CH Tides, Water Levels & Vertical Datums 5

Question 1

The relationship between NAVD 88 (land survey datum) and MLLW (chart datum) at a given coastal location:

Accepted Answer

Varies spatially and must be determined by leveling from benchmarks

Answer

The separation between NAVD 88 and MLLW varies by location and must be determined through leveling connections to tidal benchmarks at each site.

Question 2

A 'bench mark' in the context of a tide station refers to:

Accepted Answer

A fixed, stable physical mark with a known elevation relative to the tidal datum

Answer

Tide station bench marks are stable physical monuments with published elevations referenced to the station's tidal datum, used to recover or verify the gauge datum.

Question 3

What hydrographic phenomenon explains why tides in the Bay of Fundy can exceed 16 meters in range?

Accepted Answer

Near-resonance between the tidal forcing period and the bay's natural oscillation period

Answer

The Bay of Fundy's natural resonant period (~13 hours) is close to the semidiurnal tidal period (~12.4 hours), causing near-resonant amplification of the tidal range.

Question 4

In harmonic tidal prediction, the 'epoch' (κ) of a tidal constituent is:

Accepted Answer

The phase lag of the constituent relative to the equilibrium tide at the prime meridian

Answer

The epoch κ (kappa) is the local phase lag of an observed tidal constituent relative to the corresponding equilibrium constituent at Greenwich.

Question 5

Which statement correctly describes 'mean tide level' (MTL)?

Accepted Answer

MTL is the arithmetic mean of mean high water and mean low water

Answer

Mean tide level (MTL) is computed as the simple average of mean high water (MHW) and mean low water (MLW), which may differ from the average of all water level observations.

(CH) Certified Hydrographer Practice Test

(CH) Certified Hydrographer Practice Test

CH Tides, Water Levels & Vertical Datums 5