The center of Europe has received lot of rain last week. The floods in Germany, Czech Republic and Austria are breaking records as far as they remember. This is the Old World, they have records going back for long time. One city in Austria, Grein, decided to do something about the floods. The Danube is very nice to look at, so they want to keep the river most of the time. They just do not want the river in the bedroom. Welcome to the world of Austrian engineering. The video below fold is very impressive, especially around 40 sec mark. One of the great infrastructure investments.
These metallic walls worked great at the center of Prague as well. The several blocks were spared from flooding there comparing to the similar 100-year flood in 2002.
You can put such temporary walls very quickly in a day. It is much faster than sandbags. You do have to make holes in the ground ahead of time - they are reinforced with concrete. You can cover holes after that. Why have I never heard or seen this technology in US?