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<br />002838 <br /> <br />TABLE 2 <br />Summary of steps and concepts for developing multiple streamflow recommendations <br /> <br />1. Average ann ual <br /> hydrograph <br />2, PHABSIM flow <br /> analysis <br />3. HEC-2 analysis <br /> <br />4. Frequency of <br />occurrence curve <br /> <br />5. Flow duration <br />curve <br /> <br />Indicates timing of high and low flows <br />Indicates slopes for rising and falling limbs <br />Can be used to index daily drawdown rate <br />Establishes minimum instream flow to maintain fish <br />Late summer/fall flows are usually set lower than base flows <br />Used to estimate extent and elevation of riparian habitat in sampled <br />reach <br />Estimates elevation of bankfull conditions and floodplains in sampled <br />reach <br />Estimates discharge (Q) nee'ded to provide bankfull flows and to main. <br />tain riparian zones and floodplains <br />Indicates return period for peak flows (determined from historical rec- <br />ords or from HEC-2 analyses) <br />Establishes the extent to which riparian and valley flow requirements <br />exceed the average annual hydrograph <br />Demonstrates flow duration associated with specific exceedence values <br />Demonstrates that recommended flows do occur in time <br /> <br />higher flows than riparian vegetation. <br />Floodplain landforms, which are generally <br />considered to be represented by topo- <br />graphically flat areas, often include side <br />channels, oxbow lakes, wetlands, swamps, <br />and ponds. To date, there are no univer- <br />sally accepted or recognized methods for <br />determining flow quantity or duration <br />needed to maintain riparian habitats and <br />their surrounding floodplains. Franz and <br />Bazzaz (1977), Harris et al. (1987), and <br />Stromberg and Patten (1990) have initiated <br />modeling approaches to measure riparian <br />response to altered flow regimes but these <br /> <br />specific stream discharges, For a specified <br />discharge and channel configuration, the <br />program calculates an initial water surface <br />elevation. The interaction between hy. <br />draulic variables and channel dimensions <br />can assist in evaluating the dynamic rela- <br />tionships between discharge and habitat <br />characteristics over time and space. <br /> <br />Riparian Flows <br /> <br />Riparian and floodplain flows are used <br />synonymously in this discussion even <br />though some floodplains could require <br /> <br />1200 <br /> <br /> 1000 <br />iij' <br />co 800 <br />E <br />w <br />CJ 600 <br />0:: <br />0( <br />J: <br />(,) 400 <br />en <br />0 <br /> 200 <br /> 0 <br /> J <br /> <br /> <br />CHANNEL 0 <br />3% ORAWDOWN <br />1 % DRAWDOWN <br />10% DRAWDOWN <br /> <br />F <br /> <br />A <br /> <br />s <br /> <br />o <br /> <br />N <br /> <br />D <br /> <br />A <br /> <br />M <br /> <br />J <br /> <br />J <br /> <br />M <br /> <br />MONTH <br /> <br />FIGURE 2. Curvrs (Omp~rin8 (h~nnel m.lintrn.lnce flows (mJ /sf!cond) (using thr Rosgrn f!t .II. 1986 <br />method) to the me.ln monthly hydrograph for Salmon River at Whitebird, Idilho. <br /> <br />M. T, Hill et aL <br /> <br />205 II~ <br /> <br />