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- Total number of questions : 20
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Coastal Engineering [ Question No: 1 To 20 ] :
The single most effective measure against loss of life from storm surge has historically been
A tsunami warning system for a distant source relies principally on
Assertion (A): Fishtail groynes are sometimes described as hybrid structures.
Reason (R): The splayed head performs a sheltering role alongside the drift interception function.
All of the following are inputs to a coastal structure design EXCEPT
Cathodic protection of steel sheet piling in sea water works by
A design that permits a defined level of armour damage is justified because
Match each adaptation strategy with what it does.
List I
A. Protect
B. Accommodate
C. Retreat
D. Avoid
List II
1. relocate assets landward over time
2. resist the process with defences
3. prevent new development in the risk zone
4. adapt land use to the changing risk
A detached breakwater placed offshore typically produces
Sediment transport in the swash zone is difficult to measure because
State whether the following is true or false.
A small error in predicted current speed produces a much larger error in predicted sediment transport.
Bed load transport refers to sediment that
Consider the following statements about tidal inlets.
1. Inlet cross section reflects a balance of tidal scour and wave infilling.
2. A larger tidal prism supports a larger stable throat area.
3. Inlet size is determined by the offshore wave height alone.
Assertion (A): The tidal wave rotates about an amphidromic point rather than simply oscillating.
Reason (R): The Coriolis effect deflects the flow and turns the standing wave into a rotating one.
The form factor used to classify a tidal regime is the ratio of
Assertion (A): Scale effects in a wave flume model arise principally from viscosity.
Reason (R): Froude scaling is preserved while Reynolds similarity cannot simultaneously be.
State whether the following is true or false.
Stokes wave theory predicts a small net drift of water in the direction of wave travel.
Assertion (A): Swell arriving at a coast shows a period that decreases over time.
Reason (R): Longer waves travel faster and therefore arrive from a distant storm first.
Salt marshes and mangroves attenuate waves principally by
Assertion (A): Rip currents often occupy gaps in an offshore bar.
Reason (R): The gap provides the path of least resistance for the returning flow.
State whether the following is true or false.
Construction of a dam on a river can cause erosion at the coast many kilometres away.
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20
Coastal Engineering [ Question No: 1 To 20 ] :
The single most effective measure against loss of life from storm surge has historically been
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: timely warning combined with accessible shelters
The historical evidence is unambiguous. Bangladesh reduced surge mortality from hundreds of thousands in 1970 to a few thousand in comparable later events, and the change came from cyclone warnings that reach the villages, a network of raised shelters people can reach on foot, and volunteers who ensure they go. Embankments help but are overtopped; warning and shelter address the exposure directly.
A tsunami warning system for a distant source relies principally on
Your Answer : (Not Answered)
Correct Answer : C
Seismic networks detect the event within minutes and deep ocean pressure recorders confirm the wave. Confirmation matters because most large earthquakes generate no significant tsunami. False alarms rapidly destroy public compliance.
Assertion (A): Fishtail groynes are sometimes described as hybrid structures.
Reason (R): The splayed head performs a sheltering role alongside the drift interception function.
Your Answer : (Not Answered)
Correct 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 sense of hybrid. A fishtail groyne intercepts longshore drift like an ordinary groyne, but its splayed head also stands across the incoming waves and shelters the beach behind it, which is what a detached breakwater does. Because it performs both functions it belongs to neither family cleanly, and it is chosen where both drift and wave energy are contributing to the erosion.
All of the following are inputs to a coastal structure design EXCEPT
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: the number of visitors expected at the site each year
Visitor numbers may bear on the amenity case for a scheme and on the tolerable overtopping discharge if people stand behind the crest, but they are not an engineering input to the structure itself. The design proceeds from the wave height at the toe, the extreme water level for the chosen return period, and the geotechnical properties of the bed, which between them fix the armour, the crest level and the foundation.
Cathodic protection of steel sheet piling in sea water works by
Your Answer : (Not Answered)
Correct Answer : A
A sacrificial anode or an impressed current supplies the electrons instead. It is normally combined with a protective coating so that the anodes last considerably longer. Coating and protection are complementary measures.
A design that permits a defined level of armour damage is justified because
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: the cost of a zero damage design is disproportionate
Armour mass rises with the cube of wave height, so designing for no movement at all under the most extreme condition costs far more than designing for a few per cent of units displaced and repairing them afterwards. The damage level is chosen by comparing the extra capital cost against the expected cost and consequence of repair, which is a straightforward economic calculation once the damage can be predicted.
Match each adaptation strategy with what it does.
List I
A. Protect
B. Accommodate
C. Retreat
D. Avoid
List II
1. relocate assets landward over time
2. resist the process with defences
3. prevent new development in the risk zone
4. adapt land use to the changing risk
Your Answer : (Not Answered)
Correct Answer : D
Most real strategies combine several of these across a single coastline. Which one applies where is a planning decision informed by the physical assessment rather than dictated by it. Most coastlines use several of them in combination.
A detached breakwater placed offshore typically produces
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: a salient or a tombolo of accreted sand in its lee
The structure shelters the water behind it, so waves diffracting round its ends carry sediment towards the quiet zone and deposit it there. The result is a bulge in the shoreline - a salient - and if the structure is close enough inshore or long enough, the bulge grows out to meet it and forms a tombolo. The sediment that builds it comes from the longshore drift, so accretion here means less arriving further along.
Sediment transport in the swash zone is difficult to measure because
Your Answer : (Not Answered)
Correct Answer : B
Conventional instruments perform poorly in a thin aerated and rapidly reversing flow. Yet the swash zone accounts for a substantial part of the total profile change. Measurement difficulty and importance coincide here.
State whether the following is true or false.
A small error in predicted current speed produces a much larger error in predicted sediment transport.
Your Answer : (Not Answered)
Correct Answer : D
Transport varies with a high power of velocity in nearly every formula. Hydrodynamic accuracy is therefore a precondition for transport accuracy. The power law amplifies every velocity error. Getting the flow right comes before the transport.
Bed load transport refers to sediment that
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: moves by rolling, sliding or saltating in contact with the bed
Bed load stays in contact with the bed or returns to it after each hop, its weight borne by intergranular contact rather than by the fluid. The distinction from suspended load is not merely descriptive: the two are computed by quite different formulations and respond differently to a change in shear stress.
Consider the following statements about tidal inlets.
1. Inlet cross section reflects a balance of tidal scour and wave infilling.
2. A larger tidal prism supports a larger stable throat area.
3. Inlet size is determined by the offshore wave height alone.
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: 1 and 2 only
Statements 1 and 2 are the O’Brien argument: the throat area settles where tidal scour balances wave infilling, and a larger prism drives more scour and so supports a larger throat. Statement 3 leaves out the tide altogether, which is the dominant term - waves supply the sediment but it is the tidal prism that keeps the channel open.
Assertion (A): The tidal wave rotates about an amphidromic point rather than simply oscillating.
Reason (R): The Coriolis effect deflects the flow and turns the standing wave into a rotating one.
Your Answer : (Not Answered)
Correct Answer : B
Both are true and the reason gives the mechanism, and rotation is anticlockwise in the northern hemisphere. Amphidromic systems are the reason tidal range varies so much around a sea basin. Range is near zero at the point and largest at the edges.
The form factor used to classify a tidal regime is the ratio of
Your Answer : (Not Answered)
Correct Answer : B
It is usually written as the sum of K1 and O1 divided by the sum of M2 and S2. Values below about 0.25 indicate a semidiurnal regime and values above three a diurnal one. Intermediate values indicate one of the two mixed regimes.
Assertion (A): Scale effects in a wave flume model arise principally from viscosity.
Reason (R): Froude scaling is preserved while Reynolds similarity cannot simultaneously be.
Your Answer : (Not Answered)
Correct Answer : B
Both are true and the reason gives the conflict, and model tests use the largest practicable scale to reduce it. Roughness and permeability of armour are the properties most affected. Armour stability tests are especially sensitive.
State whether the following is true or false.
Stokes wave theory predicts a small net drift of water in the direction of wave travel.
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: True
Linear theory gives closed orbits and no net transport, but at second order the orbits do not quite close: a particle moves slightly further forward at the crest, where it is higher and the velocity greater, than back at the trough. The resulting Stokes drift is small but persistent, and it matters for the transport of pollutants and larvae.
Assertion (A): Swell arriving at a coast shows a period that decreases over time.
Reason (R): Longer waves travel faster and therefore arrive from a distant storm first.
Your Answer : (Not Answered)
Correct Answer : D
Both are true and the reason gives the dispersive sorting, and this allows the distance to the generating storm to be estimated. The rate at which the period falls gives the travel time directly. Swell period is a record of how far the waves have travelled.
Salt marshes and mangroves attenuate waves principally by
Your Answer : (Not Answered)
Correct Answer : B
Stems and roots extract momentum from the wave as it passes over. Attenuation increases with the width of the vegetated belt and with stem density. Attenuation accumulates along the flow path. Belt width dominates the protection achieved.
Assertion (A): Rip currents often occupy gaps in an offshore bar.
Reason (R): The gap provides the path of least resistance for the returning flow.
Your Answer : (Not Answered)
Correct 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.
State whether the following is true or false.
Construction of a dam on a river can cause erosion at the coast many kilometres away.
Your Answer : (Not Answered)
Correct Answer : C
The dam traps sediment that would otherwise have reached the shore. Deltas and beaches downdrift of the river mouth then erode as the supply is cut off. The effect appears far from the dam itself. Sediment starvation travels the whole length of the river.
Marks
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20