If we look at (say) 5 cities that will be flooded by a 1 metre rise: Groningen, Leuuwarde, Alkmaar, Lelystad and Westland, they will by themselves produce a population of 540,000 that will have to be relocated. In addition, there will be hundreds of other cities, towns and villages needing to be looked after.
Furthermore, Amsterdam, Rotterdam and Den Haag (combined population of 1,807,000 - over 10% of the country's total population) will have become low-lying offshore islands. They will lose their inhabitants rapidly.
Even places like Antwerp (population 461,000) will have become costal towns, possibly liable to flooding.
Just taking those places into account and disreagrding the rest, we are looking at the need to relocate almost 20% of the population: 2,808,000 people. That's using today's population figures, not projected populations in 2100
However, it must be borne in mind that the Google map does not appear to account for sea defences, which are bound to have a mitigating effect, but I still think the best option for the Dutch would be to move inland.
Even if they tried to contain the migration within their own borders, without proper control and planning, civil strife is sure to erupt.
Am I being so outrageous to call for people to take control of their own destiny? They won't be able to do it by themselves.
TYWD.