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Phase 4 of the North Portsea Island Coastal Flood Defence Scheme
New coastal defences are being built as part of the North Portsea Island Coastal Flood Defence Scheme, which have been designed to reduce the risk of coastal flooding and erosion to the area over the next century. The Eastern Solent Coastal Partnership have successfully gained approval and Flood Defence Grant in Aid funding for £58.5million to implement these works, which when constructed, will provide one of the highest standards of coastal flooding protection in the country. The implementation project has been split into five phases of works, two of which are complete and the third phase is under construction.
- Phase 1 -Anchorage Park: the construction of 1.4km of earth embankment with rock revetment toe completed in 2016 at a cost of c.£5m;
- Phase 2 - Milton Common: the construction of 1.5km of set back earth embankments and rock revetment structure, completed in 2016 at a c.£3m;)
- Phase 3 - Tipner Lake: is the construction of 1.9km of a seawall which commenced April 2017 and is programmed for completion by the end of Autumn 2019;
- Phase 4 – Eastern Road and Kendall’s Wharf: is the construction of a seawall with road raising at the entrance to Kendall’s Wharf;Phase 5 – Ports Creek: 1.3km of earth embankment with a rock revetment toe to be constructed in 2023 and 2024.
Phase 4 is the next phase of works with a combination of two distinct sections: Kendall’s Wharf and Eastern Road. The full length of the frontage is 2.4km (300m for Kendall’s Wharf and 2.1km for Eastern Road). Construction is due to start in September 2019, with completion of the construction works by October 2022 excluding landscaping works which will be completed by February 2023.
The new defences at Kendall’s Wharf will tie in with those built at Anchorage Park in 2016.
Figure 1:Anchorage park completed
The first c.150m of sea defence will be a raised earth embankment with a continuation of the 3m wide coastal path. This embankment will tie into the area of road raising landward of Kendall’s Wharf, where the road will be raised by approximately 1m. South of the road will be 150m of steel sheet pile wall and will tie into the coastal defences at Eastern Road.
Figure 2: Artist impression of cross section
Figure 3: Artist impression of cross sectionAt Eastern Road the works will include the demolition and removal of the existing seawall in the southern section of the site, and the construction of a vertical reinforced wall with a stepped revetment. In the northern section, the existing seawall will be encased and the existing path behind the seawall reconstructed. Landscaping works will be carried out to enhance this much loved coastal region including new access points to a public footpath, four slipways and three access steps.
In addition to reducing the flood risk for North Portsea, Phase 4 of the works will introduce environmental enhancements to the area. Enhancements include texturizing part of the seaward face of the wall to encourage marine growth and habitation. We will also be introducing tidal pools to the foreshore and introducing an offshore bird island, creating important habitats as a high tide roost site for birds.
Figure 4: High roost site for birds – artist impressionThe project team look forward to sharing more information on this phase of the project during summer 2018.
WHAT WILL IT LOOK LIKE?
The design at the Eastern Road mirrors the seawall design at Tipner Lake. The wall will stand 1.2m above the new path level along the length of the frontage. The new path will be a minimum width of 2m which will connect to Milton Common coastal paths in the south and Anchorage Park coastal paths in the north. Extra seating and viewing areas and planting will also be introduced to the frontage to improve the area.
WHAT IS A 1 IN 500 YEAR STANDARD OF PROTECTION?
The level of flood defence is measured in terms of a flood event return period. Where a flood event return period is an estimate of the likelihood of an event to occur. The higher the time period the greater risk of a more severe flood. A 1 in 500 year provides the highest standard of protection in the country, outside of London.
WILL I STILL BE ABLE TO USE THE FOOTPATH DURING CONSTRUCTION?
In order to build the works safely, the area will need to be closed to public. This will include closing the footpath between Milton Common and Anchorage Park for the duration of the works. The footpath along the Eastern Road will remain open for the duration of the works.
WHY ARE YOU DOING THIS?
To reduce the risk of flooding from the sea over the next 100 years to over 4,000 homes, nearly 500 businesses and transport network.
WILL WE STILL BE ABLE TO SEE THE SEA?
The maximum height of the wall, above the shared cycle and foot path, will be 1.2m therefore maintaining the sea view. Furthermore, there will be areas where the ground level rises to the top of the wall, with the use of handrails as protection, that will provide a much clearer view for all.
HOW LONG WILL IT TAKE?
Construction is programmed to start Autumn 2019 for the works to the road at Kendall’s Wharf, off the Eastern Road. These works are anticipated to take 6 months, with construction of the seawall expected to commence Spring 2020. The seawall construction is programmed to take three summers, completing in Autumn 2022.