If the Civilization is very advanced, and has atomic energy, esp[ecially fusion energy, they don't need vast dams for vast amounts of hydropower.

They can use some fusion energy to power food synthisizers. And if they haven't developed yet, they can build vast indodor hydroponic and aeroponic farms with the "sunlight" from electric lamps. See varioups questins and answers about how much land or in that case "land" is needed to feed someone.

Similarly, they can build cities inside vast climate controlled buildings. A city with a hundred levels of single story "buildings" and a little ofver 1,000 feet tall would occupy as much space as a city with 100 times as much area of single story buildings built on the ground.

A city with a thousand levels of single story "buildings" and a little over 10,000 feet tall would occupy as much space as a city with 1,000 times as much area of single story buildings built on the ground.

In sort, such an advanced society should be able to house and feed a much larger population than present day Earth on a much smaller proportion of th e Earth's land area. Thus they would not have much trouble with rising sea levels.

Thoughthey would want to build dykes around many famous cities to preserve them as islands amid the rising waters.

They can produce all their engergy from fusion, various forms of solar and wind power, etc., elmininating all need to burn fossil fuels and release carbond dixoide into the air.

Thus they can stop adding to the problem of global warming. And they can build vast hydrogen fusion powered facilities to captured carbon dixide from the air and convert it to solid compounds, which can then be buried. Thus they can work to reduce the carbon content of the atmosphere faster than it would naturally decline.

And they can build gazillions of mirrors and put them in deserts and floating in equatorial sea waters to reflect some sunlight back into space, to help cool the planet.

If the civilization is very advanced, and has atomic energy, especially fusion energy, they don't need vast dams for vast amounts of hydropower.

They can use some fusion energy to power food synthisizers. And if they haven't developed food synthisizers yet, they can build vast indodor hydroponic and aeroponic farms with the "sunlight" from electric lamps. See various questins and answers about how much land or in that case "land" is needed to feed someone.

Similarly, they can build cities inside vast climate controlled buildings. A city with a hundred levels of single story "buildings" and a little over 1,000 feet tall would occupy as much space as a city with 100 times as much area of single story buildings built on the ground.

A city with a thousand levels of single story "buildings" and a little over 10,000 feet tall would occupy as much space as a city with 1,000 times as much area of single story buildings built on the ground.

In sort, such an advanced society should be able to house and feed a much larger population than present day Earth on a much smaller proportion of the Earth's land area. Thus they would not have much trouble with rising sea levels.

Thoughthey would want to build dykes around many famous cities to preserve them as islands amid the rising waters.

They can produce all their engergy from fusion, various forms of solar and wind power, etc., elmininating all need to burn fossil fuels and release carbond dioxide into the air.

Thus they can stop adding to the problem of global warming. And they can build vast hydrogen fusion powered facilities to captured carbon dioxide from the air and convert it to solid compounds, which can then be buried. Thus they can work to reduce the carbon content of the atmosphere faster than it would naturally decline.

And they can build gazillions of mirrors and put them in deserts and floating in equatorial sea waters to reflect some sunlight back into space, to help cool the planet.