Restoring the Nation's Rivers and Streams: Lessons Big and Small

The national effort to reverse undesired conditions on large rivers and small streams is unprecedented in its scope and poses a significant challenge to geoscience. Restoration combines geological and ecological engineering, occurs within the arena of public policy, and challenges the geoscientist because project performance can be readily compared with project expectations. The nature of the problems faced in advancing restoration practice and policy differ for large rivers and small streams. In the case of rivers regulated by large dams, sophisticated monitoring and expensive mitigation programs typically implement state-of-the-science understanding of sediment transport, channel form, and riverine ecology. The failure to achieve stated goals after a decade of effort in the Grand Canyon Adaptive Management Program, Cal Fed, and elsewhere typically stems from ambiguously defined, and mutually incompatible, program goals written by stakeholders representing relict and artifact environmental and societal resources. Although the impossibility of achieving full restoration is apparent, the goals of these programs also change and are constrained by unwillingness to disrupt traditional water uses. In contrast, small stream restoration typically proceeds without deep understanding of the unique physical processes or history of each channel. Although the goals of these projects are typically more narrowly defined, the goals typically are not quantitatively articulated and cannot be quantitatively evaluated. Because the range of possible intervention strategies is large, application of state-of-the-science understanding to small stream restoration depends on development of functional relationships between different intervention activities and relative environmental benefit. These relations can be defined for specific categories of channels and have defined uncertainty. Post-project monitoring and analysis allows definition of these relations.