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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3.13.2 &lergy n1-'pahW's

WEe riprap structures are insufficient or unectIDIli.cal to control. ili! storm runoff,
calClete energy dissiIBtor structures (stilling basins) SIall be provided in accardarK:e with
lEIXM ''Stroctures, Sectim 2.2 Frergy DissiIBtors."

Far cu1va-ts or storm sewers ..nere ili! Froode nmiJer
at ili! outlet SIall be excess of 2.5, ili! lEBR Type of VI impact Rri 11 i f1g iIlsin be used.

3.13.3 0ECk Stro:tures

'Ibm! is a nmdnun permissible ve1oc:i.ty for IIBjor design storm runoff in grass-l.iJled
channels. (he of tOO lIDl'e camm uetOOds of cmt:rolling tOO floo velocity is to redoce tOO
channel invert slope, 1ohi.ch requires a chock drop to DBke up for tOO elevatim differerre
occur:ing ..reo ili! channel slope is reduced.

'Ire design criteria for the chock drops, SIall be in accordance with tre lEIm ''Stroctures,
Sectian 3 Olannel Drops."

3.13.4 ~

'Ire design of bridges for ili! <kdway area SIall be in a:c.ordance with ili! lEIXM
''Stroctures, Sectim 4 Bridges."

3.13.5 Jrrigl"Hnn IlI.tch On-i'lgl"

Three basic types of ditch croosings of drainage.ayare defined as follaos:

Type 1. Canplete separation of storm flow and irrigatim flow. Type 1 structures occur
frequent! y as a fl\lll! or pipe crossing of a gulch by ili! ditch or as a storm sewer
under the irrigatioo ditch.

Type 2. Discharging tre storm flaos into the ditch, then I"P1"""';!Jg "exz:ess" flaos in tre
ditch 00ck into tre drainageway utilizing a fonml control structure. The Type 2
structure 1000ld be used where tiJe ditch has Ioater' rights on the stream in
questi.m. In additim, the structure requ:ira1:ents for this cootrolllBY be less
expensive than canplete flow separatioo (Type 1 structure), €SJ"""i,,11y for tOO
larger drainage.ays. Ibwever, this nethod requires lIDl'e JJBintenance of the ditch
to cle3n rot silt, sand, mxl debris.

Type 3. Discharging tre runoff into tOO ditch, w.l.tlxJut returning tre runoff lBck into the
drainageway.

'Ire Type 3 structure require a thorough analysis of tOO ditch capabilities and tOO
storm runoff peaks mxl voltm!S, and my require a detentian or retention pond to
reduce tOO nmoff to tOO ditch caIBhilities and or historic flow levels.

Fa::h irrigatim ditch croosing of a drainage.ay will have its own unique design
requ:ira1:ents and therefore, a typical ditch crossing configuratim does not exist. Unless
agreed to in writing by the ditch canpany and the TOl/ll, mly Type 1 structures will be allOl6l
in the Ordway area.

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