Measuring and Interpreting Stream Channel Response to Management Changes: A Cattle Grazing Case Study.
Patricia F. McDowell and Andrew Mowry (2002).
Association of American Geographers Annual Meeting 2002.   

Abstract:  We examined the response of channels to elimination of cattle grazing, by comparing channel morphology of a treatment reach (grazing eliminated) and an adjacent control reach (grazed) at eleven sites in national forests in the Blue Mountains of eastern Oregon.  Response characteristics measured included channel width, depth, pool abundance, maximum pool depth, and residual pool depth.  At most sites, the channel responded as expected – the treatment reach was narrower, deeper, and/or had more pool area than the grazed reach.  Response of maximum pool depth and residual pool depth was mixed, with pools deeper in the treatment reach at about half the sites, but equal or shallower at the other sites. 
                 To understand why response was uneven, we also evaluated how base values of the response characteristics (i.e., control reach values) varied across the eleven sites, and how magnitude of response varied across the sites.  We expected base values to be scale dependent (i.e., related to drainage area or standard discharge).  We expected magnitude of response to be influenced by geomorphic controls -- sites that were steeper, less sinuous, more confined, and more limited in sediment supply and/or transport should be less responsive to management change.  The results generally supported these hypotheses, but not at all sites.  Land managers need to be able to document the effectiveness of management changes.  To do this, they need to understand and account for the multiple influences on response.  We will discuss the challenges in understanding why some sites do not respond to management changes.    

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