually take place until 7th July.
The three main Display Boards leading to an Environment Agency preferred option may be seen by clicking on the following links.
A brief summary of the options short list and the factors leading up to their choice of option is below:
Options 1 and 2 Raise floodwalls and embankments to provide a 1 in 5 or 1 in 10 year (respectively) level of protection against flooding from the river.
Option 3 Raise floodwalls and embankments to provide a 1 in 200 year level of protection against flooding from the sea.
Option 4 A combination of the options above to manage the risk of flooding from the river and the sea.
Two other options of the six originally short-listed are still in the frame but may be 'long-term aspirations to be delivered outside of this project.'
Regrettably all of the studied options yielded very low benefit/cost ratios and are therefore unlikely to attract Government funding. A possible direction could be their partnership Funding approach introduced in 2012.
The EA now want to hear opinions on their preferred option and subsequently intend to refine the design, seek to source the funding shortfall and, once secured, prepare a business case for the project.