FLOOD07531

• County: Ouray
• Community: Ouray
• Stream Name: Uncompahgre River
• Basin: Gunnison
• Title: Floodplain Information Report
• Date: 4/1/1978
• Prepared For: Ouray County
• Prepared By: A & S Consultants
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

I

I

I

GLOSSARY

I

Fl~drreq""ncy. (Se" Probability.) The.wernge .ccurrence interval of
~eclfic discharges Or water stages which cause flooding.

I

I

eha"""l. A natura 1 or artificial "a~ercourse of perc~ptible ,,"tent with
definite bed and banks to confine and conJuct continuously 0<
periodically flowing water.

II
I

Flood Peak. The m~ximum instantaneous discharge of a flood at a given
location. It usually occurs at or near the time of the flood crest.

Back~ate~Effect. The rise in surface elevation of flowing water up-
stream from and as a result of an obstruction to flow.

I

Cloudburst. A sudden and extremely ht>3VY downpour of rain tl1at iss","ll
i"arealextent; of short duration; and may be accorr.panled by ligh t-
ning, thunder, and strong gusts of wind.

I

!l-~~~lai~. An area in and adjacent to a stream, whlch area is subject to
flooding as the result of theoccurre"ceofa IOO-yearflood nnd
whlch area thus is so adverse to past, current, or foreseeable con-
struction or land use as to constitute a signiflcant hazard to public
health and safety or to property.

I

Co[weyanceCspacity.
s. Channel conveyancc capacity is the rate of discharge, in cubic
feet per second, which Can flow in a water course with the
~ater surface not greater than the height of the channel banks.

I

flood Profile. A graph sho~ing the relationship of watcr surface elevation
'to location, the latter generally expressed as distance above mouth
for a stream of water f1o~ing in an open channel. It is generally
drawn to show surface elevation for the crest of a apecific flood,
but may be prepared for conditions at a given time or stage.

I

I

b. Floodway conveyance capadty is the rate of discharge in the over-
flow portion of the floodway which cen pass through a specified
area at depths and velociti"s governed by the hydrllulic dimen-
aions of the floodway.

I
i I

Flood Sta~e. The stage or el~vation at which overflow of the natural
banks of a stream or body of water begins in the reach or area in
whIch the plpvat10n i~ measured.

I

Designated Floodplnin. The Area desi8nated as a floodplain by official
action of the board of county commissioners or city council with the
prior concu,rcnce of the Colorado Water Conservation Board.

I

Flood~ay Zone. The channel of a stream and those portions of th~ adjoin-
ing floodplain which are reasonably required to caHy and discharge
the fl,"od~'aters of a 100-year flood. It is the dcsignated floodplain
less than thc low hazard zone, if any such low hazard zone has been
identified. If no low hazard zone has been identified, the.n the tcrms
"designated floodplain"[llld "floodway zone" shall be considere das
being synonymo~s.

I

I

I

~. An oVerflo~ on lands not normally covered by wat~r and that are
l1""d or u~ablc by TIliln. 1'1"c>Js t,'lve two "~S<>Iltial ch..r"cl"rhtics;
the inundation of land is t".",yorary; ilud the land is adjacent to and
inundated by overflo~ from a river or stream or an ocean, lake or
other body of st~nding water.

I

Intermediate R~gional Flood. A lype of flood, including the ~ater surfnc~
elevation and territorial occu~ation thereof, ~hich cao be expected
to occur ataoy time in a giv..n area based llpon recordedhistorica I
precipitation and other valid data, but with an nv<~rage statistical
one percent chance of b"ing equalled or excccded durio!: any on.. yea r.
Tl,~ L~,," i~ u~~d LllL~Lch""!;",,bly witb d."." l'""c,,ot fl""" "" one hun-
dredyearflood. {See definition for lOO-year flood.)

I

~ormally a flood is considered as any temporary rise in streamflow or
Hage, but not the l'ondin~. of surface ~'ater, that results in signifi-
cant adv~rge effects in the vicinity. Adverse effects may include
damage~ from oVerflo~ of land areas, te~porary back~ater effects in
sewersandlocaldrainagechannels,creationofu"sanitaryconditions
orotherunfavorablesituationsbydepositionofmaterl"-lslnst,,,"-'"
channels during flood "ecessions, use of ground w~tet coincident ~ith
increased streamflow, and other problems.

I

I

I

Left

Bank.
aathe

Thebnnk
observer

of the left side of
looks downstr~"m.

a river, stream or water course

I

I

cw

lIazardZones.
100-yearflow
half feet.

That
will

area of the floodplain in ~hich the waters af 11
nat attaIn a ,,,,,,,imum depth greater than one and

one-

I

Flood, IOO-Year. A type of flood, including the ~at"r surface elevation
and territorial occupation thereof, ~hich c~n be e"pected to occur
nt any time in a given nt<,ab:lsed\lponrecordedhistoriC3lprecipi-
tat ion :lnd oth~r valid data, but with an av~rage st3t1~tical one per-
ccnt chance of being equalled or e~cccded during anyone year. The
term :is used i".tercbange.'bly >lith " o~e perc~"t 0"",] "r Inter"lediat"
R"giun",l Flood. (See ddinitlon for Int"un~diat~ R"gional Flood.)

I

I

I

Probabilit}C. Thc annual chance of occurrence of specific hydrologic "vents,
such as ra.infall over a specified aro'a or peak ,Hseh<\rge at" specified
location expressed in perc~nt, e.g., 5% representing one chance in 20
of thp ~v~nt oecllHing ;n ~ny yp~r or ~n :lv~rag~ r~~"rr..nce of once in
t"~nty years.

I

floodCre"t.
fl"odat

The ~a"lmurn ~t"ge
" "iv~" location.

or Pln'ation r..~ch"d hy th~ ,caters or "

I

R"Je(ence Po.lnt. A n",.b(.rc.d ~OI11t ld"ntifytn/: ~ 5p~dfic 10"atLon for

1

I

I

-12-

'I

-:\1-