My personal headcanon is that the Romans absolutely would have built the Qattara Depression Project if the Roman Empire had survived into the Atomic Era. They would be so excited about the incredible feat of engineering and the opportunity to test their latest military technology that they wouldn’t stop for a single second to consider whether they should.
I would argue that the downsides aren’t as serious as this video makes them out to be, but I’ll admit I’m not an expert…
1. Radioactive Fallout: fallout would be significantly reduced by performing underground detonations, which would be necessary anyways as above-ground detonation would hardly accomplish the goal of breaking up the soil. Furthermore, you could wait for ideal atmospheric conditions to increase the chance that the wind carries the fallout into the desert, rather than toward the Mediterranean or the Nile.
The creator seems to think that the fallout would make the canal unsafe for long-term human use, but the reality is that fallout from nuclear weapons decays on far shorter timescales than he is assuming. For example, the largest crater ever made by humans (with nukes, of course) became safe to walk in without protective clothing 7 months after the test. After all, Hiroshima and Nagasaki are cities that millions of people live in today. (By comparison, fallout from nuclear reactor accidents is much more persistent, which is why the area around Chernobyl is still restricted today even .)
2. Seismic Activity: The original plan called for detonating all 213 nukes at the same time, which raise the objection that it could trigger seismic activity in the Red Sea. I’m not a seismologist, but why not detonate them one at a time and monitor seismic activity continuously throughout the project?
3. Landmines: In a timeline where the Roman Empire survived, history would have gone entirely differently. Geopolitics would have been entirely different and perhaps no landmines would have ever been laid there. But I concede that it is a problem with the project for our timeline.