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Understanding Tidal Datums. Dr. Patrick R. Michaud Conrad Blucher Institute Division of Nearshore Research February 9, 2001. Presentation Overview. Definitions Understanding Tidal Datums Computing Tidal Datums Other Notes. Tidal Datum Definitions.
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Understanding Tidal Datums Dr. Patrick R. Michaud Conrad Blucher Institute Division of Nearshore Research February 9, 2001
Presentation Overview • Definitions • Understanding Tidal Datums • Computing Tidal Datums • Other Notes
Tidal Datum Definitions Tide – The periodic rise and fall of the water resulting from gravitational interactions between Sun, Moon, and Earth. High water – The maximum height reached by a rising tide. Low water – The minimum height reached by a falling tide.
Tidal Datum Definitions Higher High Water – The highest of the high waters (or single high water) of any specified tidal day due to the declinational effects of the Moon and Sun Lower Low Water – The lowest of the low waters (or single low water) of any specified tidal day due to the declinational effects of the Moon and Sun
Tidal Datum Definitions • National Tidal Datum Epoch – The specific 19-year period adopted by the National Ocean Service as the official time segment over which tide observations are taken and reduced to obtain mean values for tidal datums.
MHHW, MHW Mean Higher High Water (MHHW) – The average of the higher high water height of each tidal day observed over the National Tidal Datum Epoch. Mean High Water (MHW) – The average of all of the high water heights of each tidal day observed over the NTDE.
MLW, MLLW Mean Low Water (MLW) – The average of all of the low water heights of each tidal day observed over the NTDE. Mean Lower Low Water (MLLW) – The average of the lower low water height of each tidal day observed over the NTDE.
MTL, MSL Mean Tide Level (MTL) – The arithmetic mean of mean high water and mean low water. Mean Sea Level (MSL) – The arithmetic mean of hourly heights observed over the NTDE.
