"Houses will have to be moved by their owners or be washed away."
A key warning of the approaching disaster might be the inability to re-insure their homes - unless a back-stop earthquake-style national scheme was developed.
The east and north of both main islands were predicted to dry out, while the West Coast of the South Island could expect more rain, Renwick said.
Crops and land use would have to change. Agriculture in Canterbury, Marlborough and the North Island's eastern areas might have to move to less intensive dry-land farming. The future of widespread intensive dairy farming might be limited.
Agricultural irrigation "is just going to come under more stress as eastern regions dry out.
"There will be greater competition for water resources.
"Any tourism associated with glaciers would be gone, along with the water supplies that go with snow and ice."
Renwick urged New Zealand to become a world leader in the move to carbon neutrality - not emitting more carbon than is absorbed - by means such as converting to 100 per cent renewable energy sources and switching to electric vehicles.
A carbon-neutral New Zealand could join like-minded countries to move the rest of the world to reach the goal.