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<br />In determining p,,"k flow" of the Fraser River bdow the Tenmi1e
<br />Creek confluence, " ..u1tiVl~ ,egression analysis u:dng data from 6 gages
<br />W3S ~!:lplo;,ed" This method corr~lates actual annual peak flood data of
<br />thetributa.y b"sins to the USGS Granby station. Fo. further details,
<br />the;.'rightreportshou1dbeconsultcd.
<br />
<br />HYDROLOGIC AND HYDRAL'LIC DETERMI~ATIO~S
<br />
<br />In detennining
<br />C,eek confluence, peak
<br />considered.
<br />
<br />peak flows for the Fraser River ahove the Tenmile
<br />discharge and time of concentration effects .'e,e
<br />
<br />F100d Hi(;~oq._
<br />
<br />For a partial flood history
<br />Engineer's report should be consulted.
<br />the USGS gage on the FrllserRiver
<br />was 2500 cfs on June 8, 1952. The gage
<br />the confluence with Tenmile Creek.
<br />
<br />in the G.anby a.ea, ;,'dght Water
<br />The highest peak flow recorded at
<br />at Granby (1905-1909, and 19>8-1955)
<br />was located just do,",,,strea:n from
<br />
<br />In dete<mining peak flows for Tenmile Creek, a composite
<br />fre'luency-disc~"re~ cllrv(' was prepared. The composite C\1rv" was balled on
<br />hoth rainfall IInd sno.'melt fre'luency-discharge curves. The rainfall
<br />frequency Curve was based on the Soil Conservation Service (SCS) method
<br />with 11 6-hour st"rm <,vent "nd '" S('~<; Curve number of m.5. Th" snowmelt
<br />runoff frequency curve waS hasedon a regression equation with area and
<br />mean basin elevation as variables. The regression equation was one
<br />developed by the u~GS in their Water Supply Pape. No. 1683.
<br />
<br />Flood Characteristics
<br />
<br />The frequency discharge curve for
<br />shown in Figure 2. The fre'luencycurve for
<br />is sh<.>"" in Fi8un~ 3.
<br />
<br />the F.aser River
<br />Tem:lile Creek
<br />
<br />near Granbyis
<br />at the mouth
<br />
<br />Flooding on t~e Fraser River is c1lused pdr.tsrily by snowmelt runoff
<br />as evid~nced bv the fact that approximately 80 percent of the recorded
<br />peak annual flows at the USGS g"geon the Fraser Rive. (just do"nstream
<br />fn'", its confluence with Tenmile Creek) occured during the month of June.
<br />Snowmelt runoff flo<.>ding is the principal cause of flooding on the Fraser
<br />River both upstream IIlld downstream from the Tenmile Creek cOllflu"nce.
<br />
<br />BYdraulic Analysis
<br />
<br />A hydrological aMly"i" of flooMnc along Terunile Creek sho.'~ that
<br />its flooding is caused primarily by intense .ainsto.ws.
<br />
<br />I
<br />
<br />An analysi~ of the hyd.aulic characteristics of Fraser Rive. and
<br />Tenmile Creek "1)8 ;>Nformed by "'right ,,'ater Engineers, Inc. in o.der to
<br />determine wate. surface elevations for the lOO-yellr flood. Cross-section
<br />data wa~ t8ken from new 2' contour mapping prepared from recent aerial
<br />photos tak~n by Intrasearch. This cross-section data became input to the
<br />U.S. Army Corp~ of Engineers HEr...2 step~backwater computer program.
<br />
<br />Hydrol<JEicAnalysis
<br />
<br />A hydrological analysis of flows of
<br />"a~ perfo,med by Wright Water Engineers in
<br />Dev€!l<.>proent Company. A summary of peak
<br />~iven as follows,
<br />
<br />J:"raserRivcr and TenltlilcCrcek
<br />its report fo. Silvercreek
<br />flows &,d their fr~'lue~Cies is
<br />
<br />Rou8hlL"~s coefficients (M<lnning'~ "0" values) were also
<br />HI'C-2 input. Roug~n"ss values for Frase. River were 0.035
<br />Channel and 0.080 for the overbank areas. For Tenmile Creek these
<br />were 0.035 for the channel arca and 0.060 for t~c overbank areas.
<br />
<br />used as
<br />for the
<br />values
<br />
<br /> Recurrence interval
<br />Area dexription ~. SOvr. 100 yr" 'f/;'
<br /> cfsJ (ds) (efs) "
<br />fraserR. helu.,renmUeCr. confl. 1900 2000 J300 '4SO
<br />Fraser e. abover",,,ml1eCr. confl. 3000
<br />Tenmil..Cr. " itsmouth* 230 ,so 580 1100
<br />
<br />The
<br />(Plates 2
<br />tabulated
<br />
<br />corr.puted 100-year flood is outlined on the flooded
<br />to7), plotted on the flood profiles (Plates 8 to
<br />in the "C,oss-section Informntion" tables (iables 1 alld
<br />
<br />are"
<br />11),
<br />2).
<br />
<br />maps
<br />,,'
<br />
<br />Flooded Ar~as
<br />
<br />The areas co'"ered by the 100-year flood are ~h"Wll in Plates 2 to 4
<br />for the Fraser River and in Plates 5 to 7 for renmile Creek"
<br />
<br />.. Peak flo.'s for TCllmi~e Creek were actnllllv calculated for the
<br />1"._,~~ 1'"'" ,. 5""~~,~~o" 11_."."_..,,. r~mn~n"'~ ~~n~"~'" Be.C3es~
<br />_~,~. _M_~ _ ~-'""~. ._~.. ~.." ~ ...~..,- UVMe_"I ~ e'-e~~~/'
<br />U,.. 'lOutll of Ter.rnile Creek is less than 0.7 miles downstre"", from
<br />tl:epropertylirnit, the flo."scalculilted by 'lriHl-.t"""t,,r Engineees
<br />"~"..nri ~lly apply t~ the [l\(}uth "" w"U.
<br />
<br />,
<br />
<br />,
<br />
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