FLOOD04639

• County: Las Animas
• Community: Trinidad
• Stream Name: Pinon Canon Dam
• Basin: Arkansas
• Title: Pinon canaon Dam Flood Control
• Date: 10/1/1951
• Prepared For: CWCB
• Prepared By: COE
• Floodplain - Doc Type: Project

and me teorological indiee!! whidh gate! 8. maX1ltn.lJn a'1rerage precipi ta tJ.on
of 3..46 inches 'in a ~.hour poriod with a ~~imuml-h9ur rainfall of
2.39 inches. . ";

. }-02., After ini tial loss conditions were satisfied, the minimum
infiltration rate, of 0.40 ineh per hdur' was used. The standard project
flood was dpinputed by ap-p'lying the esUmated I'Und:ffto the adopteQ:unit
hydrograph. This resulted in a flooc;. at l'inon Canon Dam site with Ii
peak: discharge ofl.,,40Q eubic feet per second and a voluIile of 393aore-
feet, which is equivalent to 6.46 inches of runoff. The above flood
was select13d for .~he standaruproject flood because the. volume would
be more critical f.or desi@'!of the dam, althou.gh a more intense rain
of shorter duration. eou;L.d have been eelected tl1at w.ould pr.oduee a peak:
of ab.out ~cubiefeet per second 'at the dam site, but of a smaller
volume. Such a flash flood was .estimated for use in the econ.omio
studies. Th.e standard project floodiselected for the prOject.design
is about 42pel'Clmt and 65 percent o:t the spillway desi@'! flood in
peek die.charge, an.c1. .yolmno respeetiveJ,y. '

. },,03'.~~~},'!1_~~i~n flood, !J!he .maXimum possible precipitation
was o'Q1iained frOUI Flydrometeorol.ogiCal Sedti..on by, letter, dated 26 Oct-
.. Ober1.951, Subjeet: "Review of lIMS R~port 17. 14aJ':imum Possible Predpi-
tati.Qu.overthe Peqos River of New M~xi.co; II forwarded as an inclosUl'e
wi'0n a let.ter from Office, Chief 0" 'Ir:;ineers, dated 29 October 1951,
SulJ je.et; "SpillwayFl.o.od St",i;'Jl" ,'~J~,":;ogordo Dam. n Studies wEire made
using Table I of the refrc".~d. :Lot tel' from Hydrometeorological Seetion
which is the m.od rect'ln study a\Tail!l.ble and which shows seyeral storms
that were,c.omputeiLfrom observed datil- in the regien of Trinidad, 0.01.0-
rado. The resultirigpreoipitation for the maximum 6-hour period,
arr~ged in critical order by 3~minute intervals, the 12~hour storm
adopted mass c;J):'ye, and the estimated spillway design fl.o.od hydrograph
are sh.own .on plate 1.

3-04. An average of the three J,~gest storm centers whieh occurred
in the general region of Trinidad, Colorado, for whieh data were .given
"in table 1. :referenced, in parag;-aph 3-+03 was sele,eted to give the'mlat;l,mum
possible storm. This average precip~tation wa~ obtained in the follow-
ing manner:

Storm &. Center

Adjus t
Factor

i:!arrier
C.orr.
l1er een t

Preeipitation Inehes
6-hour ' 12....hour

MaY3~'31, 1935
CherrYCr.eek Center
., Hale Cen ter
June }-5, 1921

1.45
1.33
1.67

84
68
92
Average

29.23
1"(;18.
15.36
20;59

20.6

29.23
21.71.
17.36
22.77
24.3

Seleoted Average

-4-

,Appendix I