My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
FLOOD09933
CWCB
>
Floodplain Documents
>
Backfile
>
9001-10000
>
FLOOD09933
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
1/26/2010 10:11:09 AM
Creation date
10/5/2006 4:46:02 AM
Metadata
Fields
Template:
Floodplain Documents
County
Statewide
Basin
Statewide
Title
Engineering and Design Flood-Hydrograph Analyses and Computations
Date
8/31/1959
Prepared For
US
Prepared By
US Army Corps of Engineers
Floodplain - Doc Type
Educational/Technical/Reference Information
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
60
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
<br />e <br /> <br />. <br /> <br />. <br /> <br />e <br /> <br />. <br /> <br />" <br /> <br />e <br /> <br />EM 1l10--2,U05 <br />31 Aug 59 <br /> <br />C.640 <br />q.=- <br />I. <br /> <br />(3) <br /> <br />, 1..=t.+0.25(1.-I,) <br /> <br />(4) <br /> <br />640('. <br />qpR=- <br />t.. <br /> <br />(5) <br /> <br />qptp <br />qpR=-- <br />t.. <br /> <br />(5a) <br /> <br />Q.=q. A <br /> <br />(6) <br /> <br />c. The distance to the center of area may be taken as the mean distance off a cumulative area- <br />distance curve Of' estimated as the distance to the renter of gravity of the drainage area above a particular <br />station obtained in tllf' following manner: <br />Trace tbe outline of the drainage basin on a piece of cardboard and trim to shape. <br />Suspend the eardboard before a plumb-bob by means of a pin near the edge of the card- <br />board and draw a vertirallinl'. In a. similar manner, draw a second linr at approximately a 900 <br />angle to the first.. The intersection of the two lines is the center of gravit!T of the area. Transfer <br />the point to the original map for liSP in determining Lea. <br />d. Thr distance ['w is measured along the principal stream channel to a point approximately <br />opposit(l thr renter of area. Thr distance L is equal to Lea, plus the remaining distance to the upper <br />basin limit, following approximately the prineipal st.ream channel. <br />t. The average value of the product 640 C. is approximately 400, as determined by Snyder, for <br />basins in tlw fairly mountainous Appalachian Highlands, and the corresponding average value of <br />(1/ is 2.0. Analys('s of unit hydrographs for various sections of the country have indicated an extreme <br />range in values of 640 (1p and rr, of from 600 and 0.4, respectively, for southern California to 200 and 8.0, <br />respectively, for sectiolls of states bordering on the eastern Gulf of :\lexico. T f hydrologic records are <br />availa,hlr for a rrpresentative portion of the drainage area under study, or for nea.rb~r basins of similar <br />ehara('lpristies, the eoefficients 640 ('. and r', should be computed therefrom. Special field observations <br />to dptprmillp tile lag may be practicable and desirable in many cases. If the drainage area is formed <br />by two or morr important tributari{'s of different characteristics, unit hydrographs should qe computed <br />srparau.J,v for rach and thr f('sults combined to obtain a graph for the total area. Reference is made to <br />Snyd('I"s original papPI' 7 for additional details regarding thr derivation and use of the equations given <br />nbov('. <br /> <br />20. CONCENTRATION OF RUNOFF NEAR PEAK, a. A study of unit hydrographs for a large <br />nurnlH'1' of drainage basins has revealed an approximate relationship between the peak discharge rate <br />find tlIp \\:idth of unit bydrographs at ordinates exceeding approximately 50 pereent of the maximum. <br />R,'slIlts of till' stlldy are showll in plate Xo. 7. Curves Kos. W-50 and W~75 in plate No.7 were drawn <br />to pnvplop tllp majority of values of unit h:njrograph widths measured at discha~ge ordinates equal to <br />!)O llnd if> pprcput of tlH' peak ordinate, respectively, as obtained from the study of a large number <br />of ullit hydrographs for druinagf' basins of various configurations and runoff characteristics. <br />b. If j'('liable rainfull,runoff reeords are not available for deriving unit hydrographs for a particular <br />draillugp arra, CUI'VPS Nos. 'V-50 and 'V-75 of plate Xo. 7 may be used in determining conservative <br />widths for s,\'llthetic unit hydrographs having various peaks. III the event unit hydrograph data are <br />availahlp for r(>pres('lItative portions of a basin, und it is desired to modify such unit. hydrographs to <br />represrllt mol'P cOllsrrvativf' runoff ralf's, tll(> kno\vn width values may be plotted on plate No.7 and <br />CUI'V(,S appliCftble to the specific basin may be drawn through these points parallel to Curves Nos. 'V-50 <br />and ''''-7 f'l , as illustratrd by ('urYf'S A-A' and B~B', respedively. <br /> <br />11 <br />
The URL can be used to link to this page
Your browser does not support the video tag.