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Registered Civil Engineer (Port & Waterway) study materials
Registered Civil Engineer (Port & Waterway) study resources

Registered Civil Engineer (Port & Waterway) practice questions

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Question 1Port and waterway planning, hydrology, and site investigation

In port and waterway planning, what does the term 'hinterland' refer to?

  1. The landward area a port serves and draws cargo from Correct answer.
  2. The submerged channel maintained between the breakwaters
  3. The offshore anchorage where vessels wait for berths
  4. The terminal apron used for container stacking

Explanation

Hinterland is the inland catchment region whose trade flows are routed through a port, and its population and industrial base largely determine cargo demand forecasts. It is distinguished from the foreland, which is the overseas set of trading partners reached by sea.

Question 2Port and waterway planning, hydrology, and site investigation

Which tidal datum is conventionally used as the reference level for charted depths and drying heights in port and waterway charts?

  1. Highest astronomical tide
  2. Mean sea level
  3. Mean high water springs
  4. Chart datum, approximating lowest astronomical tide Correct answer.

Explanation

Chart datum is set near the lowest astronomical tide so that charted depths are mostly conservative and predicted depths are rarely less than charted. Using a higher datum such as mean sea level would overstate available water and create grounding risk.

Question 3Port and waterway planning, hydrology, and site investigation

A wind blows over a fetch of 20 km with a sustained speed of 15 m/s. Which qualitative statement best describes the resulting significant wave height compared with a 5 km fetch under the same wind?

  1. It will be identical because wave height depends only on wind speed
  2. It will be smaller because short fetches produce steeper seas
  3. It will be larger only if the water depth exceeds 100 m
  4. It will be larger because wave growth is fetch-limited until full development Correct answer.

Explanation

In fetch-limited conditions, significant wave height grows with fetch length for a given wind speed, so the longer fetch yields the larger sea. Growth continues until the waves reach their duration- or fetch-limited equilibrium, after which further fetch adds little height.

Question 4Port and waterway planning, hydrology, and site investigation

In a tidal current analysis for a navigation channel, the 'stand of the tide' refers to which condition?

  1. The brief interval near high or low water when the current reverses and slackens Correct answer.
  2. The period of maximum flood velocity
  3. The horizontal offset between predicted and observed tide
  4. The vertical rise between consecutive high waters

Explanation

The stand of the tide is the short period around high or low water when the water level barely changes and the tidal stream slackens before reversing direction. It is a key consideration for scheduling vessel transits through constrained channels.

Question 5Port and waterway planning, hydrology, and site investigation

A site investigation for a new quay wall encounters soft estuarine clay over dense sand. Which in-situ test is most appropriate for profiling undrained shear strength continuously with depth in the clay?

  1. Cone penetration test with pore pressure measurement Correct answer.
  2. Seismic refraction survey
  3. Standard penetration test at 1.5 m intervals
  4. Plate load test on a prepared platform

Explanation

Piezocone testing gives a near-continuous profile of cone resistance and pore pressure, from which undrained shear strength in soft clay can be correlated reliably. It is faster and more continuous than spot sampling or penetration tests.

Question 6Port and waterway planning, hydrology, and site investigation

Which parameter is the primary basis for classifying a port by the size of vessels it can accommodate?

  1. The number of available berths
  2. The design vessel's deadweight and draft Correct answer.
  3. The terminal's annual throughput capacity
  4. The length of the quay apron

Explanation

Ports are commonly classed by the design vessel they can receive, expressed through deadweight or, more critically for waterways, the maximum draft that can be served. Draft directly controls which vessel classes can enter the basin and berth.

Question 7Port and waterway planning, hydrology, and site investigation

In a hydrological study for a river port, the 'rating curve' is used to do which of the following?

  1. Relate discharge to water surface elevation at a gauging station Correct answer.
  2. Convert rainfall depth to runoff volume for a catchment
  3. Estimate sediment transport as a function of velocity
  4. Predict tidal range from harmonic constituents

Explanation

A rating curve expresses the empirical relationship between stage and discharge at a specific cross-section, allowing continuous water level records to be converted to flow. It must be periodically updated when the channel geometry changes through scour or deposition.

Question 8Port and waterway planning, hydrology, and site investigation

A proposed breakwater is to be founded on a seabed of loose fine sand in a high-energy wave climate. Which design concern is most directly indicated?

  1. Reduced wave reflection at the structure face
  2. Excessive settlement of the armour layer into the core
  3. Increased chloride ingress into the concrete armour units
  4. Liquefaction and scour of the foundation under cyclic wave loading Correct answer.

Explanation

Loose saturated fine sand can develop excess pore pressures under cyclic wave loading, leading to liquefaction and foundation scour that undermines the structure. Foundation treatment or a geotextile and filter layer is typically required.

Question 9Port and waterway planning, hydrology, and site investigation

Which survey method is best suited to mapping the seabed of a turbid harbour basin for a dredging design?

  1. Side-scan sonar only
  2. Magnetometer survey
  3. Multibeam echosounder survey Correct answer.
  4. Aerial photogrammetry

Explanation

Multibeam echosounding provides dense, accurate bathymetric coverage and works independently of water clarity, making it standard for dredging quantities. Side-scan sonar images texture but does not give reliable depths.

Question 10Port and waterway planning, hydrology, and site investigation

In planning a port basin, the 'nautical depth' provided is typically the charted depth plus which allowance?

  1. The siltation allowance only
  2. The wave run-up on the quay wall
  3. The tidal range at spring tides
  4. A net under-keel clearance under the design vessel Correct answer.

Explanation

Nautical depth is the depth needed to keep the design vessel safely afloat, comprising static draft plus allowances for squat, heel, wave response and a net under-keel clearance. It is the governing criterion for dredge level design in channels and basins.

Question 11Port and waterway planning, hydrology, and site investigation

A catchment of 50 km² receives 80 mm of rainfall in 6 hours. Using a simple rational-method estimate with a runoff coefficient of 0.4, what is the approximate peak discharge?

  1. About 18.5 m³/s
  2. About 7.4 m³/s Correct answer.
  3. About 44 m³/s
  4. About 2.7 m³/s

Explanation

The rational method gives Q = C·i·A, with i the rainfall intensity in m/s. Intensity is 0.080 m over 21600 s, about 3.70×10⁻⁶ m/s, so Q ≈ 0.4 × 3.70×10⁻⁶ × 50×10⁶ ≈ 7.4 m³/s.

Question 12Port and waterway planning, hydrology, and site investigation

Which factor most strongly governs the long-term maintenance dredging requirement in an estuarine access channel?

  1. The height of the terminal lighting masts
  2. The colour of the navigation buoys
  3. The number of pilot boats stationed at the port
  4. The balance between tidal flushing and sediment import into the channel Correct answer.

Explanation

Siltation in an estuarine channel depends on the net sediment flux, which reflects the competition between tidal scour and sediment supply from the estuary and littoral drift. Understanding this balance allows designers to align the channel with natural scouring flows.

Question 13Port and waterway planning, hydrology, and site investigation

In port master planning, a 'design vessel' is selected primarily to do which of the following?

  1. Fix the number of customs inspectors required
  2. Determine the tariff schedule for cargo handling
  3. Set the dimensions of channels, berths and turning circles Correct answer.
  4. Establish the insurance premium for the terminal

Explanation

The design vessel represents the largest or most demanding ship the facility must serve, and its length, beam, draft and manoeuvring characteristics set channel widths, berth lengths and turning basin diameters. Future fleet trends must be projected so the port is not obsolete on opening.

Question 14Port and waterway planning, hydrology, and site investigation

A tidal harmonic analysis of a port's water levels yields a form factor of 0.15. This indicates which type of tide?

  1. Mixed, mainly diurnal tide
  2. Diurnal tide
  3. Semidiurnal tide Correct answer.
  4. Mixed, mainly semidiurnal tide

Explanation

The form factor is the ratio of the sum of the principal diurnal amplitudes to the sum of the principal semidiurnal amplitudes. Values below about 0.25 indicate a semidiurnal regime, while higher values progress toward mixed and diurnal types.

Question 15Port and waterway planning, hydrology, and site investigation

Which statement correctly describes the purpose of a sediment budget in a coastal port study?

  1. It measures the salinity profile across the estuary mouth
  2. It records the financial cost of dredging contracts
  3. It lists the vessels that visited the port in a year
  4. It quantifies the sources, sinks and transport pathways of sediment in a defined coastal cell Correct answer.

Explanation

A sediment budget accounts for all inputs, outputs and storage changes of sediment within a defined coastal cell, revealing whether the shoreline or channel is accreting or eroding. It underpins predictions of dredging volumes and the impacts of new structures.

Question 16Port and waterway planning, hydrology, and site investigation

In a site investigation for a port expansion, a borehole log records 'SPT N = 8 at 6 m depth in silty sand below the water table'. Which interpretation is most appropriate?

  1. The sand is cemented and impermeable
  2. The sand is loose and may require ground improvement before loading Correct answer.
  3. The sand is very dense and will not settle
  4. The sand is unsuitable for any foundation and must be removed

Explanation

An SPT blow count of 8 in saturated silty sand indicates a loose state with potential for settlement and liquefaction under seismic or cyclic loading. Ground improvement such as vibro-compaction or stone columns is commonly considered before placing heavy terminal loads.

Question 17Port and waterway planning, hydrology, and site investigation

Which of the following best defines 'freeboard' for a coastal revetment or quay wall?

  1. The vertical distance from the design water level to the top of the structure Correct answer.
  2. The slope angle of the armour layer
  3. The depth of the structure below chart datum
  4. The horizontal width of the crest

Explanation

Freeboard is the height of the structure crest above the design water level, set to limit wave overtopping and provide a safety margin. It is determined from wave run-up and overtopping discharge criteria appropriate to the exposed assets behind the wall.

Question 18Port and waterway planning, hydrology, and site investigation

A navigation channel is to be designed for one-way traffic with passing only at widened sections. Which parameter most directly determines the required channel width in a straight reach?

  1. The terminal's annual container throughput
  2. The tidal range at spring tides
  3. The design vessel's beam plus bank clearance and manoeuvring allowances Correct answer.
  4. The design vessel's length overall

Explanation

Channel width for one-way traffic is built up from the vessel beam plus allowances for manoeuvring, bank suction and clearance to the channel edges. Length and throughput affect scheduling and turning basin size but not the straight-reach width.

Question 19Port and waterway planning, hydrology, and site investigation

In hydrological frequency analysis for a port drainage design, a 50-year return period rainfall has which interpretation?

  1. It is the maximum possible rainfall for the site
  2. It will occur exactly once every 50 years
  3. It has a 2 percent probability of being exceeded in any given year Correct answer.
  4. It occurs only during spring tides

Explanation

The return period is the reciprocal of the annual exceedance probability, so a 50-year event has a 1/50, or 2 percent, chance of being exceeded in any single year. Over a 50-year design life the probability of at least one exceedance is much higher, about 64 percent.

Question 20Port and waterway planning, hydrology, and site investigation

Which combination of survey data is essential before finalising the dredge volume for a new berth pocket?

  1. Pre-dredge and post-dredge bathymetric surveys referenced to a common datum Correct answer.
  2. A single pre-dredge survey only
  3. A soil classification report without any depth data
  4. Aerial photography of the terminal and a tide table

Explanation

Dredge volume is the difference between the seabed surface before and after dredging, so both surveys must be reduced to the same vertical datum and referenced to the same horizontal control. Without a common datum the computed volume is unreliable for payment and acceptance.

Question 21Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

In linear (Airy) wave theory, the deep-water approximation is conventionally applied when the water depth exceeds roughly what fraction of the wavelength?

  1. One hundredth of the wavelength
  2. One quarter of the wavelength
  3. One half of the wavelength Correct answer.
  4. One twentieth of the wavelength

Explanation

Deep-water theory becomes accurate to within a few percent once depth exceeds about half the wavelength, because the orbital motion then decays to negligible amplitude at the bed. At that threshold tanh(kh) approaches unity and the dispersion relation reduces to the deep-water form.

Question 22Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

Which dimensionless group is the standard predictor of whether a coastal sediment particle will be mobilised by wave action on the seabed?

  1. The Reynolds number
  2. The Shields parameter Correct answer.
  3. The Keulegan-Carpenter number
  4. The Froude number

Explanation

The Shields parameter compares the bed shear stress exerted by the flow with the submerged weight of a grain, and threshold motion occurs near a critical value of about 0.05 for steady flow. Wave-induced thresholds are usually expressed as a modified Shields parameter based on the peak orbital velocity.

Question 23Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

Spring tides occur when the Earth, Moon and Sun are approximately aligned. What is the resulting tidal condition?

  1. Larger tidal range with stronger flood and ebb currents Correct answer.
  2. Equal day and night tidal range with no current variation
  3. Smaller tidal range with weaker currents
  4. A single daily high water with no low water

Explanation

Alignment of the three bodies adds the solar and lunar semidiurnal constituents in phase, producing maximum tidal range and correspondingly stronger tidal currents. This is the spring-tide condition, occurring near new and full moon.

Question 24Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

In a tidal estuary, the term 'tidal prism' refers to which quantity?

  1. The volume of water entering and leaving the estuary between low and high water Correct answer.
  2. The maximum cross-sectional area of the estuary mouth
  3. The horizontal distance the flood tide penetrates upstream
  4. The vertical distance between mean sea level and highest astronomical tide

Explanation

The tidal prism is the volume exchanged through a section during a tidal cycle, obtained by integrating the tidal elevation over the water surface area. It is a key parameter in inlet stability and flushing analyses.

Question 25Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

Which non-dimensional parameter is used to classify the degree of stratification in an estuary by comparing tidal mixing with buoyancy input?

  1. The Ursell number
  2. The estuarine Richardson number Correct answer.
  3. The densimetric Froude number
  4. The wave steepness

Explanation

The estuarine Richardson number combines river buoyancy flux with the mixing power of the tidal current, and its magnitude separates well-mixed, partially mixed and strongly stratified conditions. Larger values indicate that buoyancy dominates mixing.

Question 26Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

Wave shoaling over a gently sloping bed causes which combination of changes before breaking begins?

  1. Height, wavelength and celerity all remain constant
  2. Height increases, wavelength increases and celerity increases
  3. Height decreases, wavelength increases and celerity increases
  4. Height increases, wavelength decreases and celerity decreases Correct answer.

Explanation

Conservation of energy flux across shore-parallel contours, combined with a shrinking group velocity, forces wave height to grow while the dispersion relation shortens the wavelength and slows the celerity. The process continues until the steepness or depth-limited criterion is reached.

Question 27Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

In a coastal engineering report, 'significant wave height' is conventionally defined as which statistic?

  1. The mean of all wave heights in the record
  2. The mean of the highest one-third of wave heights in the record Correct answer.
  3. The height exceeded 50 percent of the time
  4. The maximum wave height in the record

Explanation

Significant wave height is the average of the highest one third of the waves in a sea state, which corresponds approximately to the visual estimate an observer would make. For a Rayleigh distribution it is about four times the standard deviation of the surface elevation.

Question 28Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A wave train in water 8 m deep has a wavelength of 40 m. Using the linear dispersion relation, what is the approximate phase celerity?

  1. About 3 m/s
  2. About 11 m/s Correct answer.
  3. About 6 m/s
  4. About 22 m/s

Explanation

With kh equal to about 1.26, tanh(kh) is roughly 0.85, giving c equal to the square root of (9.81 divided by 0.157) times 0.85, which is close to 11 m/s. The result lies between the shallow-water limit of 8.9 m/s and the deep-water value for this period.

Question 29Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A wave with deep-water height 1.5 m and period 10 s approaches the shore normally. Using linear theory and neglecting friction and breaking, what is the approximate shoaled height in 5 m depth?

  1. About 1.9 m Correct answer.
  2. About 1.5 m
  3. About 1.2 m
  4. About 3.0 m

Explanation

The shoaling coefficient is the square root of the ratio of deep-water to local group velocity, and for a 10 s wave in 5 m depth it is roughly 1.25. Multiplying 1.5 m by this factor gives approximately 1.9 m.

Question 30Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

Waves approach a straight shoreline at an angle of 30 degrees to the bed normal in 10 m depth and shoal onto 2 m depth. Applying Snell's law for linear waves, what happens to the approach angle?

  1. It becomes 90 degrees at the 2 m contour
  2. It increases toward parallel approach
  3. It stays exactly 30 degrees
  4. It decreases, tending toward normal incidence Correct answer.

Explanation

Snell's law requires the ratio of the sine of the wave angle to the celerity to remain constant along the ray, and celerity falls as depth decreases. The angle therefore reduces, which is why waves tend to arrive nearly perpendicular to a straight shore.

Question 31Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A deep-water wave has height 2.0 m and wavelength 60 m. What is its deep-water wave steepness, and what does it imply?

  1. About 0.33, well above the breaking limit
  2. About 0.033, below the usual breaking limit of roughly 0.14 Correct answer.
  3. About 0.003, far below any breaking limit
  4. About 0.14, exactly at the breaking limit

Explanation

Steepness is height divided by wavelength, giving 2.0 divided by 60, or about 0.033. This is well below the deep-water limiting steepness of approximately 0.14, so the wave is stable and will not break in deep water.

Question 32Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

In a partially mixed estuary, the residual (tidally averaged) circulation typically shows which pattern?

  1. Landward flow near the surface and seaward flow near the bed
  2. Landward flow at all depths with no vertical structure
  3. Seaward flow near the surface and landward flow near the bed Correct answer.
  4. Seaward flow at all depths with no vertical structure

Explanation

Buoyancy from river inflow drives a seaward surface layer, while the barotropic pressure gradient set up by the sloping surface drives a compensating landward inflow at depth. This gravitational circulation transports salt upstream and is a classic feature of partially mixed estuaries.

Question 33Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

An estuary has a mean cross-sectional area of 800 m2 at its mouth and a tidal range of 2.4 m over a surface area of 4.0 square kilometres. What is the approximate tidal prism?

  1. About 4.0 million cubic metres
  2. About 1.9 million cubic metres
  3. About 9.6 million cubic metres Correct answer.
  4. About 19 million cubic metres

Explanation

The prism is the product of the tidal range and the water surface area, giving 2.4 m times 4.0 million square metres, or about 9.6 million cubic metres. This is the volume exchanged through the mouth over half a tidal cycle.

Question 34Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

The spring tidal range at a port is 4.2 m and the neap range is 2.2 m. Using the common classification based on the form factor, how should the tide be described?

  1. Mixed mainly diurnal, since the form factor is about 2.5
  2. Diurnal, since the form factor exceeds 3.0
  3. Mixed mainly semidiurnal, since the form factor is about 1.4
  4. Semidiurnal, since the form factor is about 0.31 Correct answer.

Explanation

The form factor is the sum of the principal diurnal amplitudes divided by the sum of the principal semidiurnal amplitudes, which for a range-based estimate is the ratio of the diurnal to semidiurnal contributions. A value below about 0.25 to 0.5 indicates a semidiurnal tide, and here the ratio is roughly 0.31.

Question 35Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

For a sandy beach, which combination of conditions most favours the development of a reflective beach profile?

  1. Fine sediment and high wave energy
  2. Fine sediment and strong tidal currents
  3. Coarse sediment and low wave energy Correct answer.
  4. Coarse sediment and high wave energy

Explanation

Reflective profiles are steep and narrow with a prominent berm, forming where the beach face can keep pace with swash and offshore sediment loss is limited. Coarse grains settle quickly and low-energy waves favour this state, which is captured by the Dean parameter.

Question 36Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A current of 1.2 m/s acts alone on a sandy bed and produces a certain transport rate. When a wave orbital velocity of 1.0 m/s is superimposed, the net sediment transport typically changes in which way?

  1. It stays unchanged, because the wave is oscillatory and has zero net drift
  2. It decreases, because waves cancel the current-driven transport
  3. It increases, because the combined bed shear stress exceeds the sum of the separate effects Correct answer.
  4. It becomes zero, because the wave reverses the current direction

Explanation

Wave and current boundary layers interact nonlinearly, so the combined shear stress is greater than the linear superposition of the individual stresses. The enhanced stress raises the transport rate above the current-only value, an effect well documented in combined-flow experiments.

Question 37Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

Which mechanism is primarily responsible for the landward migration of a tidal inlet's flood-tidal delta and the associated sediment bypassing?

  1. Longshore drift crossing the inlet without entering it
  2. Flood-dominated residual transport through the inlet throat Correct answer.
  3. Wind-driven surface drift within the estuary
  4. Ebb-jet scour concentrated at the seaward margin

Explanation

Where flood currents dominate the inlet throat, sediment is carried landward and deposited in the flood-tidal delta, which builds into the estuary. This flood dominance is a recognised cause of inlet infilling and of sediment bypassing to the back-barrier.

Question 38Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A wave gauge records a sea surface with significant wave height 2.5 m and peak period 9 s. Using the deep-water approximation, what is the approximate peak wavelength?

  1. About 250 m
  2. About 63 m
  3. About 126 m Correct answer.
  4. About 14 m

Explanation

The deep-water dispersion relation gives wavelength as g times period squared divided by two pi, so 9.81 times 81 divided by 6.283 yields about 126 m. The significant height does not enter this calculation in linear theory.

Question 39Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A coastal structure is to be designed against wave run-up. Which parameter most directly governs the Iribarren number used to classify the breaker type on the structure slope?

  1. The structure slope, the wave steepness and the deep-water wavelength Correct answer.
  2. The wind speed and the atmospheric stability
  3. The longshore current velocity and the beach width
  4. The tidal range and the sediment grain size

Explanation

The Iribarren number is the slope divided by the square root of wave steepness, so it depends on the structure slope and the incident wave height and wavelength. It classifies breakers as spilling, plunging, surging or collapsing and is central to run-up formulae.

Question 40Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A tidal current of 1.0 m/s flows across a sand bed with a median grain diameter of 0.3 mm. Which statement best describes the expected transport regime?

  1. Transport is negligible because the grain size exceeds the sand range
  2. Transport occurs only in suspension with no bedload component
  3. The bed is fully mobile and transport scales strongly with the excess shear stress Correct answer.
  4. The bed is immobile because the Shields parameter is below the critical value

Explanation

For a 1.0 m/s current over a 0.3 mm sand, the Shields parameter is well above the critical threshold of about 0.05, so general bedload and suspended transport occur. Transport then increases steeply with the excess of shear stress over the critical value.

Question 41Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

In an estuary with strong tidal currents and negligible river inflow, the salinity intrusion length is most sensitive to which factor?

  1. The offshore wave climate
  2. The Coriolis parameter at the site latitude
  3. The atmospheric pressure at the estuary mouth
  4. The strength of tidal mixing relative to the tidal mean velocity Correct answer.

Explanation

Without river buoyancy, the upstream salt flux is set by the balance between tidal dispersion and the residual circulation, so mixing intensity and tidal velocity control the intrusion length. Stronger mixing shortens the intrusion by diluting salt more rapidly.

Question 42Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A wave of period 12 s propagates into a harbour through an entrance of width 60 m. Applying linear diffraction theory, which statement about the wave field inside the harbour is most defensible?

  1. Diffraction spreads energy laterally behind the breakwater, and the pattern depends on the ratio of entrance width to wavelength Correct answer.
  2. Energy propagates only along straight rays, leaving the area behind the breakwater completely calm
  3. Diffraction eliminates all wave energy at the harbour head regardless of geometry
  4. The wave length inside the harbour is set by the entrance width rather than the period

Explanation

Diffraction redistributes wave energy into the geometric shadow behind breakwaters, and the resulting pattern depends on the ratio of the gap width to the local wavelength. With a 12 s wave in deep water the wavelength is roughly 225 m, so the entrance is narrow relative to the wavelength and spreading is pronounced.

Question 43Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A tidal channel has a mean depth of 6 m and a tidal amplitude of 1.8 m. Which approach best explains why the observed flood current exceeds the ebb current in this channel?

  1. Flood dominance arises from the distortion of the tidal wave in shallow water, combined with channel geometry and frictional effects on the ebb Correct answer.
  2. Flood dominance is caused by the Coriolis deflection of the tidal wave alone
  3. Flood dominance results from the offshore wave climate forcing the inlet
  4. Flood dominance is a direct consequence of the salinity gradient reversing during the ebb

Explanation

In shallow water the tidal wave steepens and the duration of the flood is shortened relative to the ebb, so peak flood velocities are higher for the same prism. Friction and channel geometry further modify this asymmetry, producing net landward sediment transport.

Question 44Coastal and estuarine hydrodynamics, waves, tides, and sediment transport

A beach nourishment project places sand with a median diameter of 0.5 mm on a native beach of 0.2 mm. Using the concept of the overfill ratio, what is the expected consequence?

  1. No fill volume can be computed without wave data, since the overfill ratio depends only on wave height
  2. More volume than the native fill volume is required, because the coarser borrow sand is less compatible and a larger adjustment factor applies Correct answer.
  3. Exactly the native fill volume is required, because grain size does not affect compatibility
  4. Less volume is required, because coarser sand is always more stable and fills a larger area

Explanation

The overfill ratio compares the native and borrow grain-size distributions and adjusts the required volume for compatibility. A borrow material coarser than the native beach generally requires a larger adjustment factor, so more volume must be placed to achieve the design profile.

Question 45Geotechnical engineering for marine and waterfront structures

In a port development on soft marine clay, a 22 m thick normally consolidated clay layer is to be surcharged. Why is staged construction with monitoring usually preferred over placing the full embankment fill at once?

  1. Staged fill reduces the total settlement by eliminating secondary consolidation
  2. Staged fill lowers the groundwater table so effective stresses decrease
  3. Staged fill allows excess pore pressure to dissipate between stages, preserving shear strength and preventing bearing failure Correct answer.
  4. Staged fill increases the preconsolidation pressure by cyclic loading of the clay

Explanation

In normally consolidated marine clay, rapid undrained loading raises excess pore pressures and reduces effective stress, so a single-stage fill can trigger bearing capacity failure or lateral squeeze. Staged placement lets pore pressures dissipate, gaining strength between stages, and monitoring confirms stability before the next lift. Total settlement is not eliminated, only the rate of loading is controlled.

Question 46Geotechnical engineering for marine and waterfront structures

For a gravity quay wall founded on dense sand, which parameter most directly governs the sliding resistance at the base?

  1. The plasticity index of the sand
  2. The undrained shear strength of the sand
  3. The friction angle between the base concrete and the sand Correct answer.
  4. The coefficient of consolidation of the sand

Explanation

Sliding resistance of a gravity wall on granular soil depends on the effective normal force and the interface friction angle between the base and the soil, often taken as a fraction of the internal friction angle. Dense sand is drained, so undrained strength, consolidation coefficient, and plasticity are not the controlling parameters for base sliding.

Question 47Geotechnical engineering for marine and waterfront structures

A sheet pile quay wall is to be driven through a soft clay layer into a sand stratum. Which design condition typically controls the required penetration depth?

  1. The passive resistance available below the dredge line against rotation and translation Correct answer.
  2. The permeability of the sand stratum
  3. The corrosion allowance on the exposed steel above water
  4. The axial capacity of the sheet piles under vertical quay loading

Explanation

Anchored or cantilever sheet pile walls derive support from passive earth pressure developed below the dredge line, so the embedded length must be sufficient to mobilize that resistance against rotation and translation. Axial capacity, corrosion allowance, and permeability affect other aspects but not the penetration depth for stability.

Question 48Geotechnical engineering for marine and waterfront structures

In a coastal reclamation project, a sand drain (prefabricated vertical drain) system is installed in soft clay before surcharging. What is the primary function of the drains?

  1. To reduce the final settlement magnitude
  2. To prevent saltwater intrusion into the clay layer
  3. To increase the shear strength of the sand fill
  4. To shorten the drainage path so primary consolidation occurs within the construction period Correct answer.

Explanation

Vertical drains reduce the horizontal drainage path length, dramatically accelerating primary consolidation so most settlement occurs during surcharging rather than after the structure is in service. They do not change the ultimate settlement magnitude, the fill strength, or saltwater movement.

Question 49Geotechnical engineering for marine and waterfront structures

A berth structure uses a block-type quay wall with a rubble mound foundation. During seismic design, which failure mode is most characteristic for this wall type?

  1. Tensile rupture of the concrete blocks
  2. Buckling of the sheet piles behind the wall
  3. Uplift of the wall caused by wave overtopping
  4. Seaward displacement and settlement of the wall due to liquefaction of the foundation sand Correct answer.

Explanation

Block quay walls on rubble foundations are vulnerable to seaward displacement and settlement when the foundation or backfill sand liquefies during an earthquake, reducing effective support. Concrete tensile rupture, wave uplift, and sheet pile buckling are not the governing seismic modes for this configuration.

Question 50Geotechnical engineering for marine and waterfront structures

Which in-situ test is most commonly used to evaluate the liquefaction potential of a saturated sand layer at a port site?

  1. Plate load test
  2. Pressuremeter test in clay
  3. Vane shear test
  4. Standard penetration test with energy correction Correct answer.

Explanation

Liquefaction assessment is conventionally based on the corrected standard penetration resistance (N1,60) or cone penetration resistance, correlated with cyclic stress ratios. Plate load tests, vane shear, and pressuremeter testing provide other parameters and are not the standard basis for liquefaction evaluation.