Characterizing aquatic habitats for long‐term monitoring of a fourth‐order, regulated river in the Pacific Northwest, USA

Abstract

A pragmatic approach to the long-term monitoring of rivers leverages available information with targeted field investigations to address key uncertainties relevant to management decisions. An over-arching management issue for many rivers is how reservoir operation affects the amount and location of in-channel sediment and the resulting distribution of aquatic habitats. We integrate remotely acquired and field-survey morphologic data for the Cedar River, Washington, to constitute the current status of aquatic habitats and benchmarks for long-term monitoring that will inform streamflow management. Four key habitats (river edge, side channels, riffles, and pools) are feasible to monitor with high-resolution aerial imagery, a longitudinal profile of the river, and a side channel inventory, but full characterization of the functional differences within these habitats requires additional information. Habitat use information such as redd surveys will continue to be important for long-term monitoring where it cannot be inferred reliably from physical habitat characteristics.

Influences of valley form and land use on large river and floodplain habitats in Puget Sound

“…However, exact river stage information was difficult to ascertain because photograph acquisition may have occurred over a protracted period within one region. A recent study using aerial photography to assess riverine habitats found that braid channels could be obscured during high river stages as gravel bars are inundated (Konrad et al, ). Consequently, this may also result in underestimation of braid length when imagery was acquired during periods of higher flow.…”