Fundamental elements of ecologically healthy watersheds in the Pacific Northwest Coastal Ecoregion

Characteristics of streams and rivers reflect variations in local geomorphology, climatic gradients, spatial and temporal scales of natural distur-bances, and the dynamic features of the riparian forest. This results in avariety of stream types which, when coupled with the many human uses ofthe Pacific Northwest coastal ecoregion, presents a difficult challenge inidentifying and evaluating fundamental, system-level components of eco-logically healthy watersheds. Over 20 types of streams are found in westernOregon, Washington, and British Columbia and in southeastern Alaska, aregion where extractive forest, agricultural, fishing, and mining industriesand a rapidly increasing urban population are severely altering the land-scape. Yet stream characteristics remain the best indicators of watershedvitality, provided the fundamental characteristics of healthy streams are ac-curately known. The premise of this article is that the delivery and routingof water, sediment, and woody debris -to streams are the key processes reg-ulating the vitality of watersheds and their drainage networks in the PacificNorthwest coastal ecoregion. Five fundamental components of stream cor-ridors are examined: basin geomorphology, hydrologic patterns, water qual-ity, riparian forest characteristics, and habitat characteristics. Ecologicallyhealthy watersheds require the preservation of lateral, longitudinal, and ver-tical connections between system components as well as the natural spatialand temporal variability of those components. The timing and mode of in-terdependencies between fundamental components are as important as themagnitude of individual components themselves.
Key words. Stream, river, watershed, Pacific Northwest, riparian, sedi-ment. woody debris.