Holderness Coastline - Coastal Erosion

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  • Holderness Coastline -Coastal Environments (erosion)
    • Information
      • 4 km in land from where it was in Roman times
      • North of England, runs between Flamborough Head & Spurn Point
      • Average annual rate of erosion is 2 metres per year
      • Loses 2 million tonnes of material per year
      • Made up of chalk & till (glacial deposits) which is soft bolder clay
      • Features - Caves, Archers & Stacks
    • Processes
      • Weathering & Mass Movement - Free fall, Mud flows & Slumps
      • Erosion - Abrasion, Hydrolic Action & Attrrition
      • Transport - Longshore drif & Tidal
    • Causes
      • Human
        • Coastal defences - Hard engineering acts like a groyne, increases erosion further up coast
        • Offshore dredging - 4 million tonnes  removed in 2000, concerns some illegally removed closer to the shore, increased steepness of sea bed
      • Physical
        • Geology - lithology is soft & permeable, little supply of material from long-shore drift, no internal structure
        • Waves - Wind speed, length of fetch, length of time the wind blows
        • Geo-morphology (shape) - breaking point of waves is at the foot of the cliffs, beach presence (sand abs Coastal  orbs less wave energy)
    • Consequences
      • Physical
        • Cliff Retreat - When eroded, if underlying clay is removed the change is permanent, coastline developes a stable shape that lies right angle to the prevailing wind
        • Rotational slumping - especially after prolonged rainfall causes curved rupture surface, some internal cohesion, highly saturated toe
        • Wildlife - Biodiversity has declined in the salt marshes due to reduced supply in sediment
      • Socio-economic
        • Cost - Coastal defences are expensive, some sea defences abandoned due to cost
        • Settlement Loss - 4km of coastline lost in last 2000 years with at least 30 settlements lost already, main road through Mappleton is only 50m from cliff, propeties loose value
        • Economic Loss - Farm land lost or loses value, gas terminals are threatened


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