Tidal range
The tidal range ( ndd. Tide, tiet = time) is the difference between the peak level (floods, HW) and the lowest water level ( low water, NW). It is the arithmetic mean of Tidenstieg (TS) and Tidenfall (TF). The reference level for HW and NW the chart datum ( SKN ) came in the last few years in addition to the respective official reference height.
As the tides depend on the position of the moon and the sun to the earth, the Tidenkurve changes in a manner dependent on the phases of the moon period. The time interval between two successive high water is about 12 h 25 min, so that shift the times of high tide and low tide of the day. Also the tidal changes. This is called the maximum spring tide, the minimum neap tide.
In addition to the tidal influence wind direction and wind strength the real average water level and thus high water level ( HWH ) and low water height ( NWH ). It is particularly threatening when a storm surge with a spring tide coincides.
Considerable influence on the tides, the geomorphology of the ocean and its coasts. Thus, the tidal range in the western Baltic Sea is only about 30 cm, on the German North Sea coast around 2 to 3 meters. In the estuaries the tidal rivers such as the Elbe and Weser, is the tidal range due to the funnel effect to about 4 meters. Tsunami as Ebbetal migrate upriver until they run out at the Tidengrenze. As the tide of the same needs to Tidengrenze about 6 hours, for example, in Geesthacht tide when the tide is in Cuxhaven, and vice versa. The lithosphere is subject to tides, is in the range of a few decimeters.
Higher than in the German coastal waters is the tidal range, among others at Saint- Malo in France or in the Severn Estuary and the Bristol Channel between Wales and England, he or she can reach 12 meters ( in Sudbrook ). Particularly high Tidenhübe there are also on the east coast of North America: Probably the biggest tides of the earth can be found at the Bay of Fundy in Canada between the Canadian provinces of New Brunswick and Nova Scotia. There, the tide of the Atlantic Ocean pushes into a bay and causes a tidal range of up to 15 meters; a similarly high value reaches the south-west of Ungava Bay in the Canadian Arctic. The maximum value for the Pacific Ocean is achieved in Penschinabusen the Sea of Okhotsk with just under 13 meters.
The tidal range can be used in tidal power plants to generate electricity. This happens for example for over 40 years in the Rance tidal power plant in the Bretagne, France.
Expansion projects in tidal rivers can lead to an increase in the tidal range. Reclamation and the construction of flood barriers enhances the funnel effect. Dredging and river regulation lead to acceleration of flows. The local peak of the tidal shifts upstream. Since the flow acceleration concerns except the pendulum motion of the Tidestroms the overall movement of the river water towards the sea, the lowering of the low water levels is more pronounced than the increase of the floods in the rule. The development of measures of the same in the last 50 years have led to an increase in the mean tidal range at the level St. Pauli of 1.50 meters in 1840 to more than 3.60 meters ( 2003).