[mikeash]

It seems to me that maps like this are not very useful, and understate the problem. They treat sea level as something that only varies over long periods of time, ignoring daily and weekly variations.

The major problem with a 1m sea level rise isn't that land which is currently 1m above sea level becomes permanently flooded. The major problem is that land which is 2m or 3m or 4m above sea level becomes flooded way more often.

Local sea levels vary with winds, tides, and perhaps more importantly storms. A smallish rise in sea level might mean that catastrophic storm surge goes from a 500-year event to a 10-year event (numbers pulled out of my nether regions, just meant to illustrate the idea).

For example, much of the damage from Hurricane Sandy was caused by its huge 13ft storm surge. If sea level rises by 1m, then a storm with only 10ft storm surge will match it, which means damage on that level will happen way more frequently, and a repeat of Sandy would be vastly more damaging.

I think what a map like this needs is a setting which shows where the (for example) 100-year flood level is now, and where it moves with the given sea level rise. This is way more complicated, of course, but would do a much better job of showing the real problems.