 After this the Old Rhine (here called the "Uitwateringskanaal") did not flow naturally into the sea, but was held back by a lock.When necessary, the lock can be opened to allow the river to flow out to sea.The shore and the entrance to the canal were also strengthened by dikes

During World War II, most of the buildings of Katwijk aan Zee were demolished by the Germans to make way for the Atlantic Wall.