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<br /> <br />ASSESSMENT OF THE SCOPE OF THE PROBLEM <br />, <br /> <br />Box Elder Reach <br /> <br />Examination of the cross sections in this reach. for three <br />di st i nct ly different di scharges, shows no changes, Thi s i ndi cates that <br />the bed and banks are primarily composed of resistant material and. <br />further. that the stream characteristics of concern will not be <br />significantly altered by the construction of ypstream reservoirs. Since <br />the channel is deeply entrenched in bedrpc~its configuration and its <br />meander pattern should not change markedly, at least not within the <br />engineering time scale. The pool and riffle sequence as well as sub- <br />strate material will also not be affected since reservoir release flows <br />will have smaller magnitudes than historical floods. <br /> <br />Therefore. there is probably no additional data or analysis <br />required for this reach. <br /> <br />Li ly Park Reach <br /> <br />In terms of fish spawning grounds. it is not certain which of the <br />three distinct reaches are of most interest to biologists; therefore. <br />all three reaches will be discussed briefly. <br /> <br />The problem consists of predicting the changes to meander pattern, <br />channel configuration. substrate material and pool and riffle sequence. <br />We can consider these changes for each reach. <br /> <br />Reach No. 1 <br /> <br />Reach No. 2 <br /> <br />Reach No. 3 <br /> <br />a) Meander <br />Pattern <br /> <br />No change, <br />stable <br /> <br />Some change <br /> <br />Minor changes <br />possible <br /> <br />b) Channel <br />Configuration <br /> <br />No change. <br />bed-material <br />stable <br /> <br />Some change. <br />depends on <br />backwater <br /> <br />Some change. <br />depends on <br />reservoir <br />releases <br /> <br />c) Substrate <br /> <br />No change <br /> <br />Some change, <br />depends on <br />backwater <br /> <br />Some change. <br />depends on <br />reservoir <br />releases <br /> <br />d) Pool & Riffle <br /> <br />No change <br /> <br />Some change <br /> <br />Uncertain <br /> <br />It appears that Reach No.1 will not undergo major changes. A <br />reservoir upstream will probably reduce flood peaks and the existing <br />pool and riffle sequence will probably not be disrupted. <br /> <br />As for Reach No.2. there may be some changes to the meander <br />pattern and the channel configuration if there is significant bank <br />erosion. which could be occurring along the right bank. In regard to <br />substrate. pools, and riffles, there may be some infilling of the pools <br /> <br />25 <br />