Church Street Flood Alleviation Scheme, Whitby

Scarborough Borough Council is the Coastal Protection Authority on the North Yorkshire coast. Colleagues from the Projects Unit at Scarborough District Council described some of their recent work in Whitby. 

What was the purpose of this work?

The primary aim of the Church Street Flood Alleviation Scheme is to improve the climate resilience of the community.

What flood risks arise from increased storm surges and sea-level rise?

Church Street is located on the right bank of the River Esk in the harbour of Whitby, on the North Yorkshire coast. Whitby has a long history of tidal flooding, with records back to the 1800s. Prior to construction of the scheme, tidal flooding of the Church Street area occurred relatively frequently with increased major flooding occurring in more recent years, most notably in the December 2013 and January 2017 storms.

The height of the existing quay wall varied along its length. The risk of the majority of the quay wall overtopping - when the water level rises above the height of the wall – by 2050 is before a 1 in 50 year event. At its lowest point the standard of protection was less than 1 in 3 year. This meant that every year there was a 33% probability of flooding in this area. Taking predicted sea level rises into account, by 2050 the standard of protection (SoP) at the lowest point decreased to the 1 in 1 year event (100% annual probability of flooding), in the absence of a formal flood defence.

In other words, increased flooding to many residential and commercial properties as well as the main transport route to the eastern side of the River Esk were a major concern going forward. Continued flooding of Church Street would impact on the tourism appeal of Whitby and could potentially be a threat to the viability of the town.

What has been done to improve the climate resilience of the community?

This has been achieved by construction of a new L-shaped floodwall designed between the Fleece Pub and Eskdale Wharf along Church Street to prevent flooding and reduce the probability of flooding to a 1 in 100 year event (1% Annual Exceedance Probability).  The new floodwall includes a 250mm freeboard allowance, meaning that residual uncertainity in the Flood Risk Assessment and design is accounted for, in line with UK Government guidance for flood defence design and construction.

Also, existing walls were raised around the Fleece pub and property level protection measures installed. These include new flood doors and flood protection air bricks.

Fifty-four residential and eight commercial properties benefit from direct flood protection.

The scheme was designed using the latest sea level rise predictions and is the first phase.

How are you planning to respond to the further predicted rise in sea level?

The second phase of the scheme will take place in 2051, when predictions of sea-level rise have been realised.  This work will involve raising the existing defences to a minimum 1 in 50 year standard of protection (SoP), taking into account further predicted climate change after 2051. This is up to the end of the 100-year appraisal period.

To prevent outflanking – where the flood water finds a way around the barriers - due to sea level rise the defences will be extended to the north and south.

Who are the partners that collaborated on this project?

The Church Street Flood Alleviation Scheme is a partnership project made possible with funding from the Local Growth Fund, Environment Agency Grant in Aid, Yorkshire Regional Flood & Coastal Defence Committee Local Levy Fund, Scarborough Borough Council and North Yorkshire County Council.  The contractors were ESH Construction.