Romsey flood alleviation scheme
Updated 26 November 2020
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Background
The Environment Agency is working in partnership to develop a permanent flood scheme for Romsey. It is working with:
- Hampshire County Council
- Test Valley Borough Council
- local flood action groups
- other partners
This is in response to the flooding that occurred in the town over the winter of 2013 and 2014. During this event, 36 residential properties and 44 commercial properties were reported as being flooded. The Environment Agency has historical records which indicate that prior to the winter of 2013 and 2014, flooding occurred in Romsey in the 1960s, 1995 and 2000 to 2001.
The main flood risk in Romsey is from the River Test. As a chalk river, the Test is influenced by high groundwater levels in the underlying chalk during prolonged heavy rainfall.
The majority of the flood risk lies to the west of the town as it follows the main River Test channel and its various tributaries. To the east of the town, the main flood risk from rivers is located around the Tadburn Lake Stream, running from east to west and converging with the main River Test south of the A27.
During a flood event the area known as Fishlake Meadows and fields to the west of the town act as a flood plain by filling with, and storing, water.
Surface water flooding can occur when the highways drainage network becomes overwhelmed and unable to cope. This happens when the volume of water needing to drain away (from usually intense storms) is greater than the capacity of the drainage system. Surface water flooding can also occur when the ground is saturated from previous rainfall. This results in rainfall being unable to soak into the ground and flows along the surface instead.
The scheme
The proposed scheme includes fluvial and surface water elements which work in conjunction with each other to reduce the risk to 186 properties.
Fluvial elements include:
- a flow-control structure at the opening of the Fishlake Stream on the River Test (north of the town) - this will help to manage river flows directly through the town during future flood events
- two bridges/spillways along The Causeway to improve western floodplain drainage back into the River Test, downstream of Sadler’s Mill
- a penstock over the existing culvert outlet, immediately north of Timsbury Bridge on the River Test
- a series of earth embankments within the floodplain to manage overland flows
- demountable defences (removable defence) along Greatbridge Road (north of Timsbury Bridge) and Riverside Gardens
Surface water elements
- additional drainage and kerb raising in the Mainstone area to improve the highway drainage, and to prevent flows to properties set at a lower level to the existing highway
- an overland flow route directing water away from a low point on the existing A27 highway by Mainstone
- an overflow pipe under the existing A27, where the stream is currently culverted under the existing highway
The highway drainage will also be improved in Middlebridge Street where works will include improvements to the highway drainage network and additional points of discharge to the River Test via Holbrook Stream
Project timeline
The tilting weir at the head of Fishlake Stream is now operational and can be used to reduce flows down Fishlake Stream.
The spillways and bridges at the Causeway have been completed.
The water main diversion to the north of Romsey near Fishlake Stream has been completed allowing for construction of the northern embankments to take place in 2021.
The penstock at Timsbury bridge is still to be installed and is planned for 2021.
All the embankments in the southern section of the scheme by the Causeway are functioning. However, due to the very wet weather experienced towards the end of the Autumn a small part of embankment was not completed to the required standard. Therefore, works will continue in 2021 when conditions are deemed suitable.
A gap will remain in the embankment behind the Causeway where the Southern Water pipe runs through. This is because it was unsafe to build over the top of the pipe until the pipe is replaced. A temporary barrier will be deployed here in the event of a flood.
The flow control structure behind Mainstone is now fully operational and can be used to limit flows through the stream behind the properties.
After the winter, construction will begin again to complete the remaining elements of the scheme.
Completion is currently forecast for September 2021.
Community engagement
The Environment Agency and project partners held a public information event early in October 2018 and late February 2019 at Crosfield Hall, Romsey. To view the information boards from the event please visit Hampshire County Council’s website.
Contact
For more information about the scheme, please contact the Romsey flood alleviation scheme project team at the Environment Agency on 03708 506506 or email romseyfloodresilience@environment-agency.gov.uk.
Postal address:
Romsey District Office
Canal Walk,
Romsey,
Hampshire,
SO51 7LP