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<br />,. <br /> <br />001764 <br /> <br />41 <br /> <br />Previous Recreation Investigations: Sand bars serve as campsites for rafting groups and <br />are highly valued by the boating public based on size, boat mooring quality, wind protection, <br />access to side canyon hikes, scenery, and shade. Historically, these beaches were replenished <br />annually by sand and silt transported by the river during spring runoff. Approximately 93% of <br />this sediment now settles out in Lake Powell, so the be:aches downstream are eroding due not <br />only to the river's clear, sediment-free flows (Kearsley et aI., 1994), but also due to the way that <br />the remaining 7% of the sand supply is currently being managed through dam operations. <br />Camping beaches are also being eroded through gullying induced by monsoon rainstorm runoff. <br />Due to the lack of periodic, sediment-enriched floods, these increasingly degraded beaches are <br />not being replenished. Since dam operations began in 1963, most pre-dam beaches have become <br />considerably smaller, while some have disappeared completely. Another factor contributing to <br />the loss of campable areas in the CRE is vegetation encroachment, which is a direct result of the <br />lack of frequent scouring floods under current dam op(~rations. The size and availability of <br />camping beaches is directly tied to visitor experience parameters in that the decreasing size, <br />abundance, and distribution of campsites constrains th4~ visitor carrying capacity of the CRE and <br />may lead to crowding or reduction in visitor access, th'~reby creating adverse impacts to visitor <br />use values in the CRE. <br />In 1994, change in campable area from previoUls studies was analyzed using aerial <br />photographs (Kearsley et aI., 1994). This analysis rev(~aled that loss of campsites was an <br />ongoing process. The researchers noted that not all sand bars responded in the same manner to <br />flows and vegetation encroachment, and that campsite availability in critical reaches (Marble <br />Canyon, the Inner Gorge, and the Muav Gorge) had de:creased the most. Effects of the 1996 <br />controlled flood at selected campsites were also evaluated, and it was found that the increase in <br />the number and size of campsites was of short duration (Kearsley et aI., 1999). The post-BHBF <br />data indicated that while floods temporarily increased Icampsite number and size, the beneficial <br />effects to campsites were temporary, and that campsite: size rapidly degenerated to pre-BHBF <br />levels and then continued to erode more slowly. Although the effects of the 1996 artificial flood <br />were temporary, periodic "floods" above power plant (;apacity appear to be the only feasible <br />means of depositing sediment and rejuvenating camping beaches above normal fluctuations <br />(Kearsley et aI., 1999). <br /> <br />GCMRC FY2006 Annual Work Plan (Draft February 15,2005) <br />