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<br /> <br />~ ~ ~ <br />ll. ll. U <br /> <br />~ ~ <br />< < <br />U U <br /> <br />~ < <br />< ~ <br />U ll. <br /> <br />~I~~~~~~~ <br />.>:~:;:::~: ~ r; ~ ~ ~ :;; ~ <br />~i~c;;;-~ii8 <br />.......~...~. c::; ~ ~ ~ ~ ~ g <br /> <br />li_iiaii~ <br /> <br />......'n"". "~ i '" '" ~ <br /> <br />..... <br />III <br />....l <br />l<l <br />< <br />E-< <br /> <br />I"e I"e 1"8 1"8 I"e 1"8 1"8 <br />00 ~ 00 "d" N 00 0 <br />~ ~ ~ ~ fri ~ 0 <br />V) \0 \0 r-- r-- r- 00 <br /> <br />ii' <br />III <br />~ <br />Cl <br />:t <br />< <br />I>. ~ <br />~ ~ <br />U ;: <br />Z III <br />::> ~ <br />~ ~ <br />~ I>. <br />~ ::g <br />III 0 <br />~ ~ <br />o ::> <br />~ ~ <br />III ~ <br />o l<l <br /> <br />g <br />E-< ~ <br />'" ~ <br />i1i ~ <br />~ 0 <br />~ ~ <br />e g <br />~ ~ ffi 0 <br />U U N E-< U <br />~ ~ III ~ i: <br />.~ j ~ ~ ~ <br />~ ~ ~ ~ ~ <br />~ ~ ~ III ~ <br />III III III ~ 0 <br />l<l l<l l<l 0 U <br /> <br />_ N fl"'I "d" V) \C r-- <br />o 0 Cl 0 000 <br /> <br />4.0 HYDRAULIC ANALYSIS <br /> <br />4.1 <br /> <br />Base Maooine: <br /> <br />Base mapping selected for the delineation of the 50-year and 100-year floodplains on the <br />Gunnison River consisted of 7.5 minute D.S.G.S. topographic quadrangle maps. A total of 11 <br />quadrangle maps were used in compiling the base maps for the Gunnison River study reach. The <br />contour interval for the maps was either 20 or 40 feet (see Figure 8). Due to the small scale of <br />the base maps (1 "=2000'), the 50-year and 100-year floodplain boundaries could not be shown <br />as separate in most cases. <br /> <br />~ <br />- <br /> <br />4.2 Stream Reaches <br /> <br />~ <br />o!! <br />~ <br />Il <br />o <br />~ <br />>-~ <br />0- <br />~g <br />",< <br />lIl> <br />U~ <br />zg <br />~~ <br />2:i:t <br />of!! <br />o....l <br />g~ <br />ll. <br />,::g <br />~~ <br />lIlZ <br />00 <br /><- <br />E-<E-< <br />z< <br />Ill::> <br />~g <br />O!:: <br /><ll. <br />~lIl <br />::g~ <br />tiu <br />ZO <br />lIlZ <br />0- <br />ffifg <br />~lil <br />E-< <br />~~ <br />~~~ <br />:.:lIl< <br />IIlll.U <br />U ' , <br />~~~ <br />Olll< <br />"'ll.U <br /> <br />Preliminary work on the floodplain mapping of the Gunnison River included dividing the entire <br />study into separate reaches. The reaches were classified by estimating stream floodplain widths. <br />The width classifications were refmed once cross-sections were plotted. The width classifications <br />selected are based on the distance from one side of the river to the other at a ground elevation <br />15 feet aboye the low water level. Those classifications are: <br /> <br />Broad <br />Medium <br />Narrow <br />Canyon <br /> <br />>0.5 mile wide; <br />0.2 - 0.5 mile wide; <br />0.1 - 0.2 mile wide; <br /><0.1 mile wide. <br /> <br />Based on these standards, there were 12 separate stream reaches classified for a total of 43.5 river <br />miles. That is an average of 3.6 miles per reach. These 12 stream reaches are listed in Table <br />4 and they are shown on Figure 6. <br /> <br />12 <br />