Large-scale Dam Removals and Nearshore Ecological Restoration: Lessons Learned from the Elwha Dam Removals

Abstract

Large dam removals are emerging as an important ecosystem restoration tool, and they often have direct influence on the marine nearshore zone, but dam removal plans give little consideration to nearshore restoration. We provide an overview of the relationship between large-scale dam removals and nearshore restoration, using the Elwha dam removal project, in Washington State, United States, as a basis. The following steps are essential for incorporating nearshore restoration planning into future dam removals: 1) Conceptual and technical modeling of nearshore physical and ecological processes at the drift cell scale to define nearshore priorities and geographic areas to be conserved or restored; 2) Acquiring seasonal field data to inform models, including: water quality; sediment delivery volumes, timing, trajectory and composition; and basic fish community data such as abundance, size, species composition, and trophic components; 3) Mapping nearshore habitat areal extent and ecological function prior to, during, and after dam removal, including vegetation composition and invertebrate community composition; 4) Defining and addressing the implications of habitat barriers and fish management actions for nearshore ecosystem function prior to dam removal. Structures and hatchery practices that conflict with nearshore ecosystem function for wild species prior to, during, and after dam removal should be identified and eliminated; 5) Anticipating nearshore invasive species colonization as a result of dam removal; 6) Developing and implementing long-term adaptive management plans to ensure nearshore restoration goals are identified and met. These steps must begin as early as possible in the planning process.