If sea level rise was real and became a problem

If the worst case scenarios for sea level rise come true and we get between 30 cm and/or 9 metres of sea level rise in 100 years, what's the worst that could happen?

• We would need to rebuild our coastal resorts. We do that anyway about every 60 years. They are not built to last and go out of style soon after their paid off. If its profitable no government funds are needed. If its not profitable blow it up and make a park.
• We would have to jack up or move a few hundred historic buildings. At five million each that's a few billion and half that will be millionaires 'moving house'. 
• Some low lying towns will need to dig a hole and build a hill in or next to town. If they are smart all new structures will be multi-story and will be built on that hill or will be connected to it with a bridge at 3 to 9 meters above sea level. Turn the hole into a nice lake and put floating houses on it. Most towns already own the needed earth moving equipment. In 100 years you can heap up a lot of dirt. (I do not trust dykes and levee banks, too many have failed, why make them when for the same cost you can raise the town.)  If you loose crops in a flood then you were growing the wrong crops in the first place. Grow something you can harvest before the flood season. 
• We need to farm coral in the pacific to make more sand fill to adjust the hight and shape of about 300 atolls. The coral will grow up to match sea level rise but there will be lags and cases where the natural process messes up the real-estate values- atolls move about; real-estate boundaries don't (they could and should on atolls but don't now). 
• We would need to "build up" on those islands and out over the lagoon or the open sea with floating factories, malls and apartments. Most of the low islands of the Pacific, Caribbean and Indian ocean are under developed and needs reconstruction anyway. Those Island nations own millions of hectares of sea bed with minerals; They only think their poor. If its profitable government need not interfere.
• Some coastal farms will need to switch to growing salt tolerant crops or fish. We already have a salt water irrigated grain:  Palmer's grass ( Distichlis palmeri ) A biofuel crop: Salicornia bigelovii and a sugar crop: Nypa fruticans.(mangrove palm) There are many other halophytes, salt tolerant plants, being developed as crops.
• Some third world estuarine systems will need to be redesigned and rebuilt with all of the above measures. However since they are third world countries they need the development anyway. If they can't discover (or refuse to accept) the tools of modern democracy, development and capitalism then they will stave long before the sea rises to get them.

That's it! A few trillion dollars of free enterprise and profitable development or redevelopment that would have happened anyway. The occasional million dollar community investment in the form of donations to educational institutions and heritage foundations so they can re-educate builders and farmers and move the odd historic building. It need not be done at all with taxpayer funds.

Sea level rise is much slower than a tsunami. While the latter is horrendous; even the elderly in some cases outran the Japanese 2011 tsunami. Whole cities can outrun sea level rise!