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<br />The drainage basins of the stre~m5 under study ITe within San Juan
<br />and La Plata Counties. They are bounded on the east by the draInage
<br />P,- R' Grande and Gunnison Rivers; on
<br />divides of the Florid!!, Los ,nos, 10 .
<br />,.~ Uncompahgre Rtvsr; and to the
<br />the north by the drainage dll/ide 0 ,ne
<br />'''h SanMiguel and Dolores Rivers. ElsM
<br />west by the drainage divides 0 ,e
<br />vat Ions In the Animas drainage vary from more than 14,000 teet along the
<br />.', S,- ,.,~ "-"otelns to about 6,500 feet at Durango.
<br />western slopes of '" .. .~ " .....~
<br />From the San Juan ~~untains, the AnImas River flows In a $Outherly
<br />1 t the nearly m!le wide Animas
<br />direction through steep narrow canyons n 0
<br />Valley, "hlchext<lnds forapproxlrnately 15 miles fo Durango. Three
<br />periods of glaciation have carved the valley Into a wtde, gently sloping,
<br />shallow valley. At the southern end of the valley, terminal mori,llnes,
<br />'>db glaclerslconflnethevalley
<br />(high m(lsses of rock and earth depos ,e Y
<br />lit the character of the river
<br />floodplain. Oownstreamfromthspon, .
<br />changos from a meandering, slowly moving stream with the characterIstic
<br />wide flood platn to a relatively straight, swiftly flowing stream with
<br /><I narrow flood plain that bisects thll ctty of Durango. The flood
<br />carrying capacity ot the AnlmQs River In the valley is rela:ivelY small,
<br />t d rea Channel capacity Is
<br />whl\ethrough the remainder of the s uya
<br />suffIcient to pass moderate floods.
<br />
<br />relatIvely small basin with headwater elevations In eXCess of 8,000 feet.
<br />Ory Gulch Creek follows a course generally parallel to JunctIon Creek,
<br />joinIng that stream about 1/2 mIle upstream from the Animas RIver.
<br />
<br />Lightner and Junction Creeks rIse In the La Plata Mountains to the
<br />northwest of Durango at elov~tlons greater than 12.000 teet, and f 1<:1" 1n
<br />for most of their length. ~lthin the study area,
<br />as s"lttly tlowlng streams occupying generally
<br />moderately sized valleys. rney Mvesutflcl<3nt
<br />. tloodflowswlthoutslgnlflcantproperty
<br />channel capacity to poss minor .
<br />....I-..'+-' nf tlow and floi,ltlng debrIs carried
<br />However, tho high .~ ~~ " ~
<br />''''''1.'', minor floods to produce substantial
<br />~trei,lrns can cause .~ ul
<br />
<br />Vegetation on the mountain slope~ consists of grasses, bru~h,
<br />Ponderosa PIne, and extensive stands of Douglas Fir and Aspen. On the
<br />foothill slopes, ni,ltlve vogetatlon consists of scattered PI;;on PI ne,
<br />Juniper, and Oak, and shrubs such as mountain mahogany, servIce berry, and
<br />silgebrush. On tne valley floors, native vegetation has been drastlcaJly
<br />modified by agricultural operations. The basIns have a semi-arid clImate
<br />with topography signifIcantly Influencing precipitation and temperature.
<br />No""al Mnual precipitation ranges from more than 50 inches In the highest
<br />headwater regions to about IS Inches In Durango. Nearly half of the
<br />no""al annual precipitation occurs as rain during the months of July
<br />through October. Tne remainder of the (IOnual preclplhtlon occurs nearly
<br />uniformly througnout the remaining eIght months of the year. In the
<br />higher headwater regions, most precipItation occurs as snow. Snowpi,lcks
<br />of nearly 12 feet, wltn a water content of almost 5 feet, have been
<br />observed. Suo1'ltllers are short, moderately warn 'filth dally maximum ternper-
<br />atureslnthenlnetles,andarebrokenbyperlOdsofraln. Wlnter-sare
<br />relatively long and cold. Temperature extremes at Durango hi,lve ranged
<br />from i,I summer high of 98 degrees to a winter low of -20 degrees.
<br />
<br />DEVELOPMENTS !NTHE FLOODPLA!NS
<br />
<br />a southei,lsterly direction
<br />both can be characterized
<br />wellde/lncdchi,lnneIS,ln
<br />
<br />TOO
<br />portions
<br />
<br />drainage basin of Dry Gulch Creek Is situated between
<br />of the bilslns ot Ugntnur iIOd JUl\ctl;;m Crecks. It Is II
<br />
<br />the lower
<br />
<br />The flood plains In the study aroa are devotcd to agricultural, resl-
<br />dentlat,corrm<)r'"\;14I,recr,,,,,tlon4I,ondgov..rnmunt4Iu,;,,,;. Dt.vetopments
<br />along the Animas River include the Durango Sewage Treatment Plant, a
<br />sectlonot the downtown oortYllercllll dlstrlct,aStateflshnatchory,a
<br />mobile homo p"rk, residenCes, tri,lnsportatlon facilities, and extensive
<br />agrlculturi,ll Improvements In the Animas Valley. u. S. Highway 160, many
<br />resldences,andcOrmlCrcllll establlshmentSi,lre loci,lted In the flood plain
<br />of LIghtner Creek. The flood plains of Junction and Dry Gulcn Creeks are
<br />primarily residential in nature and Include a rest home on Junction Creek
<br />i,lnd dlOClbile hOlTle pari<. and a school on Dry Gulch Creek.
<br />,
<br />
<br />damage.
<br />by these
<br />d"rIk>ge.
<br />
<br />)
<br />
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