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<br />. FES J5 '90 17:2~ <br /> <br />= <br /> <br />HYPOTHESIS TESTING <br /> <br />1. Effects of oa. operations <br /> <br />A. Effects of the Maanitude of Dailv Discharqe Fluctuations. <br />Minimum Discharqes. and Rate of Change (Ra~Dinal of Fluctuating <br />Oi9charqes <br /> <br />1. Question: How siqnificant are discharge fluctuations, <br />minimum discharges, and ramping in the degradation or aggradation <br />of beaches? <br /> <br />~-1.1. There is no significant relationsnip between <br />discharge fluctuations, minimum discharges and ramping, and the <br />processes of beach degradation or aggradation. <br /> <br />Justification: The "normal" operations of Glen Canyon Dam <br />during low and normal water years are for peak loading wnich <br />creates discharg. fluctuations. These discharge fluctuations <br />vary daily, monthly and seasonally, producing ditterent <br />discharge volumes and having difterent minimums. The rate <br />at which the daily discharges change (ramping), during <br />increasing and decreasing diSCharges, are tied both to power <br />demands and the ditterence between the maximum and minimum <br />daily discharges. Based on aerial photo interpretation, <br />camping beaches have increasingly diminiShed in size over <br />the past twenty years, with the exception of some beach <br />building during the 1983-86 high water years. Fluctuating <br />discharges with daily high discharge volumes and steep <br />ramping rates (especially the down ramp) have been related <br />to beach degradation by most observers but the connections, <br />if they exist, have not been quantified. <br /> <br />Information Needs: Short-term changes in beach surface <br />topography will be measured, using representative beaches <br />(or above new high water zone ~eposits) in different reaches <br />ot the Canyon. Relationship of these changes to: (a) <br />discharge fluctuations (assuming they are within normal <br />operating ranges), (0) minimum diSCharges, (c) discharge <br />rate changes (~) seasonal differences (e.g., frozen <br />surtaces), (e) wind, (f) wet vs dry surfaces, (g) beach face <br />topoqraphy (e.g., steepness), (h) eddy sediment storage <br />conditions, (1) hydrodynamics of eddies (current movements <br />within eddies), (j) sediment composition, and (k) armorinq <br />will be determined. <br /> <br />This will require an initial survey of each beach and then <br />the establishment of an intensive microtopographic <br />measuring system on the beaches, as done during the October <br />1989 5000 eta re.earch discharge. Surface temperatures and <br />wind patterns will have to be determined tor each beach. <br />Eddy sediment storage and hydrOdynamics of eddies will be <br /> <br />2 <br />