Historical geography — dike breakthroughs

File with historic dike breakthroughs. Dike breakthroughs have occurred numerous times in Fryslân. A dike break-through usually left behind deep wheel or kolk, around which the dike was then shifted on the sea side. Many kolks have now disappeared. Rather abrupt turns in (former) dikes indicate as a rule an earlier breakthrough. The kolks resulting from dike failures should not be confused with the so-called dyke-delts or dike pits, which occur in different places inside dikes. The latter were created by stabbing clay sods for the purpose of the construction, restoration or raising of the nearby dike.