Coasts 1.2

• High Energy Coastline


  • Wave heights range from 0.2m - 3.5m on average
  • North west dominant wave direction
  • 1500km fetch (large!)
  • 6-8 waves per minute on the Flamborough head coastline
• Erosion rate of clay at 0.8m and limestone 0.1m a year
• Stacks are found isolated at the end of headlands
• Rainfall averages 40mm a month
• Cliffs between Saltburn and Robin Hood's Bay are higher with a stepped profile
• These areas are north facing and exposed to high energy waves
• Sources of sediment


  • Sediment has been driven onshore as sea level rose at the end of the last ice age
  • Sediment is also supplied by cliff erosion, sandstone, limestone and boulder clay
  • River Esk supplies a limited amount of sediment due to the construction of weirs and reinforced banks
• Saltburn has experienced a net increase in beach sediment of 9245m3 between 2008 and 2011 while Filey Bay has experienced erosion
• Geology


  • Mudstones
  • Clay
  • Limestones
  • Sandstone
• Mudstones


  • Weka lithology, vulnerable to hydraulic action, pounding and abrasion
  • Significant addition of small sediment into the system
• Clay


  • Weak lithology vulnerable also to abrasion, hydraulic action and pounding
  • Significant addition of small sediment to the system
• Limestones


  • Vulnerable to weathering, carbonation and solution
  • Sediment is mostly dissolved so has limited impact
• Sandstone


  • More resistant to geomorphic processes, providing larger sediment
  • Providing much of the material for the beaches, larger sediment size means that much of the material remains locally
• Erosional Landforms as a result of Physical factors


  • Headlands and Bays (geology)
  • Selwicks Bay
  • Robin Hoods Bay
  • Geos and Blowholes (50 Found across the coastline)
  • Funnel Shaped Depressions
  • Shore Platforms (waves)
  • Beaches (waves)
  • Cliffs (geology)
• Selwicks Bay


  • A bay where features such as Joints, caves, arches and stacks can be found
• Robin Hoods Bay


  • Weak shale cliff has been eroded with sides of more resistant bands of limestone
• Geos and Blowholes


  • Blowholes are formed when major joints in the chalk enlarge
  • Geos form when the gap between the blowhole and the cliff collapse
• Shore Platforms


  • Shoreline Platforms
  • Shore platform has formed at robin hoods bay
  • Sloping at a 1 degree angle with ramped sections of up to 15 degrees
  • Formed over the last 6000 years after erosion into the shale cliffs
• Beaches


  • Very few well developed beaches only really found in sheltered low energy environments
  • Because of low input of sediment from rivers and slow rate of erosion from the resistant rocks on the coastline
• Cliffs


  • Cliffs made of strong chalk, tightly bonded mineral particles, about 20-30 metres high
  • Geologically the cliffs are horizontally bedded with a vertical face overlain by weak glacial till
  • Stretch of coastline from saltburn to flamborough head is 60km long
  • Cliffs between saltburn and robin hoods bay are higher with a stepped profile
  • Formed from resistant limestones
• Limestone present, leads to lots of joints and cracks and then blowholes/geo's
• Hard rock erodes about 10cm a year
• Soft rock erodes about 80cm a year
• Formation of bays and headlands leads to the development of erosive landforms like caves, stacks and stumps
• Beaches within bays, form over thousands of years but can be changed very quickly due to seasonal events like storms
• Lack of formation of depositional landforms like spits, tombolos and bars due to the high energy environment and low sediment accumulation
• Formation of the Shoreline Platform over the last 6000 years at robin hoods bay creates negative feedback, as the wave which eroded the cliff releasing sediment that generates a shore platform, now loses energy as a result of the shore platform, reducing cliff erosion
• Soft coastline like at Filey Bay rotational slumping often occurs
• Holbeck hall collapse at Scarborough where 60m of cliff lost overnight
• Hard coastline like Flamborough cliff collapse is most likely
• Interrelationships


  • Tidal range
  • Wave refraction
  • Bays and headlands
  • Prevailing Wind
  • Limestone cliffs
  • Cliff retreat and wave cut platforms
• Tidal range


  • High Tidal range
  • Marine processes attack larger area
  • Leads to large range of coastal features
• Wave refraction


  • Orthogonal wave refraction focusses energy on the headlands
  • Increases rates of erosion and sediment input
• Bays and headlands


  • Selwicks bay features, and interrelationships between and refraction and erosional landforms like stacks
• Prevailing Wind


  • Long Fetch of 1500km leads to more erosional landforms
• Limestone cliffs


  • The strong structural integrity of these structures leads to geos and blowholes forming
  • As it has lots of joints and cracks and a complex structure
  • Limestone cliffs erode and weathers through carbonation, as a result it has a low sediment contribution
• Cliff retreat and wave cut platforms


  • Wave cut platforms rely on cliff retreat for their formation, like robinhoods bay 500m wide platform
  • This consequently results in a platform that dissipates wave energy preventing further cliff retreat
• Low Energy Coastline


  • Waves are not as powerful
  • Rate of deposition exceeds rate of erosion
  • Characteristic landforms include beaches and spits
• Nile Facts


  • 6650KM in length
  • Nile catchment area is about 3 million KM2
  • Sea levels rise 1.2mm a year
  • Average nile discharge is 86 billion m3 a year
  • Has a sediment load of 125 million tonnes
  • More than 80% of the niles discharge occurs during the flood period between august and september
• Aswan High Dam (1964) reduced the nile discharge resulting in increased coastal erosion along the delta