FLOOD09447

• County: Statewide
• Community: Malta Montana
• Basin: Statewide
• Title: Reconnaissance Report Flood Control for Milk River at Malta Montana
• Date: 12/1/1991
• Prepared For: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Level of Protection. Ar... of prot.ction were identifi.d conforlling
to the three subareas r.ferr.d to throughout the .tudy. Both lOO.year .nd
SOO-y..r d..ign lev... were .v.luat.d for .11 thr.. .ub.r....

Lev.. Alia_.nt. Four l.v.. .Ugnmentl v.re .valuat.d b.s.d on the
loc.tion of .xl8ting development and .ound .ngin.ering judpant. Th.
.lignment. and the .ub.re.. they protect .re .hown on pl.ta 3.

lIh.rever pos81ble, leve.. were pl.c.d betw..n the riv.r channel .nd
the .xi.ting d.v.lopment to prot.ct the maximum numb.r of ho.e.. busi-
ness.s, .nd industri.s. lIhere development occurred too clos. to the riv.r
to perllit the construction of ..rth-b.llIed l.v.... floodvdb vera us.d.
Engine.ring judgment .nd fi.ld obs.rv.tions vera .pplied throughout the
process to identify vi.bl. .lignment..

Hydr.uUc. . Levee .Ugnments 1. 2, and 3 encro.ch into the FIS
floodv.y to som. degr.. .s .hown. Lev.. .lignment 1 .ncro.ch.. .lightly
into the floodv.y upstr... from the r.ilro.d bridg.. Lev.. .lignment 3
.ncro.ch.. ..v.r.l hundr.d f.et into the floodv.y .. it follow. the
exl8t1ng lev... Both lev.. .Ugnment. 2 and 3 .ncro.ch into the noodv.y
betw..n the U.S. Highw.y 2 bridge and the r.ilro.d bridge. Encro.chment
in the .rea between the bridges had minor eff.cts on the v.ter .urfac.
profiles. Lev.e alignment 3 provide. the high..t increa.e in water
surface.-O.4 foot; however, Montana floodvay requirement. specify that a
maxilDUll water surfac. increase of 0.5 foot 18 acc.ptable. lIh.n the
O.4-foot ris. is considered with the f.ct that the floodvay .ncroachment
for the l.ft bank was not present, it beco.... appar.nt that the levee
alignments propos.d may violate thb floodvay regulation. Approvel of
these plans may be subject to studie. ahowing that the noodw.y with the
proposed levee .lignment does not exceed Montana floodvay criteria or to
an exemption to the floodvay criteria may b. needed.

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