FLOODING BY STORM SURGES

In open coastal areas, the rise in water level due to a surge is usually represented by a single peak surge generated by a wind storm. On top of this, the effect of waves should be determined. In an enclosed or semi-enclosed body of water such as a lake or harbour a storm can cause the oscillation of the water surface which can result in a multipeak surge hydrograph. 

Extra-tropical storms are migratory frontal cyclones that occur in the middle and high latitudes. Such storms produce their highest winds in the cooler season of the year because they are energized mainly by the temperature difference between air masses, which is at its most pronounced in this season. 

For sites on rivers or estuaries that flow into large bodies of water, the computed probable maximum storm surge will require empirical or mathematical routing upstream of the point of interest. Sites on large enclosed bodies of water should be analysed for surges by the use of one or two dimensional surge models. 

In Ref. [6], cyclonic phenomena are grouped into extended pressure systems and detailed descriptions of their characteristics are provided. 

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