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<br />The South Channel downstream of the Del Norte flow split has stability problems due to
<br />,he ,,,.,'" fl,w ~~= "0 \ow fl<'W', oo'y high flo~), .", ,100 =" "", , high
<br />sediment producing area.
<br />
<br />,ppw~h~ = ,,,,,,, ., "",'''''' - oc h" wi'" - ,he hlgh'y ''1''''''_' """" ,f "",,h<,
<br />D and E between Monte Vista and Alamosa. Sediment deposition causes loss of capacity
<br />and channel meandering evidenced by bank erosion. Measures are needed to balance the
<br />,," ,,' ""m, ,f "'i",,"' """p,,,"d ,,\0 ,h<~ ,~"" w,'" "', "'""", ,..",pm< "'"
<br />storage capacities in the reaches themselves.
<br />
<br />Sediment deposition downstream of Monte Vista is responsible for loss of channel
<br />conveyance, leading to flooding problems during high flowS and, in some cases, even
<br />"riog ,oc,,,1 C,.."" "'h"ri"'. Short I~'" "",,,,,,, ,ft'" "",h h'" h,d h.."'"
<br />effectiveness and have largely shifted problems to upstream and downstream areas. A plan
<br />for enhancing channel capacity while improving geomorphic stability is needed.
<br />
<br />Bank erosion occurs downstream of the Alamosa Levees and on the Alamosa National
<br />Wildlife Refuge because this reach is sediment deficient. Critical banks needs to be
<br />stabilized and/or sediment delivery from upstream reaches needs to be increased.
<br />
<br />Channel instability has adversely impacted the effectiveness of numerouS diversion
<br />structures throughout the study area through bank migration and sediment deposition.
<br />
<br />The numerous abandoned channel cutoffs and oxbows in the Rio Grande floodplain,
<br />p",,"'Mly '"''''''''''' ,,"oo" V.... pro,id, 1.._" "pportu",,~ 'oc i..p""m, 'h<
<br />flow and sediment transport and storage capabilities in the study area.
<br />
<br />~
<br />
<br />plaza area need to be
<br />
<br />Erosion and deposition problems in the vicinity of the Sevenmile
<br />addressed.
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<br />
<br />The safety of individuals within the floodplain is threatened during flood flowS in the upper
<br />portions of the river where recreational uses are highest. Plans should be developed for
<br />evacuation in case of high water
<br />
<br />Sediment transport through the Alamosa Levee reach (Reach F) has been adversely
<br />",,1"'''' m port by ,he "b""'."" ,,,",'" by"" W""id, ",,,h ",,"'oo doo>. 5""'="
<br />transport capacity in the leveed area needs to be increased.
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<br />
<br />lncreased sediment production from the watershed upstream of South Fork may playa role
<br />in the oversupply of sediment found in the reach downstream of Monte Vista. This
<br />deserves further investigation beyond this study effort.
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<br />
<br />"" ""Y''' ,f ",,,,,, ,"'"''' hob'''' " "', RI' G..,d' =rid'" w~ -' oo Ib~' ",mpo""" RlpM'"
<br />V "ct<rti"", RIp"'" W\ldI"', "'" ",h""" Thi' ""ioct ,~I,dod " ,.,,,,h ",H" "f "', ,oIl'w'''''' "",,,,
<br />,,"""''' _p""hOO "'" , ,om",,'''' ., h\,."i, ,,"""'~i _"", w'ldh" h,bi'" ""Y">; ",,,,,,,
<br />w\ldl'" bob"" ",iy,i>; "" 'd,,""''''''''' " I~," p""mm, ,,, "', '''P'''''''''''' ,,'p.n" ", ",,,,,.
<br />habitat conditions.
<br />
<br />Riparian Habitat AnalysiS
<br />
<br />ES.3.4
<br />
<br />ES-IO
<br />
<br />"" RI, ",,,,,, d,.n" "d ""'" """y""" " "iq"iy rioh i, prod"h,\ly "d " '-' \0 w\ldh" ~
<br />w,iI ~ 'om" _'oti'.,. RI"",,, ""'~ .. " I"''''''' h<""" ,,,,,,"," "d ",...." ",I",m"" ,""
<br />_",,,,y ,,,,h," ,~h"""" "" "".n" ,,' poIi"""" b,f,~ "''' ,,,,h "', ,q"'" """,m"" " ""
<br />w'"- ,"'... _"ily " "" m'" .nd ,"~ w,h ~ lb' S" C," V,""" "p~'~ ,,.,,,,"' ,1Tcr" rnre
<br />",_ "f ,,,,h ",ct<rt"" "'. " "~,,"y ~re hI,'"~''''' "",," """ W""od'" ..~. iI""''' of ,,-
<br />~, ripori" hobi~' ,,,I,,,, ~",i ", floo""" ~d "dl",,"' """pori, "",-", ,f woI" q,"h'" fl,h
<br />and wildlife habitat; and socioeconomic values.
<br />
<br />from ri," "",,, 103.6 ,_gh ri," ,~h" 76.6 'R,~h<' iI. C "d 0), '''''' h~ ""'0 · ", d"- i,
<br />,h_' i",," h<"'''' \941 ~d ,'',. Eoob ,,~h w'Ib" "", ,',cr """,,, ... ","'hI.d ,h"~' ""rt"",
<br />,,, m"""cr ,,,,,,ff'. H..~,,,ily 'h< ",.,,' ,,,,,. ,f momd" ,,<otT' -, ,,, h'" """""" d mi" ""
<br />pori"" "om 1941 " '963. Th" w~ ,'''' ,he P"''''''' "..,,~.iy high<< ~d "om """"fly '",''''''' ""
<br />fl'w,. ^' Ib, ,,,,,,~I i",," "'''~... "" ,h~"i "01'" ~d "dl",,"' ,,,,,port "",tly ,,,~.=. ""
<br />".""1"""""''''' "'ro,gh "" .,,'ghw>od "",h w\1\ b. d.p'"'''''' down'-' 1, ,~",i ""'... Ib' pori""
<br />f'om 1963" \998 "dl'''''' ~ '_"" I, ,_,I ,,,"" """""".'y bd'w , .,,.;gh""'" ",pcr """h.
<br />Chmm<' "",.h w\1\ i~- ~ "" d,-- ,,,,,, -..-''" Ib' ,,,,,<iy d""h"" ""mofl, ""
<br />development will increase meandering and decrease channel slope. Sinuosity will increase.
<br />
<br />RNcr ,~,'"' 76."""" ,,,,'oo 36.6 ,,",~ ". ,~"",, '"h"""...... f,om \94\ " 199'. ,,,ly'C, 0'
<br />,~" ,.", "N". ""d" d'" "d fl,ld ~""",',,'''''' ,""'''''' ,h. bod """,do"'" ,,,' " ,""" _I"
<br />"d "',..".,,"' " ,",,,,,,,, h<"''''''' " "', dom"~' prob',,". 0, , "",,,,,,, ",.1', h"" _,,,, ,.""",
<br />""'" ,,", 'W" "",h" '" bre' "om"""" " "', 'o~ -". "'""',, doo>', i,w ".", "'-
<br />""''''''.. ""..,I.'", of doh'" '0 , ,'W ",..1" _ "" ""'y'" ,.n"" ,f ,,~ "" ""'" ,..""
<br />the sediment transport capacity of this river reach.
<br />
<br />Th' ""ire' "... ,b"i"d ,,,'" 1''"''-'"'' ,,,dy "" ,,, ,he y'''' 1941. 1963 "" I ",. A"'''
<br />pho'" ",re ,..,,,h501 ",,,,.,,, USGS q'od""" m,p> "d '''''m.... " ,,", ,,'" ph"~. u,m, ,he
<br />USGS ."'" Md ,,,,;ro' ,. 1',"," _p""'" , q'~'''''W' ,,.,,,,i" ,'''', ,""'" " d'" phm'onn 'rom
<br />1'" ,"""" 199' "" ,omp,",d. S"" ,10m'" ,,01"'" ,h""'" ,,,,'h "d ,,,,,,,, """,". i, crd" '"
<br />"",hi< _. ,,,,,,,,mod'" ,,'h< bl.~i'" ",~g" '" bod d~.'" Md iI' reioti""h\ I' ,,, odi'"'''''' 10
<br />1""_' COOT bd"'" ~""" ,_,,", do~ W~ ,_"" ,... Ib' ..o~""', '"'y''' ", bddgo
<br />_ "",1dod hod ,I~.'''' ,h~,,, ., , fl"d po'" ".,,, "" llridg') .,,, Ib' '''' '" '" IS y"". """'y,
<br />...10, ,obi" " "', Dol Nort. M""" Vi'" ~d Ai""'" ""... gog'" wro< ,,,,,po"'" '"" ,he ..om,""i'
<br />,,.IY'''' G'" do.. i\k< "', "''''' ,.... ,Ii'w . "",w ", b<d "~,,,," ,..,'" " · ""d po"" U,hk, Ib,
<br />"''''' _ "" "",d ", reoonI ,,,.. "dw""" "'''' . "",""""y ,,,,or "d " "~'''Y _""",,, "
<br />the air photo record.
<br />
<br />Th' Ri, Gnmd'" ,,,",,,,"'-dom',,'" .""",. Th" m"'" ",' "" ,h"""d ,hon,,, "'" '" ,h' r,old Md
<br />,"""5"" ~ ,_" ,,,~h\h" ,~~ '" , """"" \0 """"" " ""m'" """"'" "d " , ,,,,,,-'
<br />w,,,, d"'h.... Th' ,'~, " "by_h~IiY ,m,i"C ~ Ii ""'" S..,h f,d< ~d -." ~ "N"h ""
<br />"'''' "..,,,,,,,,, "r .,oob A. ^' ,,,,, ., "''' " ",.hI' """,po.'" '" WOM ~d "',..."' Jood w,"''''
<br />moj" ,"""" " ""',.."~",,. """ "" ""', "." "'...' i, ,h"""ol hod ',-~' "d m"''' "'oO'" I,
<br />channel length or sinuosity over the analysis period.
<br />
<br />GeomorpholOgy AnalysiS
<br />
<br />ES.3.3
<br />
<br />issues must be addressed in the RGHRP plan.
<br />
<br />Isolated severely eroding banks between South Fork and Del Norte could be stabilized to
<br />minimize sediment production to downstream areas, as well as to protect adjacent land.
<br />
<br />Eroding banks in and downstream of South Fork are threatening existing and proposed
<br />development, adversely impacting valuable aquatic and wildlife habitat, and contributing
<br />sediment to the lower river reaches where sediment deposition is a problem.
<br />
<br />The following key stream geomorphology problems and
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<br />
<br />ES-9
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