Tidal Characteristic Numbers of Water Level
- 1 Motivation
- 2 Definition of the Tidal Characteristic Numbers of Water Level
- 2.1 High Water Level (HW)
- 2.2 Low Water Level (LW)
- 2.3 Tidal Range
- 2.4 Mean Tide Level
- 2.5 Mean Flood Water Level
- 2.6 Mean Ebb Water Level
- 2.7 Flood Period
- 2.8 Ebb Period
- 2.9 Flood Period : Ebb Period
- 2.10 Tide Period
- 2.11 Flood Period : Tide Period
- 2.12 Ebb Period : Tide Period
- 2.13 High Water Time (T_HW)
- 2.14 Low Water Time (T_LW)
- 2.15 Flood Tide Rise
- 2.16 Ebb Tide Fall
- 2.17 Inundation Period
The calculation and graphic display of the tidal characteristic numbers of water level contributes to a large amount for an improved understanding of the tide induced dynamic processes in coastal seas and estuaries.
- Calculating high water, low water as well as flood tide rise, ebb tide fall and tidal range highlight the potential and kinetic energy which is related to the tidal wave. These quantities are spatially varying in dependence on the ratio between dissipative processes (e.g. bottom friction) and (re-) enforcing ones (namely resonance in shallow channels or concentration of energy due to a converging coastline and bathymetry).
- The mean tidal level does vary moderately compared to the the above mentioned quantities. Anyway, there exists a clear relationship to the fresh water inflow, the wind induced setup or nonlinear interactions of the tidal harmonic constituents.
- Differences between mean flood water level and mean ebb water level give us some first information concerning asymmetry of the tidal wave, which is e.g. caused by the different shape of the tide during tidal rise and tidal fall.
- The spatial variations of the high water time or the low water time gives a good impression of the speed of propagation of the crest and trough of a tidal wave within a study area. If the lines of equal time of high and/or low water are separated by large distances this indicates an apparently fast propagating wave, normally related to strong reflexion of the tide at boundaries. This speed of propagation should not be confused with the celerity of the tidal wave, which can be significantly smaller.
- Flood period, ebb period and tide period, as well as the various relationships between these numbers give some information about the asymmetry of the tidal wave, which are reflected in the different periods for the rise and fall of the water level elevation. Asymmetries which are already visible in the tidal wave have a good chance to become much more pronounced in current velocity asymmetries; the latter ones result in e.g. tide induced suspended sediment transport processes.
- Exact knowledge of the inundation period can be relevant to ecologists or hikers crossing tidal flats (from the coastline to a dry sandbank). Also for improved navigation - professional or for leisure - this is a really relevant information.
Definition of the Tidal Characteristic Numbers of Water Level
High Water Level (HW)
Low Water Level (LW)
Mean Tide Level
Mean Flood Water Level
Mean Ebb Water Level
Flood Period : Ebb Period
Flood Period : Tide Period
Ebb Period : Tide Period
High Water Time (T_HW)
Low Water Time (T_LW)
Flood Tide Rise
Ebb Tide Fall
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