HOUSTON (AP) — The explosive expansion of Houston subdivisions into prairies far to the west helped make the city affordable for the average 345 people who moved there each day, but it also paved over thousands of acres that the U.S. Army Corps of Engineers had intended for a reservoir and other flood-control projects to help against deluges like the ones from Harvey.

The push of subdivisions and freeways across what once was hundreds of square miles of flood-absorbing tallgrass prairies was part of the U.S.-leading population growth of Houston and surrounding Harris County. But the go-go-grow...