peace river development 13~ ,3ll &~:~~/l~

13~&~:~~/l~ .

PEACE RIVER DEVELOPMENT

, 3LL····,····T· ..SITE·C PROJECT

LANDSLIDE GENERATED WAVE STUDYMOBERLY AND TEA CREEK SLIDES

FORBRITISH COLUMBIA HYDRO AND POWER AUTHORITY

VANCOUVER, B.C.

BY

WESTERN CANADA HYDRAULIC LABORATORIES LTD.

PORT COQUITLAM, B.C.

72021 NOVEMBER, 1981

SmithJ

Typewritten Text

Hearing Exhibit 78: Submitted by Diane Culling at the Dawson Creek Hearing Session, January 8, 2014

72021


PEACE RIVER DEVELOPMENT

SITE - C PROJECT

LANDSLIDE GENERA TED WAVE STUDY

MOBERL Y AND TEA CREEK SLIDES

FORBRITISH COLUMBIA HYDRO AND POWER AUTHORITY

VANCOUVER, B.e.

BY


Port Coquitlam, B.e.

November, 1981


TABLE OF CONTENTS

Paqe

5.1 Scale Selection

5.2 Model Construction

5.3 Instrumentation

6.0 TEST PROGRAM

6.1 Phase I Testing

6.2 Phase" Testing

7.0 TEST RESULTS

1.0 PURPOSE

2.0 INTRODUCTION 2

3.0 SUMMARY AND CONCLUSIONS 3

4.0 DESCRIPTION OF THE PROPOSED SITE-C DAM AND RESERVOIR 4

5.0 MODEL DESCRIPTION 5

5

5

7

8

8

9

10

107.1 Phase I

7.1.1. Slide Distance - Time Profiles 10

7.1.2 Test Results of Alternative III 10

7.1.3 Test Results of Selected Arrangement (Alternative iliA) II

7.1.4 Discussion

7.2 Phase "

7.2./ Slide Distance - Time Profi les

7.2.2 Test Results

7.2.3 Discussion

7.3 Concluding Remarks

REFERENCES

TABLES

FIGURES

12

12

12

12

13

16


LIST OF TABLES

I. PHASE I TEST RESULTS

2. PHASE II TEST RESULTS


LIST OF FIGURES

I. LOCATION MAP

2. SITE PLAN

3. ALTERNATIVE III ARRANGEMENT

4. ALTERNATIVE IlIA ARRANGEMENT

5. MODEL LAYOUT

6. TYPICAL SECTION THROUGH MODEL DAM SHOWING COLLECTION TROUGH

7. MODELLED SLIDE PROFILES

8. DISTANCE TIME PROFILE SLIDE AREA 4

9. DISTANCE TIME PROFILE SLIDE AREA 6-1 PHASE I

10. DISTANCE TIME PROFILE SLIDE AREA 6-2 PHASE I

II. DISTANCE TIME PROFILE SLIDE AREA 6-3 PHASE I

12. DISTANCE TIME PROFILE MOBERLY SLIDE PHASE I

13. SLIDE AREA 4 ALTERNATIVE III PHASE I WAVE TRACES

14. SLIDE AREA 4 ALTERNATIVE iliA PHASE I WAVE TRACES

15. SLIDE AREA 6-2 (F = 30) DISTANCE TIME PROFILE



18. SLIDE AREA 6-3 (HYPOTHETICAL) DISTANCE TIME PROFILE

19. SLIDE AREA 4 ALTERNATIVE IliA PHASE II WAVE TRACES

20. INITIAL WAVE GENERATION SLIDE AREA 4 PHASE II


1.0 PURPOSE

The purpose of the model study discussed in this report was to invest igate the

nature, magnitude, and sequence of waves generated in the proposed Site-C reservoir by

the hypothesized landslides in the Moberly and Tea Creek areas. In addition, the

interaction between waves and two alternative project arrangements studied for Site-C

was to be delineated as was the elevation of runup on the reservoir shoreline on the bank

opposite each slide. The sensitivity of wave heights to increases in the estimated slide

depth and velocity was also to be investigated.

Note: It is not the intention of this report to imply or suggest that such landslides are

likely to enter Site-C Reservoir but rather to study the consequences of a scenario

where such slides are assumed to take place.

WESTERN CANADA HYDRAULIC LABORATORIES LTD

2.0 INTRODUCTION

?

The proposed Site-C dam axis is located on the Peace River in the northeast ofBritish Columbia, 5 km southwest of the city of Fort St. John (Figure I). The BritishColumbia Hydro and Power Authority is investigating the site for a proposed hydroelectricdevelopment. A dam at this location would create a reservoir 80 km long in the PeaceRiver Valley from the confluence of the Moberly and Peace Rivers to just downstream ofthe Peace Canyon dam.

The Peace River Valley has a history of landslide activity in this reach of the river.Previously active zones and potential zones of slide activity have been identified andinclude the Moberly and Tea Creek slide areas shown in Figure 2. Part of the engineeringstudies carried out on the Site-C project was an assessment of the effect of slide-inducedwaves should future landslides occur in those zones and enter the reservoir with highvelocities. Due to the complex nature of the wave generating mechanism and theirregular shoreline of the reservoir, landslide generated waves can best be studied bymeans of a physical model. B.e. Hydro provided Western Canada Hydraulic Laboratories(WCHL) with assumed volumes and velocities of slides to be tested in a hydraulic modelstudy.

At the time the model study was commissioned, B.e. Hydro was considering twoalternative project arrangements, Alternative III and Alternative IliA. The modelinvestigation included both alternatives. Wave heights, volume and duration of damovertopping (if any), and wave runup along the bank opposite each sl ide were to bedetermined for each alternative arrangement.

An undistorted model of the eastern end of the proposed Site-C Reservoir wasconstructed at a scale of I:400. This report describes the model, test program, and testresults of simulated landslides from the Tea Creek and Moberly areas entering the Site-CReservoir.


3.0 SUMMARY AND CONCLUSIONS

3.1 An undistorted I:400 scale model of the eastern portion of the proposed Site-CReservoir was constructed to investigate landslide generated waves from hypothisizedslides in the Tea Creek and Moberly areas. Five simulated slides - Slide Area 4, SlideArea 6-1, Slide Area 6-2, and Slide Area 6-3 in the Tea Creek slide zone and the MoberlySlide Area - were tested to measure wave heights, wave effects at the dam and runup onthe reservoir bank opposite each slide.

3.2 Assumed slide distance-time histories, slide volumes, and slide cross-sectionalprofiles were supplied by B.e. Hydro.

3.3 Two dam configurations, Alternative III and Alternative IliA, were tested in Phase Iof the test program. Sensitivity of generated waves to increases in slide thickness andvelocity was investigated in Phase II of the study. Only the selected alternative(Alternative iliA) was employed in this phase of testing.

3.4 Wave heights were measured at single points in the approach channel; on theupstream face of the dam; upstream and downstream of the Peace and Moberly Rivers;and upstream and downstream of the slide under invest igation.

3.5 Phase I testing showed that the Slide Area 4 generated the largest waves; 5.5 m inthe approach channel and 6.1 m on the dam face. Neither dam configuration appeared tohave any substantial advantage relative to wave heights. No overtopping occurred andwave runup was recorded (Tab Ie I).

3.6 The results of Phase II testing showed that the initial generated wave whichpropogated across the reservoir increased significantly with increased slide thickness andvelocity as evidenced by the higher wave runup recorded on the bank opposite the slide.The waves propogating toward the dam also increased but not as significantly.Overtopping of the dam (crest at el. 469.4 m) was observed in several tests but theovertopping was very localized and the volumes of water were too small to measureaccurately. The amount of overtopping observed, extrapolatated by the model volumescale, would probably be less than would be observed in prototype because of surfacetension effects. The overtopping observed in prototype would not, however, besignificant.

WESTERN CANADA HYDRAULIC LABORATORIES LTD.I...,.

4.0 DESCRIPTION OF THE PROPOSED SITE-C DAM AND RESERVOIR

The Site-C Dam Project is located just downstream of the confluence of theMoberly and Peace Rivers. The proposed dam would maintain a normal water surface atEI. 461.8 m and would create a reservoir about 0.8 km wide and 80 km long on the PeaceRiver and 0.5 km wide and 9 km long on the Moberly River.

At the time this model study was initiated, B.e. Hydro was considering twoalternative project arrangements, Alternative III and Alternative lilA, shown in Figures 3and 4. Both arrangements are similar in that their main section is earth filled, spanningfrom the left embankment across the river valley. The crest of the dam is at EI. 469.4 mleaving approximately 7 m of freeboard above the normal reservoir water level. WhiIe theearth filled sections of both arrangements are located at approximately the same point onthe left bank, the axis of Alternative IliA is positioned slightly downstream from that ofAlternative III. On the right bank, an approach channel with invert at EI. 435 m leads tothe powerhouse and spillway intakes on each arrangement. The approach channel ofAlternative III is longer than that of Alternative IliA.

Five slide zones have been identified in the downstream portion of the proposedSite-C Reservoir. The Moberly Slide Area is located on the left bank of the MoberlyRiver as shown on Figure 5. On the left bank of the Peace River, the Tea Creek slidezone consists of four slides, Slide Area 4, Slide Area 6-1, Slide Area 6-2, and Slide Area6-3. Their location is also shown in Figure 5.

WESTERN CANADA HYDRAULIC LABORATORIES LTO

5.0 MODEL DESCRIPTION

5.1 Scale Selection

Similarity of surface wave phenomena between model and prototype requiresequivalence in the transference parameter called the Froude Number. Thus ageometrically scaled model with Froude Number equivalence will correctly reproducewaves and their characteristics provided other modelling scale effects such as viscosityare kept small.

Viscosity effects can be minimized by choosing a model scale which maintainswater depths large enough to relegate viscous attenuat ion of waves to areas very c lose tothe shore. Previous studies I, 2, 3, undertaken at WCHL have indicated that the minimummean water depth should be on the order of 6-8 em, however, larger depths are desirable.

A scale of I:400 was chosen for the Site-C Project study to achieve adequate waterdepths in the model. The model scale was undistorted (horizontal scale equal to verticalscale) to correctly reproduce wave reflection and refraction. The resulting geometric,kinematic, and dynamic relationships between prototype and model are:

Quantity

LengthVelocityTime

5.2 Model Construction

Relationship

Lp = 400 LmVp = (400)1/2 Vm = 20 Vm

Tp = (400)Y2 Tm = 20 Tm

The I:400 scale model of Site-C Reservoir was constructed indoors at WCHL'sfaci lities in Port Coquitlam. Since a model of the reservoir in its entirety at this scalewould be immense, only the eastern portion of the reservoir was modelled includingapproximately 6 km of the main reservoir from the dam to a point just upstream of TeaCreek on the Peace River and approximately 3 km up the Moberly River (Figure 5).

The model reservoir was moulded in sand-cement underlain by a polyethylene liner.Plywood, female templates perpendicular to the longitudinal axis of the reservoir wereused for control of contours to an elevation of 520 m. This provided the equivalent of

WESTERN CANADA HYDRAULIC LABORATORIES LTD ..----------------------------------------,,"6-----,

58 m of freeboard, at full reservoir, to contain any wave action caused by the slide. Thetemplates were placed at 400 m intervals over the entire lengths of the Peace andMoberly reaches. Special care was taken to accurately reproduce the topography at theconfluence of the Peace and Moberly rivers and at the dam by using additional templatesas appropriate.

Only the dam structure upstream of the crest was included in the model. The crestitself was formed from one edge of an 8 inch diameter PVC pipe cut in half longitudinally(Figure 6). The remainder of the half pipe formed a catch basin downstream of the crestto collect any water overtopping the dam. The earthfi II section and the excavatedportions of the right and left banks were moulded in a bentonite and pea gravel mixture tofacilitate the change over of the two dam configurations during testing. While theapproach channel to the powerhouse and spillway was accurately modelled, no attemptwas made to reproduce gates, spillway, or riprap protection.

Wave absorbers were constructed at the upstream extremities of the model on thePeace and Moberly reaches. These absorbers included weirs set at the normal reservoirwater elevation 462 m preceeded by permeable gravel beds sloped at 100•

The assumed slide velocities were generated and controlled by a hydraulic powerunit and piston. Piston rod velocity was set by a flow control valve which was opened andclosed by a cam to reproduce a predetermined velocity profile for the slide. The distancethat the assumed slide travelled into the reservoir before coming to a halt was alsocontrolled by the cam. A velocity and distance amplifying lever arm connected the pistonto the slides. The lever arm length and pivot location was adjusted according to thedesired travel and maximum velocity of each slide.

The assumed slides were simulated using steel pipes and tubing strung togetherwith cables. Slides constructed in this manner possessed the necessary flexibility tofollow slip plane contours. The sequence of diameters of the pipe and tubing was chosento closely approximate the estimated slide profile when at maximum velocity (Figure 7).Only the portions of the slides that entered the reservoir were modelled.

5.3 Instrumentation

Wave data were obtained at 6 different locations in the reservoir, labelledA,B,C,D,E and F in Figure 5, and listed in the table below.

WESTERN CANADA HYDRAULIC LABORATORIES LTD.I

Wave Record

Approach Channel

Dam Face

Upstream Dam

Upstream Moberly

Upstream Slide

Downstream Slide

Location

AB

CD

EF

The recorders at downstream slide and upstream slide (E and F) were located just

downstream and just upstream of each slide and thus their location on the model changed

for each test slide. The location of the remaining water level recorders (A, B, C and D)

was not altered during the test program. For Slide Area 6-3, the upstream Moberly and

downstream slide wave records were obtained at the same location.

The instruments used were point driven water level recorders which follow the

water surface keeping the electrical impedance between the point and the water constant

by means of a feed back circuit and a servo motor. The response time of these

instruments to a change in water level is approximately 25 cm/sec (model) and these

instruments are accurate to within .= 0.3 mm (model). No calibration of the water level

recorders was performed since they are periodically calibrated as part of laboratory

procedure.

Slide velocities were calculated from distance-time curves of the slide.

Calibrated, ten- turn potentiometers were employed to indicate the distances travelled by

the slides. Pulleys, attached to the potentiometer spindles, were turned by wires attached

to the slides. Change in potentiometer resistance was sensed on a chart recorder which

also supplied the time base. The slope of the distance versus time curve represents the

slide velocity.

The elevation of runup at selected points around the reservoir was measured by

survey levels. Initially, the runup line was marked by finely ground gilsonite. However, it

was found that the wet line left after each test was a more accurate indicator of runup

than the gilsonite. By reducing the data subsequent to each test, time was gained for the

drying of the model before the next test proceeded.

QWESTERN CA.NADA HYDRAULIC LABORATORIES LTD.

6.0 TEST PROGRAM

The study test program consisted of two phases. The first phase concentrated onthe interaction between waves created by either of the assumed Moberly and Tea Creekslides and the two alternative project arrangements. The second phase investigated thesensitivity of the wave characteristics and magnitudes to variations in the slide velocityand cross-sectional profile. The selected project arrangement was used in Phase IItesting. Wave runup data on the reservoir bank opposite each slide was also noted in bothtest phases.

6.1 Phase I Testing

The assumed slide input data for each of the five slides was supplied by B.e. Hydrois shown below:

Slide Slide Slide Slide MoberlyArea 4 Area 6-1 Area 6-2 Area 6-3

Maximum Velocity Tested 33.3 11.2 7.0 15.8 17.7m/s

Maximum Velocity 32 12 8 14 18Specified m/s

Total Volume 4.0x 106 3.2x 106 6.1 x I06 1.5x106 1.6x107Entering Reservoirm3

Maximum Slide 25 30 42 30 58Thickness m

Slide Width 530 L~50 680 640 830m

Distance from Dam 4.0 2.5 2.0 1.3 1.5km

WESTERN CANADA HYDRAULIC LABORATORIES LTD.r---------------------------------------'j/I-----,

The test program featured each of the slides entering the reservoir with the approximatedtime-distance relationship specified. All slides were run twice with each alternatearrangement for a total of 20 tests. Wave traces; overtopping volume and duration, ifany; and wave runup were recorded for all tests. The normal reservoir water elevation of462 m was used throughout the study.

6.2 Phase II Testing

The sensitivity of wave heights, overtopping, and runup to increases in slidevelocity and thickness were investigated in Phase II. For the slides, Slide Area 4, SlideArea 6-2, and Slide Area 6-3, the hypothesized input were altered as follows:

Slide Area 4 The estimated depth of slide at maximum velocity was increased keepingthe total slide volume and slide velocity the same as Phase I (SeeFigure 7).

Slide Area 6-2 Two additional distance-time histories were tested giving maximum slidevelocities of 14 m/s (F = 60)1 and 18 m/s (F = 30) but keeping the slidecross-sectional profile and total slide volume the same as Phase I.

Slide Area 6-3 Two additional distance-time histories were tested giving maximum slidevelocities of 32 m/s (F = 00) and 40 m/s (hypothetica02 keeping the slidecross-sectional profile and total volume the same as Phase I.

The phase II slide input data is summarized in the following table:

I. The value of F is indicative of energy dissipation as the slide travels in itstrajectory. The lower the value of F, the less energy dissipated and the higher theslide velocity.

2. Hypothetical refers to an unrealistic energy dissipation which has no basis inphysics but was used in the study to give extremely conservative slide velocity.

WESTERN CANADA HYDRAULIC LABORATORIES LTD.III

SlideArea 4

Slide Area 6-2F=60 F=3°

Slide Area 6-3F =00 Hypothetical

Maximum Velocity Testedm/s

Maximum VelocitySpecified m/s

Total VolumeEntering Reservoirm3

Maximum SlideThickness m

Slide Widthm

33.3

32

4.0x I 06

25

530

12.5

14

1.2x107

58

680

17.1

18

1.2x107

58

680

34.3

32

1.5x 106

30

640

45.0

40

1.5x I 06

30

640

Under the Phase II set of slide input parameters there were five slide test conditions, one

for Slide Area 4, two for Slide Area 6-2 (F = 60 and F = 30), and two for Slide Area 6-3 (F

= 00 and hypotheticaO. Each slide test condition was tested twice for a total of 10 tests.

The selected arrangement (Alternative iliA) and normal water elevation of 462 m were

used for Phase II. Wave traces; overtopping volume and duration, if any; and wave runup

were recorded for all tests.

WESTERN CANADA HYDRAULIC LABORATORIES LTD.I I

7.0 TEST RESULTS

7.1 Phase I

Tests were documented in Phase I using the assumed input slide data noted insection 6.1 for each of the five slides. Each slide was tested twice.

Wave heights above reservoir pool level were recorded upstream and downstreamof each slide; upstream (U/S Moberly) and downstream (U/S Dam) of the confluence of theMoberly and the Peace Rivers; and on the earthfi II and approach channel of the dam.Runup was measured on the bank opposite each sl ide.

7.1.1 Slide Distance - Time Profiles

A comparison of the distance-time profi les (model measurements compared toinput data) for each slide with those specified by B.C. Hydro are shown in Figures 8 to 12.The tested profiles generally follow the input data well, especially in the region ofmaximum velocity, (maximum slope of curve). Small discrepancies appear either at thebeginning or the end of the traverses. These disparities are considered minor since theyoccur in the low velocity areas of the slide trajectories.

7.1.2 Test Results of Alternative III

The results of tests are listed in Table I (Tests I to 10). The water level trace forslope 4, representative of water level traces for each slide tested with the Alternative IIIconfiguration, is shown in Figure 13.

The largest waves registered in the approach channel were created by the SlideArea 4 slide and Moberly slide with amplitudes of 5.5 m and 5.2 m respectively. Wavesgenerated by Slide Areas 6-1,6-2 and 6-3 were relatively small in comparison, 1.7 m beingthe largest as a result of a slide at Slide Area 6-3. The wave recorded at the dam as aresult of a wave at Slide Area 4 was 6.1 m, the largest wave registered •.

No overtopping of the dam was observed for any of the waves created by thepotential slides.

WESTERN CANADA HYDRAULIC LABORATORIES LTD.r---------·-----------------------------h, <...~---,

Runup on the bank opposite each slide is noted in Table I. Slide Area 4 slide and

Moberly area slides overtopped the physical model boundaries and water was prevented

from spi Iling out of the model by sand bags p laced on the bank.

7./.3 Test Results of Selected Arrangement (Alternative iliA)

Test results with the selected arrangement are shown in Table I (tests 11-20) with

a typical water level trace (Slide Area 4) shown in Figure 18. In general, the results for

Alternative IliA are very similar to those of Alternative III. The largest wave recorded by

the water level recorder at the dam of 6.1 m and in the approach channel of 5.1 m was

again created by SIide Area 4. No overtopping occurred in any of tests I I - 20.

Run up was not noted in these tests since the slides were unchanged from the

Alternative III tests.

7.1.4 Discussion

Waves generated by individual slides on the Peace River bank (Slide Areas 4, 6-1,

6-2 and 6-3) were observed to possess the same celerity (wave speed) typical of shallow

water waves. Since each slide produced a major wave and several following minor waves,

waves of longer period did not overtake and superimpose with shorter period waves

forming a large wavefront which is possible with deep water waves. The major wave

created by these slides ran up the opposite slope and was largely dissipated without

propogating upstream or downsteam in the reservoir. A portion of this initial wave

travelled along the right bank towards the dam in conjunction with a smaJler wave which

diffracted from the end of the slide and expanded to span the width of the reservoir. The

portion next to the right bank had a larger amplitude and was observed to be almost a

breaking wave. This breaking wave was dispersed upon encountering the Moberly River

branch of the reservoir.

Waves approaching the dam from the Moberly slide were more complex in nature.

The water level trace upstream of the dam shows a doub Ie peak on the wave approaching

the dam. This indicates that a wave reflected from the left bank follows close on the

heels of the initial wave. Superposition of primary and reflected waves account for the

relatively large wave experienced by the dam considering the location of the slide, and

probably accounts for a considerable negative wave (trough) which follows the initial

peak.

WESTERN CANADA HYDRAULIC LABORATORIES LTD.1<

As expected, the water levels recorded at the face of the dam and in the approach

channel were higher than those measured just upstream of the dam. Waves impinging on

the earthfill dam shoaled as they encountered the sloping face of the dam. While the

gradually decreasing depth did not lead to breaking waves, it did lead to an increase In

wave height. Simi larly, the water level recorder in the approach channel was located In

the vicinity of reflecting boundaries. The water level at this point was due to the

superposition of reflected and incident waves. Wave heights in the approach channel were

thus larger than the incident waves. The measured wave heights, however, were not twice

the height of waves recorded upstream of the dam. This was due the fact that the

approaching wave defracted into the approach channel with a resultant decrease in wave

height entering the channel.

Table I also shows markedly different maximum water levels recorded at the same

location for repeat tests. This is not due to any experimental error or instrument

malfunction. The single most important cause in differences between data in wave

experiments is the fact that wave heights are measured at a single point. The wave

heights recorded, however, are in some instances the result of diffraction or superposition

of incident and reflected waves. A slight shift in the position or phase of the incoming or

reflected wave trains will result in a different amplitude history at a single point.

The water level recorders on the face of the Dam and in the approach channel are

situated in areas of relatively shallow water and also in areas close to reflecting

boundaries. The implications of this are:

I. the waves steepen and become very non-linear in the shallow areas

ii. the initial wave crests have not passed the measuring station before it is

influenced by reflected waves.

Due to the combination of wave steepening and reflections, one would expect complicated

wave patterns with some variation in maximum wave height at a single point from test to

test.

No data recorded or observations made during the tests indicated that Alternative

iliA had any substantial advantage over Alternative III v.,rith respect to effects of landslide

generated waves. Neither structure was overtopped during the Phase I test program and

wave heights recorded for each slide were approximately the same for each afternat ive.

WESTERN CANADA HYDRAULIC LABORATORIES LTD

A general observation was that Alternative IliA funnelled waves towards theapproach channel more than Alternative III. This observation is not, however,substantiated by the water level traces which show Alternative IliA with slightly smallerwaves in the approach channel. Neither alternative showed a tendency for waves to betrapped in the approach channel, reflecting from boundaries at the upstream anddownstream ends of the channel and feeding upon the energy of incoming waves ..

7.2 Phase II

The Phase II test program was carried out on the selected arrangement,Alternative IliA. The assumed slide data for Slide Area 4, Slide Area 6-2 and Slide Area6-3 were changed to test the sensitivity of the generated wave heights to various assumedvolume or velocity of the slides (see Section 6.2). Data were recorded as in Phase I.

7.2.1 SIide Distance-Time Profi les

A comparison of the distance-time profiles for Slide Area 6-2 F930), Slide Area6-2 (F::60), Slide Area 6-3 (F::00) and Slide Area 6-3 (hypothetical) are shown in Figures 15through 18. The tested profi les are a good approximation to input data, especially in theregion of maximum velocity. The Phase II distance-time profi Ie for Slide Area 4 isidentical to that of Figure 8 obtained in Phase I testing with only the slide thicknesschanged.

7.2.2 Test Resu Its

The results of Phase II test ing are listed in Table 2 (Tests I to 10). Arepresentative water level trace (Slide Area 4) is shown in Figure 19.

The maximum water levels recorded on the face of the dam and in the approachchannel were again due to a slide at Slide Area 4.

Localized overtopping was observed for tests 3, 4, 6, 8, 9, and 10. In each case, thevolume of overtopping was too small to accurately collect and measure. The location ofthe overtopping is shown below:

WESTERN CANADA HYDRAULIC LABORATORIES LTD. 15

Test Slide

3 and 4 6-2 F=30

7 6-3 Hypot8 6-3 Hypot

9 and 10 4 Phase II

Where Overtopping Occurred

Powerhouse intakesRight abutment of earthfi II damRight abutment of earthfi II dam and center ofearthfill sectionPowerhouse intakes and left abutment of earthfiJ Isection

Runup on the reservoir shore line was measured for all tests. In all but tests I and2, the waves overtopped the highest extent of the model opposite the slide at el 520 m andhad to be contained with sandbags.

7.2.3 Discussion

An increase in wave heights was observed in the Phase II test ing over thecorresponding slide in Phase I testing. This can be observed in the wave heights recordedboth upstream and downstream of the slide (recorders E and F). The runup on the oppositebank was increased significantly over Phase I testing. The initial wave, as illustrated inFigure 20 for Slide Area 4 Phase II, propagates across the reservoir and runs up theopposite shoreline, largely dissipating its energy in doing so. The waves which propagateup and down the reservoir formed through diffraction of the initial wave. While thesewaves showed an increase in heights over Phase I testing, they did not show the dramaticincrease demonstrated by the runup. A comparison of wave heights in the reservoir withrunup on a qualitative basis, however, was impossible since the runup overtopped themodel in all but tests I and 2.

As indicated by the data in Table II, increasing the slide velocity lead to the mostsignificant increases in recorded wave heights. This result is probably due to the fact thatincreasing the velocity not only increased the rate at which material was entering thereservoir but also increased the total slide travel and thus the total volume of materialwhich entered the reservoir.

The overtopping which was observed was localized and the volumes involved weretoo small to collect and measure with any accuracy. It is interesting to note that thewave traces do not indicate wave crests higher than the dam crest except on the dam facein tests 9 and 10. This indicates that the waves which locally overtopped the damstructures were the result of the superposition of reflected waves which locally created a


wave higher than the dam crest. More extensive overtopping was not observed in tests 9and 10 because the waves barely cleared the dam crest and were prevented from spillingover by surface tension effects. This is a recognized scale effect in models of this type.While the prototype can expect slightly larger volumes of overtopping than those whichwould be extrapolated from the model, they would not be significant and thus should notbe a source of concern.

7.3 Concluding Remarks

There is considerable precedence for hydraulic model studies of waves generatedby material rapidly entering a reservoir or other confined body of water. Where prototypedata were available (see Reference 2 and 3) hydraulic model studies predicted waveheights quite accurately. It can therefore be expected that the model study results,reported herein, are a good representation of the wave phenomena to be expected in theprototype under similar slide conditions.

Approved:

S.R.M. Gardiner, Ph.D., P .Eng.Manager, Spec ia I Projects


REFERENCES

I. WCHL Report, "Hydraulic Model Studies of Wave Action Generated by Slides intoMica Reservoir, 1970, 1970".

2. WCHL Report "Kitimat Arm Slides", 1977.

3. WCHL Report, "Model Studies of Mud Flow Entering Swift Reservoir", 1980.


TABLES

SITE C LANDSLIDE GENERATED WAVE STUDY

TABLE I

PHASE I TEST RESULTS

TEST II I DAM SLIDE MAXIMUM WAVE ELEVATIONS ABOVE POOL W.L. (m)* VOLUME DURA TION RUNUPI CON- AREA --,-- OF OF ON

FIGUR- APPROACH DAM U/S DAM U/S MOBERLY U/S SLIDE D/S SLIDE OVER- OVER- OPPOSI TEATION CHANNEL TOPPING TOPPING BANK

RECORDER RECORDER RECORDER RECORDER RECORDER RECORDER m3 (see) (EI. M)A B C D E F

I III 4 4.9 5.8 @ 4.7 5.2 9.1 0 - 5182 III 4 5.5 6.1 4.6 5.2 5.2 9.1 0 - 5183 III 6-1 0.7 1.5 0.9 1.3 2.4 4.0 0 - 4814 III 6-1 0.6 1.1 1.0 1.7 2.4 4.4 0 - 4835 III 6-2 1.3 1.9 1.0 1.5 1.7 2.6 0 - 4716 III 6-2 1.5 1.7 1.0 1.6 1.7 2.6 0 - 4727 III 6-3 1.0 2.7 1.7 6.7 5.8 6.7 II 0 - 4768 III 6-3 1.7 2.4 1.8 6.7 5.8 6.7 II 0 - 4929 III Moberly 5.2 3.7 3.2 @ 7.3 13.4 0 - 51810 III Moberly 2.9 3.9 3.2 @ 6.1 13.4 0 - 518II iliA 4 4.6 6.1 4.0 5.5 5.5 8.2 0 - -12 IliA 4 5.1 5.5 3.5 4.0 5.2 8.2 0 - -13 iliA 6-1 1.2 1.2 0.7 0.9 2.4 4.0 0 - -14 iliA 6-1 0.6 0.9 0.5 1.0 2.1 3.7 0 - -15 IliA 6-2 1.3 1.6 0.9 1.0 2.2 2.4 0 - -16 iliA 6-2 1.5 1.6 0.9 1.6 2.2 2.2 0 - -17 iliA 6-3 1.7 2.2 1.5 6.1 6.1 6.1 II 0 - -18 iliA 6-3 1.7 2.4 1.7 6.7 6.1 6.7 II 0 - -19 iliA Moberly 3.9 3.9 3.2 3.3 9.1 10.7 0 - -20 iliA Mober Iy 4.0 4.2 3.2 3.3 7.9 10.4 0 - -

* Normal Pool Water Surface EI 462 m.@ Water Level Recorder malfunctioned.II U/S Moberly and D/S Slide are at same location.

SITE C LANDSLIDE GENERATED WAVE STUDY

TABLE 2

PHASE II TEST RESULTS

TEST II DAM SLIDE MAXIMUM WAVE ELEVATIONS ABOVE POOL W.L. (m)* VOLUME DURA TION RUNUP INITIALCON- AREA OF OF OVER- :>N BANK RESER-

FIGURA- Approach Dam U/S Dam U/S Moberly U/S Slide D/S Slide OVER- TOPPING OPPO- VOIR

TlON Channel TOPPING (see) SITE WATER

Recorder Recorder Recorder Recorder Recorder Recorder 3 SLIDE ElEVA-mA B C D E F (el m) ION(m)

I iliA 6-2 (F=6°) 3.9 3.9 2.3 3.0 11.0 10.7 --- --- 512.9 462

2 iliA 6-2 (F=6°) 1.0 3.7 2.7 3.0 9.8 10.4 --- --- 510.4 462

3 iliA 6-2 (F=3°) 3.8 5.1 2.8 3.7 12.5 13.4 Powerhouse (unmeasurable) 520.0 462Intake

(unmeasurable)

4 iliA 6-2 (F=3°) 3.5 4.2 2.7 3.7 12.2 12.2 Powerhouse (unmeasurable) 520.0 462Intake

(unmeasurable)

5 iliA 6-3 (F=0°) 1.7 2.3 1.8 14.6 8.2 14.611 --- --- 520.0 462

6 iliA 6-3 (F=0°) 1.7 3.3 2.0 14.6 8.2 14.611 --- --- 520.0 462

7 iliA 6-3 (Hypot.) 2.4 2.4 2.3 13.4 9.8 13.411 Right Abutment (unmeasurable) 520.0 462of Earthfill Dam(unmeasurable)

8 iliA 6-3 (Hypot.) 4.4 3.7 2.6 13.4 11.6 13.411 Right Abutment (unmeasurable) 520.0 462and Center ofEarthfi II Dam(unmeasurable)

9 IliA 4 5.5 7.3 4.9 6.7 5.5 13.4 Powerhouse Intake and (unmeasurable) 520.0 462left abutment of

Earthfi II DamPhase II (unmeasurable)

10 IliA 4 5.5 7.9 4.9 7.3 5.5 12.8 Powerhouse Intake and (unmeasurable 520.0 462left abutment of

Earthfi II DamPhase II (unmeasurable)

* U/S Moberly and D/S Slide are at same locationsII U/S Moberly and D/S Slide are at same locations


FIGURES

III

II

FIGURE 1

"t

\Site - C

\Fort St. John

8

8G d ..ran e Prairie

\I

L T A.

A

!

\

--~--u . S . A.

SITE - CLANDSLIDE GENERATED WAVE STUDY

MOBERLY a TEA CREEK SLIDES

LOCATION MAPWESTERN CANADA HYDRAULIC LABORATORIES LTD.

beiI663'1A-WCH

FIGURE 2

TEA CREEK SLIDE AREA 4



SITE PLAN

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bci16639A-WCH

RESERVOIR


FIGURE 3

30 000 E

SCALE I' 5000



ALTERNATIVE mARRANGEMENr

RESERVOIR


SPILLWAY

FIGURE 430 000 E

SCALE I , 5000



ALTERNATIVE m AARRANGEMENT

FIGURE 5

TEA CREEK SLIDE ZONE

NOTE' RECORDER E AND F WERE POSITIONED U/S AND D/SRESPECTIVELY OF THE SLIDE BEING TESTED.

FOR SLIDE AREA 6-3, RECORDER F WAS NOT USED.

SLIDE

.- RECORDER AIN APPROACH CHANNEL



'";<..2..o

..a

61ft MODEL, (I' 62.5)

2000 m PROTOTYPE, ( I' 25000)

1!500,1000.500,

() WAVE RECORDER

o.....I

o,

500

I-

MODEL LAYOUT


TOE ELEVATIONVARIES 1

II~

El. 432.0m If1

BENTONITE a PEA GRAVEL MIX

TROUGH FROM

~

aU PVC PIPE

"

. b-. \J'. 4~

D".

~

": .,-. -~

SCALE I : 5 model--- I: 2000 proto.

J>~ .. :' 4' . 'Vt).' ~ .~4, . ~ •

~~

,A_'

~

.f> ••.~---:-,~-;--y-.-~..:J.,

- Co c,.)'I. """

",'

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bcil6638 A-WCH



TYPICAL SECTIONTHROUGH MODEL DAM

SHOWING COLLECTION TROUGH

"G)C:::0IT!

Q)

VOLUME ENTERINGRESERVOIR PHASE I

TEA CREEK SLIDE AREA 6-1

~

-""./ "-

C /. _

TEA CREEK SLIDE AREA 6-3

TEA CREEK SLIDE AREA 6 - 2

MOBERLY SLIDE AREA

FIGURE 7

TEA CREEK SLIDE AREA 4 PHASE I

TEA CREEK SLiOE AREA 4 PHASE II


~o 0 ~o 10011'I PROTOTYPE:L- --' , , ( I' 2000 )

10 10 20 30 eM MODEL•... ~ . , , ( I ' 5 )

SITE - C

LANDSLIDE GENERATED WAVE STUDY


MODELLED SLIDE PROFILES

80

500

70

90

/0 12 14 16 18 20 22 24 26 28 30 32 34 36 -386 82 4

--- -~ -----v-

0

U"

0(b0

j ).--

?/.)?

//~

- fl

~

t{-

lV ?-'V I I I I I I Io

100

200

300

400

60

wuz;:!(/)

o

e

TIME (SEC)

o - MODEL

(-) INPUT DATA


SITE- C

LANDSLIDE GENERATED WAVE STU DY


DISTANCE - TIME PROFILESLI DE AREA 4

"G>C:::0rrtCD

bc'l6638 A-WCH

(

--- ..----/

/

V/1>/

/

Vi--------

V-----

/--- ---- ----- -----

V/'

I------- --- --

V"/

(D

-l-----"

180

160

140

120

E 100

wu

~ 80l-I/)

o60

40

20

oo 2 4 6 8 10 12

TIME (see)

14 16 18 20 22 24

LEGEND

o MODELINPUT DATA

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bdl6638 A-WCH

SITE - C

LANDSLIDE GENERATED WAVE STUDYMOBERLY 8 TEA CREEK SLIDES

DISTANCE - TIME PROFILESLIDE A REA 6-1 PHASE I

/~

//

)V--- /

---- ----- ---------- --- /(I/ --

/-- -- --

/(

7p

~

90

80

70

60

E 50

wo

~ 40r-ef)

o30

20

10

oo 2 4 6 8 10 12

TIME (sec)

14 16 18 20 22 24

LEGEND

o MODELINPUT DATA

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bcil6638 A-WCH

SITE - C



DISTANCE - TIME PROfiLESLIDE AREA 6-2 PHASE 2

11

G>C::ufT1

o

- r----~ ----- ------ ;...--

- +--1 (vL" ---

(v-+ j---r - /V-+-1- I

/

Y---,--------i~ __~ ---1·· .-f- -- ---.-.- -- ---->/

I--- ----~-----~ -~___~ __L~ ----

--.-.-.-- /--------- r----~- ----~- ------ r--

V(n ----- ..--- "-------- .. /

/~-+------- j------ ------ -- ------- ---- --

I-- -------- ---"-"-'- 7 --- --- r---'

r---- ------ r---- -'- -'- --- ---

~~

260

240

220

200

180

160

E 140

wuZ 120~l-(/)

o 100

80

60

40

20

oo 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

LEGEND

o MODELINPUT DATA

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bcn 6638 A-WCH

TIME (sec)

SITE - C

LANDSLIDE GENERATED WAVE STUDYMOBERLY a TEA CREEK SLIDES

DISTANCE - TIME PROFILESLIDE AREA 6-3 PHASE 1

"G>C::u[1l

/</0 D:>

"-

I ---- I----"

V/~"- r--

!1--------

'l~/

(I/

/r~ ~

360

320

280

240

E 200

wu

~ 160l-(/)

o

120

80

40

oo 4 8 12 16 20 24

TIME (see)

28 32 36 40 44 48

SITE - C

LANDSLIDE GENERATED WAVE STUDYMOBERLY a TEA CREEK SLIDES

LEGEND

o MODELINPUT DATA

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bdl6638 A-WCt!

DISTANCE - TIMEMOBERLY SLIDE

PROFI LEPHASE I

."G>C:urrI

N

FIGURE 13

.

l -,,

500 520 540 560 580 600 620

:, 460 480 500 520 540 560 580

:

I!:i 440 460 480 500 520 540 560

.

~;

400 420 440 460 480 500 520


MOBERLY a TEA CREEK SLIDES120 140

SLIDE AREA 4 ALTERNATIVE illPHASE I

WAVE TRACES

APPROACH CHANNEL

I-"" --- -------... -----10..sZ 5o;::0"">'j 5w

10200 220 240 260 280 300 320 340 360 380 400 420 440

TI ME IN PROTOTYPE SECONDS460 480

DAM FACE

--- ~ ~ --I-----...... ...--- - -.--/ - ----65

;:::; 0wj;j 5

10160 180 200 220 240 260 280 300 320 340 360 380 400

TIME IN PROTOTYPE SECONDS420 440

UPSTREAM DAM

~IO ----...... - I-Z 5Q

~ 0>wj;j 5

10140 160 180 200 220 240 260 280 300 320 340 360 380

TIME IN PROTOTYPE SECONDS400 420

120 140 160 180 200 220 240 260 280 300 320 340 360 380TIME IN PROTOTYPE SECONDS

UPSTR EAM SLIDE DOWNSTREAM SLIDE

E20 E 20

ZIO Z 100

~ 00f- 0> ""w >

t;j 10 w 10--'w20 20

0 20 40 60 80 100 120 140 0 20 40 60 80 100TIME IN PROTOTYPE SECONDS TIME IN PROTOTYPE SECONDS


UPSTREAM MOBERLY

10100

I 1------- f-----'- I ....--- ......•••---r------ I -I

500

460

440

520

480

460

540

500

480

560

520

500

580

540

520

600

560

540

FIGURE 14

620

580

560

400 420 440 460 480 500 520

120 140



SLIDE AREA 4 ALTERNATIVE ill APHASE I

WAVE TRACES

-APPROACH CHANNEL

4

2 2of: 0'">~ 2w

4

I---""" -....., --

/ ~ -------- " .,,---- ,/ -----I '-. ------ ~I ---I -----.. v-----

200 220 240 260 280 300 320 340 360 380 400 420 440 460 480

DAM FACE TIME IN PROTOTYPE SECONDS

6

~ 4

2 20

~ a>wG:J 2

4160 180 200 220 280 300 320 340 360 380 400 420 440

TIME IN PROTOTYPE SECONDS

UPSTREAM DAME 4

2 20>=:; ~Ow~ 2

4140 160 180 200 220 240 260 280 300 320 340 360 380 400 420

TIME IN PROTOTYPE SECONDSUPSTREAM MOBERLY

4

/ "--- .r-- ~/' ~ /\ ~ ~

~/' ''\ ---""" ~ V "-.J'" /

\---------

'-. ../100 120 140 160 180 200 220 240 260 280 300 320 340 360 380

TIME IN PROTOTYPE SECONDS

UPSTREAM SLIDE DOWNSTREAM SLIDEEIO 10

~ 5 ~2

~ 0 0>= 0

w '"~ 5 > 5w-'w

10 100 20 40 60 80 100 120 140 0 20 40 60 80 100

TIME IN PROTOTYPE SECONDS TIME IN PROTOTYPE SECONDS

WESTERN CANADA HYDRAULIC LABORATORIES LTD,

240

- ·~~---·_·

I

~-------

----J-L----------J-, I

I I I

j I!

-.---~- -~--.-----n_-~-~-T--

200

160 --~-~

~ 120E

I1JUZ

~ 80(/)-0

40

--I--I

~~4-J

I

o-- ~_ .._-~-- -~-

o 4 8 12 16 20 24 28 32 36

TIME (sec)

o MODEL(-) INPUT DATA

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bdl6638 A-WCH

SIT E - C



SLIDE AREA 6-2 F= 3°DISTANCE- TIME PROFILE

"G)C:::0rrt

01

200 --- --- --------

~~~-~-~--- -----~-~-~ -~-~ ---~---~~-I

I

I I I

120 --------t- ~----- ~ - -- 4- --- - -]- -1-

Bo---L- -L-~ ...--['--.--1- - --1-- ---.-.----~----~----j~I

~ I- ~--_-:--:-~I

I I I I

I I

wuz<:tl-(/)

o

160 ~-

40

o

o 4 8 12 16 20

TIM E (see)

24 28 32 36

o MODEL

(-) INPUT DATA

SITE - C



SLIDE AREA 6-2 F= 6°DISTANCE - TIME PROFILE

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bcil6638 A-wCH

m

--~-

o-~-

_ _ n _

- -f- __ i_.-I

o

--------- -_ .._---~_ .._--------200

100 ------

300 ~ u _

w(J

z«l-(/)

o

4 8 12 16 20 24 28 32 36

TIME (sec)

o MODEL(-) I NPUT DATA

SITE - C



SLIDE AREA 6- 3 F = 0°DISTANCE -TIME PROFILE

'TJ

G>C::0fTI

WESTERN CANADA HYDRAULIC LABORATORIES LTD.bcJl 6638 A-WCH

---~--- -------- ---- ..- .~---_.-

-~------- -'-._-~----

,it----I

I

I 0 I I

t r--------l-------t-~--- ----~- -- -

: I-i III-m- ----1-----

I

I I

-- ·-1---·· iI I

I

oooo

-~----- -------

100

400

500

300

200

E

w()

Z<tI-00

o

o 4 B 12 16 20 24 28 32 36

TIME (sec)

o MOD E L(-) INPUT DATA

SITE - C



SLIDE AREA 6-3 HYPOTHETICALDISTANCE- TIME PROFILE

"G)c:urr1

WESTERN CANADA HYDRAULIC LABORATORIES LTD. ex>bcil6638 A-wCH

FIGURE 19

.-500 520 540 560 580 600 620

.

./ ~ - -~ - ..,,- ..•...•-!

460 480 500 520 540 560 580

-,

,i 440 460 480 500 520 540 560

i

!

.....•• ------400 420 440 460 480 500 520

DATUM FOR WAVE PROFILE CORRESPONDS TO EL. 462 m

SITE - C

v--- LANDSLIDE GENERATED WAVE STUDY-...... / MOBERLY 8 TEA CREEK SLIDES

120 140 SLIDE AREA 4 ALTERNATIVE .IIIPHASE n

WAVE TRACES

APPROACH CHANNEL

./ .......•••.•~ ~ -----.....•..•..

..•.•....•. --10200

10

!z 50i= 0..> 5w-'w

220 240 260 2.80 300 320 340 360 3BO 400 420 440 460 4BO

DAM FACETIME IN PROTOTYPE SECONDS

5

10160

--- ~V "'-.. ~ ./' ......•.•.... .-" -..... --./ - - -- ...r ......•.-- ..••.•

~-5 10

Z 50I- 0~w-'w

IBO 200 220 _ 240 260 2BO 300 320 340 360 3BO 400 420 440

UPSTREAM .DAMTIME IN PROTOTYPE SECONDS

...- "-- ./" ....••...... --r-... .r--..~ ......•.---- - --- f-""

5

10

140

5 10

5z0

0;::~w-'w

160 IBO 200- 220 240 260 2BO 300 320 340 360 3BO 400 420

UPSTREAM MOBERLY TIME IN PROTOTYPE SECONDS

10100 120 140 160 - IBO 200 220 240 260 2BO 300 320 340 360 3BO

UPSTREAM SLIDE DOWNSTREAM SLIDE15 15

~ 10 E 10

z 5 z 5Q 0

!i 0 i= 0> ~w-' 5 w 5w -'

10 w 100 20 40 60 BO 100 120 140 0 20 40 60 BO 100

TIME IN PROTOTYPE SECONDS TIME IN PROTOTYPE SECON DS

W~STERN CANADA HYDRAULIC LABORATORIES LTD.

.: 10

Z 50;:::.. 0>w-' 5w

./ -~ '\..../' ./'--- ~"- ~ ............-r-

" -

peace river development 13~ ,3ll &~:~~/l~

Documents