Policy paper

Monktonmead flood risk management

Updated 29 June 2017

There are 3 main sources of flooding in the Monktonmead area: river, sewer and surface water. These interact with each other, so the situation is complex.

Monktonmead Brook flows into the sea just east of Ryde Marina. A culvert (a large pipe that carries water underground) carries water to an outfall on the beach, and a pumping station helps to pump river water into the sea when the tide is in. Sand on the beach has been building up in and around the outfall, and requires constant clearing to prevent it restricting the flow of the river into the sea.

During heavy rainfall, river levels increase and the pumping station, which has a limited capacity, can be overwhelmed. This may cause the river to overtop its banks and cause flooding.

In addition, surface water run-off from the roads enters the combined sewer system. This is then overwhelmed by the amount of water and can flood local properties. During intense rain storms, surface water flooding can be experienced independently of other factors. Both of these types of flooding can also occur when the brook itself is within its banks.

Working in partnership

To reduce the risk of flooding, partners who manage flood risk work together.

In Ryde:

• the Environment Agency manages flood risk from main rivers and the sea.
• Isle of Wight Council manages flood risk from non-main rivers, surface water and groundwater.
• Southern Water manages flood risk from sewers.

What the Environment Agency is doing

The Environment Agency is looking at how to improve the way Monktonmead Brook flows into the sea.

In August 2014, the Isle of Wight Council and the Environment Agency reviewed existing reports as well as suggestions from the public. This identified a long list of over 25 potential options to reduce flood risk from Monktonmead Brook.

A shortlist of options were identified and presented to the community of Ryde in March 2016 during a 2-day workshop where the community were able to view and comment on the proposals and share local knowledge.

Funding has now been secured for the project and the Environment Agency is aiming to enter into the detailed design stage in August 2017. Engagement is ongoing with local residents through this stage of the project.

The Environment Agency plan to start construction in late 2017, avoiding the tourist season. However this is subject to several factors, such as planning approval, weather conditions and other environmental constraints.

What the Isle of Wight Council is doing

The Isle of Wight Council has completed a plan examining how to reduce flood risk from surface water for the Ryde and Binstead area.

This plan can be found here.

What Southern Water is doing

Southern Water has completed improvement works to reduce the risk of sewer flooding in The Strand, Ryde.This work was completed in late 2015.

For more information on these works please visit Southern Water’s website.

The options

The report from August 2014 showed that the greatest benefits will be achieved either by maintaining a clear outfall for the brook so that it drains through gravity alone, or by removing the outfall structure completely and discharging all flows directly onto the beach. Options that could provide a clear outfall are:

• do the minimum (continue existing maintenance, clearing sand from around the outfall in response to unfavourable weather forecasts, and regular pumping operations).

• clear the outfall by significantly reducing the beach levels (the Environment Agency has recently carried out this work so that they can monitor the effectiveness over the winter and see if it could be a feasible long-term option).

• clear the outfall by diverting it through the harbour wall and into Ryde Marina, where sand accumulates more slowly and would reduce the level of blockage at the outfall.

• removing the outfall completely and replacing it with a pumping station to pump flows directly over the existing seawall and onto the beach.

High-level assessments of the following options have shown they are not financially viable, appropriately effective or technically possible. These include:

• diversion into the canoe lake: this would be expensive and ineffective.

• maintaining a self-cleansing outfall: this was unlikely to be effective and could have the potential to increase flood risk.

• using ‘tideflex’ valves: there are uncertainties over its effectiveness and how it may damage the outfall structure.

• long extension to existing outfall structure: it would need to be very long before it was effective and it has environmental constraints.

• diverting the outfall along the marina wall: this wouldn’t work due to the existing high beach levels.

• extending the brook’s flood banks: this would give an insignificant reduction in flood-risk.

• flood storage within the railway tunnel: this would cause a major disruption to infrastructure and be very expensive.

Preferred option

Following engagement with the community and an options appraisal process the preferred option to be taken forward to detailed design comprises of two work elements.

1. Flood storage within the Simeon recreation ground achieved through the construction of flood walls around the perimeter of the recreation ground and adjacent to the railway line and the Monktonmead Brook.

2. Installation of a new outfall into Ryde Harbour and removing the existing outfall currently extending onto the beach.

For information on the location of the new outfall element of the works, please see the Monktonmead outfall works location plan.

Community engagement

The Environment Agency will continue to speak to residents and businesses that may be directly affected by the proposals and anyone interested in the scheme. The Environment Agency will also be sending out regular newsletters and email updates, as well as providing updates to the Ryde Flood Action Group.

If you would like to sign-up for e-updates, please email: monktonmead@environment-agency.gov.uk.

Contact

Email: monktonmead@environment-agency.gov.uk.

Telephone: 03708 506 506 (Monday to Friday, 8am to 6pm).