And why is the slider maximum at 2000m? Afaik, even if you melt most of Antarctica, it wouldn’t provide much more than 100m. About 12m (melting Greenland + West Antarctica) is a more plausible scenario - and that still floods plenty of cities.
One of the things these maps massively understate is the effect of tides and wave action as the sea levels rise.
I have seen estimates that in low-lying non-rock coastlines a 1m rise in sea level can lead to a 100m retreat in the coastline due to storms and wave erosion.
This is an aspect of sea level rise that I started to think about after moving to the shore of a large reservoir created by damming a river.
The difference between high water (late spring or early summer) after spring runoff and low water (late winter or early spring) is frequently 5 metres or more. The steep, sometimes vertical, terrain is just deeper water at the shoreline. The beaches and low lying terrain might see the shoreline move as much as 100 metres with maybe 5 times that incursion along seasonal creek beds.
If the water gets higher than usual, it can overtop a small rise and fill a basin, adding a hundred meters to the extent of a shoreline overnight.
It’s missing the Netherlands
Nice, but hardly a new idea, I made one for the Norfolk coast back in 1996. And recall a colleague made one for whole of Denmark, also last century.