Storms to pocket beaches - Lecture 7

Question 1

What is a pocket beach?

Answer 1

Also known as an embayed beach

Beach framed at both ends by rocky headlands

Question 2

What is beach rotation?

Answer 2

(Reversing alonshore currents)
Oblique waves from one direction drive alongshore sediment transport - erosion at updrift boundary and accretion and downdrift
Reversal in wave direction reverses this process

Question 3

What are the 3 modes of change for pocket beaches?

Answer 3

Wave exposure alongshore
Reversing alongshore current
Sandbar influences

Question 4

What are the processes in the wave exposure alongshore mode of change?

Answer 4

Cross-shore sediment exchange proportional to wave exposure longshore
Alongshore-uniform flattening/steepening of berm slope

Question 5

What are the processes in the reversing alongshore currents mode of change?

Answer 5

Alongshore sediment exchange due to oblique wave angles

Alongshore-uniform berm slope

Question 6

What are the processes in the sandbar influences mode of change?

Answer 6

Cross-shore sediment exchange dependent on sandbar dissipation of storm waves and longer recovery rates
Inverse response in berm slope

Question 7

What is alongshore transport on the coast?

Answer 7

Breaking wave creates current
Wave breaking stirs up sediment with is advected alongshore
Net transport = long-term shoreline change through gradients in sed flux

Question 8

What does the amount of alongshore transport depend on?

Answer 8

Breaking wave height

Breaking wave angle relative to shoreline