Autobiography of Sir John Rennie, F.R.S., Past President of the Institute of Civil Engineers / Comprising the history of his professional life, together with reminiscences dating from the commencement of the century to the present time.

by Sir John Rennie

After the plan had been published and promulgated for some time, all sorts of objections were raised and attacks made upon it. I replied coolly and steadily to them all, and the more it was investigated, the more the world became convinced of its practicability. Still it was impossible to combine the various conflicting interests, and equally difficult to form a company for such a vast and novel undertaking. The public naturally said, if the drainage and navigation interests and the landed proprietors, who were so much interested, did not see their way, how could it be expected that a company should? Thus the affair, although frequently agitated, lay in abeyance for several years. Its chief supporters, Lord William Bentinck and Mr. Hoseason, having gone to India, there remained none of sufficient energy and influence to push it forward. At length the late talented and indefatigable Lord George Bentinck became member for Lynn, in succession to his uncle, Lord William, when he became Governor-General of India. Lord George was unanimously chosen chairman, and examined most minutely, with his usual sagacity, every detail of the measure, and was perfectly satisfied of its practicability and value, but thought that it was too great to be undertaken as a whole, and that it would be better to divide it into two parts, one comprising the Ouse and Nene, the other the Welland and Witham. I must not omit to mention that the late Prince Consort was much pleased with the plan, and expressed his approbation to me of it. It was accordingly decided to form a company for the Norfolk half, including the Ouse and Nene, and to reclaim 35,000 acres of land from the Great Wash; and at the end of 1845 the requisite plans were prepared and notices given for a Bill to be applied for in the ensuing session, under the title of the Norfolk Estuary Act. The Company originally calculated that the land gained from the estuary would have indemnified them for making the new cut for the Ouse; and so it would, if they had been allowed all the land below high-water mark, without having any other burdens entailed upon them. But unfortunately this was not the case; they were saddled with the maintenance of the Great Cut, although, strictly speaking, it ought to have been maintained by the navigation and the drainage interests, which alone derived the benefit from it. The land frontagers claimed all the land, or green marsh, to be embanked at the expense of the Company, who were only to receive a certain portion of its improved value; the Ouse bank owners were to be indemnified to some extent also. The Crown was to have a commission of five per cent. upon the expenditure; and the Church was to have a certain portion, or tithe, upon the land gained: indeed, so many restrictions were placed on the Company that their calculated profits were materially reduced; nevertheless, as a number of the shareholders were otherwise greatly interested in the improvement of the drainage, frontage, &c., they calculated that if the shares were worth nothing, they would still be the gainers. I protested as much as I could, without avail, against all these restrictions, and I doubted much whether the Act could or would be carried into effect with any benefit to those shareholders who simply looked to their profit from the shares. It turned out as I expected. The Act passed during the session of 1846. Still there was no prospect of the Norfolk Estuary Act being carried into effect, on account of the restrictions above mentioned; and the Company wisely determined not to proceed unless the drainage and navigation interests, which were so materially concerned, came forward with a handsome contribution towards it. The Middle Level proprietors had obtained a Bill, in the year 1846, for the improvement of their drainage, which was much opposed, and in which I took a leading part. However, they carried their Bill, and the works were designed and commenced under Mr. James Walker; but they soon found that the work would be comparatively valueless. The Norfolk Estuary Act had now been carried, and they therefore entered into negotiations with the Norfolk Estuary Company, and these negotiations finally ended in the Middle Level Commissioners and the Lynn Corporation, who represented the drainage and navigation interests, agreeing to contribute each the sum of 60,000l. towards the completion of the new channel for the Ouse, contemplated by the Norfolk Estuary Company, upon condition that the late Mr. Robert Stephenson should be joint engineer to the Norfolk Estuary Company with myself, to which, of course, I had no objection; and it was agreed that an Act of Parliament should be obtained in order to ratify this agreement, which passed in the year 1850.

At that time a former Act rendered it necessary that before any improvement was made in any port or harbour, a Commission should be appointed by the Admiralty to investigate the plan, the Commission to hold its inquiry in public; Captain Washington and Captain Veitch were appointed by the Admiralty for this purpose. They held their court at the townhall, Lynn, and, singular to relate, the gallant gentlemen advocated a curved instead of a straight channel, which, under the circumstances, was so contrary to the practice of every good hydraulic engineer, that their report was simply ridiculous, and when produced by the Admiralty before the Committee of the House of Commons on the Bill, was proved by the best engineers to be wrong, and was therefore ignored by the Committee, and the plan proposed by Mr. Stephenson and myself was unanimously adopted. The Bill accordingly passed, and the agreement between the Middle Level Commissioners, the Corporation of Lynn, and the Company, the two former contributing 60,000l. each, was ratified; still there were several restrictive clauses, such as entailing the maintenance of the works upon the Company, giving up the whole of the green marsh to the several frontages, which materially abridged the profits of the Company, and increased their risks, and which I in vain protested against. The main cut commenced on the lower side of Lynn, and was continued in a straight line 2½ miles. We calculated that certain dimensions were ample in the first instance, because it was not necessary to excavate the cut artificially to the full depth, as we knew that as soon as the current began to act upon it, it would in a short time be adjusted to its proper capacity for the admission and discharge of the tidal waters, in the same manner as had taken place in the Nene estuary outfall already mentioned. From the lower end of the above cut the channel for a distance of two miles farther to deep water was to be trained through the sands, formed by guide walls of rough stone raised to about the level of half tide, with beacons upon it at certain distances to indicate the channel; and when once the channel had been thus trained, the remainder of the banks to their full height above high water would be raised naturally by the silting up on each side, combined with the gradual process of embanking the land from each of the shores of the estuary, if properly managed.

Messrs. Peto undertook the contract of the main cut. The land having been bought, and everything arranged, a day was fixed for turning the first sod, at the upper end near Lynn. The ceremony was performed by the late worthy Sir William Foulkes, the chairman of the Company, on the 1st of November, 1850. On that day a grand procession, consisting of the Company, the Corporation and trades of Lynn, the Earl of Leicester, Lord Lieutenant, together with numerous gentry, and other spectators, attended the ceremony, which went off with great éclat, and the whole, as usual, terminated with a grand dinner to about two hundred persons at the townhall. Unfortunately my friend Mr. Stephenson was abroad and could not attend. The excavation of the great cut proceeded rapidly for some time, until Mr. Stephenson and myself, judging that enough had been done, and that the current would do the rest more effectually, ordered the dams to be removed at both ends and the water admitted, which was accordingly done. As soon as the fen proprietors heard of this, they were greatly alarmed; they said that the Company had violated their agreement with them, and had gone contrary to the Act of Parliament, in not excavating the cut to the full depth required before letting the water in. We endeavoured in vain to persuade them to the contrary. They immediately applied for a mandamus to stop the works and restore the dams until the cut had been excavated to the full dimensions required by the Act, and obtained an injunction, so that we were compelled to restore the dams and stop out the water. We determined, however, not to give up the point, and argued the question before Vice-Chancellor Turner, and were beaten. We then applied to the Admiralty, who would not assist. We appealed from the Vice-Chancellor’s decision to the Lords Justices of Appeal, and were again beaten; still we would not give up, and at last we found that there was no alternative but to get a new Act of Parliament allowing us to make the cut in any manner we pleased, provided that we made it of the dimensions originally agreed upon. The Eau Brink Commissioners opposed us by every means in their power, but our evidence, which was given by the first engineers of the day, so completely satisfied Parliament that we carried our new Bill as we wished it.

Thus, after a severe struggle for two years, we carried our point; but this was so much valuable time lost, besides a great deal of money spent in litigation. Having obtained our new Act, we set to work immediately to remove the dams of the cut, and to let the water in, and at the same time to commence the dam for stopping up the old channel of the Ouse at the lower end of the town of Lynn, near the upper end of the new cut. As the dams and bottom of the river near them were composed of strong clay, it took some time to remove them so as to admit the waters freely into the cut; but as soon as this was done, the scour began to have a sensible effect; this was increased by the closing of the dam across the old channel, so that within a few months afterwards not only had the new cut been scoured out to the full depth required by the old Act, but considerably beyond it. Thus Stephenson and myself were proved in the right, and the opposition entirely in the wrong.

The effect on the port of Lynn was very remarkable. The depth of water at spring tides was 18 to 20 feet, and neaps 14 to 16 feet; and there was a regular depth at low water of spring tides of 9 to 12 feet in the cut, so that the largest vessels could always come up and depart with their full cargoes either at spring or neap tides, and the channel was so direct and easy of navigation, that pilots, of whom there was a large establishment, became in a great measure unnecessary, and their numbers were considerably reduced as well as their charges, and the increase of trade soon enabled the town of Lynn to pay off the 60,000l. contribution to the estuary works.

The drainage interests also derived a similar benefit by the lowering of the low-water mark 6 feet, which, together with that obtained by the Eau Brink Cut, was altogether 11 feet. The Middle Level Drainage, upon which a large sum had been expended, obtained an increased fall of between 3 and 4 feet, which enabled the Commissioners to drain the greatest portion of their lands naturally instead of artificially. In fact, the Port of Lynn by means of these works has become one of the best on the east coast of England, at the least expense, and with the most moderate dues; indeed, if the Drainage and Navigation had paid double the money which they did to this great work, and which in justice they ought to have done for the benefits it has conferred upon them, they would have been more than amply indemnified.

The Estuary Company having now completed the cut, turned their attention to the best means of reclaiming from the Wash the 35,000 acres which had been allotted to them by the Crown, or at least as much of it as they could; but unfortunately there were so many different opinions among them and their advisers, that they lost a great deal of time and money in pursuing improper measures. I, who originally designed the undertaking, and had acquired great experience in this department from having carried on successfully similar works in the Great Wash and elsewhere, always adhered to one system, namely, to work with nature, and never to go against her; if we did, I invariably found that we were beaten.

We knew, from a variety of experiments that had been made, that the alluvial matter held in suspension by the waters in the Great Wash was an ascertainable quantity; that this alluvial matter was transferred from one place to another, according to the prevailing winds and currents; and that it was only deposited where circumstances were favourable, such as eddies and sheltered stagnant places. Now my great object (after having confined the fresh and tidal waters of the river Ouse to one adequate channel, so as to preserve the drainage and navigation in an efficient state) was to cause to be deposited the alluvial matter that was held in suspension in the waters spreading over the other parts of the estuary. This could only be done effectually by arresting the progress of the flowing and ebbing waters in such a manner, that as much of the alluvial matter as possible might be deposited in the places most convenient, that is, in those places where it was desired to raise the soil above the level of high water of neap tides. When this level is reached grass may be expected to grow, and in a very short time the whole is converted into a green marsh. The process simply this: when the deposit has reached a certain number of feet above low water of spring tides, a species of light green vegetation first covers the surface in patches, then by degrees extends over the whole; the reclaimed land still continues rising, and at a higher level above low water samphire makes its appearance; the accumulation of soil still goes on increasing, when the samphire disappears, and grass succeeds it, and in a short time afterwards the place assumes the appearance of a level green marsh well adapted for grazing cattle. After it has arrived at this stage, which it does at about the level of high water of neap tides, the accumulation is very slow; on our coasts it seldom attains a much higher elevation, except where the sand is blown up by strong winds from the sea, which forms dunes or banks, that, as in the case of Holland and other places, sometimes attain an elevation of 30 feet and upwards above the level of the highest tides. This, however, is not the case around the shores of the Great Wash; there the marshes are simply produced by the gradual deposit of alluvial matter in the manner above stated.

The great object, therefore, as I have said, is to facilitate this deposit or accretion as much as possible by artificial means. Nature, if left to herself, though sure, is very slow. We must therefore assist nature, by following and working in unison with her laws. We must go to work gradually, and not by great and expensive operations check the currents violently and at once, which would only produce an equally strong current elsewhere, so that while we gained in one place we should lose in another. By a series of light works composed of bushy fagots or other similar materials, raised about 12 or 15 inches above the level of the sands, and disposed in a series of lines at certain distances from each other, not continuous, but in lengths, so that the ends may overlap each other, the currents will be gently checked without being wholly obstructed, the water between them will be rendered stagnant, and the alluvial matter with which it is charged will be deposited. When the deposit has reached to the top of these works, the works themselves should be raised higher in the same place, or in an intermediate position, as circumstances shall render advisable. Where a certain space is intended to be raised or warped up, it is generally better to commence at the upper end and work downwards; the works themselves are less expensive, the height to be raised is less, and the water impelled by the mass of the tide behind brings up a greater quantity of alluvial matter, and in proportion as the space above is warped up it accumulates in a greater degree below. In carrying on works of this kind, wherever we find that there is a tendency to make a channel, and with it a strong current, it must be checked gradually from the upper end, so that the quantity of water passing through it may be decreased, and this channel will soon fill up. When a certain space has been naturally or artificially raised to the level of a fine green marsh, provided that there be a sufficient quantity to pay the expense, it should be embanked entirely from the sea. As to the expense incurred in embanking it, and the value of the land when embanked, generally speaking, we shall seldom err if we take as a rule that the land should be worth double the cost of embanking. When we have an estuary to deal with from which we may expect to reclaim several thousand acres of land, it resolves itself into a serious question both of time and money as to the best mode of accomplishing it. One object should be as far as practicable to reduce the extent of main or barrier banks, and if the situation be well adapted for the purpose, a barrier bank may be commenced at the lower end, and gradually pushed forward in proportion as the space above it exhibits a tendency to silt up; in combination with this the minor operations should be carried on, so that the one may assist the other. When a sufficient quantity of marsh above the barrier bank has been formed, it may be embanked from the sea, and by keeping the barrier bank always sufficiently in advance the interior banks will become less costly, as they will not be exposed to the main force of the waves during storms; otherwise each separate bank must be made a barrier bank, and the whole cost will be materially increased. The propriety of adopting either the one system or the other will greatly depend upon the peculiar local circumstances.

With regard to the quantity of land, when fit for the purpose, to be embanked or enclosed at one time, this also will, like the other, depend upon the local circumstances. Generally speaking it is safer to confine the operation to about 400 or 500 acres; and the proper time for closing the embankment is during neap tides, when the work will be much facilitated.