1.5 Holderness Coast

Question 1

What is the Holderness coast? Why does it erode so fast and what are the risks to it

Answer 1

• 85km of coast, retreating 2.6cm year claiming 32 towns and villages which have fallen into the sea.
• 237 properties at risk

Why erode so fast:

• Geology - most soft clay part of glacial deposit
• Fetch and prevailing winds - NE prevailing winds, fetch of 800km of north sea
• Tides and LSD - flows south, transports material along the coast, sediment imbalance as harder chalk does not erode enough to provide material and backwash removes more sediment than deposited. Beaches narrow and do not protect cliffs
• Low pressure from atlantic: winter storms in North Sea intense - low pressure raises sea level causing high tides and storms
• Subaerial attack - sand and clay cliffs easily saturated by rain and water

Question 2

What are some key features of the Holderness coast?

Answer 2

Flamborough head - headland with all features. Chalk resistant to erosion

• Horizontal bedding planes assist development of WCP - form close to high tide when shingle carried in and retreat
• Vertical joints - waves penetrate cliffs
• Wave quarrying from hydraulic action
• Wave refraction focusses on headland
• Sub aerial processes

Holderness cliffs:

• Weight causes material to slide seawards along slip planes
• Increased shear stress causing MM
• carries 500,000 tonnes of sediment - little material for rest of system

Spurn head - sediment deposited here where winds and waves and estuary created recurved spit, growing 10cm a year

Question 3

What human factors affecting coast?

Answer 3

• Presence of people along coast - population and caravan parks
• Natural processes e.g. groynes
• Global warming - rise in sea levels and increased storminess causes coastal flooding

Question 4

What has been the general management scheme

Answer 4

9,2km of land protected
2km of frontage
-Maintenance by EA

Question 5

What is done at Hornsea?

Answer 5

• 3km stretch of housing and holiday resort
• Increasing population
• 1990s sea wall made to protect houses
• £5.2m cost
• Sand dune regeneration benefit ecosystem

Question 6

What is done at Withernsea

Answer 6

• Timber groynes build beach
• Straight seawall absorbs
• Recurved sea wall avoids scour at base
• Rock armour and riprap installed to absorb energy
• Offshore breakwaters force waves to break offshore

Question 7

What is done at Easington

Answer 7

Home to gas terminal - 30% of UK gas

• Employs 1000 people
• 1km rock revetment added

Question 8

What done at Kilnsea and Spurn Head?

Answer 8

• Kilnsea allowed to erode and flood in gradual and controlled way, allowed beached and cliffs to erode as there is no funding
• Kilnsea wetlands were created by digging lowered area to south of village, compensating for loss of wetlands from coastal erosion
• Downdrift defences abandoned so erode and move inland
• Groiwng 10cm per year, 3% of sediment deposited here
• Defences abandoned due to winter storms and growing cost saved
• Evidence suggests spit will repair itself and be good wildlife habitat although salt marsh and habitats may be lost

Question 9

What is done at Mappleton?

Answer 9

• £2.2m project in 1991 protecting 50 properties, main road and village protecting by sea erosion. 2 rock groynes made of concrete resistant to erosion trap LSD sediment, creating beach
• Rock revetments absorb energy - 450m line of rock
• Regraded cliff behind - vegetation planted
• 50 year guarantee on coastline
• Larger sandier beaches at Mappleton so waves do not reach base of cliffs and no longer threat to settlement
• No slumping on the cliffs and no properties or road lost
• Soft engineering done in beach nourishment however not much as itis expensive and erodes quickly - led to

Question 10

What are the failures of Mappleton?

Answer 10

• Area south of the point no longer as much erosion, not replenished as trapped by defences so beaches have little settlement, are narrower and have higher erosion rates. This is called terminal scour however these areas are seen as less important.
• Caused MM, high high water marks, more erosion, less sediment
• Eroded 1m per month, owners scared for poroperty
• Sand Le mere caravan park eroded, moving backwards as managed retreat
• Ringborough farm eroded 2m per year - offered council support to avoid having to pay to safely demolish properties

Sand Le mere hard engineering - rolls back to protect small section of land, embankment added and drain installed to take flood water inland and over to humber estuary
-Embankment flooded, £600,000 new scheme to replace it