Dunkirk transgression
The Dunkirk transgressions were tidal bulges or other sea level-related marine transgressions (risings), often heightened by river floods, affecting the North Sea and adjoining low land. Most of this land is vulnerable to such events being below or approximately at sea level. Three events and mass evacuations, at least, are seen, some stretching to land above-sea level today. The events affected the Low Countries and other land near the German Bight, Thames Estuary and The Wash. They spanned from the late Roman period until Early Medieval Europe. Outline knowledge The exact scale of each event with notable human impact in duration, being hypothetically determined, is debated. The cause of each is also somewhat debated, however tidal bulges have been a continuing cyclical problem of the North Sea in the centuries since. Chronology The main parts of the Low Countries were lightly populated until about 200 BC, when the climate and environment became more amenable to human habitation. Conditions remained favourable until 250 AD, and the region became densely populated. Fens below sea level were highly vulnerable to a tidal bulge until great dams and sea walls were built as shown in the North Sea flood of 1953. A series of