Tides Etc
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Tides, etc. A2 Geography - Coasts
Tidal Surges Surges – surges are changes to the normal predicted astronomical tidal patterns that occur during abnormal meteorological conditions. Two factors that contribute to the formation of tidal surges: – Strong winds (can change the height by up to 2-3m) – Changes in atmospheric pressure patterns (e.g. Intense depressions can alter the height of coastal waters by around 1 cm per millibar.
Tidal Surges (con’t) • Positive Surges – Lead to abnormally high tide and may cause flooding
• Negative Surges – Lead to low tidal conditions and may be a hazard to navigation.
Tidal Bores Tidal bores are large waves that surge up rivers and estuaries with the oncoming tide; effectively forcing a reversal of the river’s flow. • Only can occur when the estury is hypersynchronous – (wedge shaped) the sides must converge quick enough upstream to outweigh any effects of friction that might be created by the estuaries bed.
Tidal Bores (Con’t) • There are 60 rivers in the world that experience regular tidal bores that coincide with the spring tides. • Qiantang River in China regularly reaches 8m in height. • In Britain biggest tidal bore is the river severn – regularly reaches 2-3m in height
Tidal Surges Surges – surges are changes to the normal predicted astronomical tidal patterns that occur during abnormal meteorological conditions. Two factors that contribute to the formation of tidal surges: – Strong winds (can change the height by up to 2-3m) – Changes in atmospheric pressure patterns (e.g. Intense depressions can alter the height of coastal waters by around 1 cm per millibar.
Tidal Surges (con’t) • Positive Surges – Lead to abnormally high tide and may cause flooding
• Negative Surges – Lead to low tidal conditions and may be a hazard to navigation.
Tidal Bores Tidal bores are large waves that surge up rivers and estuaries with the oncoming tide; effectively forcing a reversal of the river’s flow. • Only can occur when the estury is hypersynchronous – (wedge shaped) the sides must converge quick enough upstream to outweigh any effects of friction that might be created by the estuaries bed.
Tidal Bores (Con’t) • There are 60 rivers in the world that experience regular tidal bores that coincide with the spring tides. • Qiantang River in China regularly reaches 8m in height. • In Britain biggest tidal bore is the river severn – regularly reaches 2-3m in height
