Coastal landscapes

What processes are used in erosion

• hydraulic action

• Abrasion

• Attrition

• Solution

What are the processes in transportation

• solution

• Suspension

• Saltation

• Traction

What processes are usually contained within sediment cells

Processes of erosion, transportation and deposition

What are sediment cells generally considered as, and why is it technically not correct

• generally classes as closed system (meaning sediment from one cell isn’t transferred to another)

• But unlikely due to variations in wind direction and tidal flows

• There is also smaller sub cells within

What are the boundary of sediment cels determined by

The geography and the state of the coastline and topography

What are costal systems classes as

Open systems where both matter and energy can move in and out

What is an input and give example

• material or energy moving into the system from outside

• Precipitation, wind, introductions of sediment, energy (tidal and current)

What is an output and give examples

• material of energy moving from the system to the outside

• Ocean currents, rip tides, sediment transfer, evaporation

What is a store and give examples

• individuals elements or parts of a system

• Beach, sand dunes, erosional landscapes, depositional landscapes

What is positive feedback

Process tends to increase the change in the system

What is negative feedback

Process seeks to counter the change and maintain equilibrium

What is a ready state equilibrium

• variations in energy and the morphological response don’t deviate too far from the long term average.

• E.g along a coast that experiences consistent wave energy conditions, the gradient of a beach may be steeper or shallower depending on the time of the year. BUT the average annual gradient is similar year or year

What is a dynamic equilibrium

• involves a change in equilibrium conditions but much more gradual

• E.g the response of coasts to the gradual rise in sea levels experienced due to climate change

What are the 4 factors that all beaches in dynamic equilibrium involve

• supply of sand

• Energy of the waves

• Changes in sea levels

• Location of the shoreline

  It is the balance of these factors and how they interact with each other that determine weather of a beach erodes or grows.

How is positive feedback seen in the coasts

• where a transfer leads to increase or growth

• Coastal management can inadvertently lead to increase of erosion elsewhere. Groynes trap sediment, depriving areas further down and can increase erosion.

• Seawalls have same effect by transferring high energy waves elsewhere along the coastline.

• As a spit forms, the rivers velocity is further reduced with increased friction. This leads to an increase in spit head material accumulation and yet further river velocity reduction.

How is negative feedback seen in coasts

• where a transfer leads to decrease or decline

• When the rate of weathering and mass movement exceeds the rate of cliff foot erosion a scree slope is formed. Over time, this apron of material extends up the cliff face protecting the cliff face from sub-aerial processes. This leads to a reduction in the effectiveness of weathering and mass movement.

• Sediment is eroded from the each during a storm, the sediment is then deposited offshore forming an offshore bar. This means waves are now forced to break before reaching the beach dissipating their energy and reducing further erosion when they reach the beach.

• When the storm calms, normal waves conditions rework sediments from offshore bar back to the beach and the loop continues.

How is dynamic equilibrium seen in coasts

• this represents a balance within a constantly changing system

• Constructive waves build up a beach, making it steeper. This encourages the formation of destructive waves that plunge rather than surge.

• Redistribution of sediment offshore by destructive waves reduce the beach gradient which in turn, encourages the waves to become more constructive.

• This state of constant dynamic equilibrium between the type of wave and the angle of the beach.

what’s a sediment cell

• sketch of coastline and its associated nearshore within which the movement of coarse sediment. (Usually closed system)

What determines the boundaries of sediment cells

Topography and shape of the coastline

Explain why sediment cells are unlikely to be completely closed systems

Variations in wind direction and the presence of tidal currents

Why is understanding of sediment cells important

For managing our coastlines and to put in strategies

What are physical factors affecting coastal landscape systems

• currents

• Wind

• Waves

• Tides

• Geology

How do waves break

• when waves enter shallow water the deepest circling water molecules come into contact with the sea floor.

• Friction between the seafloor and the water changes the speed, direction, and shape of waves.

• The deepest part of the wave will slow down more than top of wave, wave begins to steepen as the crest advances ahead of the base.

How does wind create waves

• wave energy generated by drag of winds moving across ocean surface

• Higher wind speed, and the longer the fetch, longer waves and more energy they have

• Offshore winds then drive waves to the coast

Name 3 processes that can be carried out directly by wind without involving waves

Erosion, transportation, deposition

What does aeolian mean

Erosional, transpirational, and depositional processes by WIND

Explain constructive waves

• they are allowed to run their course without interference from those ahead or behind.

• Flat and low in height, their swash carries material up the beach, forming a berm, with the energy consequently dissipated over a wide area so has a weak backwash

• They are associated with the progressive steepening of a gently sloping beach

Explain destructive waves

• destructive waves break more frequently, with the force of the swash reduced by the previous wave’s backwash.

• The steep waves plunge onto a smaller area, concentrating their energy.

• Meaning backwash has little time to infiltrate and will carry shingle and sand to form breakpoint (longshore) bar

What are the different ways waves break

• spilling → steep waves breaking onto gently sloping beaches

• Plunging → moderately steep waves breaking into step beaches; plunges vertically downwards

• Surging → low angle waves breaking onto steep beaches, wave slides forwards and may not break