It takes a tremendous amount of water to go from 3 meters to 4 . Living right by the river , I keep an eye on it all the time and will be surprised to see it go much past 3.5 . Even at 4 meters it still had about 8 feet of dyke left at the train bridge . I was pretty worried when it got to the 4 meter mark 2 years ago but I looked at the dyke at the time and have to give credit to our officials for the great job they have done with their dyke maintenance to keep us all safe . And this includes the gravel extraction , which is vital to maintain the level where it is , inspite of the well meaning , but misguided opposition of some . If not for those extractions the dykes would have to be continually raised as the bed fills in , which is impossible .
The upheavel that will be caused by the very high water will be so much greater then any extraction will ever be , that the extractions would be trivial by comparison . But the fish will survive this high water like they always have .
Anyway as the water goes way past 3 it takes a very large amount to maitain that high level and will drop very rapidly once the heavy rain subsides . Will probably get to under 3 meters in a couple of days , but then it takes some time to drop the next half meter , to where it gets into decent fishing levels again.