12
Breadth of chaauel in feet.
شعرت اعداد
13
The following table is made from the ship-channel survey made in November 1908, and compared with that made in March last or four months later :—
Cross section XI, 18-5 feet
150
380
700
1,230
X, 18:5
230
370
730
1,050
•
IX, 18-1 VIII, 20-0
130
230
650
1,080
500
620
830
1,360
These figures speak for themselves; the only dredging done during the quarter in this part is a little on the edge of the shoals opposite to widen the channel just above Ó.U. base, cross-section XII; so that any increase in depth and breadth of the channel is almost entirely owing to scour.
Upper part.-Cross-sections I to VIII. This includes the "passage" from concave It should be borne in mind that the to concave, or from the left to the right shore. ultimate breadth of the new channel between the normal lines-here about 2,000 feet apart-is calculated for the whole of the Whangpoo stream at low water, whilst as yet a considerable part flows the other way through ship-channel.
As explained more than once, the transfer of stream has to be done gradually so as to prevent any tide killing. Now in this upper part the stream along the "passage," not guided on the one or other side, and, of course, training works between the normal lines being out of the question, naturally must be liable to shiftings, especially in a stream-bed like this. The only possible way left to force the stream in the direction desired, i.e., in that of the leading marks already placed by the direction desired, ie, in that of the leading marks already placed by the harbourmaster, is dredging, and lately it was necessary to have all the three powerful dredgers at work in this part.
Breadth of channel in feet.
November 1909.
March 1909.
Cross sections.
Cross section
area,
Greatest depth.
Cross section
area.
Greatest depth.
Sq. ft.
Feet.
Sq. ft.
Feet.
About 900 feet below Fisherman
Sq. ft.
27,289
38.0
26,167
30.0 decreuse 1,072
2,800 feet lower down
27,351
42-6
25,862
26,500
38.5
25,170
42.0 38.5
1,489 1,330
2,000 feet lower down
25,289
37.5
Opposite Lower Gough
24,905
30.0
24,312 37.5 23,344
17
1,700 feet lower down
23,686
29.5
26,277
25.6
23,940 24,018
36.0 31.0 increase 26-8 decrease 2,250
977 1,561 2
At Taiking Creck
Just below Lower Gough mud deposit
At
From this we may conclude that, though not much, natural silting has commenced over the whole length of ship-channel, mainly by narrowing of the channel. Fisherman and up to the Kajow Creek, before an open space of water, the depth of water increased with from 2 feet to 3 feet in these four months. This has been caused by contracting the stream between the works made there. For the same reason the depth of water over the inner bar is now marked more than it used to be.
Opening junk-channel--The opening of junk-channel for most of the shipping would relieve much the sinking parties now hard at work in the upper end of ship- channel. As to depth of water no difficulties would be met with except for the deepest ocean steamers, but on account of the shiftings above-mentioned-it being found necessary to have all the dredgers at work in the upper part of junk-channel, and these with their spread of anchors just in the line of the new fairway--it is considered better to postpone such an opening yet for a while.
JOHS DE RIJKE.
Depth at low water in feet deepest
18
17
15
12
Cross section VII, 19-2 feet
440
680
1,190
1,380
25
VI, 19-4.,
760
800
870
1,600
V, 25.4
310
500
860
2+
IV, 29.3
$60
530
1,100
ג
III, 27·4
300
570
1,160
11, 26.8
1, 28-3
500 870
890
1,010
970
1,080
All the cross-sections are 1,200 feet apart, the fourteen together thus a length of stream of 16,800 feet.
Taking the new river over its whole width between the normal lines, I can say But the latest soundings that also in this upper part not any silting has been found. shows a loss in depth here and there in the route indicated by the leading marks in the "passage," as also a narrowing of the channel once formed along the concare at and above Upper Gough. This has been caused by shifting, or matter replaced during high flood tides running strongly over the flats left of the old junk-chaunel bank. The flats on the left side, with less than 9 feet of water at low water still extend downward to about 1,300 feet below Upper Gough section, and, I fear, will cause more or less trouble yet for some time.
The only remedy besides enforced dredging is by going on vigorously in restraining the flow along the ship-channel, and thus diverting more and more of the ebb tide into the junk-channel.
Stream along the ship-channel.-The ship-channel may be taken as commencing We know about how much from the upper end of Gough Island, as it was in 1907. the stream along the junk-channel has increased already by dredging and training and, as a matter of course, the stream along the other way--the ship-channel-must have decreased. The capacity of a stream is determined by the wetted perimeter of the channel and the velocity. That the velocity has decreased in a marked degree is found in preceding reports, but from this does not follow at once a decrease in cross- section. The latter means silting, and with the very fine matter in suspension, as here the velocity must decrcase considerably before any settling can be expected.
Shanghae, April 23, 1909.
Survey.
Junk-channel was sounded three times during the quarter. Lines run 300 feet to 400 feet between the normal lines. In January from storm to signal, in February from storm to half-way between salient and limit, and in March from storm to Pheasant Point; besides this eleven lines of soundings were run at salient and two lines between salient and limit. Fourteen lines were run from the shore to the normal line between Dyke End and storm, and eight lines of shore soundings were taker 300 feet apart from Dyke End Crib. Twenty-five lines of soundings were run into deep water from the two Dolphin poles at the inner bar. That part of the river between Signal and Joss House Jetty was sounded. Lines 300 feet to 400 feet apart, and sweeps (fifteen lines) taken at Princes and Fort Jetty station. Twenty lines, 80 feet apart, were run around Woosung Spit buoy,
The shore line was surveyed from Pheasant Point to two stones, and the land from Woosung Creek to Joss Range was surveyed from the shore to about 500 feet inland. Forty-seven lines of shore soundings were taken between Kajow Creek and the Standard Oil Company's wharf.
The grass line between Black Creek and the Flour Mill point was measured, and fourteen lines of shore soundings, 750 feet apart, were run into deep water. The ship-channel was sounded from Telegraph to Kajow Creek, lines 400 feet to 500 fect apart.
Shanghae Harbour.-The bund line between Birts wharf and Soy Chee cotton mill was checked. The frontage of B.C. Lot No. 2,703 was measured to ascertain the area of land to be reclaimed.
Office Work.-All the above surveys have been plotted on the standard maps, and various tracings were prepared for the engineering department.
H. CHR. MÜLLER.
430