Coasts (section C) and Dorset v Holderness

How does the structure of the coastline affect the rate of coastal landform change?

• Discordant coasts are when the varying rock bands run perpendicular to the sea, and this creates headlands and bays

• Concordant coasts (rock bands parallel to the sea) usually result in a more uniform coastline with a slower rate of erosion, but if the hard resistant layer is breached, the softer rock behind may erode rapidly

Why does rock type matter in landform change?

• Igneous rocks are highly resistant and erode slowly

• Sedimentary rocks or unconsolidated till (clay) erodes rapidly due to weak bonds

• Weak bedding planes and joints and faults also increases the rate of erosion via HA

How does prevailing wind direction affect the rate of coastal landform change?

The most frequent wind direction determines the angle at which waves approach the shore, driving LSD

How does fetch affect the rate of coastal landform change?

A longer fetch (a greater distance of open water which the wind blows on) creates more powerful, high-energy destructive waves, which increase the rate of erosion and landform retreat

What impact do extreme weather events have on the rate of coastal landform change?

Storm surges and severe gales can cause episodic erosion, where a single storm can erode several metres of cliff in hours (which might otherwise take decades)

• this could destroy depositional landforms like spits

• or move massive amounts of sediment offshore

What are groynes, and how do they manage the rate of coastal landform change?

Wooden/stone fences built perpendicular to the sea, are designed to trap sediment moved by LSD, building up a wide beach and absorbing wave energy.

What is the unintended consequence of using groynes to reduce erosion?

By trapping sediment in one area, groynes starve the coast of its natural sediment supply. Without a beach to protect them, areas further down the coast will receive quicker erosion rates

How does the wave type affect the rate of landform change?

• Constructive waves have a strong swash and a weak backwash, building up landforms like beaches and spits

• Destructive waves from high-energy antecedant conditions have a weak swash and a strong backwash, removing material and eroding landforms

Unintended consequences of sea walls and revetments?

Physically, Often cause waves to bounce back with more force, eroding the beach material at the base of the wall which over time undermines the structure itself

Socially, the walls could be considered an eyesore and negatively impact coastal tourism

Unintended consequences of riprap?

• gaps between rocks allow water to flow through

• boulders can become unstable or slippery, risky to the public

• rocks are often not local to the area, changing the local ecosystem

Unintended consequences of soft engineering beach “nourishment”?

• constant battle against the sea, new sediment often wash away

• dredging sand from the seabed can kill marine organisms and disrupt underwater habitats

Unintended consequences of managed realignment?

• highly controversial as involves giving up land

• farmers and homeowners lose their property, more effects of this

Unintended consequences of hold the line?

Balance between sediment being added to and removed from a sediment cell (coastal system), and while the town is safe, teh cliffs can no longer provide the sand/pebbles for beaches further down the coast. Increased erosion elsewhere

Why is the geology of Holderness a primary factor in its rapid erosion?

Most of the coast is boulder clay (glacial till) which is structurally weak and produces shallow, sloping cliffs. When saturated, these cliffs are prone to rotational slumping

How does the fetch in the North Sea impact the Holderness coastline?

Long fetch of over 500-800km, but the Atlantic currents also circulatte around the UK into the North Sea, bringing powerful destructive waves

Low pressure systems in winter further drive NE winds and higher sea levels

What is the context of groynes in Holderness?

Groynes protect the local beach but disrupt LSD which starves the cliffs further south of sediment, leaving them exposed to wave attack and increasing erosion rates there

Compare the cliff profiles of Holderness and Dorset

• Holderness has a low, unstable profile prone to slumping

• Dorest has vertical white chalk cliffs which are more resistant

How does the orientation of rock strata affect the Dorset coastline?

Dorset has a concordant coastline which can lead to wide coves IF a resistant layer is breached. It also has discordant sections like Swanage Bay where headlands and bays can be created

How does wave refraction affect the Dorset headlands?

As incoming waves approach the shore, they bend around headlands. This concentrates wave energy on the headlands, increasing erosive power and creating landforms like caves, arches, and stacks

How do climate and fetch differ for Dorset compared to Holderness?

Dorset is influenced by the SW prevailing winds from the English Channel - while it has a shorter fetch than the open Atlantic, the prevailing winds drive consistent LSD and sediment transportation along the spit

Discussing the statement “geology is the most important factor in affecting coastal landscapes”

No, as without the climate/weather (waves and weathering) the geology would not change,

However make sure to discuss both sides