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<br />01182
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<br />IIU:'1PB",C': C11liB HABITAT ~IO[)ELLlS(j
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<br />383
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<br />Fls~rt 2 Sh.l.Jcd contour plm of ,h.. (11""1 '\lld~ Ic:"h <R II ~l,)\t of Ihe ~rud) rC.1.ch..< hJ.'''.l. umi!.!.! ,lure." ilh =ir.."IJrio" l~r.CS in the let' of
<br />,kbn< !In,, a deep hole in tbe beJroc"- ell.1.nn..! JlI" n,:rC.l.rn from lhe r"Jeh inlet .lnd im:~lllJr bJ.nh Con:Ollr inl......3l is 2 m. Da;.hed linei are
<br />~m:Jm 1..1.<,CS,uni!th of c,"h d.l.>h rcpre>>enls IrJ,d dl.,l~,,'e III }oJ., RQ" j, from ldlU> rijl.ht
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<br />The bed of the Colorado Rh'cr in Grand Canyon is about60<;t- bedrock l:llu", bloch. or boulders, wilh sand depos-
<br />ils primarily in the rccin;ulation zones :Ind. to a lesser degree, along the ch;mnd sid,:s (t1"w;lTd and Dolan. 1981;
<br />Wilson, 19S6; Schmidt and Graf, 1990). Each of the Mudy reaches. \\ith the c.\ceplioll of the Aoo\e Lava-Chuar
<br />(ALO reach. is bounded by rapid.. and hJ.'; a r,:circulation zon.... near the reach inlet (Figure 2). The ALC reach is
<br />houmkd on the up"ln::am end hy a naITO\\ pJ.tl of the channe11hat e\pands (00 graduJ.lly to fonn a rapid_ A debris
<br />fan on the east side of the ri\er (ri\'cr left) midway through lhc ALC re:lch form.. a constr:lined recirculation wne.
<br />The n::ach.:.. \ar)' in Ic::ngth frum 0_25 to I km. \\ith roughly proporlion:ll difference;; in welled area (Table I).
<br />
<br />METHODS
<br />
<br />Our melhod" arc described in four seclion;" Fir..t, we describe the hydrodynamic mooel u~d to predict two-dimen-
<br />sional fu::lds 01 d.:pth and velocity und.::r a r:lng.:: of discharges in each study rC:lch. Second. we describe our meth~
<br />od,; for dc\duping map.. of shoreline type so thJt our imk\ of suilablc:: habitat can be stralified by co\'er type. Third.
<br />\\e summa rile how our indke.. orsuitab1c hJbilal a\'ail;:!biJit}' are computl."d and the analyses used 10 e~'alu;:lIe the
<br />efiel."lS of impoundmenl and allemative operating regim6. Finally, \~e dcscrit>c the particlc.trJ.cking algorithm
<br />u\cd 10 simu\:ttc the dispersal of young fi,;h.
<br />
<br />Hydrodynamic model
<br />
<br />The topographic data used by the hydmJ~namic model con..ist of combined sc:1.S oi bathymetric measurements
<br />taken from hydrographic suneys and contours developed photogfilmmetrically from aerial photographs for eleva-
<br />tions abO'e thc ....ater surface at the time of the hydrographic suneys (\\'iele et of.. 1996). Computational grids
<br />representing 6.25 m2 (2.5 m flI'r side) \\ere deri\eJ from these combined data.
<br />The hydrodynamic model is the flow comronen! of a two-dimensional flow and sand transport model that has
<br />been applied 10 reaches of the Colorado Ri\er in the Grand Canyon to Slud} depositional processes and to predict
<br />the response of sandba~ 10 dam operatiom and sand supplied by tributary floods (Wiele t( or., 1996. 1999; Wiele.
<br />1997). ~lodel predictions of sand erosion and deposition ha\e agreed \~ell with cross-sections measured before and
<br />after a tribulary flood (Wiele tl 01., 1996) and with daily bathymelric measurem<::nts during a high dam release
<br />(Wiele. 1997; Wiele tt (//., 1999). Accurate predictions of erosion and deposition provide a sensiLi~'e test of the
<br />accuracy of cakulaled flow lields Row depthS in the model arc largely determined by the downmeaffi boundary
<br />conJition for the flow component of the model. whkh specifies the water surface ebation for the modelled dis-
<br />charge. The:: flow model soh'c,> a combin..d iann of the \enically av<:'raged momentum and continuity equ:ltions
<br />L:sing lhe tin it.:: diiference method of Casulli {19(0). The local friction coefficient is derived from the logarithmic
<br />\cl\XiIY profile (Keulegan. 1(38) and the roughness parameler.:Q, is relJted to Ihe me.:lSured deviations of the bed
<br />around the smoothed griJJ.:d bed topog.raph:- lklJils of th.... model can ~ found in Wiele CI af. (1999).
<br />
<br />C,-,p>rightt::, ~OOJ John Wlte)' &. SOll~.lld
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<br />R"a RtJ.lopplic. 20; 379-400 (2CllJ4,
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