CO129-351 - Public Offices - 1908 — Page 78

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firms should be sent to the Huangpu Conservancy Board with the letter, copy of which forms Inclosure 8 in this despatch.

Inclosure 1 in No. 1.

Memorandum.

I have, &c. (Signed)

ALL we know about the works for improving the Wangpoo is-

J. N. JORDAN.

1. The project put forward by M. de Rijke in 1898-that is, nine years ago; 2. An article in the "North China Daily News"; and

3. The Quarterly Reports of the Conservancy Board.

The project of 1898 must be called obsolete, as the river has in the meantime changed very much. A mere glance at the line of 18 feet depth (see the annexed sketches) shows the great alterations that have taken place. Whereas at the time of the putting forward of the project the continuous line of 18 feet depth from Shanghae down-river did not extend to the Kao Chiao Creek, it runs at prescut, according to the soundings of 1906, right through as far as the inner bar. I believe I am not mistaken in assuming that even the inner bar has been disappearing more and more, and that therefore there is 18 fect of water at low-water as far as the outer bar. This point, however, will be referred to again later on. Just now I only wish to emphasize the fact that a depth of 18 feet at low water, which it was intended to create by De Rijke's project for the Whangpoo, exists beyond doubt to-day from the arsenal to the inner bar. In spite of these changes in the river, which are also borne out by the Quarterly Reports, nothing has been heard of a remodelling of the original project.

The project is obsolete also, inasmuch as it is not founded on the financial base which was established by the Agreement, only lately concluded between China and the Powers. A project, with estimate of costs, is, however, required to prove that the proposed works can be carried out technically and within the limits of the available means. And, lastly, it should be mentioned that De Rijke's project extends up-river only as far as the Point (Point Hotel), whereas, by the Agreement, China is obliged to improve the Whangpoo from the arsenal to the mouth of the river.

These three points-changed river, new established financial base, extension of the project as far as the Arsenal-should suffice by themselves to justify the call for a new project.

I will now try to describe briefly the chief points of De Rijke's project-closing the ship channel and dredging the junk channel. The annexed sketch shows the "normal lines." It appears from them that the Whangpoo is to flow only through one arm, namely, the junk channel. Actually, even to-day it flows only through one arm, but it is the ship channel-not the junk channel-in which there is scarcely any current. The project therefore intends nothing less than to turn the mighty river from the ship channel into the junk channel, to deflect an entire river of the force of the Whaugpoo. Should this extremely dangerous and exceedingly costly undertaking be successful, what will be the result? The curve at Pheasant Point will have become a little flatter. This curve, it is true, is at present rather short, but wherever I inquired of English and German captains, I have never heard of difficulties for naviga- tion. One must not forget that in the narrow Suez Canal there is a curve of only 1,130 metres radius, whereas the radius at Pheasant Point measures 1,700 metres, and the river at that place would show a navigable width of 1,000 feet.

Besides, in case, the protruding point of Pheasant Point would have to be dredged away, as has always been proposed by M. de Rijke.

The advantage of flattening the curve at Pheasant Point must therefore be regarded as too inconsiderable to justify the deflection of a river-the ship channel ---which in all its parts already has the depth the project intends to bring about.

The author of the project expects much from the working of the flood tide. A glance at the chart shows that the flood tide has produced nothing but a short stretch of deep water at Woosung, whereas the continuous depth of 18 feet water from the Arsenal to the inner bar at least is entirely the work of the ebb tide. Nor could anything else be expected, for in the first place the flood tide ruus on an

* Not printed.

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3 hours 40 minutes, the ebb tide, on the contrary, 6 hours 50 minutes, that average is nearly double the time, and in the second place the flood tide carries most of the sediments into the river and deposits them where the ebb tide is weak, whereas the equable ebb current carries the sediments into the Yang-tsze. This is very clearly seen in the junk channel. In the latter the flood tide has deposited its sediments because the ebb current passes through the ship channel. Naturally the improvement of the bed of the ebb current in the ship channel has carried with it an increased silting up of the junk channel. It would, therefore, for this reason also appear to be more advisable to pass through the ship channel with the ebb tide because the nature of things affords security that the navigable course, as soon as determined within its banks, will always be preserved. The inner bar need scarcely be taken into account; even if most of it has not already disappeared, it is certainly decreasing. This pleasing fact is due to a measure of M. de Rijke's, which was, it is true, most It had been found out, as was, in probably taken with a different object in view. fact, known before, that on the lower portion of Gough Island cross channels had formed, through which the incoming flood tide partly ran into the ship channel. In order to compel the flood tide to run through the junk channel the future navigable course, the cross channels were close by a long dam. The consequence was not indeed, an improvement of the junk channel, but of the ship chanuel, for whereas formerly also part of the ebb water was able to run through cross channels into the junk channel, the ebb current in the ship channel was now constrained by the new dam, and had to pass with its full force the inner bar, therewith, however, the inner bar lost its raison d'être—that is, it is disappearing. In spite of this extremely favourable condition of the river in the ship channel the latter is now to be given up at enormous expense and exceedingly great danger to navigation. The question of expense need not detain us long. Of course, even where the configuration of the river is very simple, it must be very much more costly to dig a new river bed, and to divert a river into it, than to retain an old bed with a sufficient depth of water. To what a vertiginous height the expenses of improving the Whangpoo will mount will perhaps be clear when one considers that, at the very spot where there is a most powerful current, a dam is to be built right across the river in order to block it. From the chart it is seen that at the upper end of Gough Island the new portion of the river leaves the junk channel and crosses the ship channel, the new right bank of the river, closing the ship channel in a concave line. Assuming that they have succeeded in building this new bank across the river, then as at present proposed, it will have But the the foundation on the present river bottom, that is, at a depth of 18 feet. river gives evidence in all its concave banks of a strong inclination to scoop out its bed to a depth of 30 feet to 40 feet, which means that the new bank would have only a short lease of life and soon fall in, its foundation being undermined. Then the river will divide anew, perhaps, in two equal arms, which, on that account, are useless for navigation, not to mention the difficulties caused by the remains of the dams.

But the greatest difficulty would be the construction of the dam itself.

At present they are busy pushing forward the dam from the upper end of Gough Island. This will go on right enough so long as they are not in the main current, but as soon as the latter will have been reached the river, made still more furious by the constraint put upon it, will with all its weight resist the intrusion. Behind the end of the dam whirlpools will form, which will tear up the river-bed and cause the dam to fall in; besides, the river, forced by the dam of Gough Island, will seck to still more undermine its right bank. How great the technical difficulties caused by the strong current will be may be estimated by the fact that nearly all the defence works in the ship channel (see Quarterly Reports of the Conservancy Board," Shore Defence Works") have fallen in, and have apparently for the present been given up; and this notwithstanding their being called in August 1906"the most urgent work which is now occupying M. de Rijke's attention." If the mere defending of an old bank causes difficulties, what is to become of the new concave lines?

And now, in conclusion, let me say a few words on the great danger to navigation.

To dredge the junk channel without leading through it the water of the ship channel is technically impossible. M. de Rijke is of the same opinion, and intends, therefore, to begin by making the ship channel lower by means of dams of sink-work, "which will help to kill the tide in that part of the river." Then he continues: "These dams will be put down in eight or more places, and by degrees the current will be deflected towards the junk channel." Accordingly, they will begin dredging

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