Laserfiche WebLink
<br />In order to examine a wider range of flows than the actual experimental flows, we <br /> <br />simulated the mesohabitats at differing discharges between 1 and 600 cfs for each habitat cluster <br /> <br />sampled and then extrapolated the result to represent the totals for each stratum and for the entire <br /> <br />length of the study area. <br />Riffle Wetted Perimeter and Area vs. Discharge <br /> <br /> <br />We analyzed the riffle habitat-discharge relationship in two ways. First, wetted perimeter- <br /> <br /> <br />discharge relation was simulated using the hydraulic model for each cross section where riffle was <br /> <br /> <br />the only habitat type. The percentage of the total wetted perimeter at various discharges was <br /> <br /> <br />determined by assuming the wetted perimeter at 600 cfs was the maximum available. <br /> <br /> <br />A curve break approach (Gippel and Stewardson 1998) was used to determine at what <br /> <br /> <br />discharge habitat conditions declined most rapidly, such that small additional reductions in <br /> <br /> <br />discharge result in disproportionate loss to stream riffle area. A similar approach was taken to <br /> <br /> <br />determine base flows for the Yampa River (Modde et al. 1999) and several other streams (Gippel <br /> <br /> <br />and Stewardson 1998). The rate of greatest change was determined by fitting a linear regression <br /> <br /> <br />through the wetted perimeter-discharge relationship and finding the discharge that gives the <br /> <br /> <br />largest positive residual. An example is given in Figure 4. When the wetted perimeter-discharge <br /> <br /> <br />relationship was linear (determined by eye), no curve break was calculated. <br /> <br /> <br />The second way we analyzed the riflle habitat-discharge relation was to calculate riffle <br /> <br /> <br />surface area for each habitat cluster and expand the result to the entire study area at each <br /> <br />simulated discharge. <br /> <br />8 <br />