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<br />. <br /> <br />~::::a .as .,~o ~7:32 <br /> <br />c. :..J <br /> <br />Intorwation Heeds: The number, surface area, and location of <br />camping beaches at discharges of 31,500 cts and 33,200 cfs <br />need to be determined. A detailed (0.5 m contour) <br />topographic/ bathymetric map of the Canyon can be developed <br />from the aerial photographs taken during the 1000 cts <br />constant discharge period in April 1990. Beaches (location, <br />number and area) above high discharge stages can be <br />determined from the map and stage recordings taken through <br />the Canyon during research discharge periods. <br /> <br />10. Question: 00 dam operations (e.g., magnitude of stage, <br />magnitude of fluctuations and/or ramping rate) affect the <br />atability of cultural resource sites along the Colorado River in <br />Grand Canyon? <br /> <br />ft.-l0.1. There is no significant relationship between the <br />magnitude of stage, magnitude of discharge fluctuations and/or <br />rampinq rates and the stability of cultural resource sites along <br />the river in the Grand Canyon. <br /> <br />Justification: Recent evidence indicates that spillover <br />flooding in 1983-1986 may have initiated erosion of cultural <br />resource sites along the river. Progressive erosion of these <br />sites may warrant protective mitigation or excavation. <br /> <br />Inforwation Heeds: The extent of erosion of pre-dam sediment <br />deposits-is not yet known. Determination of whether the <br />erosion is short term and of young sediments, or whether <br />impoundment and sediment starvation has initiated erosion of <br />ancient sediment beds will require aging of the sediments. <br /> <br />II. Effects of Recreation <br /> <br />A. Effects of Fishina Activities <br /> <br />11. Question: How does fishing activities affect other <br />canyon resources, especially in the Lee's Ferry reach (Glen <br />Canyon DUI to CR mile 14)? <br /> <br />ft.-l1.1. There is no significant relationship between beach <br />stability and fishinq activity, inclUding boating, in the Lee's <br />Ferry reach. <br /> <br />~titication: Recent studies indicate that riverside <br />~edim.nts are reworked by the wake. of motori~ed boats in <br />the tailwaters reach above Lee's Ferry. Also, angler use of <br />riverside habitats froll Lee's Perry to CR Mile a may affect <br />populationa of the newly discovered Euphorbia species that <br /> <br />14 <br />