136 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[April, 



into the ]k'o', so as to raise the entire surface to the level of the original tiile. 

 15 feet at Kiincom, which woiilil occupy about a day and half, there would 

 be a depth of ]1 feet at Bank Quay ; and, supposing'tlie river is then alloMed 

 to flow on tlirough the pool as usual, we must add the fall or declivitv in the 

 surface necessary to give it the reijuisite velocity ;— this would be about 2 or 

 3 inches in a mile, and the distance being, say 7 miles, we should have an 

 additional depth of from ] foot 2 inches to 1 foot 9 inches to add. making 

 the total depth at Bank Quay from 12 to 13 feet, being a gain of from 4 to 5 

 feet ilcptli of water. 



As tlus deptli is 2 or 3 feet more than is rc(|uired to float a vessel of 10 

 feet drauglit. it will he sufficient if we retain a tide rising 12 or 13 feet at 

 Runcorn, or l.") or 16 feet over the old dock sill at Liverpool. It is of im- 

 portance to mark this, as you will perceive Iiy observations I shall have to 

 make upon tlie scouring power I propose to substitute, 



Laymg aside for the present any consideration of the effect which may be 

 produced below Kuncom. I can see no objection nhich can reasonably be 

 urged against it. but the (-.ossibility of the river sraduallv siltmg up. by the 

 deposition of material brought down by fli)ods. Th* mode I have to suggest 

 of scouring out the channel, will, 1 think, almost entirelv remove the possi- 

 bility of (his being the case, in tlie navigable channel ; but^ even without that. 

 I do not think it would have such an effect. The river would maintain its 

 course and current along the deep, depo.siling whatever it might bring down 

 on the sandbanks and shallows at each side, where there would be little or 

 no current, thereby gradually raising and preparing for agriculture purposes, 

 an I nprofitable waste of sands, washed over now by every high tide by which 

 the) are frei|uently removed and carried into the deeps. ' 



I know many instances of rivers maintaining a distinct course through 

 large lakes ; but two, which must be familiar to nearly everybody, will be 

 suflicient to mention. The Rhone through the Lake of (Jeneva. a distance of 

 37 miles, and the river Bann,for 18 miles through Lough Neagh, in Ireland ; 

 each river maintaining a deep and distmct channel through the entire length 

 of lake. The Rhone, how ever, and, I have no doubt, the Bann also, forms a 

 delta on first entering the lake. 



I think that, generally, the channel would be improved; and if deposit 

 was to take jilace in the upper part of the estuary, where the river would 

 first enter into comparatively still water, it might easily be removed by 

 dredging. 



The benefits to the town of Warrington, in particular, must be too obvious 

 to need any remark. The Sankey Canal would obtain a much better entrance 

 than it has now; and the Mersey and Irnell Comjiany would have so much 

 of their navigation permanently improved, and rendered available for a large 

 class of vessels, which they may then take on to Manchester. 



We now come to consider the efiect which niavbe produced upon the chan- 

 nel below Runcorn Gap. and upon the entrance to the port of Liverpool. 



It would be of little use to .suggest plans for the improvement of the upper 

 part of a river, if the mouth were to become so choked up that no vessels 

 could enter: ai.d.in the maintenance of a good entrance to the port of Liver- 

 pool, the Mersey and Irwell Canal Company is as \itally interested as any 

 other party can be. 



I hope to be able to show, that, so far from the suggested works being likelv 

 to do injury, they will assist in scouring out and deepening the channels all 

 the way out to sea. 



Much evidence was given, in the trial betwixt the Old Quay Company and 

 the corporation of Liverpool, in 1827, relative to the scour of the river ; and 

 from that it appears, that the most effectual in cleansing ai'd deepening the 

 channels is that produced by the ebb tide, when about half down, and the 

 land floods : tlie latter losing much of their power, however, in the lower part 

 of the estuary. 



As this accords strictly with my own observation, and the information of 

 those connected w ith the river and daily navigating it, I have no hesitation in 

 taking it as the fact. 



It appears, then, that the early part of the ebb tide is of little service in 

 improving the navigable channels of the river ; and indeed this must be ob- 

 vious, when it is considered that the water is then running with pretty nearly 

 equal veliicity over the whole bed of the river, and removing probably more 

 sand from the banks into the channels than it carries out of them. 



Now. if any considerable portion of the water that is thus wasted, as it 

 were, could be retained until the tide was half down, and then set at liberty, 

 it would have the efiect of keeping up the river for some hours longer at the 

 most effectual scouring point, and be thus enabled to work deeper into the 

 channels, and carry the sand or slit removed further out to sea. 



1 think 1 can make it clear, that this will be the result of the scheme pro- 

 posed during spring tides; and that, during neap tides, or whenever prevented 

 from flowing beyond the gap. the water will rise higher at Runcorn than it 

 can now. .and eonsequently increase the velocity of the ebb. In either rase 

 there « ill be a strong tendency to improve the channels both above and belo\» 

 Liverpool. The estuary will contain, to begin with, nearly if not quite as 

 much tidal water as it does now. and under regulations which will render it 

 of more efl'cctual service, while eventually the improvement of the deeps will 

 enlarge its capacity. 



The Tipper part of the estuary and river, from Runcorn (iap to Ilowley 

 M eir. at W arriugion, containing at liigli water of spring tide (including Hal- 

 ton Marsh) about 1.300 acres, is about l-17th of the entire area of the estuary 

 above Rock I'erch. In spring tides, at high water, it contains from l-25th 

 to 1 -30th. and in ne.ap tides from 1 -40th to 1 -50th of the w hole body of water. 



Mr. Giles, in his evidence for tlie corporation at Lancaster in the suit be- 

 fore referred to, calculates the contents of the river at ordinary spring tides, 

 from Runcorn to Warrington Bridge, at 10 1-3 million tons, or about 13,733,000 

 cubic yards. As a 1,5 feet tide at Runcorn falls 8 feet to half ebb, consider- 

 ably more than half the quantity has flowed out before that time, so that the 

 remainder, say six million cubic yards, is the only pDrtion that is eflectually 

 employed in scouring the deep. As this is six hours in ebbing out, the velo- 

 city becomes so trifling towards the end as to be ineffectual. 



In neap tides the effect is proportionably less. 



The late Mr. Kiinmo. in his evidence for the company in the same cause, 

 gives from actual measurement the ordinary flow of the river above Warring- 

 ton, .and the depth of a very heavy flood over Woulston weir, from whicli I 

 Iiave been able to ascertain its volume. 



From Mr. Nimmo's observations, the fair average of the onlinary quantity 

 may be taken at 40.000 cubic feet, or 1.480 cubic yards per minute. 



The flood appears to have been about .580,320 cubic feet, or 21. 493 1-3 cubic 

 yards per minute, or nearly one million and a half yards in a hour. — probably 

 nearly e^ual to the tide at half ebb. It was running at the rate of 113 yards 

 in a minute, or nearly four miles an hour. 



It is half ebb at Kijncorn rather earlier than at Liverpnol ; and from half 

 ebb to the commencement of the flood tide at Liverpool, tliere is about three 

 hours. It is during this period that I would propose to discharge the water 

 wliich would be retained above our embankment. 



I have stated, that a 15-feet tide at Runconi has fallen ei|;ht feet, or to 

 half ebb. If flood-gates were constructed in the bank. 60 yards in length, 8 

 feet in depth, and opened at half ebb so as to obtain an average pressure of 8 

 feet to the bottom of the discharge, tlie quantity discharged in the three 

 hours would be nearly six million cubic yards, or about the whole quantity 

 now contiiined in the estuary with a similar tide at half ebb, and requiring 

 six hours to flow out. 



If the iliscliarge sluices occupied 100 yards in length instead of 60, being 

 then 1 -4th of the w idth of the gap, the discharge in the three hours would 

 l)e more tlian nine millions and a half cubic yards, bein" half as much again 

 as all the water now left in the estuary at half ebb, and more than 2-3rds of 

 the whole contents measured at high water of spring tides, and nearly equal 

 to the whole (juantity at half ebb added to three hours of such a flood as Mr. 

 N mmo mentioned. The discharge would be at a velocity of 10 feet per se- 

 cond, or nearly seven miles an hour, and would, after mixing with the other 

 water, maintain a velocity of three or four miles much greater than the mean 

 velocity after half ebb at present. 



There cannot be a doubt, I think, that, under such regulations, the scour- 

 ing power would be greatly increased : and. while below the gap, the direct 

 force of this power would be employed |in deepening the channel and carry- 

 ing out the sand and silt to sea, the velocity of the current above the gap 

 would be so much increased and confined to a particular direction, that the 

 channels there would also be deepened, and any casual deposit carried out; 

 so that, independent of other improvements, th' channels of the whole river 

 would be improved from Warrington to the sea. 



After these discharges the pool might be refilled at the next tide, or when- 

 ever the tide rose more than 13 feet at Runcorn. At the luwest spring tides, 

 for three or four days together, and at the highest, for seven or eight days 

 together, perhaps twice each day, but at any rate every alternate tide, much 

 less frequently than this would, I am satisfied, be (ouiul amply sufficient. 



The next point is, tliat, by the tides being prevented from flowing beyond 

 Runcorn Gap. they would rise higher there, and. by thus attaining a greater 

 head or elevation, which will be another advantage besides, would produce an 

 increased velocity in the ebb. 



The tide flows past Runcorn at the rate of five miles an hour ; and if stopped 

 there by an embankment, and prevented from flowing up to Warrington, and 

 filling that part of the estuary, the momentum, which impels it forward for 

 an hour after it has turned at Liverpool, would cause it to impound in front 

 of the embankment. From calculations I have made. I am disposed to think 

 that the additional rise would probably be about l-20ih of the total depth of 

 water, or from four to nine inclies, according to the height of the tide. This 

 amount, small ,as it appears, would be of service in neap tides. 



I have now, I think, gone over the main points which appear to me mate- 

 rially to bear upon the question ; and I hope I have succeeded in explaining 

 them in such a maimer as to render them intelligible, and enable you to un- 

 derstand my views. 



If I am any thing nearly right in the data I have taken, and the conclu- 

 sions I have drawn from the calculations I have made, the advantages in every 

 point of view must be considerable, nor are these advantages confined to the 

 navvigation only ; the adjoining landowners may reclaim a large portion of 

 the land above Runcorn, which is now covered at high tides ; a good road, 

 with draw or swivel bridges over the locks, may be formed on the top of the 

 embankment, and thus join the two counties of Lancaster and Chester in a 

 very much superior and more convenient manner than is now afforded by the 

 dangerous and inconvenient ferry. Even a railway viaduct, if carried at a 

 sufficient height, w ould then be no objection ; and many miles of railway 

 travelling might be saved to the London and Liverpool traffic, by crossing 

 here, and joining the Grand Junction at Prestonbrook. 



It only remains to explain shortly the kind of works which would be re- 

 quired. 



The width of the strait at Runcorn Gap is about 1,250 feet. The bed of 

 the river consists of about 35 feet of rock on the Cheshire side, dry at low 

 water ; about 745 feet of sand and silt in the middle of the river, e,\tending, I 

 believe, to a considerable depth, partially dry at low water ; and about470 teet 

 of rock, all above low water, on the Lancashire side. The rock extends in- 

 land on each side, rising considerably, particularly on the Cheshire side, above 

 high water level. 



1 would propose to construct tw o sea locks in the rock on the Cheshire side ; 

 one ISO feet by 40 feet, and the other 120 feet by 30 feet, with hydraulic 

 gates, so that they may be self-acting, and used for the purpose of .scouring. 

 In the rock on the Lancashire side. 1 woulil recommend the construction of 

 the self-acting flood-gates, and between the limits of high and low water 

 there is ample space for fen, with 30-feet clear water openings in each : the 

 gates to be revolving on an upright axle, placed a little on one side of the 

 centre, so that one leaf of the gate should be rather larger than the other. 

 The gate, of course, must open only one way. the larger half turning up the 

 river: when, therefore, the ffood tide rises higher than the surface of the 

 water on the upper side of the gates, the pressure being greater upon the 

 larger leaf than the smaller, the gate opens, and the water is treely admitted. 

 When the tide li:is reached its greatest height, and begins to fall, the pressure 



