FLOOD07353

• County: Statewide
• Basin: Statewide
• Title: Hydraulic Engineering volume 2
• Date: 1/1/1994
• Prepared By: American Society of Civil Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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HYDRAULIC ENGINEERING '94

Table I, Radio-b'aCked sediment particle parameterS and navel distances.
Final Fmal Travel Tune Travel
Rock II B~axis Volume Mass SpGr Distance Duration Ve\ocily
(mm) (mI) (g) (10) (min) (mImin)
10 72 204 502 2.46 732 180 4,1
12 76 213 547 2.57 1065 270 3,9
13 84 242 593 2.45 m 200 . 5,0
14 71 232 601 2,59 686 170 4,0
15 80 235 602 2.56 796 185 4,3
16 76 278 718 2.58 713 175 4.1
17 86 303 728 2.40 347 215 1.6
18 82 299 763 2,55 357 125 2,9
19 77 312 803 2.57 562 160 3,5

signal to indicate whether the particle is at test or in motion, These particles, rocks 12
and 17, tefem:d to as the momtored rocks, were monitored continuously and the
duration of the test and motion periods wete recorded, The motion sensors used in
this study were built with a delay of 5 s, with the tesult that only test periods
exceeding 5 s were detected, Motion periods of less than 5 s were detected if foUOW<<!
by a detectable test period. Motion periods of 1 s or more were used in the analysis.

The radio. implanted rocks were placed in the stream at mid-channel. The initial
motion period of the monitored rocks was not included in the analysis; however, after
the first movement they were assumed to have become part of the natural movable boI.

Shvly Site

Phelan Creek is a glacier-fed river located on the north side of the Alaskan Rang'
in Interior Alaska, The study site was located approximately 1.6 Ian downstream of
the tenninus of Gulkana Glacier, at an elevation of 1125 m. The drainage area is 31
lan2, of which 70% is glaciated, This study was conducted on 17 August 1990 at a
discharge of 16 m3s- J, near the annual peak, Continuous monitoring lasted about 2
hr, while sediment b'aCking lasted about 4 hr, The entire tracking period took place OIl
the rising limb of the diurnal hydrograph. About midway through the monitoring
period, mean velocity for the stream cross section was 1.93 10 s-1 with a maximwn
mean (in a venical) velocity of 2,82 10 s-I at a total depth of 0.73 10,

The study reach was about 1000 10 in length with an average gradient ofO.OS
milO, The size of the tracked rocks (b-axis diameter hetween 66 and 86 mm, Tabk
I), falls hetween the D50 and D65 of the bed material as determined by the pebble
count method (Wolman, 1954) on a shon reach within the study reach. At the time of
the study, the stream was capable of easily transporting material in this size range; in
fact, much larger material was in transpon, as evidenced by the sound of boulders
frequently heard roUing in the stream. The data collected in this study are intended 10
show the characteristics of movemeDl of coarse bedload in the size range well below
the maximum size the stream is capable of transporting,

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Describing sediment transpon as a setics of motion and rest periods of the
individual sediment particles was proposed by Einstein (1950), Ergenzinger and

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MONITORING GRAVEL MOVEMENT

Schmidt (1990), using a radio tracking tecbuique, made the fim Ii ld
''''p length, distance lraveled during the motion period, and n: t e.od ~ts of
lhi, study, we utilized the motion sensor installed with the ~ pen , 1II1ll1on, In
measure 18 and 29 pairs of motion and rest ' ods ~ th tran~tters to
IINo-hour monitoring period. The length of:tion or, e two mOllltored rocks over a
bolh rocks, although most were less tlUIO 20 s In =ods ran14 fium 110 190 s for
periuds :o'ere variable and a single, long resl ~ acco:;.~ ~ e engthhalfs of n:sl
monllonng bme The actual pen:enta f . or over the IOtal
forrockl7 and i7,1% for rack 12 ,eodis~ll1ebuthl1O,enrockof s W~lnand' motion Was 4,3%
L..' era! th .. ' u, motJon resl periods 'ed
~I, In gen ,e majortly of the motion periods OCC'_.' di' , van
,^" IS ted by , ~'OU 10 SbllCl epIsodes of
n~on even . sel"l1'!' relaovely long rest periods (Fi I) Abou '
lhe total Orne 10 mooon of rock 17 OCCIIITed in one ' g, 'sode,' ! two-thirds of
movement o( rock 12 occlllTed in four distinct e ' monoo epl while the.
vanable length (Fig, 1), These data suggesl truJ'~:gr~condiby ~st periodlha s of
easoly transpun the material size once the rocks ' , v), twns t could
10 motion (or e,reoded Il1Otion ePisodes, were pUI m monon they tended to stay

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Rock '17

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':"J200-
is 1000
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Roct 112

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2000 4000 C5000 1000 0 0
TOTAL SAMPLING 11MB (s) ~ 4000 6000 aooo
F' ,v,ALSAMPUNG 11MI!~)
19ore 1. Penods of motion and rest for monitored k
roc s.
Travel distances were measured twice tl
,he moniloring period crable 2) Th arrock 12 and ~ for rock 17 during
10 " '. The average ",,"spun v~loci e a~erage ",,"sport velOClnes were 0,36 and 0.50
."'on episodes and 0 5110 s-1 for Iy 0 rock!2 was 0.25 10 s-I after the fll'St three
kknlical to lhat of rock 17, where ~ ~:fu!'I~ (Fig" I), The lalle~ value is nearly
l:'Jl1sodc. The b'anSport velocities nl()(t()n penods occtuTed m one motion
measured by Schmid. and Ergen';;~~) Phe: Oeek are ~parable to those
\-c1ncilies of 0.50 m 5-1 Th .' w reponed maxunum transpon
_imum average wa~ vel~:=';:':d"Y of26~,50fm s-I was 18% of the
\'c1ocuy. or -/0 0 the average cross-sectional

'n Ihis slOOy, only mean ste length
''''<I distances, the rocks had.Jill s were measured crable 2), For similar
.'"mes the grain diamerer c~ % mean step Ieng!hs of 5,9 and 7,8 Ill, or 77 and
by hostein (1950). Howe~er in a~O- e ~a1ue ,!f 100 IIlIlCS the grain diameter asSUmed
Ilcp' for a mean step length of 84,3 10 IUJ~ pen~ rock 12l1'!'veJ.ed 253 10 in three
In. mean step length of 13,7 10 or 181d II~ tuneS.the.gnnn diameter, Thisresulted
'ho", "'JlOl1ed by Schmidt and Ergenzin;;:(I99!J:'" diameter, values similar to
The distribution of the d ti '
f/t,juc:ncy of shon duration resrura "." of ~t penods is '!ig~y skewed with a high
In upooential function (Einste:,mo:s (yFtg, 2). The distribunon can he described by
, ,angandSayre, 1971), ThePheIanCreei<

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