- Created by: stephloupoole
- Created on: 24-04-14 18:02
Hard Engineering - Isle of Wight
The Isle of Wight Council, like all others on the UK coast, has four coastal defence options:
Hold the line - retain the existing coastline by maintaining current defences or building new ones where existing structures no longer provide sufficient protection.
Do nothing but monitor - on some stretches of coastline it is not technically, economically or environmentally viable to undertake defence works. The value of the built environment here does not exceed the cost of installing coastal defences.
Retreat the line - actively manage the rate and process by which the coast retreats.
Advance the line - build new defences seaward of the existing line.
Examples of the different approaches
-Monks Bay -Wheerlers Bay
-Western Cliffs -Castle Cove
-Castle Haven -East of Freshwater -Seagrove Bay and Seaview
Hard Engineering - Isle of Wight - Monks Bay
Cliff failure resulting from a combination of high-energy destructuve waves and high rainfall during the severe storms of the winter of 1990/91 gave additional impetus for upgrading coastal defence here.
The Scheme involved constructing an offshore breakwater, six rock groynes and a rock revetment to reinforce the existing sea wall using 25,000 tonnes of Norwegian granite.
it also required beach nourishment using 40,000m^3 of sand and gravel, reprofiling the slope and installing land drainage to check the active mass movement of the cliffs on the western side of the bay.
the collective value of the property far exceeded the £1.4million cost of the scheme. it was completed in 1992 but sedimentation of the rock groynes has since been a proble,
Hard Engineering - Isle of Wight - Wheelers Bay
The ageing sea walls were in danger of collapse which would have reactivated ancient landslides.
Property on the cliff behind was becoming unsaleable. Over 15,000 tonnes of Norwegian granite was placed seaward of the existing defences to form a rock revetment and the coastal slopes were regraded to make a shallower profile before installing land drainage.
The Scheme was completed in 2000 at a cost of £1.6million and has led to a recovery in property value. Further work from Wheelers Bay to Ventnor's eastern esplanade is beind considered
Hard Engineering - Isle of Wight - Western Cliffs
Western Cliffs (Ventnor)
High Energy waves were removing chalk blocks which protected an ancient landslide complex upon which houses had been built. There was a danger that the landslides would be reactivated if sufficient chalk was removed.
£1.2 million of carboniferous limestone was brought in from the Mendip Hills in somerset to construct a 700m long rock revetment along the base of the cliffs using blocks weighing 6-8 tonnes. A series of limestone rock groynes was also constructed at 100m intervals at the base of the cliffs.
Hard Engineering - Isle of Wight - Castle Cove
the existing wooden revetments were becoming progressively ineffective as the clay cliffs retreated.
property valued in excess of £10million was increasingly at risk as coastal processes activated ancient landslides.
The scheme stabilised the environmentally sensitive cliffs by removing the topsoil, stabilising the slopes with thousands of tonnes of chalk and installing land drainage before replacing the topsoil.
The cliff was protected by a rock revetment of somersset limestone, a concrete walkway and a gabion wall. The defences cost £2.3 million and were completed in 1996.
Hard Engineering - Isle of Wight - Castlehaven
A £6.2 million coast protection and slope improvement scheme was completed in 2004. The scheme included a 500m rock revetment to protect the cliff at Reeth Bay. An extension syste, of drainage pipes and syphon drains was provided to reduce surface and groundwater levels, thereby reducing landslides
Hard Engineering - Isle of Wight - East of Freshwa
East of Freshwater
Where the A3055 passes over a chalk ridge at Afton Down it is now within 11m of the cliff edge. Sea defences to prevent further cliff erosion would be economically unjustifiable and environmentally unacceptable. the council has therefore devised a scheme that stabilises the cliff top b anchoring the top of the cliff face chalk on the landward side of the road. The cost is £750,000
Hard Engineering - Isle of Wight - Seagrove Bay an
Seagrove Bay and Seaview
The crumbling sea walls and unstable slopes forced the council to intervene and protect property as part of its 'Hold the Line' policy.
A Scheme costing just under £1million and completed in 2000. included a new concrete sea wall with 200m of rock revetment placed in front of the wall to dissipate the energy of the waves. Rock groynes were constructed as a further layer of protection.
Mass movement on the soft clay cliffs has been significantly reduced by installing land drainage.
Further north at Seaview a £4.7 million scheme was completed in 2004. This consisted of a 550m stone - faced reinforced concrete sea wall fronted by a rock revetment. On the landward side a nature reserve has been developed
Hard Engineering - The Netherlands - A national Sc
Management of the Dutch coastline is divided into 3 main areas; the Delta Region, The Zuider Zee and the Coastal Dune area
The Delta Region - Is an area consisting of islands and peninsulas running between the distributaries of the rivers Rhine, Maas, Lek and Scheldt. Flooding has been a major problem here, but the disastrous floods of 1953 forced the Dutch government to design a shceme that would control similar events in the future. The Delta Plan consists of; - A series of dams that seal off the channels between the large islands to keep out the sea. - Two channels to allow ships to reach the ports of Rotterdam and Antwerp - The creation of some freshwater areas - The East Scheldt dam, which is unlike those that had already been built. Pressure from environmentalists has resulted in the building of a storm surge barrier with sluice gates that can be lowered in times of need. the area behind the dam has remained as salt water, preserving salt marshes and mudflats for wildlife.
The Zuider Zee - was orignally a long inlet of the sea that threatened large areas of low lying coastlands when high spring tides were backed by northerly winds. A 30km barrier was completed by 1932, which created a fresh water lake, the ljsselmeer. This lake has been largely reclaimed as a series of polders providing areas for urban expansion and agriculture.
The Coastal Dune Area - the Dutch dunes occupy an area of over 42,000 hectares making them the largest area of continuous duneland in europe. currewnts and waves remove sand in some areas and deposit it elsewhere, Each year 7 million m^3 of sand are washed away. Only part of this is deposited elsehwere along the coast. The sand balance is therefore negative. As the nearshore underwater sand disappears, the beaches are gradually lowered leading to damage to the dunes behind the beach.
Managed Retreat - Abbots Hall Farm
Abbott’s hall farm is a 700 acre coastal farm, which also acts as the head office of the Essex wildlife trust, which can be found on the black water estuary (SSSI) (SPA) (SAC). Abbott’s hall farm is a place where you can view Europe’s largest coastal realignment of around 200 acres.
Abbott’s hall salt marshes were enclosed in a sea wall defence which drained the salt marshes turning them into a good farm land, Essex wildlife trust aimed to transform the farmland/marshes back into their previous abundance of life of salt marshes. They started off by breaching the sea wall in 5 different places to let the morning spring high tide flood into arable land.
“Sea levels are rising and this means that the fringe of coastal marshes, our last real wilderness, are rotting away, in turn threatening our sea defences. We must rethink the way we look after our coast, and in the Abbotts Hall Farm partnership we have a vision of a more sustainable coastline which is better for wildlife and for people." John Hall, Director of Essex Wildlife Trust,
New habitats have now been created for birds and other wildlife which helps protect some of the rarer birds that live in England eg. Wading birds.
Managed Retreat - Wallasea Island - ESSEX
work begins september 2012 after 10 years of planning
Europes largest man made nature reserve
4.5 million tonnes of earth excavated from a project is being used
completed by 2050
estimated cost £50 million
sea walls 400 years Breached sea walls
2000 Ship loads
2 meteres below sea level
lagoons and saltmarshes will be created
Soft Engineering - Easton Bavents
Location - suffolk coast, 25 miles NE Norwich
History - Market Town - most Easterly point of land in the UK
Who - Peter Boggis, built his own coastal defence to halt erosion retired engineeer mud and shingle was added - increases erosion in other areas 50 trucks a day
Natural England and SSSI - easton bavents wanted cliffs to be erroded for research.
Waveney District Council
2011 path finder scheme has a £1.534 million fund for moving people inland and giving them planning permission to build a new home.
Storm Surges - Hemsby - Norfolk
Hemsby, is located on the east coast of United Kingdom in the county of Norfolk, 8 miles north of Great Yarmouth. The parish boundaries fall into the Great Yarmouth Government District. The East Anglian coastline is generally void of coastal features, but according to a 1610 map of Norfolk, there seemed to be a headland in Hemsby called ‘Winterton Ness’. On the 15th of October, the BBC news reported that Hemsby’s lifeboat was unable to launch. This was due to a 10ft drop which has been caused by a sub-aerial process of rotational slip and sediment structure of the Norfolk coastline. The Lifeboat is usually launched from a tractor trailer, but on this occasion the Tractor is unable to navigate the drop. This has happened before, possibility following harsh spring storms and rough winter winds. The Villagers of Hemsby’s management previously has tried to alleviate the problem by adding more sand to the depleted beach, so that the forceful power of the waves are absorbed by the sand, this is a positive but it is not a long term hard management solution as the sand will slowly be pulled down the coast line by longshore drift. Also within the report it states that the storms had severely affected the Marrams Beach which is south from the life boat station and is owned by Watling trust. The beach was damaged in March 2013, and the trust again brought in sand but it was again dragged and washed away in the latest storms. The need for a harder management solution is clearly needed. On the 22nd of October, the BBC news reported that the village has invested in a new concrete sea defence, in an attempt to save villagers homes, from ‘pounding seas whipped up by easterly gales’. One property owned by Mr and Mrs Conley has been condemned because it is in imminent danger from the sea, they were commented on saying that ‘we are doing our best but were not fully confident the house will remain on Hemsby dunes for much longer because of the continued erosion and the effects of further storms’. 22nd October in Hemsby, was the day that they put in the new concrete sea defences to try to slow down the rate of erosion upon the Norfolk coast line
Storm Surges - Hurricane Sandy
When? - 29th October 2012
Where ? - USA
how many states affected ? - 24 states
how many deaths? - 148
how much did the damage cost? - $65 billion
how many homes affected ? - 650,000 homes
size of storm surge - 9ft above NGVD – 29 (National Geodetic Vertical Datum of 1929)
Deaths ranged in age from 1 to 94 years (mean: 60 years, median: 65 years); 60.7% were male
Storm Surges - Typhoon Haiyan
When? - 8th November 2013
Where? - Phillipines
HOw many people affected? - 13 million people
How many deaths? - 4,460
How much did the damage cost? - $5.8 billion
How many homeless? - 800,000
Size of storm surge? - 16ft
Age International estimates that around 1.3 million people over 50
Storm Surges - Bangladesh
Bangladesh has the worst record in the late twentieth century for storm surges
serious events occurred in 1970, 1985, 1991
suring a storm surge high winds, associated with cuclones forming to the south, push water northward up the increasingly narrow bay of bengal. This water eventually hits the coast of densely populated bangladesh. The country stands almost at sea level, covering most of the delta of the river ganges. When cyclones hit, massive waves sweep water onto the land, the water level can rise over 10m. Storm Surges travel many kilometres inland, destroying farmland, villages and infrastructure. ruining crops and drowning livestock and people.
the estimated death toll in the cyclone of 1970 was over 300,000 most buildings in the villages are flimsy constructions made form wood and are easily swept away by the flood water. The influx of salt water also causes loong term problems, for the country soils are contaminated, which greatly affects the food supply, leaving many people dependant upon aid.
Storm Surges - Canvey Island (1953 floods)
North Sea - 120 dead in Essex
large scale residential development on the low lying coastal marshland had put thousands at risk.
31st January 1953 worst storm surge since tudor times. - 307 died - 24500 houses damaged - 30,000 evacuated.
thousands of animals drowned and freat tracts of farmland were made infertile by Salt water, Just as Britain recovers from WW2.
no flood warning system + flood defence orgnised by river board
Winston Churchill declared it a national disaster.
Lord Waverly investigated flood and *** east coast can be better protected.
Queen visits Wolferton. sea 2 miles inland roads gone salt lake at wells and south lynn underwater.
Kingslyn 15 killed, Yarmouth 6 , Southwold 5, Hunstanton 40.
Coastal Floods - Towyn Floods Wales 1990
on Monday 26th February 1990, 10m waves crashed through the 140 year old sea wall at Towyn in North wales. The floods that followed were a result of the breaching and erosion of the Towyn section of the railway embankment that stretches along the coastline. A severe storm on 12 Feb has already weakened the wall in the Towyn section, making it vunerable to storm damage.
Towyn lies on the chester to Holyhead railway. where the line crosses the low - lying area known as Morfa Rhuddlan, it was protected from the sea by an embankment 3 km in length. The embankment consists of a clay core, armoured on the seaward side by slate revetments. The embankment is crested by a number of sea walls.
The flooding that occured had the following effects:
Over 5,000 people in Towyn were affected when the floods wreaked havoc in their homes and lives leaving a bill of £30 million for restoring the area.
2,800 properties were evacuated, 1,880 of them in Towyn. In Kinmel Bay and Pensarn 4,512 people were affected by flood damage.
6,000 caravans were damaged
Dalmation Coastline in Croatia - Dalmation Coast
Milford Haven in Wales - Ria
Sogne in Norway - Fjord
Isle of Arran in Scotland - Relict cliffs
Isle of Arran in Scotland - Raised Beaches
Dune de Pilat
Wave Refraction - Maverick Waves - California
The rectangle shows the location of the Maverick waves surf break, there is a narrow slope which passes from the west, which causes the Big Waves. The slope slows the movement of the waves over it. The two deep trenches either side of the steep slope, doesn’t slow the water down, this cause two angles of the wave, which shapes the wave into a U shape.
The Mavericks normally appear during the winter because of the winter storms in the North Pacific Ocean, across the west coast of America Mavericks is located on the west coast of America, this is because the fetch is extremely long and the winds very strong.
The Mavericks normally appear in the state of California just north of the small village named a Half Moon Bay, 381 Miles North of Los Angeles along the coast. It is located 658 miles south of Portland in the state of Oregon.
Landforms of Deposition
Chesil Beach - Tombolo
Slapton Sands - Barrier beach
Lulworth Cove - Bay
Flanborough head - Headland and Wave cut platform
Kingsbridge - Ria
The Old man of Hoy in Orkney Islands - Stack
Needles - Stack
Dudle Door - Arch
Old Harry and his Wife - Stack and Stump