The dammed Missouri: prospects for recovering Lewis and Clark's River

The world's dams and reservoirs are aging. The ecological effects of a half-century or more of flow regulation and sediment alteration are becoming apparent. What remains of the highly dynamic channel and riparian ecosystem of the Missouri River described by Lewis and Clark has become static. Recent long-term studies have determined that some of the impacts on the Missouri River ecosystem turned out as predicted, such as the failure of cottonwood-dominated riparian forests to successfully establish and survive on a broad scale. Other changes were surprises, such as the effect of disease eliminating a formerly dominant tree species and the appearance of mainstem and tributary deltas affecting channel slope, floodplain hydrology, and vegetation. Restoration of the river's hydrologic and sediment regime has been delayed long enough that the chances of functional ecosystem restoration have been greatly reduced and complicated. Two phases are now needed to attempt to restore the riparian ecosystem: one to repair the effects of post-dam changes (channel incision, bank stabilization) and another to reestablish pre-dam flow and sediment regimes. The prospects for restoration of this valuable ecosystem, rich in history and in goods and services provided to the public, are dim. Time has diminished the chances that restoration or even rehabilitation can be achieved. Copyright (c) 2014 John Wiley & Sons, Ltd.