Climatic circumstances

Aside from the poor condition of the many dikes in the Delta area, the flood was largely due to an unfortunate combination of climatic circumstances.

On January the 30th, a depression to the south of Iceland arose. The depression increased and moved towards Scotland. By one o’clock that night, there was a large storm field behind the depression. Originally, the depression moved towards the east, but the north-westerly storm drove the depression in a south-easterly direction. Soon, the storm field covered the entire North Sea. The storm continued to get heavier near Scotland, and then in the afternoon of the 31st of January, a hurricane developed near the northeast coast. The hurricane moved towards the Netherlands, which, at that moment, had a high tide. The high tide was intensified by the hurricane's influence and in some places within the Netherlands, water began to run over the dikes.

Via Denmark and the German curve, the storm got closer to the Dutch coast. On the night of the 31st of January, the storm over the North Sea got even stronger, reaching gales of force 11. The Dutch coast was being hit with force 10 winds.
The storm continued, and in the south-western Netherlands, wind speeds of force 9 were measured for 20 consecutive hours. The power of the storm drove the water so high that the water was unable to retreat away sufficiently. There was no ebb tide.

Dike that just survived the enormouse high tides. Clearly one can see that the dike has been undermine to the core.
Dike undermining
Shortly after midnight, the maximum whip up of the water was measured - the wind drove the water up to 3.1 metres. Three hours later, there was a spring tide. Through the combination of this spring tide, and the huge whipping up of the water, at 3h24, the highest recorded water level was reached - 4.55 metres above NAP (Normal Amsterdam Water Level).

The dikes were not designed to hold such high water levels, and around 3 o’clock that night, the first dikes broke through. The dikes at the polder side broke through first, since they were the least maintained. Reinforcements of the dikes were mainly done on the sea side, because it was expected the sea would cause the most damage there. However, things did not happen as expected. The water surged over the dikes and hollowed them out on the land side. The power of the sea was then enough to break them. The dikes near Kortgene,

Dike break at Schelphoek, Schouwen Duiveland
Dike break
Kruiningen and Oude Tonge were first to break, then the dikes near Willemstad, Heijningen, Fijnaart, Gravendeel, Strijen, and Numansdorp followed. Many more dikes failed and, in total, 89 dikes were broke through. The damages and breaches could be found over a total distance of 187 kilometres.

It could have however been much worse if the maximum whip up of the water had occurred during spring tide and not three hours later, as was the case. The water in the rivers was relatively low and the tide had not yet reached its maximum height, but still, the dikes broke through.