Rising sea levels caused by global warming threaten the future of all civilizations. Coastal cities, and especially places like Venice, could be destroyed in a relatively short time. This is a perplexing problem and I have a couple of ideas:
What if we dug channels and/or tunnels from the coastline and funneled water to massive, man-made inland lakes, in sparse barron land places with no current use? This would displace seawater and essentially act like overflow pipes, like you have in a sink to stop it from overflowing.
What if we flood the deserts with seawater? We could pump the water in using probably solar powered pumps.
In answer to my own questions, I have considered the water surface area to land surface equation. There is roughly around 3 times the water area compared to land. This means to reduce the water level by 50cm would need 1.5m of water on all the earths land. So just displacing sea water onto the land won’t be enough to make any practical difference. We would need to imagine beyond the simple (but still huge) task of filling land that could hold the water to consider building vertical containers just like we have done with office blocks. We would need to displace and contain an immense amount of water to make any difference, but what happens if we don’t do it? If water levels keep rising and in some areas land keeps sinking, it’s easy to figure out the result.
There are current deserts that sit below sea level so they could take an influx of water as it flows downhill. One project under consideration for a long time is the Qattara Depression Project https://en.wikipedia.org/wiki/Qattara_Depression_Project
As well as displacing sea water onto land, they identified further benefits of hydroelectricity as the evaporating water would cause a flow which could be harnessed for power.
Suggestions for this solution date back over 100 years but has yet to be undertaken. Combining the opportunity of modern methods of engineering construction and the increasing risk of water levels taking us towards an inevitable disaster, is now the time to look at this seriously, no matter how daunting the prospect?