That water has to go somewhere. Building a wall in one place usually results in worse flooding somewhere else. The better solution is not to build permanent structures in those low-lying areas. Then rivers can be allowed to flood naturally and less destructively. The administration also wants to eliminate a common-sense program that helps farmers turn some of their crop lands back into wetlands.
Excessive development is one reason that floods have been so bad in recent years.
Too many wetlands have been drained and paved over or converted to crop lands. That's a mistake, because wetlands act as natural sponges to soak up rains so that moisture seeps gradually into rivers. They also help purify the water supply and provide habitat for all sorts of plants and animals. It has left its riverfront in a largely natural state, as park lands where residents can enjoy the river. If Davenport builds a wall, that city will lose, and so will the next city downriver that has tried to avoid levees and walls.