Hydrological response to timber harvest in northern Idaho: implications for channel scour and persistence of salmonids

Authors

  • Daniele Tonina,

    Corresponding author
    1. US Forest Service, Rocky Mountain Research Station, Boise, ID, USA
    2. University of California, Department of Earth and Planetary Science, Berkeley, CA, USA
    • US Forest Service, Rocky Mountain Research Station, Boise, ID, USA.
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  • Charles H. Luce,

    1. US Forest Service, Rocky Mountain Research Station, Boise, ID, USA
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    • The contribution of Charles H. Luce, Bruce Rieman, John M. Buffington and Charles Berenbrock to this article was prepared as part of their official duties as a United States Federal Government employee.

  • Bruce Rieman,

    1. US Forest Service, Rocky Mountain Research Station, Boise, ID, USA
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    • The contribution of Charles H. Luce, Bruce Rieman, John M. Buffington and Charles Berenbrock to this article was prepared as part of their official duties as a United States Federal Government employee.

  • John M. Buffington,

    1. US Forest Service, Rocky Mountain Research Station, Boise, ID, USA
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    • The contribution of Charles H. Luce, Bruce Rieman, John M. Buffington and Charles Berenbrock to this article was prepared as part of their official duties as a United States Federal Government employee.

  • Peter Goodwin,

    1. University of Idaho, Center for Ecohydraulics Research, Boise, ID, USA
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  • Stephen R. Clayton,

    1. University of Idaho, Center for Ecohydraulics Research, Boise, ID, USA
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  • Shawkat Md. Alì,

    1. ETC Engineers Inc., Little Rock, AR, USA
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  • Jeffrey J. Barry,

    1. University of Idaho, Center for Ecohydraulics Research, Boise, ID, USA
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  • Charles Berenbrock

    1. US Geological Survey, Reston, VA, USA
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    • The contribution of Charles H. Luce, Bruce Rieman, John M. Buffington and Charles Berenbrock to this article was prepared as part of their official duties as a United States Federal Government employee.


Abstract

The potential for forest harvest to increase snowmelt rates in maritime snow climates is well recognized. However, questions still exist about the magnitude of peak flow increases in basins larger than 10 km2 and the geomorphic and biological consequences of these changes. In this study, we used observations from two nearly adjacent small basins (13 and 30 km2) in the Coeur d'Alene River basin, one with recent, relatively extensive, timber harvest, and the other with little disturbance in the last 50 years to explore changes in peak flows due to timber harvest and their potential effects on fish. Peak discharge was computed for a specific rain-on-snow event using a series of physical models that linked predicted values of snowmelt input to a runoff-routing model. Predictions indicate that timber harvest caused a 25% increase in the peak flow of the modelled event and increased the frequency of events of this magnitude from a 9-year recurrence interval to a 3·6-year event. These changes in hydrologic regime, with larger discharges at shorter recurrence intervals, are predicted to increase the depth and frequency of streambed scour, causing up to 15% added mortality of bull trout (Salvelinus confluentus) embryos. Mortality from increased scour, although not catastrophic, may have contributed to the extirpation of this species from the Coeur d'Alene basin, given the widespread timber harvest that occurred in this region. Copyright © 2008 John Wiley & Sons, Ltd.

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