Restoring rivers by flooding

PUBLISHED: 21 MARCH 2012   SOURCE: National Geographic

As part of a decade-long partnership called the Sustainable Rivers Project, the US Army Corps of Engineers and The Nature Conservancy are collaborating in eight river basins across the U.S. to modify dam operations for the benefit of downstream river and estuary health.  In five of those basins – the Savannah River in Georgia and South Carolina, the Green River of Kentucky, the Bill Williams River of Arizona, the Big Cypress Bayou of Texas, and the Willamette River in Oregon – the Corps is releasing ‘designer floods’ from their dams.


According to river scientists, muddy, raging flood waters can be good for regeneration and growth. They can encourage fish migration and spawning, weltand plant and floodplain regeneration, the formation of aquatic habitats, and nourishment of food chains and fisheries from essential nutrients being carried in to coastal estuaries.


The more than 50,000 large dams built on the world’s rivers have been quite effective in dampening or completely eliminating all but the biggest floods. The aquatic life in dammed rivers has suffered greatly.  Nearly 40% of US fish species are imperiled or extinct, and dams are a leading cause.

That’s why the Corps of Engineers, historically the biggest dam-builder in the U.S., is now in the business of making floods. They do it by intentionally releasing large volumes of water from their dams at specific times of the year to reinvigorate river ecosystems in a carefully controlled manner that promises maximum ecological benefit while avoiding damage to structures, roads, and farms.


Photo credit: US Army Corps of Engineers