RODNEY D. ZIMMERMAN, B.Sc.(C.8.), P.Eng

TITE UNIVERSIlY OF MANITOBA

RBGTME CONSEQUENCES OF lHE

ASSINIBOINE RIVER DIVERSION

RODNEY D. ZIMMERMAN, B.Sc.(C.8.), P.Eng.

A THESIS

SUBMIÎTED TO TIIE FACULTY OF GRADUATE STUDIES

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR THE DEGREE OF

MASTER OF SCIENCE

DEPARTMENT OF CIVIL ENGÏNEERING

I,íINNIPEG, MANTTOBA ocToBER, l.975 "REGIME C0NSEQUENCES 0F THE

ASSINIBOINE RIVEP. DIVERSION"

by RODNEY D. ZIMMER}4AN

A dissertation submitted to the Faculty of Graduate Studies of the University of Manitobu in purtilt fulfillment of the requirements of the rlegree of

MASTER OF SCIENCE

'.'''.'

@ 1975

Pernrission has bec¡r gratrtctl to the LIBRARY OIr TtlD UNIVUR- SITY OF MANITOIIA to lond or scll copies of this dissertatio¡r' to the NATIONAL LIBRARY OF CANAI)A to nticrolÌlm this ¡lissertatiolr and to lend or sell copies of the film, und UNIVERSITY MICROFILMS to publish an ubstruct of this dissertttion.

The autltor reserves other publicution rights, and neitlrer the dissertation nor extensivc cxtracts t'runr it tttay be printed or otlrer' wise'reproduced without tttc autltor's writtc¡r penrtissiotr.

æ OF frÁANIfOBA ttl

AB STRACT

Key words - (Assinlboíne RÍver, diversíon, regÍme,

degradation, quantltatlve fluviaL morphoLogy) .

Usíng Blenchrs ernpiríca1-Ly deduced modified regírne theory equatlons, an atËempt is made to quantífy predicted changes in the reach of the Assinlboíne River downstream of the diversion at Portage l-a Prairíe. Ttrese errpíríeal equations have been used because the conditions of the channels thaË províded data for the regime equations are similar to the conditÍons found in the AssíniboÍne Ríver channel

dornmstream of the Portage Díversion and because Bl-enchrs system appeared to provide the widest choice of relationships to be uËilized in an attempted quanËit,atíve prediction of this kínd. IË is estimaËed the ul-tinate depth of degradation ínnnêdiatel-y downstream of the díver-

síon síte will be about Ëhree feet in a period of about 30 years and

the downstream extent of degradatÍon wí11- be approximatel-y 20 míl-es. Also, ímmediately downstream of the diverslon site, the mean channel wídth is anticipated Ëo increase up to 2O%, the meair depËh is expected

to decrease about 57", and the mean veloc1Èy ís expected to decrèase about L5%. Howeverr the quantitative est,ímates of increased channel width, decreased depËh, and decreased velocíty are subjecÈ to doubt due to theír compuÈatíon being extremely sensitive to error propagation. .It should be noted Éhat these resul-ts are theoretical.maximums because ín the analysis, no account has been taken of the sediment sup-

plied to the dornrnstream reach by the l-3-fooË conduít under the dam. Lv

Unfortunately, no information regarding the effect of this conduit on sedíment supply was available at Èhe tíme of the study. AC I(NOI4tLEDGEMEN TS

To Dr. V.J. GaLay, my thesis advísor, I should like to express my sincere apprecíation; hís teachfngä and encouragement greatly eased the preparatíon of this thesls.

I should also 1íke to thank Prof. C. Booy and G.H. MacKay for their most helpful suggestions and comments.

Special acknor¿ledgements are due to the staff of the llater Resources Branch of the Department of Mínes, Resources and Environ- mental Management, Province of Manitoba, and Èo the Prairie Farm

Rehabílltation AdminÍstration, Manítoba Divísion, Governnent of Canada, for providíng the bul-k of the data required for this invesËigation. \ri

PREFACE

Regime. The noun t'regímet' applied to a channel or channel reach, ís analogous to "clímate" sínce it implies a behavíour that is apprecíated in terrs of mæry fl-uctuatíng factors whose average val-ues, over a sufficíenÈ period, are eíther steady or change rel-atively slow- 1y. Such a slor¿ change ís call-ed "seculartt (Latin, saeculum, age, span of Ëine). The rnínd finds no dífficulty in visualizíng a climaÈe or a regíme as a relatively steady state of large erretic fluctuationst though staÈistical technical-ítíes are involved in defining, exactly, "a sufficient period" and "a secularly changing mean". THE I'{ORLD BooK

DICTIONARY (1-963) defines ttclímate'r (Greek, Klinein, to incline) as ttthe kind of weather over a period of years, based on condítions of heat and coJ-d, moísture and dryness, clearness and cloudiness, wind and calm....tt. So t'regimett may be defíned as ttthe behaviour of a chan- ¡el , over a períod, based on conditlons of l^tater and sediment díscharge, breadth, depth, slope, meander form and progress, bar movement, etc..". Unconventional-ly, but descriptiveLy, iË could be called "the clímate of a channel-tt.

T. Bl-ench, L969. vfL

TABLE OF CONTENTS

page

Titl-e Page i

Approval Sheet l_ l- Abstract ííi

Acknowledgements .v

Preface vi

Table of ConËents Yii List of Tables viíl List of Figures íx

Symbols x

CHAPTER 1. INTRODUCTION 1

CHAPTER 2. THE DOI.]NSTREAM REACÌT 6 2.1- Discharge 6 t ,, 2.2 Sediment TransPorË 11 2.3 Channel- Prof il-e 15

2.4 Channel GeomeËry 22

CHAPTER 3. SUMMARY AND CONCLUSIONS 26

LIST OF RNFEPiENCE 28

APPENDIX A - MODIFIED REGIME THEORY EQ.UATIONS 30 '"

: i:'

v11f

LIST OF TABLES

page

1. Discharge Summary 10

2. Summary of I97L Bed-Material- Sampling 13 3. Comparison of Degraded Profile Estimates 18 1x

LIST OF FIGURES

1. Assíniboíne River Draínage Basin

2. Illustration of Diversion Consequences ,1. 3. Portage Díversion InleË trIorks '4. The Downstream Reach

5. Schematíc Representatíon of River Investigatíons Program . 6. Assíniboíne River Gauging Stations ín the Vicinlty of the Portage Diversíon

,, 7. Flood Frequency Curves

8. Hydrograph of Mean Monthly Flows

: J. Duration Curves of Mean Monthly Flor¡s 10. Rating Curve - Assiniboíne River near Portage la Prairie 11-. trIash Bore Logs and Properties of Bed-Material

' 'L2. Suspended Sediment Concentratíon

l 1-3. Sedíment Transport Rating Curve

Sedíment TransporË Duration Curves i ,I4. I 15. Ultímate Channel Degradation ',;, L6. Tlme Required for Ul-Èímate Degradation , L7. The Downstream Lirnit of Channel Degradatlon LB. Lrlater Surface Profíles - The Downstream Reach 19. Bankfull Profile - Portage l-a Prairie to Headingley 20. Mean Cross-secËion vs. Discharge Curves

2L. Hydraulíc Roughness Profil-e 22. Longitudinal- Profile of the Assiníboíne RÍver SYMBOL S

Unless other:vrise specified ín the text: A ís cross-sectional area (ft.2) C ís sedíment charge (parËs per 100'000) FU ís the bed-factor Fbo is the zero bed-factor Fs is the side factor K ís a coefficient L is ]-ength (ft., míl-es) a is discharge (cfs) S,Sc, etc.is slope (tt.lft) T is mean annual bed-l-oad transport (tons/day, acre-fË. /year)

V is mean velocity or volume of sedíment b ís channel r¡idth (ft.) r d Ís mean depËh (ft. )

d"^ is the sediment size (díameter in rmn.) at r¿hich 5O7" of the Jv sample is srnaller bY weight

ds ís depth of degradation (ft. ) f(c) is the bed-material l-oad transport function g is acceleratíon due to gravíty (32.2 f.t./sec.2) k is a meander correctíon coeffÍcíent n is Manningts n

q Ís discharge per foot width (cfslft. ) o is sËandard deviatíon v is kinematic viscosity CHAPTER 1

INTRODUCT ION

It ís only ín recent years Ëhat major engineeríng works have been constructed on the Assíniboine River. These works ínclude dykes placed do$mstream of Portage la Prairie over the lasË 50 years, the

Shel-lmouth Dam constructed in L968, and the Portage Diversion built in L969. The object of their construction is the all-eviatíon of spring flooding along the Assiniboine Valley and at l^Iinnípeg. As a síde effect the díversion and storage works cause changes in Ëhe riverfs natural regime; flows are now regulated and sediment travel in the river channel- is interrupted by the reservoirs and structures. In addition, the dykes downsËream of Portage la Prairie have altered the sediment transport capabilíty of that reach of the ríver.

A mean or average elevatíon of the bed of a ríver channel is maintained over a period of tíme because the lnflow of sedimenË Ëo the reach equals the ouÈflor¡. The purpose of this report is to present a description of the Assl-niboine River immedíate1-y downstream of the PorÈage Díversíon, to coÍment on lts present state, and assess quanti- tatívely the expected changes due to the dísruption of sediment fl-ow. Perhaps the best sunmaïy descriptíon of the Portage Diversion ís to be found in a pamphlet pubi-íshed by the Prairíe Farm Rehabilita- tíon Administratíon, Government of Canada, and the l{ater Resources

Branch, Province of Manítoba, during construction of the diversion aÈ Portage la Prairie and the ShellmouËh Dam near Russell. This descrip-

tíon Ís reproduced below:

''PoRTAGE DIvERSION A reservoir coveríng 1r610 acres r¡ith a storage capacity of L41600 acre-feet ís being created by the construction of an earËhfíll dam 1,400 feeË l-ong, and rísíng 35 feet above the bed of the Assiniboine River. A concrete spillway control st,ructure equipped with two Bascule fish-bell-y type gates, 13 feet by 75 feet in size, is Located on the south side of the darn. These gates are the largesË of their Ëype 'in North America. Also located ín this strucËure is a low-level gate-controlled' riparÍan outlet conduit. North and west of the dam aÈ the upper end of the diversíon channel, an inlet control structure regulated Èhe flow to Lake ManiÈoba. ThÍs ís accomplíshed by the use of four vertical lift gates each measuríng L44 feet by 40 feet. The díversion channel is designed to carry a fl-ow of up to 25,000 cubic feet per second. As the Portage DiversÍon ís an unlined channel-, ít was nec- essary to construcË it Ín such a Í¡ray as to keep water velocitÍes below those which would cause erosion. trrrhen Èhe diversion reservoir is ful-J-, there ís a drop of 50 feet be- 'tween the diversion channel inlet and the Level- of Lake ManÍtoba, over a rei-ativel-y short distance of 18 miles. To I keep velocities down to about. 34 feet per second, three drop structures along the diversion route are íncorporated into the desígn. The channel has widths varying from 175 feeË to 11200 feet, wlth an average width of 600 feet. The greaËer width is through the Delta Marsh area adjacent to the lake. Dykes have been built along the entire J-ength of the channel usíng much of the i-0r000r000 cublc yards of excavated mater- íal. The desígn depth of r,¡ater above the surroundlng terrain will general-ly be equal to the ground r^rater level when the channel is operating at peak discharge.tt

FIGURE 3 oresents a sÍte plan of the intake works.

!{hen constructíon of a combíned dam and diversion structure for f1-ood-control- purposes such as at Portage l-a Praírie Ls undert.aken, two changes are ÍmmedÍate1-y ímposed upon the dor,rnst,ream reach. These ímposed changes ate as fol-l-or.rs: 1. ï.Iater flor¿ a. peak flows are reduced. b. mean flow is reduced due to diversi-on and reservoir losses.

c. lor¿ flows may be íncreased somewhat depending upon storage characterístics and operation of the reservoir.

2. Sedíment flow a. structure bl-ocks bed-load transport in the natural

channeL.

b. reduced \^rater velocitíes ín the reservoir allor¿s sus-

pended parÈicles to settle. The Ínlet works r^rere so designed that the diverted flow wil-l- be as sediment- free as possíble to prevent depositíon in the diversíon channel.

Due to the nature of the Portage Diversion system, the i-mposed blockage of sediment flow is Ëemporary; that is, when the reservoír compleËel-y f 111-s with sediment, the bed-material l-oad will be passed over the diverslon splllway and sedlment supply to the dor,rnstream reach wll-l be restored as wel-l- as Èhe'origl-nal- dor.mstream slope. FIGURE 2 illus- trates the above-mentioned changes.

IË ís very imporËanü to note thaË some sediment supply wí11- be avaílable to Ëhe dor^nstream reach through the l-3 by l3-foot low l-evel outlet conduit under the dam. Due t,o a lack of data, no account of this supply is made ín the following analysis. As a consequence of the above imposed changes, oan.t parameters of the riverts regime are subject to change. These Parameters and the expected consequent changes (Galay, L966) arez

1. The most signifícanË change ín the downsÈrea¡n reach ís its expected degradatíon and flattening of the rÍverfs profíle

when the sedíment fLow is interrupted.

2. The mean channel width f.or a speeified discharge is expected to be reduced. Channel width varies dírectly with the square root of discharge (¡*/î- ); with a decrease in mean díscharge due to the operation of the diversion the mean channel wídth will decrease.

3. The water surface elevation for a specifíed dl-scharge is expected to be lowered due to degradation of the channel bed.

probably be r- , 4. The mean depth fot a specífled díscharge would increased, however, thís is noË certain and requíres verifica- tion.

5. Mean velocity at a specified dlscharge ls expecËed to be reduced wlth a possíble íncrease ín cross-sectional area.

6. Ilydraulic roughness is expected Ëo increase r,¡Íth the "sorÈing" effect of degradatíon. Unfort,unately, no informatíon regarding bed configuration was collected ín the field studíes.

7. The consequences of diversion upon channel- pattern ís unknom. 8. The rate of lateral shíft of the channel is expected to be reduced wíËh the reduction in mean discharge.

In the following chapËers the imposed changes are described more fully and consequent changes investigated with a view of assess- Íng thern quantítatively.

For the analysis used in this particular thesís, the "modífíed regime theory" equations advanced by Blench (L966, L969) are uÈilized.

It should be recognized that there are limitations to the use of the empirícally deduced equatíons of regime Ëheory; but, for the sand-bed channel of the AssiniboÍne Ríver dor^mstream of the Portage Diversíon, Ëhe condítions of this natural channel and Ëhe natural- and artificial- channels used to determíne the regime Êheory relationships are consÍd- ered sufficíently similar to warrant use of these relationships in attempting quantitative predictions . CHAPTER 2

THE DOI^INSTREAM REACI{

2.L Discharge There are four hydrometric gauges operated by the !üater Survey of Canada ín the vícínity of the Portage Diversíon. FIGURE6 shows' in schemat,íc, the relationship of the gauges to the diversfon system. The gauges are:

1. Assíniboíne River at Portage la Prairie Draínage Area: approximately 6211-40 square mil-es Records Begin: 1923 (not continuous) Mean Discharge: (16 years) L'800 cfs Extremes Recorded: Maxímum daíly díscharge 321000 cfs on April 2I, L974. Minirnurn daily discharge 25 cfs, January 2L, 1-963) (Oischarge partially regulated by reservoirs on trlbutaríes)

2. Assiniboíne River Díversion near Portage l-a PrairÍe Records Begin: APril 1-9' I97O

3. Assíniboíne River near Rossendale Drainage Area: approximateLy 621100 square miles Records Begin: L97O

4. Assiniboine Ríver near Holl-and Draínage Area: approximately 61'980 square miles Records Begin: L954

The pre-diversíon' or natural flow conditions' as well as estimated post-diversion condítions are summarized in TABLE 1. At Ëhis J point in tíme, the estimates frequency curve for post-dÍversion flows

(FIGIIRE 7) can only be considered as a best guess esËimate based on avail-abl-e informatíon.

The mean monthly fl-ow-duration estimates (FIGURE 9), however, may be consídered reasonably re1-iab1-e. These were prepared by the

Water Resources Branch assumíng the following defíned flow conditions: l-. Past - This shows the fl-ow patËern that existed for the period of record L92L to L964 as recorded by Èhe Water Survey of Canada. Miss- ing records have been reconstructed by the Prairie Províncest Ï,{ater. Board. The l,later Resources Branch has adjusted these fl-orrs elimínating the regulatory effects of the Rivers Reservoír. 2. Present - This condiËíon represents the operation of Shellmouth and Rivers reservoirs for both flood control- and water suppl-y. The fl-ood-control aspect involves drarnrl-ng down ShelLmouth Reservoir from a normal líve storage of 290r000 acre-feet, Ln November, to 1501000 acre- ,feet by the end of March. The water-supply aspect Lnvolves guarantee- ing a minimum fLow of 300 cfs at Brandon and 50 cfs at Portage la Praírie. These are arbftrary mínimum fl-or¡s beÍng wel-L in excess of existing demands at these locatíons. In addition, íf requíred, htater is assumed to be diverted via the Portage Díversion to the Delta Marsh and to Lake Manitoba provided that the flor¿ at Portage la Prairíe is ín excess of 800 cfs. 3. Future - This conditíons represents the demands as envisioned in 10 to 20 years with flood control- and conservatíon storage in the Assíníboine Basín as for item 2 above. However, the minímum flows at Brandon and Portage la Praíríe have been decreased to 2O7 cfs and 31 cfs respectíve1-y. These flows are based on providíng the future ther- m¿l and municipal díl-ution requirements at Brandon and PorËage la Prairie. In additíon, rninimum flows of 50 cfs and 880 cfs have been guaranteed f.or the Assiniboine River at Headingly and the Red River at tr'linnipeg respectively. Also, iË has been assumed that 10r000 acres would be írrígated from Èhe Assiniboine River in the AssinÍboíne River

Valley flats above PorËage 1-a Prairie, l-0'000 acres in the Portage la Prairíe area, and 101000 acres Ín the Morden-VIinkler atea. To satísfy these lncreased demands, it has been assumed that a díverslon frorn the

South Saskatchewan River at Lake Diefenbaker via the QurAppelle River System, having a capacity of 225 cfs, wou1d be available to meet

Manítobafs needs. The bankfuLl discharge determíned at different sections of the reach, under consíderatlon varies betvreen 12'000 and 13'000 cfs. At ,¡hÍs discharge, Ëhe river overtops the natural l-evees formed along the banks and spí1-1-s over to flood the lower prairle l-evel. Any fl-ows ex- ceedÍng thÍs overtop Èhe river banks and are Lost for channel-forming purposes. Therefore, the bankful-l- discharge would be consLdered to be the "dominant díscharge", that ls, the constant discharge equival-ent, for channel-forming purposes, of the variabl-e ríver flow.1'2 The con- strucËion of dykes a1-ong the reach compllcates this assumption.

1 Henderson, F.Yt., L966, p.464 2 B1-ench, T., L966, p.54.."It, is to be noted there ís no obvíous reason to expect an equivalent uníform discharge cal-cul-ated from one pheno- menon - for example, meander formatíon - to be exactly the same as from another such as sel-f-adjustment of s1ope." 9

Considering the dykes as banks of the river, albeLt arttfícial, the new or attj:fJ:cial bankfull díscharge is of the order of 221500 cfs. Thí.s díscharge event ís considered too infrequent (9"Å natural- condítlons,

0.L3"Á post-diversion conditions) for use as a domÍnant díscharge.

A domÍnant díscharge Ì¡tas calculated using the ttsedímenÈ moment approach" ouËLlned by Komura (L968). This nethod employs both the duration relatíonshíp of discharge and the duration relationship of sedíment transported in calculating a dominant díscharge. Data from the duratíon curve of mean monthly flows, FIGIIP.E 9, and the sedímenË transport ratíng curve, FIGURE 1-3, was used in the courputatíon. The calculated dominant díscharges r^rere for natural- conditions and for future conditions, 12,000 cfs and l-11800 cfs respectÍveLy. 10

TABLE 1

Díscharge Sumnary AssíniboÍne Ríver at Portage la Prairie (Period of Record L92L-I964)

Post-Diversion Natural Conditions Condítions

Probabil-íty Probabil-ity of of Díscharge Discharge Exceedence Exceedence l_n any year in any year (cfs) a/ (cfs) of mean flow 1,650 1, 380 flow at whích mean annual sediment 2, 100 l-,800 transport occurs mean annual flood 11 ,000 40 B,000 40 natural bank- fuLl L2,50O 32 L2,500 25 artificíal- 22,50O 22,500 13 bankfull- dominant discharge (com- 12, 100 34 11,800 28 puted)

1: 10 21,500 l0 8,800 10 1-:100 42,500 l- 9,6oo 1 11

2.2 SedimenË Transport

As can be seen from TABLE 2, Summary of 1971 Bed-Material

Sampl-ing, and FIGURE l-L, Wash Bore Logs, the bed and bank material of the channel is composed mainly of sands in the fine to coarse ranges. It appears from the wash bore data the sand bed-material is a thín veneer overlaying a stíff dark grey clay.

Measurements of the suspended sediment load at Portage 1-a

Praírie for Ëhe period L956 to 1968 rnrere used to determine Ëhe Total

Sedirnent Transport RatÍng Curve of FIGIIRX l-3. The Ëotal sediment load ín a river channel- consísts of a number of components transported ín dífferíng mod.es; these components are lllustrated belotr:

IAIAS11 I¡AD

TOTAL TOTAL SEDII,IENT SUSPENDED LOAD LOAD BED-MATERIAI _flMATERIAL LOAD L.AD t- BED-L.AD 'i. Ttie relationshíp between total suspended load and discharge was increased by L5% to account for the small amount of sediment that cannot be caughË by the suspended maÈerial sampler (LO%) and the bed-load (assumed to be siÒ.I The Total Sedíment TransporÈ RatÍng Curve was then used with the fl-ow duration curves of FIGURE 9 Ëo consÈruct the

Kuiper and Galay , L97L, p.48 . 'rAn investigation of various sed- íment statíons throughouË Ëhe (Saskatchewan-Nel-son) basin indÍcated thaË the measured load varied from 4% to L5% and l-0% was chosen as be- íng representative. Computations of bed-l-oad using the Eínstein bed- l-oad funcËíon and the Meyer-PeËer and Muller equat,ion indicaÈed thaË the bed-load varied from 3% to 6i4 of. the measured suspended load and a value of. 5% hlâs adoP¿sd.rr L2

I SedimenË TransporË Duration Curves for the Assíniboine Ríver at Portage la Prairie, FIGURE 14.

The total mean annual sediment transported at Portage la Prairíe was calculated as being, for natural conditions, 485 acre-feet per year; for present conditions, 4O9 acre-feet per yeat', and for future conditions, 372 acre-feet per year. Prior Èo constructíon of the PorËage Díversion, this sedíment passed through the reach. Now, r¡íth the fLood-cont,rol r¿orks in pl-ace and operatÍonal-, thís sediment is trapped by the reservoir. Near sediment-free r¡rater is released to the díversion channel duríng high flow periods and to the natural channel year-round. This condíËion wil-l- conÈínue until the reservoir is completely fi1-J-ed. As mentioned prev- iously, the Portage DÍversíon has a storage capacÍty of approximaÈel-y

L41600 acre-feeË. From the sediment transport duraËion curve (natural conditíons - upstream of Portage l-a Pral-rLe ) on FIGURE 14' Èhe mean ,annual- amount of material to be deposl-ted l-n the reservolr r¿ouLd be Ln the order of 485 acre-feet per year. Using these data, the reservoÍr ís estlmated to be fílled in 30 years. During thÍs perl-od of reservoir fÍlling, the near sediment-free water released to the natural- channel wlll "plck up" sediment approximating the load trapped by the dam and cause a flattening of the downstream profil-e by a degrading of that reach. This l-oss of material would presenËly appear to average about l-10 tons per day, or about 20.5 acre-feet per year' using 5% of t1:'e present mean annual sediment transport. Over 30 yearsr this total-s a loss of abouÈ 6l-5 acre-feet of bed-material ín the reach downstream of 13

the dan. The lengËh of reach fron which this sedíment can be expecËed to be removed and the estimated depth of degradation will be discussed in the following section.

I^Ihen the reservoír fíL1ing is completed, and the sediment, fl-ow is restored t.o the downstream reach, the process of degradation wil-l- cease. As the diversíon contínues to operate, deposition of sedíment will occur boËh upsËream and downstream of the dlversion point. The amounË of deposition wll-1 depend upon the quantíties of near sediment- free water diverted from Ëhe natural river channel Èo the díversion channel during the flood condítíons.

Using Ëhe natural mean annual- bed-load transport, Tn = 24.25 acre-feeË per year, and the present mean annual- bed-load transport' 1_ 2O.5 acre-feeË per year, and subtractíng indlcat,es abouÈ 3.75 acre- p = feeË per year of bed materlal could be expected to be deposíted in the vicinity of the diversíon af.ter the completlon of reservoir fil-ling. That Ls, assuming the downstream reach is competent enough to transport t. the presenÈ mean annual bed-l-oad with l-Ès degraded profJ.le. It 1s more

J.ike1-y thaË greater amounËs of material would be deposlted, especÍally dor¡nstream of the díversion, immediateLy after the lnÍttal- reservolr ' ' fil-ling and degradaËion phase. '' '

As sediment is irot conveniently.measured as a volume, Ëhe proportionate discharge of sedimenÈ in Èhe water-sediment compl-ex ís expressed for use ín the regíme equations as a ratío of weight discharges. The ttcharge" of any portíon of the sedíment load (e.g., bed-load charge) is defined as the weight (in air) of that portíon of the sediment flow ¿ per second, diwíded by the weight of the rúater flola per second.

The bed-load charge (C) at Q = 2rL00 cfs, the dLscharge at whLch

ñean annual- sedíment transport occurs under natural condítlons, was calculated as being equal- to 2.3 parts per 1-00'000 by weÍghË. Using

Blenchts relationships (L966, FIGURE 7.2) tl:.e bed-materlal l-oad trans- porË functíons tI("), fIl(c) and flli(c) equal L.26, L.29 and I.32 respectívely for C = 2.3 parts per 1001000. I,líth constructfon of the diversion structure, the bed-load charge (C) w111 Ëend to zeto, As C tends to zero, f(c) wili tend to 1.0, and the zero bed-facËor (FUo), wÍIl equal to the val-ue for the bed-factor (Ft), (see EQUATION 4.9).

TABLE 2

Summary of. L97L Bed-material Sampling AssiniboLne River at Portage la PrairLe

Síze - % Finer by I{elght

dr e dsO de+ dgo flÍn. mm. fltrn. mm.

L97I Data ar xs-l .33 ,42 ,79 .97

mean of XS-l, 2 and 3 .4 4.9 4.9 6.2

mean of reach XS-l to 15I .34 .63 1. I 3. 0

I SËandard devíatíon (o) equal- to 0.66 nrn. 15

2.3 Channel Profíle In attempËing to predict an ul-timate degraded profile and the downstream extenË of degradation, the most importanË factors to con- sider are the type of materíal forming the bed of the channel and the depth of this materíal. The range of sÍzes of the bed-maËerial dic- tates whether an ul-tímate degraded profíle r¿il-l- be achÍeved by a reduction of the s1-ope (and consequently a reduction in sediment transporting capabílity) or by forming an "armourrr protection of the bed (Komura and Símons, L967) InvesËigation of the bed-maËerÍal- indicated an insufficíent fraction of coarse partícles for an armouring of the bed t.o occur; that is, it was found, usíng Shiel-ds' Díagram, virtually all the material- formíng the bed was capable of being transported by the expected díscharges. In the vicíníty of cross-secËíon 1, however, referríng to the wash-bore logs of FIGURE 11., one foot bel-ow the present thalweg elevatíon enough coarse materíal may be found to províde some protection agaínst further degradation in the viciniËy of that cross-section. Fol-lowl-ng are two methods of cal-culatíng the degraded profíj-e and extent of degradation belor¡ dams; they are the stable-slope approach, and the protoËype approach.

The stable-slope approach: the stable-sIope approach (USBR,

L963) of predictíng Ëhe degraded profile assunes Ëhe characËer of the bed-material- does noË change as degradation progresses (í.e., the amount of coarse, material in the bed is negl-igible) and that Ëhe depth of the bed-materíal is greater than the expected degradatíon. t6

Computation of a stable-sl-ope using Blenchr" t.rt*. sJ-ope for- mula follows: kF-^11lr2fLi1 (c) Þ-DO = ------= (A.5) c ç6r/øQt/tz hlhere is the computed stable slope S_c k ís the meander correction coefficient, approximately

equal to L.62 (found by solvíng EQUATION 4.3 with s = 1.9 x l-0-a, Fbo = 0.785, Fs = 0.036, t1(.) = L.26,

Q = 211-00 cfs, and K = 11900). Fbo is Blenchts zero bed-factor, equal to 0.785 (see fol-Low- íng section). ttll(c) is the bed-material load transport function, equal to

1.0 as bed-load becomes vanishingLy small-. K is a constant equal- to 3.63/v Ll4, where v is kínematic

viscosity and g is accel-eratíon due to gravíty. (t< =

,¡ 1,900)

b is the channel widLh, 24O feet (FIGURE 20). Q is Ëhe discharge (1,800 cfs) at whlch mean annual sedí- ment transport is expected Ëo occur under post-dlverslon condítions. Solvíng the equation yields a stable-slope of 1.45 x 10-a feet per foot. The average slope over the length of channel- (FIGURE l-9) dornrnstream of the diversíon is 1.9 x 10-a feet per fooË. This gives a difference (AS) of 0.45 x 10-a feet per foot between Ëhe computed stable-slope and Ëhe exístíng slope L7

It can be seen that the computatíon of a sËable-slope using

EQUATION 4.5 ís relativel-y insensitive to errors ln the selection of ¡¿idth (b) and discharge (Q). In the equaËÍon, the sixth root of width and the twelfth rooË of díscharge are used thereby virtually elimÍna- ting practical- errox on their account.

Cornbining the maxímum length of degradation (1-00 miles Ëo con- fluence wíth Red River), the mean channel width (b = 240 feet) ' and _L ftS = 0'.45 x 10-q feet per foot, with Ëhe fol-lowíng two equatlons (USBR, Lg6Ð will yíe1-d the expected depth of degradaËíon at, the dam (d^) an¿ the expected volume of sediment (V) removed.

d2= 64 VÄS S 39 b (2.1)

_13 ds and L= T Ãl (2.2)

Solvíng EQUATION 2.2 yields an ultimate depth of degradation (d-)'s' of 15 feet. So1-víng EQUATÏON 2.1 then ytelds Y = 702.3 x l-06 cubic feet = L6rL20 acre-feet. At a mean rate of 20.5 acre-feet per year' it, r¡ould take 786 years to achieve thls degradation. In 30 years, the loss woul-d total- 615 acre-feet of bed- materfal. Solving EQUATION 2.1 wiËh V - 615 acre-feet ytel-ds d" = 2.9 feet. The length of reach degraded (L) then equals 105'000 feeË or 19.8 nrÍles. 18

TABLE 3

Comparison of Degraded Profile Estimates

Stable-Slope Prototype Prototype Approach Approach Approach Q=l'800 cfs Q=4,500 cfs Q=l,800 cfs

at degradation 2.9 feeË 18 feet 9 feet dam

tíme of degrada- years 6.6 years 2.8 yeaxs tion 30

length of de- 105,000 feet 48,000 feet 24,000 feel graded reach

The proËotype approach: a prototype approach (Priest and Shin- dala, L969) to degradation below dams based on laboratory data and fíeld data from Fort RandalJ-, Fort Peck and Hoover dams in the United S¿ates, ís currently used by some agencíes in thaÈ counËry. The dimen- sÍonless parameters representing the functíons and their rel-atlonships are presented on FIGUBES 15, 16, and 17. Applying these relatfonships to Èhe downstream reach yl-elds a predícted degradatíon at the darn of about l-8 feet with the required time beíng 6.6 years and the ultimate length of the degraded reach be- j:ng 46,800 feet. The Assíniboine River discharge which would be Ëhe equívalent of those used ín the construcËion of this relationship (mean annual mean monthly peak) was estímated as 4'500 cfs.

Applying Éhese relationshíps usíng Q = 1,800 cfs, the flo\^7 at which mean annual sedíment transport is expected üo occur under post- díversion condíËions, yields a predicted degradation at the dam of L9

about nine feet wÍth the requíred time beÍng 2.8 years ånd the ultimate length of the degraded reach being 24,O00 feet. It can easil-y be seen that a predícted degradation of the extent calcul-ated by the prototype approach, as Ít presently exisÈs, would require a rate of removal of bed-material- far in excess of the Assiníboine Riverts capabil-ities; therefore, the results of the prototype approach analysÍs must be rejected in this insËance

TABLE 3 provides a sunmary of the predictíons provlded by both of the foregoíng approaches.'

Cross-sectÍons at 15 selected locatlons downsÈream of the dam have been surveyed by the l{ater Resources Branch, Province of Manitoba, as part of a program to monitor the expected degradatÍon of the chan- ne1. The locations of Ëhese cross-secËíons are shown on FIGIIRE 4. At the time of wriÈíng, the results of surveying undertaken in March L97I, (díscharge approxímately 600 cfs) and May L972, (discharge approximately 8,000 cfs) are available Also avaÍl-able are cross-sections surveyed approximatel-y 25'000

feet downstream of the dam-site by the Prairl-e Farm Rehabílitation Ad-

mínístraËion, Government of Canada, in 1961-' L964, and l-971. This organization also undertook a comprehensíve rnapping (one ínch equals 400 feet) of thÍs reach of the river in 1951.

Comparison of the PtrRA cross-sectíons indicates, for that per-

íod, Èhe ríver charrnel- was rel-atively stabl-e, neíËher measurably aggrading or degrading. A comparison of the more recent l,{ater Resources Branch data was also made. Cautíon should be exercised Ín the discussíon 20

of results of this comparíson becausè of the great dlffJrence in dlscharges at the times of the surveys

The cornparison between the 1-971- and, L972 data índicates a slight îet aggradation at cross-section I-, but, Èhe channel bottom was l-owered in L972 about one-half foot for a width of about 2O0 feet. At cross-section 2, a degtadatíon averaging one foot over about 200 feeË in width was observed with a slight aggtadation extending up the banks. Cross-sectíon 3 índicaÈes a degradatíon of. the channel averaging síx feet over a 280,-f.oot wídth r^rith slíght aggradatíon on the sides of the channel. Cross-sectíon 4 showed a slight net aggradat,íon over the year. At cross-sect,íori 5, degradation was observed to average about, four feet over a 150-foot r¿idth r¡íth Ëhe thalweg itself beíng lowered in excess of seven feet. Accordíng to the wash-bore 1og fnformatlon at cross- sectíon 5 (FïGURE 11) the channel appears to have eroded over five feet through a stiff , highly pl-ast,ic, dark grey clay' This development should be investígated further in the moniËoring program. At cross-

I sectíon 6 and beyond, a net aggradation is indlcated at all cross-sec- tíons wíth the exception of cross-section 11. The degradation at cross-sectÍon lL is díscounted due to its proxfmity to â bridge síte and the great difference ín discharges at the tines of the survey.

From early observed evfdence, it would appear the process of degradation nay have begun. The reach showed a lower bed for a distance of about 121000 feet bel-ornt the dam with a higher bed downstream on the observed reach. The ultimate depËh and downstream extent of degradation calcul-ated by the stabl-e-slope approach (d--s = 3 feet; 2L

L = 20 míLes) appears, at this time, to be the best probable estimate of the extenÈ of this phenomena for the 3O-year períod during which the reservoír is filLing wíth sedíment. Caution should be exercised in any assumptíons, however, due to the wide variance in discharge at the times of the surveys. Wtrat may apPear to be sÍgnificant degradation may onl-y be Local scouring at hlgh flor¡. 22

2.4 Channel Geometry Fron the avallable cross-section and stage lnformation for the downstream reach, a mean cross-sectlon versus dlscharge relationship array was derived and is shor¡n on FIGURE 20. These relationshíps are consídered to descrÍbe the mean channel- for natural conditions. It was also consídered that sufficient observations \ilere made in the construction of these curves, and the channel sufficiently approxi- mates a ttapezoidal sectíon, to determine the bed-factor (F.) and síde- D factor (F_)-s' values of the natural channel using Blenchr s (1966 , L969) rnodified regime equatíons:

(A.1)

(A.2)

Sol-ving'sb for F- and F, with Q = 21100 cfs, the discharge at r,rhich mean annual sediment, t.ransport, occurs under natural conditlons, b = 225 feet, and d = 4.2 feex (FIGURE 20) yiel-ds Ëhe following: for Natural CondltLons F" = 0.036

FO = 1.00

The problem vre musË nor¡r address ls the relatLonship of these descriptive regime parameters before and after eonstruction of the Portage Díversion. In a sand bed river, such as the AssinlboÍne, with a smaLl bed-l-oad and with the vírtual- removal- of that bed-load by river cl-osure, the sedirnent, charge (c) wí11- tend to zexo. Usíng Blenchrs defínítio¡ of zero bed-factor (F, we find F, tends to F, as C tends bo---), b Þo- 23

J to zero, for post-diversfon conditions. For natural conditions, F66

can be derived from EQUATION 4.9, using Fb = 1.0 and C = 2.3 parts per

1_00,000.

Fb = Fbo (1 + 0.L2 C) (A. e) Hence for natural conditíons, Fbo = 0.785 an_l for post-diversion condi- tíons, Fb = Fbo = 0.785. Using the reglme s1-ope formul-a:

p _s/6p_ t ltz¡r ç¿¡ (A.3) rqt /e

and designating the present natural s1-ope of the channel Sr, = 1.9 x'10a

'and the computed post-díversion stable sl-ope tn = 1 .45 x 10-4, then AS=Snp -'S =0.45 xl-0-+ (2. 3) and _l kpbo5/6 ,"r,t /t ttt (")r, r"ni /i (c)p j-.-a = | 1r1 | = 0.45 x ^, K Qr,t/t Qnt/t I IJI 1. Q'4) Substítutíng K = 11900, k = L.62r tbo = 0.785, Qr, = 21L00 cfs, l-,800 tl(c) = L.25, F, = 0.035, and ti(c)- = l-.0 (as c Èends O'p = cfs, - 'n ' sn p to zexo) into EQUATION 2.4 yields a post diversion side-factor (F"n)

val-ue of 0.01-7.

IË shoul-d be noted that in the solutíon of EQUATION 2.4' the val-ue of the tweLfth root of the post-díversíon side-factor (Fsp) ís : found; Ëhen, that value is raised to the threl-fth power. Ttris procedure

also raísed possibLe error in the result to the twelfth porrer. Even though in subsequent calcul-ations the post-diversion side-factor value 24

J square and cube root is used, substantíal error may stJ-ll exist in the value. This r,¡oul-d appear to be the najor obstacle in obÈainíng reli- ab1-e quantitatíve estimat,es of changes ín channel wídth, flow depth' and velocíty usíng the modified regime theory equatÍons. In surmnary, for post-diversíon condítíons Fs = 0.017 and Fb=Fbo=0.7B5. Substituting these post-diversion condíËion values and Q = 1'800 cfs into Equatíons 4.1 and 4.2 gives a channel r¡idth (b) of 288 feet and a mean depth (d) of 3.7 f.eet. Solving EQUATION 4.8 with the above val-ues for TO, F", and Q gíves a mean velocity (v) of 1.7 feet per second.

Surm¡rarizíng the foregoíng as a consequence of the diversiont ít is estimated using the modífied regirne theory equatíons:

a.. mean channel width (using b = 24O feet) wíll íncrease approxi-

mately 201l

ì b. mean depth (using d = 3.9 feet) will decrease approximatel-y 5%

c. mean vel-ocíty (usÍng V = 2 f.eet per second) wil1 decrease ap- proxímately L57". Thís irnplies cross-sectÍonal- area (A) r¡il-l íncrease by I5"/" for a specified dlscharge (equation of conÈin-

uity, Q = VA). In recent years, a number of studies concerning the meandering of channels have been conducted (Ackers and Charlton' 1970; Leopold

and Wolman , Lg57). Hor¿ever, it was found (Zinrnernanr 1971) the rel-al tlonships deríved from these observaËions did not yteld satisfactory resülts when applied to the AssÍniboine Rivet. 25

There appears to be little hope at the present lime of quanti- fyíng the change in meander r¡ave length and meander shift rate.

However, íf it is accepted these trnro Parameters vary dírectly with dlscharge, then the ímposed reduction ín díscharge would effect a consequent reducË1on in"the meander wavelength and meander shíft rate. 26

CHAPTER 3

SUMMARY AND CONCLUSIONS

As a consequence of the Assiniboíne River Diversion aÈ Portage la Praíríe, the reach downstream is est.ímated Ëo degrade uP to three feet (near the diversion site) over a period of about 30 years. The downstream extent, of the degradatlon is esÈimated to be approxfunately 20 rníl-es. The degradatíon in the vicl-níty of cross-sectíon 1 may be less than thís estimate due Ëo a coarse sand and gravel layer two feet bel-ow the L972 observed channel bottom. That is, there rnay be a "local armouring" of the bed at that cross-section.

The meËhod util-ized ín this thesis to provicle quantitatlve esËímates of the Íncreased channel r¡ídth, decreased depth, and decreased velocity is extremely sensitive to error propagatíon and the results itherefore are suspect. Hor¿ever, Ëhese quantitat,ive estimates can indí- cate the order of magnítude of the expected regime consequences.

The mean channel width for a specífied df.scharge is estfmated to have a tendency to increase up to approximatel-y 20% im¡ediately doronstream of the diversion site r¿Íth Ëhis consequence being less pronounced further downsËream.

The mean depth for a speclfied díscharge Ls estimated Ëo have a tendency to decrease approxirnatel-y 5% írnmediately downstream of the diversion síte and the mean velocÍËy for a specífíed discharge is est-

ínated to have a Ëendency to decrease approximateLy L5%, These 27 consequences, as r^rell , wil-l be less pronounced further dowì:lstream. The above consequences imply a lowered water surface elevation for a specífied discharge on the degraded reach due to the degradation of the channel- bed and an antícipated net increase (slight) in the hydraulic roughness of the reach due to Ëhe "sorting" effect of degradation.

I^Iíth an ímposed reduction in discharge, the meander rnravelength and meander shift rate are anticípaËed to be reduced. Due to the consequent degradation of the bed and the tendency to increase channel width, the stability of the existíng banks is expected to be reduced and local scour at bridge sites ís expected to be increased. Subsequent monÍtoring should be directed to the ínvestiga- tíon of the consequences at specLfic locations and measures should be suggested to enhance the integriÈy of endangered structures.

It should be noÈed that these results are theoretLcal maxímums rbecause in the analysis no account has been taken of the sedLment supply prowlded to the doumstream reach by the 13- by l3-foot condult ' under the dam. Unfortunately, no lnformaËLon regardLng the effect of this conduít on sediment supply was available at the time of the study. 28

LIST OF REFERENCES

Ackers, P., and Charlton, F.G. (L970) - "DímensLonal analysis of allu- víal channels with specíal reference to meander lengtht', Jour. of Hyd. Res., Vol-. 8, No. 3.

Blench, T. (Lg57) - "Regirne Behaviour of ', Buttenrorths ''. Scient, Pub Blench, T. (Lg66) - "Mobíle-Bed Fluvíology", Univ: of Alta. Press Blench, T. (1969) - "Mobile-Bed tr'1uvio1ogv", Univ. of Alta. Press. ,:: : Galay, V.J. (1966) - "Effects of Engineering Projects and Land Use Changes on Ëhe Regime of RÍvers", unpublíshed paper. : : Galay, Dr. V.J. (L97L) - "Assiniboine River Degradatíon Investigatiön", tr^laÈer Resoutces Branch, Prov. of Man. Graf , I{.H. (1971-) - "Hydraulícs of Sedi ', McGraw-Hill- Book Company.

Henderson, F.M. (l-966) - "Open Channel- Flor^¡", Macmlllan. Inl-and üIaters Branch - "Sediment Data for Canadian Rivers", Years L96L, l-961- to L963, L964, 1965, L966, L967. Konura, S., and Simons, D.B. (1967) - "River-Bed Degradatíon Below Dams", P{oc. ASCE, Jour. of the Hyd. Div., HY4' 5335, July L967. Komura, S. (1968) - "Computation of Dominant Discharge", Proc. IAHR' 13th Congress' Japan. ..,,.:..:... KuJ.per, E. (1965) - "l^laËer Resources Developmentrt, Butterworths Scient. ''"' . Pub ' ' ".'. ,, . Kuiper, Ë., and Ga1-ay, V.J. (L97L) - "Reglme Study of the Saskatchewan- Nelson River Systemrf, Saskatehewan-Nelson Basl-n Board Report. Lakes !üínnipeg and Manitoba Board (1958) - "Report on Measures for the Control- of the Ï,Iaters of Lakes hrirrnipeg and Manitoba", Appendix 7, r':"iÈ ttlower Assiníboine River Regulationtt, Province of ManiÈoba. ,,, .,,, Leopold, L.8., tr{o1-man, M.G., and Míl1-er, J.P. (1964) - "Flrr.ti"L Eto."s- ses ín Geomorphology", !ü.H. Freeman and Company Leopol-d, L.8., and trrlolman, M.G. (l-957) - "RÍver channel patterns; braíded, meanderíng and straíght", Prof. Paper U.S. Geol. Surv. ' 282-8. 29

Maddock, T. (Lg6g) - "The Behavior of straighË open channels wíttr Movable Beds", Prof. Paper U.S. Geol. Surv., 622'^- Priest, M.4., and Shínda1-a, A. (1-969) - "Channel Degradation Downstream from Large Damstt, Water Power, Nov. Priest, M.S., and Shindala, A. (l-969) - "Time Requfred for ultinate Charrnel Degradatíon Downstream from Latge Dams", I^later Power Dec. Priest, M.S. (l-969) - "Distance DownsËream from aLarge Dam to the Limit of Ultímate Channel Degradation", Proc. IAHR' 13th Congress, Japan. Símons, D.8., and Àlbertson, M.L. (L963) - "Uniform Ï,Iater Conveyance Channels in AlLuvÍal- Material", Trans. ASCE, Paper No. 3399' Vol-. L28, Part T.

USBR (1951) - "Analysís of Flow-Duration Sedirnent-Rating Curve Method of Computíng Sediment Yleld", Sedimentatíon Sec., Denver, Colórado.

USBR (1952) - "Total Suspended Sedíment Load From Vertical Transport Distríbuttol", Denver, Colorado

USBR (1963) - "Guide for Computing Degradation", Preliminary Report, Denver, Colorado.

Wolman, M.G., and Míller, J.P. (1-960) - "MagniËude and Frequeney of Forces in Geomorphic Processest', Jour. of Geology, Vol. 68, No. l-.

Zimmerman, R.D. (1971) - "Meander Studies of the Assiniboine River'|, B.Sc. (C.8.) thesís, Univ. of Man. 30

APPENDIX A

MODIFIED REGIME THEORY EQUATIONS 31

For the analysis used in this part,icular thesís, ttt" ernpirí- caLLy deduced "modified regime theory'r equations advanced by BJ-ench (Lg66, Lg6g) are utílízed. The equatl-ons derl-ved by Blench for desígn and analysis are:

FuQ (A.1)

(A.2)

ur. Fstlrz ¡t (c) (A.3)

k ,oo zley'i (") (A.4) K bll4 di/8 k f, _rt/12 ¡t1t (c) bo (A.s) K b1l6 Qrlr2

K= 3.62 slvr/+ (A.6) d= (q2 /h)L /3 (A.7) V= (Fr Fs Q)i/o (A.8)

I'6 = F6o (1- + 0.L2 c) (À. e) and for sand-bed channels, the rough relatLon:

Fbo = 1.90 d5e (rnm) (A.10) where 'b ís the bed factor

FS is the side factor

k is a meander correction coefficíent

E is Ëhe zeto bed-factor DO 32

f(c) t-s the bed-materíal load transpoït functíon q l-s the unít water discharge per foot wldth c is the sedimenË eharge (parts per 100,000)

dso l_s the mean sediment particle díameter (mm) ,lÅ (t ,ZA\ <(N)F-v I .l' f l t

PRINCE ALBER Ëtl .f \,/, RAND .a RAPIDS ,t I r-ax a fr I \ WINN :{ i ¡ I i i , I ¡ i o âl'r. -, i I i SWIFT, I CURREF¡T ¡ Þ ¡ (f (/) I nØ -'-nd.o ff .-=t>.2, t - eãämz. ñ rn cp* SCALE IN MILES ' Þ/t.l Nofe: g< Limrts of Study Areo shown thug ñ Z. €frl .L) NATU RAL CON DITION

GHANNEf """Ëäi,ffiil

POST DAM AND DIVERSION CONDITION

prvERSþNf

o ap -l

DEPOSITION CONTROL POINT DEGRADATIÐN

FINAL CONDITION RESERVOIR FILLED

t,,

r--^-

DEPOSITION

Qn is noîurol dischorgc specf rum

QSn is noturol sedimenl f low Q9 is diversion dischorge

Qp is Qn minus QD ILLUSTRATION OF DIVERSION QSp is olfered sediment flow CONSEQUENCES

F¡GURE Ì111:;,

Y,/'/

5-ñÈ&-r=E ,NN

il3l

rl\)n \0 ¿ s \ ll

I I

\ tt S€dlG¡ t' . !oo' Hods tt tta nQ, \ \rrl PORIAGE DIYTRSION INLET WORI(I J/."4 GENERAL ARRANGEMENT OF PROJECT \\ k- \/\ U FIGURE 3 :Ï ASSINIBOINE RIVER THE DOWNSTREAM REACH-i SCALE:1.25"= lmi. FIGURE IVHAT IS THE RATE AND EXTENT OF DEGRADATION 2

OFFICE OFFICE ELD SURVE POST. SURVEY PRE. SURVEY

GEq-O6r GEOMORPTI.

lor^L 3to¡rt ¡l cuhva R¡I I¡G (DlrlY aLrt¡

î LEADS TO c6) @ 1 m FUTU RED (t ( DANG ER TO D/S STRUCTURES) t @

T LAKE MANITOBA

{

2. FED. GAUGE 5LLI9

DIRECTION OF -/ PORTAGE LA PRAIRIE FLOW t-J FED. GAUGE 5MH5 GAUGE 5MJ5 FED. GAUGE 5MJ3 INLET WORKS

ASSINIBOINE RIVER GAUGING STATIONS lN THE VICINITY OF THE PORTAGE DlVERSION

FIGURE 6 ANNUAL PEAK DISCHARGE IN C F S l¡J : É .,t 4- --l æ, 1.. lI g_ f J--_ -J'r I' T.:. ! i < I .l--¡

J---'i: --,I "_l__..i!..,11 i-. '' i--.--- j - l ..-1..:.- t-=--t-''' -f - .1l -:..1 :. - i.-. f l l" -.'-t--'-l-'- r -.J DURATION CURVES OF

FIGURE 9 r ll (9 LrJ lo J- o l¡J (9 :)8 (9a

ASSINIBOINE RIVER LA PRAIRIE -n AT PORTAGE c6) Ð CURVE m -- +'--' t---.-'

-tt o r I I 9 lo ll t? t3 15 t6 Þ I D I S CHARGE tN C. F. S. tooo r1I @

w AJn õvñE LV(,Þ

loo win.¡ giloh grovell '-s depth 3/8"O mox., i ; I vel from 5l -r- 8,2' depth ,. i .l .t,l:]il rl'li: ì irjiiÌlll i l':rrrì'r I ,i,;i i i:i:iri l-I brown, exlreme I plosti o 2. istiff, high

I i silt lenses, inum , I r ;oxidolionsj I ihord, 3. high iplos odd sm '" !'i Ì"1 ; iiiit I I

I i 820 l iilil ! iilil I I ||l

ì I iilii FllGURE' ',ii VELOCITY ( f Ps ) 23 4 o9 o

VELO itTY -SEDtMEN 1>q> ( F DISCHAR oÈ. TL <¿ I I4 "/ t- o- ol¡J j \ CONCENTF ATION \ \ -r(-/ /

v 7Ayl/\Y/ v/lì gt BOTTOM BOTTO M o 200 400 800 1400 r600 1800 ooo SEDIME N T CONCENTRATION ( p p m) AND SEDIMENT DTScHARGE ( ppm x ftls)

UNMEASU RED SEDIMENT = I5 Olo

ASSINIBOINE RIVER AT PORTAGE LA PRAIR I E

SUSPENDED SED I MENT CONCENTRATION (AFTER KUIPER AND GALAY , l97l )

FIGU R E t2 SEDIMENT TRANSPORT RATING CURVE ASSINIBOINE RIVER AT PORTAGE LA PRAIRTE

-1:..i ; __ i--.1--l

.-t , I i -ï--ii-Ì-l :l i.-l-ì

'-i: .ri--.l r'- I -l li.-.1

+567 DISCHARGE (cfs)

FI GURE r3 to 20 30 40 50to 60 70 80 90 too Percent of lime less thon FIGURE t4 @ a/ A

Fort Rondol I dom

Fort Peck dom U' E c ?, 15 o= E

G O Loborotory dqto ( Horrison ) 20 .-l O Prototype dolo d'lbI (E Comporotive doto Denison dom

ULTIMATE CHANNEL DEGRADATION (AFTER PRIEST ANO SHr\DALA , 19691

WHERE : ds is f he ultimof e degrod o l¡on

dqor' is o meo s ure of th e groi- n s ize token os the groin diometer d of 5!o/o finer

o is the stondord deviot ion from diomef er dSO belween lO ond 90 o/o f iner

A dischorge ( on overoge of onnuol peok volues of monfhly overoges over period of degrodotion )

A is cross - secfionol oreo of lhe chonnel g ¡s occelerotion due to grovity

FIGURE I5 oo.-Aond B \ x. Ron do I dom to \ Pech dqr Er)tl ._ 1"" C, / 't 0 o E 20 / .: -'lo )enison dr ¡m

/ 30

O Loborotory dofo ( Horrisonl 35 r1I !3- Prototype dofo Hoov er dom e Comporolive doto

40 ll o¿t8|,2t62024

iî5() T,, in millions D-

TIME REQUIRED FOR ULTIMATE DEGRADATION pRtEsT (AFTER AND SHI¡¡DALA , t969 )

WHERE: Tu is required lime for ultimole degrodotion

D is overoge depth. of flow for O

FIGURE 16 Lo tn fhousonds D ro 20 30

Rondol I dom

Forl Peck doln

o It c o ø:' o ,É

.= ;lo

O Protolype dofo

e Comporolive . dofo

THE DOWNSTREAM L IMIT OF CHANNEL DEGRADATION

(AFTER PRIEST AND SHTNoALA , t969 )

WHERE ' Ls is distonce downstreom , lo chonne I degrodotion.

...:.

FIGURE ]7

TH E DOWNSTREAM ,cRoss RE ACH - sEcTtoNS I TO t5 ASSINIBOINE RIVER AT PORTAGE LA PRAIRIE MEAN CROSS - SECTION vs DTSCHARGE CURVE ( FROM ANo t97l t972 W.R.B. CROSS_SECT|ON DATA )

o =

4 5 6 7 a eloqpæ DISCHARGE (cfs)

FIGU RE 20

IE ItG€X0 ¡ ! Ë : I t ¡@ ¡ -¡ I tit - ] iç T g æ ! r¿u ? ¡ ¡ ! Ìli +* t i tli ¡ l I ø a t! T .f .ørttf.É lii! Í ll ol:. Þ¡ÉliG¡ ø E9 i åoi I ¡ ¡lt q .7 ¡r I f .! I t I t¡ 'i! : ã . I t f: øZ ao c g ,. I J I . ,'! o 'a l ¡sJ i ir!! æ! c :r i Bt !l o e. oå e i o !i ' a aa a @ øa LONGITUDINAL PROFILE Þ OF låE ASSINIBOINE RIVER ottlrtce tior ¿ulcflot ct tf0 ¡tYll ¡¡¡¡urtD r¡ tt!a¡ ¡Lo¡o lr.t rrüaa . LSGEXD

e at@ E Ë Fffi IE ! dÚg€-E&tE ¡@ t I a 1 a @ t I .ÛlflrtÉ GiRiúøn¡ ¡ æ I I I o' ¡ ?:? r@ I ;Ð -¡ I iii I ¡, , t: æ= a ,r! ,. s

lr it'. 1 .l I cU:: l¡ æ! ê.,.a! rl \ ..-- .- W- .. " I t :FlFl _--- ë ' 'o o,l e Isli C Ca a ø -4--*--ì LONGITUDINAL Í Þ or lHf

ASSINIBOINE F or3l¡Èc¡ ?io¡ Ju¡ctro¡ c? tco rtytr ¡t¡3uafD t¡ ltre¡ ¡Lo¡o ?|{ rrwa