Port and Waterway Planning, Hydrology, and Site Investigation
Port and waterway planning sets the physical brief that every later design decision must satisfy, and this domain tests whether you can move from a demand forecast to layout parameters and then to a defensible ground model.
Planning sequence
- Hinterland and foreland analysis first: separate captive from competitive cargo, then forecast bottom-up (population × per-capita consumption, GDP elasticity) before any top-down trend extrapolation.
- Capacity is a function of berth productivity (moves per ship-hour), target occupancy and cargo mix, not quay length alone. Container berths are commonly planned for 50–70% occupancy because arrival variability makes higher occupancy uneconomic.
- The design vessel is the 95th–98th percentile of the calling fleet over the design horizon plus a future-vessel allowance; the largest vessel governs depth, the fleet mix governs layout.
- Phasing matters: a plan that can be built in stages without stranding capital scores better than a single monolithic layout.
Hydrology inputs
- Combine astronomic tide, surge, wave setup and run-up, river flood and sea-level rise scenario-wise; independent maxima added together overstate the level, arithmetic addition of dependent components understates it.
- Return period is chosen by consequence, commonly 1 in 50 years for operational levels and 1 in 100 for structural safety, with joint probability of surge and river flow where both matter.
- Terminal drainage design uses rainfall-runoff, a separate calculation from coastal flooding.
Site investigation
- Bathymetry by multibeam, then side-scan sonar for obstructions, sub-bottom profiler for strata, magnetometer for cables and wrecks.
- Boreholes with CPTu and good-quality sampling for triaxial testing; marine clays are often soft, sensitive and lightly underconsolidated.
Worked example
Fifty years of annual maximum water levels give mean 2.20 m and standard deviation 0.25 m. Gumbel fit: reduced variate y = −ln(−ln(1 − 1/50)) = 3.90, then x = μ + (y − 0.5772)σ/1.2825 = 2.20 + (3.3247 × 0.25)/1.2825 = 2.20 + 0.65 = 2.85 m. That is the still-water level to which setup and run-up are added for crest design.
Traps
- Treating tide and surge as independent, or adding everything without a scenario logic.
- Sizing depth on mean or median vessel rather than the design vessel.
- Reporting quay length as capacity while ignoring productivity and occupancy.