Assertion (A): Beach nourishment sand should be placed landward of the depth of closure.
Reason (R): Sediment placed beyond that depth does not return to the active profile.
Answer: A
Both are true and the reason gives the rule, and placement depth is a key design decision. Deeper placement is cheaper to dredge but may not benefit the beach at all. Placement depth is a genuine engineering trade-off.
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The depth of closure typically lies at what order of depth on an open sandy coast?
Answer: B
Values depend on the wave climate and the period considered, but this range is typical. The Hallermeier relation estimates it from the wave height exceeded a small fraction of the time. Longer records give a greater closure depth.
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The equilibrium beach profile is often described by a relation in which depth varies with distance offshore raised to the power
Answer: C
Dean's profile takes depth as proportional to distance to the power two thirds. The coefficient depends on sediment fall velocity and hence on grain size. The form is empirical but very widely used. It underpins most nourishment design calculations.
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Assertion (A): Coarser sediment gives a steeper equilibrium profile.
Reason (R): The profile coefficient increases with the fall velocity of the grains.
Answer: D
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. In the equilibrium profile the shape parameter increases with the sediment fall velocity, and coarser grains fall faster, so a shingle beach stands far steeper than a fine sand one. The practical consequence is that a nourishment using coarser material than the native beach will build a steeper profile and appear to lose volume as it adjusts.
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Consider the following statements about the equilibrium profile concept.
1. It describes an average shape rather than an instantaneous one.
2. Its coefficient depends on sediment grain size.
3. A real beach matches it exactly at every moment.
Answer: A
The first two are correct and are how the concept is used. The third overstates it, since real profiles fluctuate about the equilibrium shape continuously without ever quite matching it. It is a useful design idealisation, not a description.
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Coastal dunes contribute to shore protection by
Answer: B
The dune acts as a reservoir eroded during a storm and rebuilt by wind afterwards. Vegetation is essential to trapping the sand that rebuilds it. The dune is a reservoir rather than a barrier. Wind rebuilds what the storm removed from it.
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Assertion (A): Trampling of dune vegetation can lead to beach erosion problems.
Reason (R): Loss of the vegetation allows the sand to blow away rather than accumulate.
Answer: C
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. Marram and similar grasses trap wind-blown sand and hold it with their roots, so a vegetated dune accretes and stores a reserve of sediment that the beach draws on during storms. Trampling destroys the cover, the bare sand is deflated and a blowout develops, and the store that would have fed the beach is lost. Fencing and boardwalks address it directly.
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Three of the following are soft engineering approaches to coastal protection. Which is the odd one out?
Answer: D
A concrete seawall is the classic hard engineering solution. The other three work with natural processes rather than resisting them outright. Soft approaches keep the system able to adjust. Adaptability matters as sea level continues to rise.
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Managed realignment involves
Answer: A
Intertidal habitat created in front of the new line dissipates wave energy naturally. It is often cheaper over the long term than maintaining a defence in an unsustainable position. Whole life cost is what decides the comparison.
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Consider the following statements about managed realignment.
1. It creates intertidal habitat that absorbs wave energy.
2. It can be cheaper in the long run than holding the line.
3. It amounts to abandoning any form of coastal management.
Answer: B
The first two are correct and are the usual justification. The third mischaracterises it, since the defence is deliberately relocated rather than abandoned. Protection continues along the new line. The intertidal area in front does part of the work.
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