when relationships go wrong - sea defences
DESCRIPTION
Some of the problems generated by sea defencesTRANSCRIPT
When relationships go wrongWhen relationships go wrong
The story of a broken coastThe story of a broken coast
St Bees on the West Coast of St Bees on the West Coast of CumbriaCumbria
Cumbria is a diamond Cumbria is a diamond shapeshape
St Bees is at the St Bees is at the westernmost tipwesternmost tip
It is renowned for its It is renowned for its headland – St Bees headland – St Bees HeadHead
Management Management
The location is visited by many field groups The location is visited by many field groups as it has good examples of most types of as it has good examples of most types of hard engineering protection measureshard engineering protection measures
Promenade, Groynes, Rip rap Rock Armour, Promenade, Groynes, Rip rap Rock Armour, Geo netting and a revetmentGeo netting and a revetment
At Sea Mill lane [to the south of the golf At Sea Mill lane [to the south of the golf course] there are also gabions.course] there are also gabions.
Which are which?Which are which?
However the love affair society has However the love affair society has with the coast is a troubled onewith the coast is a troubled one
Like most affairs, over the years attitudes Like most affairs, over the years attitudes change and what was once a beautiful change and what was once a beautiful untarnished thang is now jaded by over untarnished thang is now jaded by over exposure.exposure.
Before the promenade St Bees was covered Before the promenade St Bees was covered in Sand Dunes …in Sand Dunes …
The natural ecosystem was on blown sandThe natural ecosystem was on blown sand Consolidated by vegetationConsolidated by vegetation MovingMoving FlexibleFlexible Adaptable but also a valuable assetAdaptable but also a valuable asset Sand and gravel were extracted and the Sand and gravel were extracted and the
very good natural defences were very good natural defences were compromised.compromised.
The ResponseThe Response
A variety of different management strategies A variety of different management strategies were introduced primarily a sea wall with were introduced primarily a sea wall with promenade, 9 groynes at right angles and a promenade, 9 groynes at right angles and a revetment to the South.revetment to the South.
Following a collapse of the railway Following a collapse of the railway embankment to the far south the slope embankment to the far south the slope south of the prom was re-graded, geo-south of the prom was re-graded, geo-netting introduced to stabilise the slope and netting introduced to stabilise the slope and the later rock armour added at the toe.the later rock armour added at the toe.
Something for Nothing?Something for Nothing?
Like most relationships after the initial Like most relationships after the initial commitment some investment of time and commitment some investment of time and money is needed to keep things sweet.money is needed to keep things sweet.
Sadly, West Cumbria has suffered from the Sadly, West Cumbria has suffered from the same budget cuts as elsewhere and the same budget cuts as elsewhere and the hard engineering is beginning to show signs hard engineering is beginning to show signs of a troubled time ahead.of a troubled time ahead.
PromenadePromenade
The sea wall has The sea wall has experienced some experienced some slight movement and in slight movement and in places the mastic places the mastic between the block has between the block has been stripped out by been stripped out by the sea.the sea.
No expansion No expansion fillingfilling
Originally a flat surface Originally a flat surface stones lie in the stones lie in the remaining hollowremaining hollow
In places the wall is inadequate and has been In places the wall is inadequate and has been overtopped with the beach material re-deposited overtopped with the beach material re-deposited on the surfaceon the surface
The sea wall no longer works as a barrier but as The sea wall no longer works as a barrier but as an extension to the beach. The retaining blocks an extension to the beach. The retaining blocks behind are now battered.behind are now battered.
Further up the sea wall…Further up the sea wall… A lifeboat ramp A lifeboat ramp
has been built. An has been built. An immoveable immoveable barrier which barrier which reflects the waves reflects the waves energy, scouring energy, scouring out the beach and out the beach and transferring the transferring the material off shore.material off shore.
GroynesGroynes
Generally these are in Generally these are in a bad state of repair a bad state of repair despite some attempt despite some attempt at maintenance. at maintenance.
In some places the In some places the buckle under the sheer buckle under the sheer weight of stones.weight of stones.
In others sections are In others sections are missing or fixings missing or fixings badly corroded.badly corroded.
And in other places And in other places holes right throughholes right through
You can see some of You can see some of the new sections – the new sections – sourced from tropical sourced from tropical hard wood?hard wood?
But what is the alternative?But what is the alternative?Plastic replacements used re-cycled bale wrap but would not biodegrade when they eventually come loose.
North of the promenadeNorth of the promenade
At the end of the sea wall a bridge passes At the end of the sea wall a bridge passes over Rottington Beck and is secured on a over Rottington Beck and is secured on a block of unprotected concrete. block of unprotected concrete.
The energy transferred northwards attacks The energy transferred northwards attacks the mouth of the beck undermining the the mouth of the beck undermining the foundationsfoundations
Nature continues to work around the man made Nature continues to work around the man made obstacles, the beach re-grades and the mouth of obstacles, the beach re-grades and the mouth of the beck cuts out to sea.the beck cuts out to sea.
The lined channel accelerates heavily The lined channel accelerates heavily sedimented material towards the coastsedimented material towards the coast
To the sea
Despite all this Despite all this management slips and management slips and slides still occur on slides still occur on newly deposited newly deposited material.material.
Accretion and depositionAccretion and deposition
Material moved in Material moved in shore up the mouth shore up the mouth gradually build up on gradually build up on the river bankthe river bank
At the mouth a small At the mouth a small delta appears due to delta appears due to too much material too much material
A spur growth across A spur growth across the mouth the mouth
In ConclusionIn Conclusion
A natural system was A natural system was managed using a hard managed using a hard engineering solution.engineering solution.
Maintenance of the Maintenance of the this facility has been this facility has been poor and in winter it poor and in winter it struggles to keep struggles to keep material in check.material in check.
Natural systems still Natural systems still work hard to overcome work hard to overcome the human interventionthe human intervention
Micro forms of some of Micro forms of some of the landforms appear the landforms appear especially at the especially at the fluvial / coast interfacefluvial / coast interface
The future?The future?
The adoption of soft engineering solutions The adoption of soft engineering solutions are now more widespreadare now more widespread
Further south where the cliff material is Further south where the cliff material is unconsolidated glacial clay a ‘do nothing’ unconsolidated glacial clay a ‘do nothing’ approach has been utilised effectively.approach has been utilised effectively.
Imaginative new approaches are still being Imaginative new approaches are still being developed – recycled plastic shuttering to developed – recycled plastic shuttering to line a different beck's mouth.line a different beck's mouth.
Who knows, our Who knows, our rocky relationship rocky relationship may stand the test of may stand the test of time …time …