CH Tides, Water Levels & Vertical Datums 3

Question 1

Which tidal constituent has the largest amplitude in most locations along the US East Coast?

Accepted Answer

M2 (principal lunar semidiurnal)

Answer

M2 is the dominant tidal constituent along the US East Coast and in most ocean areas worldwide due to the Moon's gravitational dominance.

Question 2

A water level gauge experiencing a datum shift would most likely be identified by comparing:

Accepted Answer

Staff gauge readings to the gauge benchmark network via leveling

Answer

Datum shifts are detected by periodic leveling between the gauge reference and the benchmark network to verify the gauge hasn't settled or shifted.

Question 3

The Great Diurnal Range (Gt) is defined as the difference between which two tidal planes?

Accepted Answer

Mean Higher High Water and Mean Lower Low Water

Answer

Gt (Great Diurnal Range) is defined as the difference between Mean Higher High Water (MHHW) and Mean Lower Low Water (MLLW).

Question 4

Under NOAA standards, how many months of water level data are typically required at a short-term tide station to transfer a tidal datum from a nearby control station?

Accepted Answer

1 month minimum

Answer

NOAA's standards allow datum transfer from as little as 1 month of simultaneous water level data if the control station relationship is strong and stable.

Question 5

What is 'storm surge' in the context of water level measurement?

Accepted Answer

The abnormal rise of water above predicted tide level due to meteorological forcing

Answer

Storm surge is the departure of water level above (or below) predicted astronomical tide caused by wind stress, atmospheric pressure, and wave setup from storms.

(CH) Certified Hydrographer Practice Test

(CH) Certified Hydrographer Practice Test

CH Tides, Water Levels & Vertical Datums 3