For decades, this desert river barely flowed, its crumbling banks losing every drop before it reached the sea. Then engineers tried something radical—throwing thousands of dead trees directly into the water.

In 2020, on a ranch near Grand Junction, Colorado, where the state line meets Utah, a work crew began driving wooden posts into the dry gravel of a creek bed. The posts were untreated pine. The fill material was dead wood collected by hand from the floodplain. The river runs 20 miles through this 76,000-acre property of canyons and desert. By the end of the decade, more than 200 such structures we…