Robert H Webb

In prehistoric times, the Santa Cruz River in what is now southern Arizona saw many ebbs, flows, and floods.  It flowed on the surface, meandered across the floodplain, and occasionally carved deep channels or arroyos into valley fill. Groundwater was never far from the surface, in places outcropping to feed marshlands or ciénegas. In these wet places, arroyos would heal quickly as the river channel revegetated, the thriving vegetation trapped sediment,...