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<br />portion, but from the vicinity of 5th Street to the upstream
<br />end, it is largely in a natural state. From 2nd Street to the
<br />south end of the study area, the stream is bordered on the
<br />east by a relatively high bluff or hill. with only a few
<br />locations where' a flood plain exists. The west side is
<br />generally flat and low, providing a flood plain of several
<br />hundred feet. Anderson Arroyo watershed is about 15.5 miles
<br />long and 3.5 miles in width, with a drainage area of about 54
<br />square miles. Elevations in this watershed range from 4,750
<br />feet mean sea level to 4,060 feet at the confluence of the
<br />arroyo with the Arkansas River. The arroyo has an average
<br />slope of 19.4 feet per mile.
<br />
<br />King Arroyo flows almost due north along the east side
<br />of La Junta and has a well defined flow channel for the entire
<br />length in the study area. It is about ten feet deep
<br />throughout with some widened areas providing small flood
<br />plains within the banks. Like Anderson Arroyo, the lower
<br />portion from the Arkansas River to 3rd Street has been
<br />partially shaped and riprapped. The remainder is in a natural
<br />state. The arroyo channel has an average slope of 24 feet per
<br />mile, and drains an area of about 25 square miles. Elevations
<br />range from 4,550 feet mean sea level to 4,050 at its'
<br />confluence with the Arkansas.
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<br />The lOO-year t'lood is dat'ined as having a 1 p<>rcant
<br />chance ot' occurring in any given year. Similarly, the 25-year
<br />flood has a 4 percent chance of occurring in any given year.
<br />The 100-year flow for the Arkansas River at La Junta is 92,000
<br />cubic feet per second (reference 1). Table 1 presents
<br />corresponding drainage areas and flows for the drainages at La
<br />Junta (reference 1,2).
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<br />TABLE 1 - SUMMARY OF DISCHARGES for the
<br />ARKANSAS RIVER & TRIBUTARIES AT La Junta
<br />
<br />:,,~:,/{::::{,:::::::-:>:::":
<br />",W .'.,':<,...,.... ::",,,_,,;_,,:_,,_:"_,_,,,_:.".'.
<br />:\T{(:t::::::;U:::":':-:::i?}{:r -:',-:-;.:;::.:.:-,.:.;-' ::::i}((L/\,!;:::(,
<br />D A ' (sqin;IUl
<br />' ">Mb4~~~J~~)r
<br />
<br />~~('~~6N(/:K,,"..,.,nm,.,.'.','....'...,..'..'."
<br />"'-:,. ...:.:.,-':.:.,-"--.,.:.,,.
<br />~2i21.0 ".'5~)..nZ$(",
<br />
<br />:"?'::;:,:<\:,::::,:\::::;:::-:\")/':: ( : .,.::'=:/:(:}(?:t:(.::::::,::\::';:,,:,::,:: ::,;: :':::+:::.::':: .:-
<br />.)211 ;OQ.Q '~J22,5.i.li;'$$O '.,. '.',.,...
<br />
<br />n_ _., ..."......___,",__..............,'
<br />. - - - - -."., ""-~,', -----.- -,..
<br />.-".,.. ,', ,',' ,',-- ....,.--. ....,',,'
<br />_n ...... _ "d., ',.... '._.H
<br />"d_ _ _ ___. ."......,'",',",',',......,
<br />',,",....,',',,' '".,-.....,.,.,." '".--,",
<br />,...,' '""',',',',','.,.--,.,,..,...,... ,
<br />,.--'.... ..... ,',',",",',....
<br />.", .'. .".2sAYli:AR>
<br />
<br />, ,,'" "..,
<br />..,--,., ,.,'"," '.
<br />."".,-" . .."
<br />',",'".".,.,"'",',," '. "..
<br />. .",'.
<br />.:-:,.,','"',,,,","',",.,'.,'.
<br />, """"", ',-- ...,..
<br />'SIlO"YW..".> '
<br />
<br />.'..156,200
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<br />Plate 2 shows the entire Arkansas River watershed above La
<br />Junta.
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<br />~ The 100-year flood
<br />has a one percent
<br />chance of occurring
<br />in any given year.
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<br />~ 100-year flow at
<br />the La Junta gage
<br />- 92,000 cfs
<br />- 4055.4 feet NGVO'
<br />= 11. 9 feet
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<br />See Figure 4 for
<br />more information
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