Anthropogenic legacies are foregone where humans live. In urban and urbanizing systems, we can work to understand the ways in which lotic process and function changes in response. Moreover, as our understanding improves, particularly with regard to compromised resiliency (Jorgensen, 1990; Wissmar and Beschta, 1998; Larson et al. 2001), we can alter the ways that we interact with the environment in order to improve ecosystem functions. Alternatively, perhaps what may happen in these urban systems is that they settle into a different system state (e.g. O’Neill et al. 1988) resulting from functional impingements (e.g. hardened banks and flow alterations) and as such do not respond or behave according to our predictions – in space or time. Therefore, the recovery trajectories that we expect for these altered systems may not be fully informed because of our poor understanding of cross-scale interactions and the ways in which they affect the nature and extent of ecosystem alterations (Peters et al. 2007).
Results/Conclusions
We analyzed historic channel edge densities (ED) by index reach, sediment gradation index (GI) characteristics, and nearly 50 years of sockeye salmon spawning distributions in four index reaches of the Cedar River, Washington before and 4 years after a major channel-changing event in the river. Historically, spawning fish more intensively utilized the upper-most reach early in the run and the lower-most reach late in the run with temporal overlap in the middle reaches. Prior to the disturbance, the spatial patterns of spawning distributions reflected the relatively fixed habitat template manifest from nearly a century of hydrological alterations including two dams and an extensive system of levees and revetments. Following the disturbance, geomorphic and sediment characteristics exhibited a significant departure from the rest of the river and spawning sockeye salmon keyed on the disturbed reach both in terms of timing and total numbers of fish.
