Why Building Trump's Wall Is Impossible

"A ridge line is ideal for a defensive wall because water flows either to one side or the other. When a wall is built that crosses a valley, it then becomes “a dam”.

The borderland along these Southwest States generally runs over high deserts with at least a thousand canyons crossing the border. People who live in these desert states know that when it rains, the flash floods can be massive and ferocious, with walls of water hurling boulders and debris through anything in its way.

Even a small ‘high security’ dam would require elaborate engineering to block illegal human transit and yet allow the water and natural debris to pass through, on very short notice! A thousand of these dams and their continual maintenance would become a major Budgetary component.. but the initial expense to build these dams would be enormous, likely trillions of dollars and taking decades."
https://www.dailykos.com/stories/2018/8/1/1785220/-Why-Building-Trump-s-Wall-Is-Impossible?detail=emaildkre