I would argue that the cost of this is worth it, these aren't first world alluvial plains where you can afford to farm and buy food from elsewhere, this is Africa.
Removing the human factor from this, we are creating non-self sustaining environments at the cost of delta's which are sustainable, and play a vital role in survival in their regions.
I assure you, if there are people living upstream of a delta in places that can't sustain life, there are people living in that delta region, who rely on it just as much.
this isn't solving a problem, it's at best moving them, and at worst creating additional problems.
Instead of attempting to make every region on the planet farm land, we should focus on solutions that take into account a balanced ecosystem, and where that can't be achieved, relocation the human population.
The same complaints can't be addressed along the Rio Grande with 80% diversion and no one is talking about relocation for the environmental catastrophe called Las Vegas. That is in a country that includes plenty of fertile land.
