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<br />By definition, the intermediate Regional Flood has an
<br />average occurrence of once in 100 years. However, it is impractical
<br />to assign a freqUency to the greater Standard Project Flood. For
<br />purposes of hazard evaluation, it is important to recognize that
<br />either of these ~jor floods can occur in any year. Floods larger
<br />than the Standard project Flood are possible, but the combination
<br />of factors necessary to produce such large flows would rarely occur.
<br />
<br />cOlmlercial and industrial delleloplllents in the south parts of Pueblo .
<br />Velocities greater than three feet per second combined
<br />"'ithd..pthsof,three feet or mOre are generally considered hazardous
<br />to life as well as to property. Water flowing in excess of four feet
<br />per second is capable of tran$nnrt'~~ n_~'_~~. ~~~
<br />...... ."7 ~=-li"~.... ~.." causing sev"re
<br />erosion of stream banks and embankm,,' 'i" ,,~n~~
<br />... 4 4~ ~ ~~..~ bridge abutments.
<br />When velocities drop below two feet per second, debris and silt
<br />deposits o<::cur, extel\din'" n, ~,~~ ~ ~
<br />~..,. 44~v" ~a~age an~ creating adverse
<br />he~lth conditions. The saturation effects of flooding of long
<br />duration can effectively weaken bridge abutments, levees, earthen
<br />dams, and other embankment ~~rks so that they fail.
<br />Property damage from great floods in the develOped
<br />areas can be overwhelming. The entire community suffers when streets.
<br />bridqes, sewers and other ~'~ii- """"."',-, ..
<br />~_~ ~ ~~ c _~ are ~e~troyed or othPr_
<br />wise made inoperative. In a~~'-'n_ .0 --- .
<br />~~.".vu" .,.~ phys~cal hazards, a great
<br />flood may contribute to illness and even deadly epidemic disuase.
<br />The sewage from sanitary sewers and stockyard wastes can become mixed
<br />with surface flood ",at"rs and treatment plants and lines may be
<br />w<lshedout. 'l:he threat to th'" h<:'alth of inhabitants isal",aysa
<br />majorconcernduringfloo<.1",aterconditions.
<br />
<br />Standard Project Flood
<br />Only in rare instenceshas" specificstr<>"",exp",ri..nc"d
<br />the large...t flood that is potentially possible. Severe as the maxiznum
<br />known flood may have been On any qiven stream. it i~ generally accepted
<br />that a larger flood ",ill occur at some till'le in the future. The
<br />Standard project Flood is defined as the flood that can be expected
<br />from the MOst severe combination of meteorological and hydrological
<br />conditions that are consid~red reasonably characteristic of the
<br />geographical area in ~hich the drainage basin is located. The Corps
<br />of Engineers, in cooperation with the NOAA weath"r Service, has made
<br />compr"hensive studies and investigations based on vast records of
<br />experienced storms and floods and has evolved generalized prooedures
<br />for estimating the flood pOtential of ~aterways. Flood characteristics
<br />of the Standard Project Flood for averaged maximum conditions within
<br />the study reach are shown in Table 3.
<br />
<br />Frequency
<br />
<br />Floodoo 1\rea~
<br />Plate
<br />
<br />and Flood Damage
<br />2 is an index map
<br />
<br />for the succeeding Plates 3
<br />
<br />IlazardsofL:lrgeFloods
<br />The hazards to life and extentofdama'le caused by""y
<br />flood depend on the topography of the flooded area, depth an~ duration
<br />of fLOodin'l' vel~ity of flow, rat~ of rise. and man ~ade develop-
<br />m..nts on th., flood plain. Future floods of !ntcrllI<>didte Regional or
<br />Standard Projec~ Flood ~aonitude on Salt Creek ~~ulQ in~ndata ~esj~~ntial,
<br />
<br />thro,,"" In "'hio11 51,,,,,, ~h~ "_",_",.'~ U h ,,__, ,
<br />,~~ ~~ ~~4~ _e __~~,.ec by th~ Standard
<br />Project Flood and the lntermediate Regional Flood on Salt Creek.
<br />Depths of flow for any 'liven river location in the study reach can be
<br />estimated from hi~h water n-n~.'i'_ .
<br />~ ~Ly 4 ~~ Suown on Pl~es 11 thro~qh 19.
<br />Plates 20 and 21 sho", selected cross sections of the river that are
<br />typical of the local reach of t.h",rlv..r from which th..yqre taken.
<br />
<br />~ll CrO$S section locations ~re shown on the
<br />plates. Channel cross $~ctions. topographic
<br />
<br />flooded areas and profile
<br />maps and aerial photo-
<br />
<br />or"phs w('r.. ,,~ed to det.,,"""ine str,,,,,," ~,.
<br />c,,"-rac..er~(jt~cs ne<'<led to compute
<br />
<br />"-nCl ch..fin~ th.. fl<:-:v:l situat.i.on.
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