The traditional way to harden infrastructure against flooding was to locate 'most everything expensive or important on higher ground. It was always the poorest

The traditional way to harden infrastructure against flooding was to locate 'most everything expensive or important on higher ground. It was always the poorest part of town that got built on the flood plain, or next to the swamp, or whatever. And when a major bridge or something had to be built at a low elevation - its construction was often "heavy stone, and lots of it"-durable.