Tidal Currents in Johnstone Strait

· Pacific Marine Science Report 81-22

TIDAL CURRENTS IN JOHNSTONE STRAIT

by W. S. Huggett and M. J. Woodward

INSTITUTE OF OCEAN SCIENCES Sidney, B.C. For additional copies or further information please write to:

DelJartment of Fisheries and Oceans '. Institute of Ocean Sciences P.O. Box 6000 Sidney, B.C. CANADA V8L 4B2 Pacific Marine Science Report 81-22

TIDAL CURRENTS IN JOHNSTONE STRAIT

W.S. Huggett and M.J. Woodward

Institute of Ocean Sciences Sidney, B.C. 1981 I °1 ABSTRACT

This report describes the tidal streams in the area of Johnstone Strait in British Columbia. Over a period of several years short-term current meter records were taken at 7 stations along the length of the strait and at 2 stations in Queen Charlotte Strait. It was found that, although tidal streams at locations where observations had been made were predictable, interpolation between stations is difficult due to the complexity of the currents. Generally the tidal streams in Johnstone Strait are semi-diurnal, with the streams at depth stronger than the surface streams and the times of turns earl ier. In the passes at the western end of the strait, times of slack water are best referenced to slack water times at Seymour Narrows .

., N

,CANADA U'§A.'-. PACIFIC OCEAN

Figure 1. Current meter positions. 3

Introduction

The purpose of this publ ication is to bring to the notice of ship and tug masters, fishermen and other seafarers, the vagaries of the tidal streams in Johnstone Strait. It is hoped that after reading this publ ication they will be able to make better use of the tidal streams in their work, and realize the difficulty of trying to present to the mariner predictions of times and speeds of the currents in Johnstone Strait and the adjoining passes.

These measurements in Johnstone Strait were taken in the years 1976, 1977 and 1978 to gain some knowledge of the propagation of the tidal wave and streams along the Strait, and to investigate the internal tide that is present in the area of Hickey Point. This latter investigation is a direct outcome from the data taken in 1973. Continuous current meter records were taken at seven stations along the length of the Strait and two in Queen Charlotte Strait, with continuous temperature and conductivity records also taken at most locations. During the course of these surveys ten oceanographic cruises were carried out with CTD (conductivity, temperature, depth) measurements taken at thirty stations stretching from south of Cape Mudge in the Strait of Georgia to Gordon and Goletas Channels in Queen Charlotte Strait. These measurements are necessary to determine the density structure of the water, to enable prediction of the barocl inic streams. At twenty of these stations dissolved oxygen, sil icate, nitrate and phosphate samples were taken. Bottom grab samples were also taken along the Strait from Yorke Island west to Hanson Island. The above data is recorded in Data Record of Current Observations Volumes VI I and VI I I.

Observations

The tidal streams in Johnstone Strait are predominantly semi diurnal with a ratio of Kl+Ol = 0.22 in contrast to the tidal components which M2+ S2 have a ratio of 0.58. The actual ampl itudes of M2 and Kl at Station 3, for example, are 28.0 cm/sec and 6.5 cm/sec respectively. Owing to their strong semi-diurnal characteristic the tidal streams follow very closely that of the M2 tide. Actual comparisons of the surface currents between Station 3 (Johnstone Strait Central) and other stations (Fig. 2) show that the time of the maximum current is practically the same as that for the M2 stream (29.98° = 1 hour), and the standard deviation of the comparisons is less than 25 minutes at all stations. The time of maximum surface streams (15 m depth) is delayed by 2h 36m from the outer Station QC2 off Masterman Island to Station 7 in Discovery Passage, and the bottom streams lag by 3h 10m (Fig. 3). Although the bottom streams lag the surface streams at both ends of the Strait, 52 min at Masterman Island and 18 min at Station 7, at Station 3 the bottom stream leads the surface stream by 16 min. Also at Station 3, the amplitudes of the diurnal and semi-diurnal constituents for the tidal streams at 225 metres depth are much larger than those of the surface streams, being a factor of 2.5 and 1.7 respectively higher (Fig. 4 & 6). These strong streams at depth are due to a baroclinic current generated by the tide at the sill just east of Station 3. The sill disturbs the equil ibrium level of the uniform density surfaces to create temporary unbalanced horizontal density gradients and hence internal tidal motions (Thomson 1976, Thomson and Huggett 1980). 4

The times of slack water (on the surface and at the bottom) vary quite remarkably from station to station and from day to day because of (a) the large residual current present, and (b) the weather conditions. The winds in Johnstone Strait either advance or retard the surface current, which affects the times of slack water. A section across Johnstone Strait at Station 3 shows the distribution of the residual current (Fig. 8). At a mean depth of approximately 115 m there is no residual current; above this depth the current is outgoing and below this depth it is incoming. This general pattern is typical of tidal estuaries, and holds good for the remainder of Johnstone Strait as shown by Figure 9, except that the mean depth for no residual current is about 75 m when east of Kelsey Bay.

The surface current in Johnstone Strait between York Island and Alert Bay is quite straightforward with the turn to flood and maximum rates at Station 10 being 10 minutes earlier than Johnstone Strait Central, and with the turn to ebb occurring at the same time. This stretch is characterized by the two ebb currents per day having nearly the same amplitude of 75 em/sec, and where, after the slack, the current quickly rises to 75% of the maximum current or better and maintains this speed for 3~ hours or more. This relationship however, does not hold when the tides are predominantly diurnal, in which case a marked difference between the two ebb currents is evident (Fig. 10). The larger tidal range produces the larger tidal current, which varies anywhere between 20 and 40 em/sec, and on the smaller tide range of the day the current varies between 5 and 15 em/sec. The flood current following the lower low water (LLW) of the day is the larger of the two flood currents and is about twice that of the other flood current, and when the lower high water (LHW) is less than 3.8 m (12.5 ft) there will be no flood current.

The bottom currents along this stretch have, conversely, a large flood bias, but, unl ike the surface where the ebb currents have the same speed for both daily currents, a large diurnal inequal ity exists with a maximum difference of 40 em/sec. The larger flood currents (85-110 em/sec) have a duration of 8~ hours, but the smaller flood currents maintain their maximum speed for 2~ hours to 3 hours. The larger ebb currents (50-70 em/sec) have an average duration of 5 hours with the diurnal inequal ity only half (20 em/sec) that of the flood currents. I· In the passes at the western end df the Strait) the times of i' maximum current are the same, or nearly so, as Johnstone Strait Central, but the times of slack water differ considerably and are best referenced to slack water times at Seymour Narrows. In Blackney Passage and Broughton Strait where the surface currents are affected by the bottom currents, the times of slack water in these narrow, shallow passes are a compromise between the two slack waters. This results in the times of slack water on the turn to flood and ebb being respectively two hours earl ier and one hour later than the surface slacks in Johnstone Strait. The slack waters at Blackney Passage are 30 minutes earl ier than off Alert Bay, but 20 minutes later than Pulteney Point. In the area between B1 inkhorn Light and Alert Bay there are strong tide rips present on the flood current. At the eastern end in Sunderland Channel the current is only half that of Johnstone Strait Central, and both slack waters and the maximum ebb occur 1 hour 40 min earl ier, and the maximum flood 1 hour 10 min earl ier than in Johnstone Strait. During the times of maximum flood and ebb there are strong tide rips or fronts 5 present in the channel between Kelsey Bay and Port Neville.

In Johnstone Strait east of Yorke Island the times of maximum flood and ebb currents on the surface occur about 20 minutes later than those to the west of Yorke Island, but the times of slack water differ widely. Again the ebb bias is very prominent, and both daily ebb currents have the same velocity of 120 em/sec. This appears to be the maximum velocity attained in that part of the channel, and the current maintains this speed for 2~-3 hours. When the range of the tide is less than 1 m, the maximum ebb velocity drops to about 70 em/sec with some diurnal inequa1 ity in the two daily ebb currents. The flood currents, on the other hand, have a large diurnal inequa1 ity with the speed of the flood current following LLW being double that of the other flood current. The maximum floods have velocities up to 110 em/sec, but when the range of the tide is less than 1 m, there is no flood current for that period. The maximum flood currents here and the maximum ebb currents west of Yorke Island are both dependent on the range of the tide as evidenced by the graphs in Figures 12-17. An appreciation of the current velocity to be expected from the range of the tide at Alert Bay can be had from these graphs.

The times of slack water are vastly different from those of Johnstone Strait Central, the turn to flood occurring 35 minutes earlier and the turn to ebb 90 minutes later. In Race Passage however the currents are the same as Johnstone Strait Central, but in Current Passage the turn to ebb occurs about 75 minutes earlier than the turn to ebb in Race Passage.

The bottom current along this part of the Strait east of Yorke Island also has a large flood bias with the flood current having a maximum speed of 120 em/sec, but un1 ike the surface current, does vary with the tidal range. The maximum flood current also has two peaks roughly 2~ hours apart with a 20-40 em/sec drop in speed between the two peaks (Fig. 11). This phenomenon was not apparent at any of the other stations in Johnstone Strait. The difference between the two daily flood currents is 30 em/sec at times, the duration of the flood current is around 8~ hours and for at least half of the time the current is running at 80% or better of the maximum speed. The ebb current is generally less than 45 em/sec, but when the tides are predominantly diurnal, rates up to 60 em/sec are present. The duration of the ebb current is about 4 hours, with the diurnal inequality greater than that of the flood stream, attaining a difference of 50 em/sec at times.

In Nodales Channel the bottom currents are more diurnal than at Station 9. The velocity of the bottom water entering and leaving Nodales Channel is only one-third of that at Station 9 (40 em/sec as opposed to 120 em/sec), and the times of maximum current vary anywhere from a half hour to five hours earl ier. When the tidal range is large the current continues to flood (north going) on the bottom in Nodales Channel on the largest ebb of the day (a continuation of the ebb in Discovery Passage).

In Race and Current Passages, situated between Kelsey Bay and Station 9, the times of maximum flood and ebb are at the same time as those at Station 9, and the times of slack turn to flood are 15 minutes earl ier than Station 9. The turn to ebb in Current Passage occurs 45 minutes earlier, and i~ Race Passage it occurs 30 minutes later than at Station 9. At the 6

north end of Discovery Passage the maximum flood occurs 10 min later and the maximum ebb 30 minutes later than at Station 9, with the times of slack water being very close to those of Seymour Narrows.

Looking at the Strait in cross-section in the vicinity of Station 3 over a 25 hour period during a time of average tide heights, large differences from one side to the other are evident on the surface in the speeds and time of the turn (Fig. 18). The flood current starts at depths around 200 m and builds up to speeds greater than 40 em/sec while there is still an ebb current running on the surface. On the surface the flood current starts along the Vancouver Island shore at about the same time as it starts at depth, but takes over 2 hours to completely cover the Strait from one side to the other, with the current along the Vancouver Island shore far stronger than elsewhere across the Strait. However, as soon as the flood current covers the entire Strait, the speed drops off dramatically to about one-third of its maximum speed. In less than 2 hours after the flood current covers the entire surface, the ebb current is starting to run along the mainland shore, and within the hour the whole Strait on the surface is ebbing. The flood current still continues to run at depth for about 2 hours after the start of the ebb on the surface. At the time of maximum ebb, the current speed is the same across the Strait, then falls off quickly on the Vancouver Island shore prior to the start of the next flood current. The ebb current runs the strongest on the surface with the speed decreasing with depth.

On a cross-section 5.5 km (3 miles) to the east of Station 3, the start of the flood current exhibits the same characteristics as it did further to the west, but the ebb current appears to start in the centre of the channel rather than along the mainland shore, and when running at its maximum is much stronger along the mainland shore. On a large flood as shown in Fig. 19, the flood current runs for 6 hours on the surface, longer at . depth, and the change to ebb on the surface is much quicker, within the hour, than on the change to flood.

A longitudinal look at the Strait between Stations 12 and 17, and on the same day as the cross-section at Station 14 was plotted, shows that at Sta~ion 17 on the bottom the ebb current runs for a very short duration, I' somethlng less than four hours (Fig. 20). A prominent feature is again the I wedge of strong flood current between 200 and 150 metres depth that persists r long after the ebb current is running on the surface, and even after it is ebbing on the bottom. Another feature is the magnitude of the flood current at Station 3 at 235 m depth where it is much greater than that at Station 12 or 14 at maximum flood.

Conclusions

Although the above features are regular in time, their complexity makes them difficult to describe and to present in one or two simple graphs. The tidal streams at any point can be predicted well, but their rapid change in behavior along the ~trait, across the Strait, and with depth requires many reference and secondary stations in the tide tables, and defies simple explanations. 7

In 1982 current meter observations will be taken at Stubbs Island, east of Alert Bay, and from these observations it is hoped that better current predictions will result for the passes at the western end of Johnstone Strait. 8

Acknowledgements

We would like to thank the many people who helped in the collection and analysis of the data, and in particular, A. Douglas, F. Hermiston, R. Thomson, J. Love and C. de Jong. C. Dale, B. Watt and K. Holman are thanked for their assistance in the preparation of the diagrams, and S. McKenzie in the typing of the manuscript. We also gratefully acknowledge the help and cooperation given to us by the officers and crews of the CSS Parizeau, CSS Vector, CSS Richardson and the CFAV Endeavour.

References

Huggett, W.S., J.F. Bath and A. Douglas. 1976. Data record of current observations Vol. XIX, Johnstone Strait, 1973, unpubl ished manuscript, Institute of Ocean Sciences, Patricia Bay, Sidney, B.C., 155 p.

, R.E. Thomson, M.J. Woodward and A.N. Douglas, 1980. Data ------record of current observations Vol. VI I, Johnstone Strait, 1976, 1977, 1978, unpubl ished manuscript, Institute of Ocean Sciences, Sidney, B.C., 288 p.

Thomson, R.E. 1976. Tidal currents and estuarine-type circulation in Johnstone Strait, British Columbia, J. Fish. Res. Board, Canada, 33(10), p. 2242-2264.

1977. Currents in Johnstone Strait, British Columbia: supplemental data on the Vancouver Island side, J. Fish. Res. Board Canada, 34(5), p. 697-703.

______~.and W.S. Huggett. 1980. M2 baroclinic tides in Johnstone Strait, British Columbia. J. Physical Ocean., p. 1509-1539.

ocean. the

known wave

Longest sun. and moon the of forces

tide-producing

the with

associated

wave

period long a wave: I da Ti

current.

observed current residual + stream Tidal

action.

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and day

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having current or tide the of

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rips. or

lines tide

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the on visible often density;

different

of water

masses two of

intersection vertical the t: Fron

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tidal ebb or flood successive two

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between

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interface. sloping a having density different

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Terms of Glossary 9 10

Turn to Maximum Turn to Maximum Flood Flood Ebb Ebb h m h m h m h m Bear Point (J9) -0 35 +0 30 +1 35 +0 20

Camp Point -0 20 +0 30 +2 05 +0 20

Current Passage -0 20 +0 30 +0 50 +0 20

Sunderland Channel (JI6) -1 40 -1 10 -1 40 -1 40

Forward Bay (JI0) -0 10 -0 10 0 00 -0 10

Masterman Island (Q02) -3 45 -1 55 0 00 -1 55

Browning Islands (QOl) -2 25 -1 50 -1 05 -1 55

Blackney Passage -1 10* 0 00 -1 10* 0 00

Alert Bay -0 40* 0 00 -0 40* 0 00 f: . Pulteney Point -1 30 * 0 00 -1 30* -1 00

* Tim e difference for II Turn to Flood" and "Turn to Ebb" to be applied to the pre dictions for Seymour Narrows.

Figure 2. Time differences between Johnstone Strait Central and secondary stations along Johnstone Strait for maximum currents and turns.

' ,

Bottom

Tide

Surface

Bottom

Tide

Surface

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135

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221

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---

Strait

-136-min

168min

40min

68min

29min

6min

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Station

Johnstone

--150°

Station

249°

234

224

228

Strait.

...... - - ;----~-,-r-- . ',' . '. :::=:;.

M2 Amplitudes

I ,,' r ' "0 C 0) >- C 10 -I-J ~ 10 E -I-J "0 III 0) lIl_ 0) 0) ~"O ~ o -I-J C"O ~ 0) 0) > en -~ 0) 0) c c 10 0) c - -I-J ~ C o 10 0) c -I-J -'-~ Cll ~ -I-J.- ~ 10 0) 3: 10 C Cll C U l/l "0 C lIl_ 0) 10 ~ ~>- O~ ~ > 10 .- "0 10 l/l l/l C 10 10 l/l ::J ..c -I-J o 10 ~ l/l o Q) 0) 0 O..c .- 10 ::J..c ~- dUVl l.I.. Cl:l Cl:l- 0.. Z Cl:l 0.. ZU 00.. VlU QOl Q02 J10 J6 J3 J9 J8 J7 JI6

-.. 0 I·' 20.9 15.9 24.2 30.3 28.0 68.0 47.4 20.0 50 1 7.8 17.5 14.6 27.0 24.0 60.6 45.2 ..c t-.;) -I-J C- 100 O) 0 III 0) ~ 40.2 -I-J 150 40.2 0) 1 ~ 43.6

200 "I 44.1 48.5 57.0 46.9 250 "I 47.0

300 --f 19.5 9.5 30.2 Figure 4. Semi-diurnal speeds of the tidal streams in em/sec. Metres Depth

w N N o \J1 o \J1 o \J1 o o o o o o o

Masterman 0' 0' W o Island o o

::T! co p Queen c: W \J1 0' 0 .., \J1 0 N CD 0 0 0 Charlotte fJ1 Strait

""1J :r OJ en N N N ~ Forwa rd enCD 0 0 0' N \..0 0 Bay 0.... 0 0 0 :r.... CD en CD 3 N N ~ Broken 3: T" N 0 0' Is lands N 0. 0 \..0 0 0 ""0 ..,c: :r ::l OJ Ul e!- CD d". Ul 0. e!- N N N N N N N ~ N N N W Port ~ 0' ex> N J::- W .., 0 0 0 0 0 0 0 Nevi lle CD OJ 3 ~

N N N N ~ Bear !Xl N W "N \..0 CD J::- N ex> Point (Xl 0 0 0 0

:r 0 w c: 0 ~ Nodales ~ -...,J ex> 0 Channel

N N N Discovery W W W o \J1 \..0 Passage o o o

Sunderland \..0 ex> o J:: Channel o 0 Metres Depth

IJ,J N N o \J'1 o \J'1 o \J'1 o o o o o o o

\J'1 Masterman o Island

\J'1 IJ,J IJ,J p Queen 0 " N -...... J 00 N Charlotte :!1 i co Stra t c "'"CD Q)

\J'1 -...... J 00 c... Forward 9- . c U) N IJ,J 0 Bay ::l"'" ~ (J) "0 CD ;><: CD I-' 0- N c... Broken (J) 0' :t::> 0 0' \J'1 3 Islands "0 -=r.-+ CD rt ~. C 0- Port c.. ~ IJ,J 00 0' 0 \J'1 -...... J 0' c... CD . . IJ,J Nev ill e l/l (J) \J'1 0 N U) IJ,J .J:=- \J'1 .-+ CD"'" III 3 (J)

::l (') 0 .J:=- \J'1 c... Bear . U) 3 U) 00 U) Point (J)"'- CD r>

0' c... Noda1es . 00 Channel

c... -...... J Discovery Passage

c... Sunderland 0' Channel

vL ~ __ _ .•>It. ~----

K1 Phases

','

'"0 C (l) >- c -I-J l- re re l/l~ ~ E -I-J '"0 l/l (l) (l) (l) 1-'"0 o -I-J I- c'"O (l) (l) > OJ I- (l) (l) C C - o- re (l) C - -I-J - C o ro (l) C -I-J ro (l) I- ro 3: ~ ro -I-Jo-- I- C ro C U l/l '"0 C l/l- (l) ro l- I- >- 0- I- > ro 0- '"0 ro l/l' l/l C ro re l/l ::I .e -I-J o re I- l/l o (l) (l) 0 o.e 0- ro ::I.e ::E- auU'l ..... fXl fXl - a..:z fXl a.. z u o a.. U'l u QOl Q02 Jl0 J6 J3 J9 J8 J7 J16

0-- I 0 0 0 0 0 0 216 224 222 18r 258 234 191 0 241 50 -l 210 0 22r 223 0 225 0 272 0 227 0 197 0 , 01 100 .e -I-J 0- (l) 0 I 208 0 l/l 150 (l) l- 0 -I-J I 201 (l) ::E 200, 204 0

0 0 0 220 198 249 ,

0 250 -1 184 212 0

300-1 200 0 139 0 227 0 Figure 7. Phases of the diurnal tidal 'streams. ) (15.040 = 1 hour) ----_._------:------~--:---:---:--...,.---:.....,.-~-:--:-~-"::'':''''~..,..-...,.,..,-:'-~=-----~------. . "'" "'...... 1 ......

I r ' "

ISLAND

100

l/) 200 LU ~ I0:: W ~

• 300

o 1 KILOMETRES 2

Figure 8. Distribution of the residual current across the Strait at Station 3. I,, ','

STATION POSITIONS aDI QD2 JIO J6 J 12 J3 JI4 JI7 J7

01 1111j?1111 II?)I 11111911 111119111[1 Ilqll?1 ,,91Ii?"'il' 1IIIIII111111 IIIIIIII111 I

100

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~~;~f. I Division:: 5 em/sec

::r.\:.:.

~::::.;:: 400

o 10 o 10 20 30 40 50 60 70 DIS TAN CE (kilometres)

Figure 9. Distribution of the residual current along the Strait. •.1.

0 0 (Y)~ If) - N dept h

~ A n f\ A ,,' I r ' If) n If) A A r- - A f\ f\ A

en A , ~n A~~ u:BO Lf IV If) ~~~ ~ r-'- ~~ V,: IV I V V

0 0 (Y) If) ~ N '- I

0 a 00 (Y)~ If) - N deDth 225

,. If) M ~ If) ~ ~ I~~ - ~ ~~ r- A ~ ~~~ I A 1\ } f\ A en f\\ Ir\y 'f\u O 1\ ~ ~ ~ '; i I IV v IV I~ v Lfu:B v ~ W v If) V r- - I I V V V 0 0 (Y) If) N I I I I I I I I I I 13 15 17 19 21 23 25 27 3 FEB/77 Figure 11. Plot of the surface and bottom currents at Station 9 with the tide (fine line) superimposed. o : ..'

o o en N ~I depth 23m

,,' I,, fI A ~ U) A

U)_ ~ - r- (\ A fI I\ ':, r

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(f) L ...... U O L O U

U) U) - r- -I I

0 0 en U) N I -I 13 15 17 19 21 23 25 27 3 FEB/77 Figure 10. Plot of the surface and bottom currents at Station 3 with the tide (fine line) superimposed. I r ' -. - ~ () () ~ I a: W « Z x ~ 100 80 60 20 40 o 0.0 t···· I Figure • • 12. .... 1.0 I and Station low TIDAL A 3 water. Plot 2.0 I of • RANGE maximum 3.0 ebb i (M) current A • and 4.0 the I tidal range 5.0 between I FEB. HIGH R MAX TIDAL JOHNSTONE = CORRELATION T~_' lower __ ' __ 77. EBB ':~~'_ TO RANGE high 27 CURRENT LOW, water _; __ ST. ~~ PTS. __ LOWER COEFFICIENT .~_.~ R 003 = .89 VS. o IV ~ ~""' ') .:::Z R. .... ----

100 JOHNSTONE ST. 003 MAR. 77, 42 PTS. MAX EBB CURRENT VS. TIDAL RANGE LOWER 80 .. . . HIGH TO LOW, R = .77 • • ~ ~ ...... , ... I'" ...... (.) • - 60 •• I- • Z I ...... ·•• ..••• tV W a: a: • • :::::> I ..../. (.) 40 X « ~ • • 2°l •

o I i I I I I 0.0 1.0 2.0 3.0 4.0 5.0 TIDAL RANGE (M) Figure 13. Station 3. Plot of maximum ebb current and the tidal range between lower high water and low water. Same as Figure 12. An indication of the current to be expected may be obtained from the above tidal range. See Figure 14. .- ." ... . ;

I , ' " 100 JOHNSTONE ST. 003 FEB. 77, 26 PTS. MAX EBB CURRENT VS. TIDA L RANGE HIGHE R 80 HIGH TO LOW, R =.47

Cf)

~ "() - 60 I Z l-.,) lJ.J tv a: a: :::>() 40 x « ~

o I I I i I I 0.0 1.0 2.0 3.0 4.0 5.0 TIDAL RANGE (M) Figure 14. Station 3. Plot of maximum ebb current and the tidal range between higher high water and low water. This tidal range does not give a good indication of the currents to be expected. ~------_ ...------..,..-...-----~~...,--,

..' 100 JOHNSTONE ST. 003

MAR. 77 I 41 PTS. MAX EBB CURRENT VS TIDAL RANGE HIGHER 80 HIGH TO LOW, R =.76 ... (j) ... "'"~ ... ~60 ...... I ... . t-.,) Z w LJ.J a: .... a: ::J 40 () A ...: x « ~ 20

o I I I 0.0 1.0 2.0 3.0I 4.0I 5.0I TIDAL RANGE (M) Figure 15. Station 3. Plot of maximum ebb current and the tidal range between higher high water and low water. This gives a very approximate indication of the currents to be expected.

......

~ « ()

_-60 x

C/)

100

0.0

Figure

1.0

{ I

16.

...

Station

low

TIDAL

water

2.0

Plot

and

,,'

...

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...

high

...

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...

•

...

water.

....

3.0

...:

iii

...

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...

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4.0

and

the

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5.0

TIDAL

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FEB.77,

JOHNSTON

LOW between

FLOOD

higher

RANGE

EST.

HIGH.

CURRENT

PTS.

HIGHER

009

.86

'" .j:>.. ~-';"- -:~~~ . '" -=-

,,' r ' ...... ,..•. ', ,I!. . 100 .. T ..~• JOHNSTONE ST. 009 FEB.??, 30 PTS. MAX FLOOD CURRENT VS .. .. TIDAL RANGE LOWER- 80 LOW TO HIGH, R=.95 ... ..--.. (/) .... ~ .. " .. __o 60 I Z .. I-..) W til 0: 0: o:::>40 x « ~

o I £ j i 0.0 1.0 2.0 3.0 4.0 5.0 iii TIDAL RANGE (M) Figure 17. Station 9. Plot of maximum flood current and the tidal range between lower low water to high water. Figures 16 and 17 will give a fairly good indication of the currents to be expected. _ -: ... ' ,C.'

Vancouver I Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 5 3

~200 11200

CD a; E E

300 300

OHR 1 HR kilometres kilometres o 2 o 2

Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 5 4 3 2 l'V I 0- o 432-----::::::::----- ~O~. - T ('0: \ . m ::=--J. ~o--;- .- 30

11200 e200 • 20~ a; a; E ~ E -10~ 300 300

2HR 3HR kilometres kilometres o 2 o 2

The shaded part of the diagram indicates the ebb tidal stream (west going); the white area indicates the flood tidal stream (east going). The figures within the profile denote em/sec (51.5 em/sec equals 1 kn).

Figure 18. Hourly cross sections at Station 3 showing progress of tidal streams through a tidal cycle, (pages 26-31). The shaded portion denotes ebb currents. _.----:: 4 .. ~ ;. i.. i, '*

Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 4 3 .,' 2 5 4 3 2 201----_ ~. 0, ------30- _

~200 ~200 ;; ;; E E -40- 300 300

4HR 5HR kilometres kilometres o 2 o 2

Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland tv 5 4 3 2 '" 5 3 'l • ...... O-:..:--~.~,.'.~ sf: ---- 70-- •..,.=...• , ..,

~200 ~ 200 ;; <::> . E ~ 10--. 300 ----- 300

6HR 7HR kilometres kilometres o 2 o 2

Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 3 5 3 2

~200 200 ,"<;W...." Q) ~.~,~. . E ,*1.~!~'~-t-"';~':'-'. r"'-'----; l ~" - &.0.

--='~~ ~.;.-= .~ 300 .:C':'~"'~'::::::~"""'X;.".•,/l 300

8HR 9HR kilometres kilometres a 1 2 a 1 2

------l'-) ex:> Vancouver I JOHNSTONE STRAIT Mainlan~Lvancouver I JOHNSTONE STRAIT Mainland 5 4 3 2 1 , 5 4 3

.,11200 200 E

300 ...... •.::,... 300

10HR 11HR kilometres kilometres a 2 a 2

The shaded part of the diagram indicates the ebb tidal stream (west going): the white area indicates the flood tidal stream (east going). The figures within the profile denote em/sec (51.5 em/sec equals 1 kn). ._------~----,------..".~~~-~~-~----~---...,..--~------~ .. _.

Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 4 3 5 3 2

E200 e200 a; a; E E

*....=:;~L.~ __- ~';';" 300 300 ....\.,"""",.},,'<,,"',..,", ,.,.,.,.,.,.~,.."""""',"':',"',,'.,'"..:.'e,·

12HR 13HR kilometres kilometres o 2 o 2

"-J '0 Vancouver I Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 4 5 4 3 2

i(l200 200 .';; E" }\

<:: ....:.:.:."..,....,.,.,.,.,.:::::;::::,.,.""",,,,,f./'P·300 300 ""\""""':"""~':""':':"""""""""'""""""..,.... ~":,,...,....,',:,',:1'+:.

14HR 15HR kilometres kilometres c 2 o 2

Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 4 3 2 5 4 3 2 " , "--."~ ~ -"~-~ ------~ ------=--20~ -~::= .~ , 40--..:...--- ~50 --- ' 50 ______---60 _ , ~200 ~200 ------60 ~ / '~ ;; -== 70- , ;; ,______. 50---- E ------60----- E 300 300

16HR 17 HR Kilometres kilometres o 2 o 2

w Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland o 5 4 3 2 5 4 3 2 ,~~ ~~~:;-~;'- ~ig-~-- _, _, :=20 ___ ----=-40~ -' 30 ______/ ______An _ 50 - -~ ___ 60-- ~200 ~,50 --- ~200

18HR 19HR kilometres kilometres o 2 a 2

,,' Vancouver I JOHNSTONE STRAIT Mainland Vancouver I JOHNSTONE STRAIT Mainland 5 3 5 3

-----:-.------','--

~200 ~200 0; a; E E --30 __ 300 "::::.: '.:"0'.:: 300 .??:~:'::':":.,.:.:.~,~'::::':"':':': ::::::::;::,:",.: :.:.:::~::,.,,..r~·'·::·:·;·;:··

20HR 21HR kilometres kilometres a 2 a 2

~ Vancouver I JOHNSTONE STRAIT Mainland Vancouver I Mainland 5 4 3 2 5 4 2

~200 :2.0 E '--- .

~ 300

22HR 23HR kilometres kilometres a 2 a 2

Johnstone Streit Johnstone Slrelt Malnlond J15 J14 J15 J14 J13

•I •.20------.:. o~ / ••

o HR ~ ."",;,,,,,:.~*,~.:1''': o km o km

John.'one Strell Mainland J15 J14 J13

-;.~. . . ------w '<0> l'.)

·'1 km Johnstone Strait Melnland JohnSlone SIr. II M.lnlend J15 J14 J13 J15 J14 J13

+'20~ o~. +40----- •• • ,~----. ~

o km o

Johnstone S'r8/' Mainland Johnstone 51'811 Mainland John5lone S Ira II Melnlend John:JIone Strall Mainland J15 J14 J13 J'5 J14 J13 J15~~ J14 J13 J15 J14 J13 .",,--- +40- .,.::) w ~ <-== ~ w '~O~ "O~/

Figure 19. Hourly cross sections at Stations 13. 14 and 15. The shaded portion denotes ebb currents. -~-~---.- .-J ...-

JOHNSTONE STRAIT ..' JOHNSTONE STRAIT 12 3 14 17 12 3 14 17

oI) " / ...... - '0;;;.-- ·~O,...... ·... "'-,...... '..... -'...... 0·...... , " ,/ '" ...... '.• 0 , " ...... , 0"0 ...... '..... ' .... '" ...... '...... 0 100 '" -.'0. ' 100 ' ..... " ...... 70 '. '...... '.J '~0, , ...... 200 ".....'.;,..--.,,~c._. 200 ,,",.~.... _0------. "'".;.------~ 300 ..::..:....,. OHR lHR

C!~il~~elr!eS~ 6 8 10 8 10 I I ! II .l I I I II ! I 1 _.,1 w ./:>..

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 171 I 12 3 14 171 __ 10 I !

--__ -- ~20_~ • --__ -- I - __ __ -20 ---30-_ ------__--W------100 ,r------40------100 ____ -40------/ --~ . / 50---- / • __ 50------7 / / ~~-- / ---- / / r ---- / ",..-- 60----7 / 200 ~ / / 200 / / / / / // / / ,,/ ./. /

300 ~::-:-:..... 2HR 300 3HR

10 8 10

Figure 20. Hourly plots of the current in thecentre of the strait between Stations 12 and 17, (pages 34-39). ','

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 17 12 3 14 17

...._·10 _---0------ __1l---30--20------_---10------...... _--.,0 ..------_----20------ 100 ~~_-_O------100 _-----30------ __--W------~--40------~ .--__---20------·-----.,- / I .~ - .,e'" / ,-_- 50------.... ., .....---3 0.---- / / / I I .-'- / 200 E / / ,-_--60-, / I 200 E .- "....._-40--/"7 // / / / II /. I / "". / / "," I / /

300 5HR

6 B 10 W 111

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 17 12 3 14 17

o ° .60 .."'-"...... 40.----- ...... __ -.60------.....--- ...... ' _-.30.------_--~------...... 0---- -~ ' . 100 ,----.. ------100 , ----- ...... 0 " ,_---.1 ------",_---.30------...... _---0---- 0 e'" 7 '" , ,_----02------. ., ...... '-_---10------",,/ ",,/ ~ , ------,-- ,_----~.'O-- 200 E I)"" 200 E "'0 -,--- ....--:2°7 /// • ,,...... :\0 // // . .... -' ""

300 6HR 300 7 HR

6 B 10 6 B 10 . '.'.--.--.------cc-.--,-cc--o-~__::_"'C"',----....,.------.

JOHNSTONE STRAIT' JOHNSTONE STRAIT 12 3 14 12 3 14 17 I I ~ I Q .~" \.....,...... _60~ .; " ~" ---..; --'"- lOa \ ~B;~~~- ~,...,...-.//. lOa " _.fCIJ------... " // \," , \ -. ,...' ./ ./ ~...... --~ :c~--- \,.-~,... .\, _ :il :c...... "" Jp./

'" ~\~ ~ .~. ~ .....--: ~ .' .",.' ---- ., .... ~ .1' ..... "" E\ ...

_~~;4'",,~~'1,<-,~~~ ----- 200 E . _ ~~,.)o!",,- ._- 200 ... -./ .JI'--- ._,\, -:"\: 'C"'_,..... \ ~._ '"t'•. ~r~. ~-~ - ~~'~_T~lor9"~ • r,. :.' - ..40----.--- ..- ,-'_. U'o \0"..... ~-~~.,., ,...------_. :?JO...• .•.•,

~...::",~'..:..:. :.', '.~:::.".:::"::...; .

300 aHR 9HR

. ". 6 8 10 . 4 6 8 10 I L,l I I , II I I I I I I I LJ e-W I JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 171 I 12 3 14 17 I I I

.--...... -...... -...... '--~- ~~~ ~~ ~ ---- '--- / ...... ~ ...'1 ... ;" --~__.-. ..-40...... -----,_., --'- 0 _, - ,~- "":'--'60 -- ---"·30_-...... lOa ..... t . lOa - ...... -. -- . • ~'::" ______.20.....---· // ,.;. ~ '"~ '"~ ~ ~ ./ 200 E 200 E . '.' -- ___--~.,0---~--

10HR

6 8 10 ~ _.~ . --~.- -_~_ .... • •._ _ " ,.::::rs:::zt£!Z5 :E£Xt:;

I, i '.' I

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 17 12 3 14 17

o ----__ --~-30._ ------20_ ~------O----10._~_ -10- _ / ------~-----. 100 //.r--_____---0-_ _---.. 100 // ----10-- ---====~~~~~~~~:=====. / / / ------./ / ----- '"~ / / / 20------'"~ "-- Q) / 'iii .--...------...50_ 200 E / / 200 E ./ / /. ------30------.------",,,,~--~------

300 12HR 300 13HR

6 B 10 6 B 10 'JW

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 17 12 3 14 17

___ 20,--- ------w- ~ _-----30------ -~----~------ 100 100 _ _------50------~~~~~~~~~~~~~~~~~:~_ __------60------/ . -__------70------~------...... - // '"~ '"~ ------~------~ --..._~ / Q) .- 0, / Q) 1 / roO 0 200 E .... '" --... 80, --"",- 200 E ./ / /--90 ././ // ./ ",/,'90--... --"'--...--... --"'--...--... / /' - ...... / roO / ./ -'. --loa ...... //

300 14HR 300 15 HR

6 B 10 6 B 10 N N <5 '"8 8 8 '"8 8 0 metre. metres . ;::; ;::; \ II 1/ \ 1/ // I I I I/ III/III 1 / 1 1 1 / \ \ 1 II I ( 7 ,~ \ 1/(ltl(/to .\ \ \ ( \ (\ . \ \. '" ) \\\\\\\\0 '" ~\\\\\\\\.' CD 0 \ \\\\\\ \1 \\\\\\ ~ ~ ~ ~ \\\\\\It>\ ",\\\\\,1.,\ \\\\\\tg\ \\\",t>~\\ \\\\\'G\\ \~'G\\\\' \\\\~\\\ ~\\\\\\\ \ \\\:"'\\\\ \ \\\\\\'\ '- \ \\\1'\\\ '- \ \\\\\\\ 0 \ \\~\\\\ 0 \ \\\\\\\ ~ \ \~\\\\I ~ til \ ~\\\\\ til \ \\\\\\' d \ \ d \1\\\\' \ \ \\\\\\ ~ ~ ~ \ \\ \ \ \\ \ en \ \\\\\\ en \ \ \ \\\\\\ Cl " \ \\ \ Cl \ :il :il -' \ \ \ \ \ :b. 0 \ \ \ \ \ \ h "'0 I \ ==t \ \ \ \ \\ \\ ~ \ \\ \ \ ~ \ \ \ \ \ \ \ \ \ .\ \ \ . ~ . \ \ .\ \ \ \ . ~

0 00 0 Cii :I: :I: ::IJ ::IJ

:::j :::j

N N 0 0 <5 '"0 0 8 8'" g 0 metres metres ;::; ;::; 7 / , 1"/ \ \ III/ /III 1 \ 1 1,11 \ 11 1/1 \ \ 1 1(lfltl'ID .I ( \ ~ \ ( \ ( \0 . \ W \ '" I \\\\\\\, .. • .1>1 1 \\\\\\, a~ o '" , \ ' I \\\\\\\ ....1 l' ~ '... \ , \ \ ~ ~ ? \\ \\t>~' Ii oo~~ , ,\\Itg\\, I \ \\ II \\\\\ I \,~c;. '" \' II \\\'\ \~,\\\\ ~\\\\\\ II \"\' ~ \\\\\\\ ~ I\\\' ...... 1I\\,\ ~ \ \ \ \ \ \ ~ Cij \\\\\\ til \ \ \ \ \ \\ d \ \ \ \ d , ~ \\\ ~ I\, \ \ \ \ \ \ ...... en \ til .... \ \ \ \ \II\\ Cl ...... \ \\ :il Cl :il ...... \ :b. 6'q \\ \ \ h ==t \ \ \ \ \ ==t \ \ \ \\\ \ ~ \ .\ \ \ . ~

B£ ..'

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 17 12 3 14 17

0 0--,6 o " ...... -- __-60..--- " on----- , '....._,.60------" '------..30.-----~----- 100 ",,'-_--- 100 , ------" " ------, ...... -0...... ~:.. ~ ,,_------.~O.---- , """" _---_10------, .. " ------~ .. , ~ ...... , , ~ 0; "~---_----0- ...... ~/ 200 E ~O 200 ~ \~'"---~------...../ ~ ...... 0· ..... 1\, . ".

300 ~:.:: 20HR 300 21HR ..'..... kilometres 4 6 8 10 6 B 10 I I I 1 r I I , I W '0

JOHNSTONE STRAIT JOHNSTONE STRAIT 12 3 14 17 12 3 14 17 I I

0 / / ---40-~ / . •. l ;" / t ;" 100 / 100 \ f ~O" ,,' \ I "...... / \ F ~ ...... / " .. _~ ,,'" / <'- ~ __ .20---- " 0; \ / " -- \ -, . I" 200 E 200 ~ \ / --- .~"\. .._-

22HR 300 23HR 10 6 8 10 :,:.

STATION POSITIONS

',' J12 J03 J14 J 17 o I II iii iii jill i III i II II i IIII Iii I III II I iii i i II Ii II ill i I I

100

~ VI ~ o Qj E

I:c a.. ~ 200

•

VELOCITY (em/sed 1 division - 5 em/sec 300

o 2 4 6 8 10 12 14 16 DISTANCE (kilometres) Figure 21. A plot of the residual current in the centre of the strait between Station 12 and 17.