John Buffington

US Forest Service - Rocky Mountain Research Station

Abstract: Riverine habitat for salmonids is intimately linked to channel morphology and fluvial processes (streamflow and sediment transport) which are, in turn, controlled by watershed hydrology and erosional processes that input sediment and wood to the fluvial system. Climate change has the potential to alter the timing, magnitude, and style of sediment, water and wood inputs to mountain rivers. Channel response to these changes may range from small-scale adjustments of channel characteristics (width, depth, grain size, etc.) to larger-scale changes in channel type (e.g., metamorphosis from a pool-riffle channel to a plane-bed morphology). Effects of climate change on riparian vegetation may also influence channel morphology in terms of bank stability (root strength), floodplain roughness, and supply of in-channel wood. Changes in channel morphology and fluvial processes can affect a variety of physical factors important for bull trout, and salmonids in general (substrate, stream temperature, bed topography and channel units, undercut banks, side channels, velocity and scour regimes, and hyporheic exchange). Although these potential impacts are well recognized, there has been little quantification of the magnitude and spatial extent of expected changes in fluvial processes and associated salmonid habitat in response to climate change. Identifying which parts of the river network are relatively stable and which are likely to cross critical thresholds in response to climate change is important for predicting the persistence of salmonid populations. Toward this end, a framework is presented for assessing the relative degree of channel stability in different physiographic settings (different water and sediment regimes), and digital elevation models are used to explore the spatial distribution of these conditions and potential consequences for salmonid habitat across the landscape.

Video Length: 16 Minutes, 24 Seconds

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How will climate change affect fluvial geomorphology and associated salmonid habitat in mountain basins?