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Shoring up Littlehaven beach defences

Littlehaven beach at night

A complete realignment of a seawall and promenade has restored a picturesque piece of coastline in England’s north east.

Littlehaven is a little known beach in South Shields on the north east coast of England. It sits nestled inside the north and south piers at the mouth of the River Tyne and forms part of the coastal defences to the town behind.

But in 2012, the man-made vertical sea wall which formed the primary sea defence was at breaking point. Waves hitting the wall were reflected, creating turbulence at its base, scouring away the sand and exposing the supporting timber piles beneath. This in turn created voids in the structure and the loss of material was putting the concrete wall on a rapid path to collapse.

 

Littlehaven old sea wall

Littlehaven old sea wall

The man-made vertical sea wall which formed the primary defence was at breaking point

This original sea wall was built in the 1940s and retained an area of higher ground which was built into the beach. At high tide there was no separation between the land and the sea.

“In terms of the problem of the dereliction of the wall, it was for the most part due to the original alignment of the wall,” says Royal Haskoning DHV technical director Nick Cooper. “The old alignment stuck out into the bay, and that made it very vulnerable to any storm that occurred.”

It is not fully known why this additional land sticking out into the bay was created, but one theory was that the coal from the surrounding mines was brought to Littlehaven and then loaded on to boats at high tide straight from this elevated platform.

Now the area serves as a car park for surrounding businesses and visitors, but its low elevation meant that the sea would frequently break over the top of the wall causing flooding. Poor drainage would cause the water to pond – Tyneside City Council estimated it had to be closed to the public for at least 10% of the year.

The old alignment stuck out into the bay, and that made it very vulnerable to any storm that occurred

Royal Haskoning DHV technical director Nick Cooper

Consultations about how to solve the problem showed the cheapest solution would be to pile large rocks in front of the wall to reinforce it. But this would not have solved the flooding problem resulting from overtopping, and would have destroyed the council’s aspirations to create a continuous walkway along the coast.

The solution came from consultant Royal Haskoning DHV which suggested that a complete re-modelling of the beach would create a far more sustainable solution.

Littlehaven overview of beach

Littlehaven overview of beach

The original sea wall was built in the 1940s and also retained an area of higher ground which was built into the beach creating an unnatural protrusion. At high tide, the land and the sea were at the same level. The black line shows the 1940s alignment and the white line shows the new alignment

The team used historic maps to build up a picture of the evolving coastline to predict its response to future sea level rises. The team also used crenulate bay theory to create a new alignment for the beach. A “crenulate bay” is a type of curved bay that develops in a logarithmic pattern due to refraction of approaching waves and diffraction by a nearby headland.

Creating the new alignment involved removing the built up section of land, replacing the lost beach and putting in a new graded concrete apron set back from the shoreline as the new defence. The apron also doubles up as a continuous set of steps down from the new promenade to the beach giving direct access to it all the way along compared to only two previous access points.

Seeing the potential of the landscape which was to be created, the council jumped at the chance to regenerate the area. Landscape architect Oobe was employed to completely re-model and revamp the previously dilapidated seafront.

Normally you’re racing against the tide on every pour which is why many of these stepped apron systems are done with precast concrete 

Royal Haskoning DHV technical director Nick Cooper

In breaking out the historic man-made construction, huge quantities of rubble were created and sand excavated. The sand was used to reinstate the beach, and the rubble from the built up land was relocated onto the land behind the newly formed alignment, raising its height and acting as an additional barrier to extreme tidal events.

“The old car park was like a basin as it was much lower, so when waves came over the top, they just ponded,” says Cooper. “In the new carpark area we raised the levels using some of this waste. Not only is it now better protected against waves coming over it in the first instance but on the rare occasions it does come over during a really big storm it is not as low lying and it is better drained.”

The new concrete “apron” was constructed behind the existing sea wall by excavating the car park area in a strip, effectively forming a cofferdam within which the team could work. The apron has a sheet pile wall at its front which goes down 3m to protect its foundations from future scour. Originally the team envisaged that the structure would be constructed from precast concrete. But early on, the purse strings were tightened and in a value engineering exercise it was proposed that it would be cast in-situ to save money.

 

Construction of the Littlehaven concrete apron

Construction of the Littlehaven concrete apron

Contractor Galliford Try suggested bringing the precast concrete manufacturer to the beach to create the same level of quality, but cast in-situ. Using steel as opposed to the more traditional timber formwork and a number of other techniques, a beautiful smooth finish was achieved

Not satisfied with the potential drop in quality and surface finish that this might have, contractor Galliford Try suggested bringing a precast concrete manufacturer to the beach to create the same level of quality, but cast insitu. Using steel as opposed to the more traditional timber formwork and a number of other techniques, a beautiful smooth finish was achieved.

“Normally you’re racing against the tide on every pour, which is why many of these stepped apron systems are done with precast concrete,” explains Cooper. “But because we had this cofferdam, we brought factory workers on to site, we used steel shutters and lots of hand working post-pour.

“It was all done to a minute level of detail, filling in all of the holes and acid etching to get a really good quality of work.”

It is an area that people choose to go to rather than an area where people choose to avoid

Royal Haskoning DHV technical director Nick Cooper

Today, sand has now been naturally deposited on the lower steps of the concrete apron by the tide and the area has been returned to its more natural form with the creation of 80m of new beach from the high tide line to the top of the apron. This ailing sea front has now been truly transformed with new elegant lighting, bespoke handrails and specially designed artwork which now grace the promenade. The area has become incredibly popular with local people and tourists.

“It is an area that people choose to go to rather than an area where people choose to avoid,” says Cooper.

Completed on 1 December 2014, Littlehaven beach was shortlisted for Civil Engineering Project of the Year in the 2015 British Construction Industry Awards .

The team

Contractors – Galliford Try

Client –  South Tyneside Council

Landscape Architect – Oobe

Artist – Stephen Broadbent Studios

Construction value – £4.6M

Total value – £5.1M

 

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