Planned PROJECT

New infrastructure to ensure Poole town centre and the Old Town are protected from tidal flooding over the next 100 years and are resilient to climate change.

Project Overview

BCP Council is working with the Environment Agency, Poole Harbour Commissioners, landowners, developers and other relevant organisations to provide a permanent flood defence scheme for the 1.5 km eastern side of Holes Bay. This remaining undefended water frontage is listed on the Environment Agency’s Flood and Coastal Erosion Risk Management (FCERM) medium term plan and currently relies on emergency temporary de-mountable flood defences.

When built, the permanent flood management scheme will complement other recent work to provide improved tidal flood protection to built-up areas of the town:

• Holes Bay Flood Defences 2018
• Poole Quay Sea Wall 2015-2019

An Adaptive Approach

BCP Council is planning a design that can be adapted in the future once we know more about sea level rise. This allows us to make best use of the available funding. It will still provide the desired level of flood protection but reduce the visual impact of the defences in the shorter term (we don’t have to raise all walls now, but can do this to keep pace with climate change).

The scheme extent will be zoned into five discreet areas with interventions planned for 2022, 2071 and 2105 including:

• a new quay wall between the bridges
• a crown wall in addition to existing defences north of the RNLI
• localised land raising and flood gates around the RNLI site

BCP Council intends to take ownership and maintenance liability for the new flood assets constructed using public funding. This is an important aspect of ensuring we can manage and adapt the defences in the future.

Progress to date

On-going: Meetings with landowners and developers to help refine the most efficient and effective flood management design to deal with current known site constraints. Discussions with the Council’s senior leadership to ensure works benefit BCP, local business and the public.

January 2021: The Environment Agency advised BCP Council that the Outline Business Case had been successful in achieving £12.4 million Flood Defence Grant in Aid (FDGiA)* to build the new infrastructure. This important step means we have the funding to progress the scheme.

October – November 2020: BCP Council’s bid was submitted to the Environment Agency’s Large Projects Review Group for consideration and scrutiny.

September 2020: BCP Cabinet approved the submission of the bid for all the primary works to construct the new tidal flood defences.

2018 – on-going: Investigatory and supporting work for the business case has included asset condition assessments, flood modelling, engineering optioneering, economic appraisals, stakeholder engagement and environmental, ground and geomorphology assessments.

2018 – BCP Council led the progression of a single scheme to protect and mitigate tidal flood risk and to help unlock land for redevelopment. An Outline Business Case began.

*FDGiA – Flood Defence Grant in Aid is Government funding available for a scheme based on a formula that takes into account the number of households protected; the estimated value of damages being prevented; and the other benefits a particular project would deliver, such as environmental improvements

Background

The ongoing regeneration of the Twin Sails area was expected to include delivery of the required flood defences to protect the wider flood-risk area within Poole Town Centre, the Old Town and new developments. To date, however, the envisaged regeneration has not fully materialised. Recent developments around the RNLI have only included flood defences along discrete lengths, leaving gaps in the defence line.

The frontage along Back Water Channel, between Poole Bridge and Hunger Hill, is in a mixture of different private ownerships.  The current quay walls act more as earth retaining structures rather than flood defences.  Many do not have a crest level higher than the land behind, have been classed as failing structures and require urgent attention.

This means that a significant risk of flooding exists both now and with the impacts of climate change.  There is currently flooding potential on a normal high spring tide with only a small surge (e.g. 0.2m). New flood defences would be built to a height of 3.51m (ordnance datum) defence crest height and provide flood protection for the next 100 years.

Potential flood damage without defences

The value of potential damages calculated in the scheme area, highlighted in red below, in a ‘do nothing’ scenario over the next 100 years is £161 million.

The Poole Harbour and Wareham, Flood and Coastal Erosion Risk Management Strategy (2014) identified that within Central Poole Cell there are 573 properties at flood risk in the present day 1% AEP event, rising to over 2,000 properties at flood risk by 2110.

AEP or Annual Exceedance Probability is the chance of a flood event happening in any given year.  Flood defences are built to protect against a 1 in 200-year flood event or a 0.5% AEP.

Environmental considerations

The flood defences are adjacent to Poole Harbour which has a range of protected special designations including: Ramsar – wetland sites of international importance (especially as waterfowl habitat), Site of Special Scientific Interest (SSSI) and Special Protection Area (SPA).

Consents for any future work is on-going along with all necessary environmental work, including:

• Environmental Impact Assessment Screening (and request for Local Planning Authority Screening Opinion under the Environmental Impact Assessment Regulations)
• Habitats Regulations Assessment Screening
• Water Framework Directive Assessment