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areas of dense riparian vegetation o 0 o 0 --...... ~ ~l:~~~~:3j;:~ ~ ' , _ _ _ ~ - ~~');>~ ~~ ~ ~~~~~"7 ~~~..,...,. rapid; navigabiiity concerns SCHMIDT 331 can be a marsh, depending on topography / occasional campsite , , , , . , ----- ..,.~..,. 7 "7 ..,. 777777 ..,.~ "7"7 "7"7 "7"777 "7"7 700000000 o 0000000 o 0 0 0 o 0 00 o 0 0000 o 0 0 - Figure 1. Diagram showing lhe distribulion of physical resources in a typical fan.eddy complex. increased from 218 10 299; 84 new campsites were created and 3 existing campsites were destroyed by Ihe flood. Thompson el al. [I 997J used photographic data collected by river guides 10 detennine that 82% of Ihe campsiles increased in size in "critical" reaches where campsile carrying capacity is low. Most river guides found IhaL camping was easier on Lbese aggraded bars [Thompson el al., 1997]. The new high-eIeyalion deposits were composed of sand Lba. had been scoured from Lbe channel, from eddies further upstream. and from low-elevation parts of the same eddy in which high-eleyalion deposition occurred. Hazel el al. [Ihis volume] detennined that the average volume of sand in the low-elevalion parts of eddies decreased by 5% and LbaL Lhe average volume of sediment in channel pools decreased by I I %. Fine sediment was winnowed from the riyer bed al Ihe Grand Canyon gage [Topping el al., Ihis volume], and sill and clay was flushed from much of the bed [Topping el al., this volume; Smilh, this volume]. Silt and clay was not redeposited on Lbe bed for at IeasL 2 months at 3 widely- spaced sites in the canyon [Blinn er al., this volume]. The concentration of suspended sand and of sill and clay decreased gready during the first days of Ihe flood [Topping el al., Ihis volume; Smirh, this yolume]. Recendy-aggraded debris fans were reworked by Ihe flood. The areas of 18 of these fans were reduced 2-42%, and their volumes were reduced 3-34% [Webb er al., this volume]. SeIectiye transport rrom the eroded edges of these fans caused the average grain size of Ihe streamside edges of these fans to coarsen. The net resull was that the width or the constricled channel in rapids increased slightly at most sites. These changes had ecological implications. The declining concentration of suspended sediment caused the intensiLy of underwater light 10 increase afler the firsl days of the flood [Blinn el al., this yolume]. Bed scour and winnowing or fine sedimenl from pools caused rOOled macrophytes, such as Elodea and Chara, as well as tubificid and lumbricuIid wonns, to be preferentially transported downstream because these species prefer fine sediment substrate [Blinn el al., lhis volume I. Newly-deposiled sedimenl in backwaters was coarser than the pre-flood substrate, and benthic invertebrates were less numerous in the same backwaters than before Lbe flood [Brouder el al., this volume]. The number of backwaters potentially available to natiye fish aL the low discharge of 227 m3ts at which post-flood aerial phoLographs were laken increased immedialely after the flood tBrouder el aI., this volume]. 5. THE STATUS OF PHYSICAL RESOURCES 6 MONTHS AFTER THE FLOOD There was widespread erosion of recently.fonned deposits in the months arler the flood, but lhe net "benefil" of the flood, in tenns of new high-eIeyation sand bars, remained. Kearsley el al. [this volume] found that 37 of the 84 newIy-fonned campsites were no longer large enough to be used for camping 6 months arter the flood, because vegetation had reestablished itself or the bars had eroded. Hazel el al. [this volume] found that Ihe thickness of high- elevalion sand had decreased 0.23 m in 6 months, but that the average change for entire eddies was only -0.02 m in the same period. Thus, mosL of the high-elevation sand Ihat eroded was redeposited al low eleva,ion in the same eddy,