There’s a newsroom joke that “we don’t write about planes that don’t crash,” but I think it’s important to think carefully about societal systems that succeed, because lessons learned matter:

The flood pulse was impressive. But it is instructive to look at how much larger it would have been if not for a pair of flood control dams built in the second half of the 20th century to protect us from our habit of building our cities in flood plains. On Sept. 13, they were two dams in the right places at the right time.

Importantly, one of the lessons is that there are always tradeoffs. Flood control success did not come without cost:

Authorized by Congress in 1960 and completed in the mid-’70s, Cochiti is one of the largest and arguably the most controversial dam in New Mexico. Its completion drowned farmlands, summer homes and culturally significant sites at Cochiti Pueblo, and seepage beneath the dam waterlogged remaining pueblo farmlands downstream. In addition, the way it altered the Rio Grande’s flows has caused lasting environmental problems downstream, depriving the riverside ecosystem of natural floods.

But on Sept. 13, it did the job we gave it when we built it, which was to protect the Middle Rio Grande Valley from flooding.