Coastal Processes and Morphology Questions and Answers

Answer: C

Larger swash under bigger waves produces correspondingly wider cusps. The regularity of the spacing is a hallmark of a self organising process. No external forcing sets the spacing directly. The pattern emerges from the swash itself.

Answer: D

Water carried shoreward by breaking waves must return, and it concentrates into narrow channels. They are a leading cause of drowning and are also efficient at carrying sediment offshore. They are the seaward limb of the nearshore circulation.

Answer: A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. Water piled against the shore by wave setup must return seaward, and it does so where the resistance is least - through a break in the bar, where the water is deeper and the incoming waves are weaker. That is why rips are found at bar gaps, and why a stretch of apparently calm water between breakers is the most dangerous place to swim.

Answer: B

Correct answer: 1 and 2 only

Statements 1 and 2 describe the circulation correctly: breaking waves raise the mean level inside the surf zone, and the excess water returns to sea in narrow rip currents. Statement 3 confuses the rip with the longshore current - the longshore current runs parallel to the shore, while the rip runs seaward across it, which is why the escape advice is to swim parallel to the beach.

Answer: C

Momentum flux from breaking waves is balanced by a sloping water surface. It contributes measurably to total water level during storms and is included in modern flood assessments. Setup can add a substantial part of a metre.

Answer: D

Correct answer: about one fifth

Wave setup at the shoreline is typically about 0.2 of the breaking wave height, so a 3 metre breaker raises the still water level by more than half a metre. It arises from the momentum flux of the breaking waves and is a real elevation of the mean level, not an oscillation, which is why it must be added to the tide and surge rather than averaged out of them.

Answer: A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the magnitude. At roughly a fifth of the breaking wave height, setup during a severe storm can add half a metre or more to the level against which a defence must work - a substantial addition on top of the tide and surge, and one that occurs precisely when those are also at their worst. Omitting it understates the design water level in the very condition that matters.

Answer: B

Correct answer: the maximum vertical extent of wave uprush above still water

Runup is measured vertically from the still water level to the highest point the uprush of an individual wave reaches on the slope. It is what determines the crest level a defence needs, and it depends on the wave height and period and on the roughness and steepness of the slope. It is distinct from setup, which is the raised mean level rather than the excursion of individual waves.

Answer: C

Correct answer: A-2, B-4, C-1, D-3

Extreme water level is built up from four contributions of quite different origin. The astronomical tide is the gravitational forcing of moon and sun. Storm surge is wind stress piling water against the coast together with the inverse barometer effect of low pressure. Wave setup is the raised mean level produced by the momentum flux of breaking waves. Runup is the uprush of individual waves above that level.

Answer: D

Correct answer: the depth beyond which profile change becomes negligible

The depth of closure is the seaward limit of the actively reworked profile: beyond it the bed shows no measurable change from year to year. It defines the outer edge of the littoral zone for budget purposes, and it decides whether nourishment sand placed offshore will feed the beach or be lost - which is why it is computed before any nourishment scheme is designed.