FLOOD09884

• County: Crowley
• Community: Ordway
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Drainage and Street Design Manual for the Town of Ordway
• Date: 1/1/1987
• Prepared For: Ordway
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Project

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liIU.lI.D 4 - CAPACl'lY CI' <IIlB <m{IlI; INlBlS IN A IJJi RJOO' (R
9H'

'Ire capacity of a curb opening :inlet in a BlIIIp (I[' laii point varies directly with tIE lmgth
of tIE :inlet and depth of water at tIE .:..luna, 'Ire inlet will operate as a lei.r until tIE
water sulm!rges tIE ",1tL...L.e. \lien tIE depth of water is about tw1.ce the 1Eight: of the "'rt......:e
(I[' 1lDI'e, it will operate as an orifice. Bell..-"C<I these two depths it will operate 9:JIeoilere
between tile b<<l.

'Ire naoograJit (Omt 1.6) is 00sed m the following C1DIi.tims:

1. 'Ire CUI'b opening :inlet (00 grate) is located at a low point in the grade.

2. All flow a:ming to tIE inlet DIISt evmtuall y enter tIE :inlet and will pcuI until
suffi.ci.ent IeId is brllt up &l tIE outflow through tIE :inlet will equal. the peak inflow
iran the gutters.

'Ire hydraulic 00sis of the .LIIIlgI3)i1 is as f~:

1. For heads (depths of water) up to tIE height of the opening.

(H!h D), tIE :inlet is 8SSIIIed to act as a lei.r with the flow passing through criti.cal
depth at tIE entrance and folioloring formJla

Q = 3.007 1lI3/2

2. For heads equal. to or greater fum tw1.ce the height of opening H/h2 2,
the inlet is 8SSIIIed to act as an orifice fol.1owing the formJla

OIL.. 5.62 h3/2(H'/h)!

This is a rt".u...~4. of the standard orifice formJla Q = a-t2gH with C = 0.7 and H'
equal. to the IeId ro tIE middle of the inlet opening (H I = H -~).

3. For tIE heads with H/h between me and b<<l, a transi.tim _ used as tIE operatial of the
inlet is inlefinite.

Procedure :

&iter tIE naoograJit with any b<<l of the three values h, Q/L, H/h, and read the third,

~ h = totallEight: of opening (ft)
L = total lmgth of opening (ft) ,
H = depth of water at the entrance (ft)
Q = total peak rete of flow to the inlet (cfs)

Nornally Q, H, and h will be kna.n, and the ...:m>g....ph can be used to determine the length
of opening L. The sprmd of the water on the street will depend upro the cross slope of t/r:!
JBVE!IeIlt.

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