The thousands of people forced to abandon their homes in recent weeks to floodwaters are victims not just of nature but of human error as well. Years of mismanagement of the vast Mississippi River ecosystem — the relentless and often inadvisable construction of levees and navigation channels, the paving over of wetlands, the commercial development of flood plains — have made the damage worse than it might otherwise have been.

The Obama administration is now completing an overhaul of the guidelines governing dams, levees and other water-related projects built with federal money. In 2007, Congress ordered the guidelines, unchanged since 1983, rewritten to require federal agencies to take environmental as well as economic concerns into account.

Historically, projects had been shaped by two main factors: the Army Corps of Engineers’ conviction that nature can be subdued by levees and dams, and its reflexive green-lighting of any flood control project that encouraged commercial or agricultural development. The new rules, Congress said, should require the Corps and other federal agencies to give equal weight to less easily measurable benefits like wildlife habitat and to “nonstructural” solutions to flood control like preserving wetlands, flood plains and other “natural systems.”

To give the Corps its due, it has performed nobly in the present emergency. Its main-stem levees have held. Its decision to blow holes in levees guarding the New Madrid floodway in Missouri clearly saved Cairo, Ill., and other places downstream; similar maneuvers in Louisiana helped protect New Orleans. These tactics had long been part of Corps emergency plans, and they worked.