Coastal ManagementCoastal Management

AS GeographyAS Geography

Have you seen any of Have you seen any of these?these?

Sea WallsSea Walls

Why?Why? LifespanLifespan CostCost ProblemsProblems

Highest protection Highest protection in the short term, in the short term, lifespan about 50 lifespan about 50 years. Halts local years. Halts local erosion. They are erosion. They are very expensive to very expensive to build. Erosion build. Erosion continues where continues where scheme ends, need scheme ends, need maintenance.maintenance.

GroynesGroynes Groynes are designed Groynes are designed

to slow down to slow down longshore drift and longshore drift and build up the beach. build up the beach. They are usually made They are usually made of tropical hardwoods of tropical hardwoods which are more which are more resistant to marine resistant to marine borers and erosion. A borers and erosion. A few are made of few are made of concrete, steel or in concrete, steel or in more recent times more recent times large rocks. They are large rocks. They are built at right angles to built at right angles to the shore and spaced the shore and spaced about 50-100 metres about 50-100 metres apart. Groynes may apart. Groynes may have a life of 15-20 have a life of 15-20 yearsyears

Terminal Groyne EffectTerminal Groyne Effect

Occurs when there are piecemeal Occurs when there are piecemeal protection schemes.protection schemes.

For instance a groyne field is built and For instance a groyne field is built and sediment builds up between the groynessediment builds up between the groynes

The coastline continues to erode.The coastline continues to erode. On the downdrift side there is a sediment On the downdrift side there is a sediment

deficit. The erosion of non protected side deficit. The erosion of non protected side continuescontinues

Terminal Groyne EffectTerminal Groyne Effect

Occurs when there are piecemeal Occurs when there are piecemeal protection schemes.protection schemes.

For instance a groyne field is built and For instance a groyne field is built and sediment builds up between the sediment builds up between the groynesgroynes

The coastline continues to erode.The coastline continues to erode. On the downdrift side there is a On the downdrift side there is a

sediment deficit. The erosion of non sediment deficit. The erosion of non protected side continuesprotected side continues

The unprotected down-drift shoreline is set-back landward compared to the protected up-drift shoreline.

Terminal Groyne Effect In ActionTerminal Groyne Effect In Action

RevetmentsRevetments This is a sloping This is a sloping

feature which breaks feature which breaks up or absorbs the up or absorbs the energy of the waves energy of the waves but may let water and but may let water and sediment pass sediment pass through. The older through. The older wooden revetment wooden revetment consists of posts fixed consists of posts fixed into the beach with into the beach with wooden slats wooden slats between. Modern between. Modern revetments have revetments have concrete or shaped concrete or shaped blocks of stone laid on blocks of stone laid on top of a layer of finer top of a layer of finer material. material.

GabionsGabions The gabion is a metal The gabion is a metal

cage filled with rocks, cage filled with rocks, about 1 metre by 1 about 1 metre by 1 metre square. They metre square. They are stacked to form a are stacked to form a simple wall. They are simple wall. They are used to protect a cliff used to protect a cliff or area in the or area in the short short termterm only, since they only, since they are easily damaged by are easily damaged by powerful storm waves powerful storm waves and the cages tend to and the cages tend to rust quite quickly. rust quite quickly. Gabions have the Gabions have the advantage of ease of advantage of ease of use and are relatively use and are relatively cheap but their life cheap but their life span is shortspan is short..

Rip RapRip Rap Rock armour or riprap consists of Rock armour or riprap consists of

layers of very hard rock with the layers of very hard rock with the largest, often weighing several largest, often weighing several tonnes, on the top. Riprap has the tonnes, on the top. Riprap has the advantage of good permeability plus advantage of good permeability plus it looks more natural. it looks more natural.

Beach NourishmentBeach Nourishment

Beach nourishment, a technique used to restore an Beach nourishment, a technique used to restore an eroding or lost beach or to create a new sandy eroding or lost beach or to create a new sandy shoreline, involves the placement of sand fill with or shoreline, involves the placement of sand fill with or without supporting structures along the shoreline to without supporting structures along the shoreline to widen the beach. It is the only management tool widen the beach. It is the only management tool which serves the dual purpose of protecting coastal which serves the dual purpose of protecting coastal lands and preserving beach resources. lands and preserving beach resources.

Cliff RegradingCliff Regrading

Restructuring a cliff face to take away the Restructuring a cliff face to take away the steep gradient. reduces instability steep gradient. reduces instability

Rising Sea Levels in VeniceRising Sea Levels in Venice

Rising sea levels pose a serious threat to Venice's fine buildings and unique network of canals. Once-minor floods - known in Venice as "acqua alta" (high water) - have become increasingly common, and more damaging. Now, work is due to begin on a multi-billion dollar scheme to protect the historic city with giant floodgates.

Protection by BarrierProtection by Barrier In normal conditions, In normal conditions,

the floodgates lie on the floodgates lie on the seabed. Tanks the seabed. Tanks inside the gates are inside the gates are filled with sea water. filled with sea water.

When high tides are When high tides are expected, compressed expected, compressed air is pumped into the air is pumped into the gates, pushing the gates, pushing the water out and causing water out and causing the gates to rise on the gates to rise on hinges. hinges.

Once raised the gates Once raised the gates form a slanting barrier form a slanting barrier against the incoming against the incoming tide. tide.

The gates are 30 The gates are 30 metres high and five metres high and five metres thick.metres thick.

A chain of floodgates A chain of floodgates will be constructed in will be constructed in three channels at the three channels at the north and south ends north and south ends of the Lido the long of the Lido the long narrow island narrow island separating Venice's separating Venice's lagoon from the sea. lagoon from the sea.

A fourth barrier will A fourth barrier will be constructed at be constructed at Chioggia, a fishing Chioggia, a fishing village at the village at the southern end of the southern end of the lagoon. lagoon.

The project is due to The project is due to be finished between be finished between 2007 and 2010. 2007 and 2010.

In two’s or three’sIn two’s or three’s

Discuss the virtues of Soft and hard Discuss the virtues of Soft and hard engineering techniques to slow or engineering techniques to slow or prevent coastal erosion. prevent coastal erosion.

Come up with a way or a combination Come up with a way or a combination of ways to try and stop the fast erosion of ways to try and stop the fast erosion at Great Cowden on the Holderness at Great Cowden on the Holderness coast. Be ready to justify your answer!coast. Be ready to justify your answer!