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

It is true that much greater quantities may be taken in at one time, according to the Dutch system, but then several closing spaces must be left open, and these must all be specially prepared for the purpose by lining the bottom and sides with wicker-work and fascines to prevent the scour, and then filling them up with clay, stone, fascines, and earth, as the case may require; and if by chance a breach should take place, which occasionally occurs under the best of management, the internal space to be filled with water is so great that the violence and strength of the inpouring current is increased in the same proportion, so that it carries all before it, scoops out great channels in the interior space, and damages the land by the great quantity of sand brought in, and it becomes difficult to clear the internal space of water. And although by this plan a less quantity of embankment is required, nevertheless the expense per lineal foot becomes greater; but where the length of the embankment is small compared to the depth of the land to be enclosed, this system, if properly managed, may be adopted with advantage. The most advisable plan must be left a good deal to the judgment and skill of the engineer-in-chief taking advantage of the local circumstances.

The above principles for warping and enclosing land I recommended in several reports to the Norfolk Estuary Company, but they were not adopted to the extent I recommended; the consequence has been that several years’ time and a good deal of money have been unnecessarily expended. But I believe that they have been finally convinced that my system was the proper one, and it has since been adopted to some extent, with considerable success, and about 1000 acres (in 1867) have been enclosed, the property of the Company, at the cost of about 15l. per acre, the land being worth 40l. They have, moreover, enclosed 600 acres more for the Prince of Wales, upon which they will be paid one-third of its improved value. As several thousand acres in the estuary belonging to the Company are rapidly approaching that state when they may be profitably embanked, I confidently believe, by proper management, that the shareholders will ultimately recover a good deal if not the whole of their capital, and perhaps a good portion of their interest also; but I shall always contend that if my recommendations had been followed from the beginning, a great deal of money would have been saved. The Company ought not to have submitted to the restrictions imposed by the Acts. The contribution from the drainage and navigation interests ought to have been double, for which they would have been amply repaid, and the land gained would have been far greater, so that even by this time it might have been a very profitable concern.

Whilst the Nene Outfall was in progress, I was employed by the Corporation of Boston to improve the outfall of the river between the Grand Sluice at the upper end of the town, and Hobhole near the mouth of the river, a distance of nearly four miles. This had previously been proposed by my father, in the year 1845, to the Corporation of Boston, previous to commencing the great drainage of the East, West, and Wildmere fens bordering upon the Witham between Lincoln and Boston, amounting to about 125,000 acres of lowland, which for the most part was little better than a marsh. It was here he proposed his grand system for the drainage of lowlands by means of catchwater drains for the waters from the highlands, and main and minor drains for the waters from the lowlands, both systems of drains being distinct and separate from each other, and which he afterwards most successfully carried into effect. In order to obtain the requisite fall, it was necessary that the outfalls of the two main drains should be carried into the Witham below the town of Boston; but in order that this might be effectual, it was also necessary that the Witham should be greatly improved between Boston and the mouth at Hobhole; and as the navigation between these two points was very defective, he thought that the Corporation should bear the expense, as they would derive the greatest benefit. For this purpose my father proposed two plans: one was to improve the old channel, partly by cutting off the bends and confining and straightening its course, and from Hobhole making a new cut to Clayhole, where there was ample depth of water at all times of tide; and the other plan was to make a direct cut within land from the lower end of Boston to Clayhole. He proposed also, for the drainage, to make an outfall for the highland water at Maudfoster, just below the town of Boston, as he said that by bringing the highland water there, it would effectually serve to keep the river open between that point and its mouth at Hobhole, and to make an outfall for the lowland waters at the latter place; and he recommended the drainage interests to contribute a certain portion of the expense towards the improvement. The Corporation of Boston declined doing anything, and the drainage was left to take care of itself. Mr. Rennie, however, foresaw that if the Witham was not improved by either one or the other of the plans that he recommended, the highland water would not be effectively discharged by the sluice at Maudfoster, and therefore he made a communication between the Maudfoster drain and the Hobhole drain at a place called Cowbridge, a few miles above Boston, where there was a gauge, so that whenever the water in Maudfoster drain exceeded the gauge it passed into the lowland main drain, and from thence into the Witham at Hobhole. What Mr. Rennie foresaw came true; the Witham, not having been improved, became worse, and the river in front of the Maudfoster Sluice was silted up, so that it could not discharge its water, and therefore the whole of the water, highland and lowland, was obliged to go by Hobhole, which drain and sluice, foreseeing what would take place, he had enlarged for the purpose.

In the year 1827, the outfall of the Witham between Boston and Hobhole had become so much silted up that at high water of neap tides there was scarcely water enough for fishing boats to come up to the town during the summer months and dry seasons, and at spring tides only sloops of very small draught could get up to the town; in fact, it might be said that at that time Boston as a seaport was lost, and the trade and navigation of the port ruined. At this the Corporation became greatly alarmed, and sent for me. I directed the late Mr. Francis Giles to make a complete survey of the river, which he did in his usual able and correct manner, and no person could do it better. Being provided with this survey, I made my report, and saw clearly that there was no remedy but to carry into effect either the one or the other of my father’s plans of 1805. As the Corporation funds were very limited, I recommended the plan for improving the old channel, partly by cutting off the bends and confining the river as far as Hobhole, and from thence making a new cut to Clayhole, as recommended by my father. There were three parties who were to contribute towards the improvement of the outfall of the Witham, namely, the Corporation of Boston, and the Witham and the Black Sluice Commissioners. The Black Sluice Commissioners demurred to the plan proposed by me, which was my father’s, on the ground that the cut ought to be made from the Black Sluice inland direct to Hobhole, otherwise they would not derive the advantages they had a right to expect from their contributions; so the whole matter was referred to Mr. Telford, who said that no improvement in the river below Boston would be of any use, unless the Grand Sluice above Boston was removed, so as to admit the tide to flow farther up the river. Now, although Telford was to a certain extent right, but by no means wholly so, because by carrying into effect either of my father’s plans there could be no doubt that considerable improvement would be made on the outfall of the Witham below Boston, as the sequel will show, nevertheless, if the Grand Sluice had been removed the tide would have flowed farther up the river and the increased quantity of tidal water passing upwards and downwards would have improved the outfall still further; but there were insuperable objections to the removal of the Grand Sluice, which neither of those parties above mentioned who were to make the improvement in the outfall could control, for the river above the Grand Sluice was under a different body. The banks must have been raised to admit the tide; compensation must have been made for the loss of fresh water, and various other interests must have been consulted that were hostile. The Black Sluice Commissioners stuck to Telford’s report, and withdrew from the contribution, so that the whole matter fell to the ground.

The outfall of the Witham became worse, and the Corporation of Boston, being left single-handed, and having determined to do what they could to improve the river, again requested my advice. I said that the best thing they could do under the circumstances would be to carry into effect by degrees, as far as their means would allow, the plan of my father already referred to for improving the old channel of the river, and to begin by cutting off the bend between Hobhole and the upper end of Burton’s Marsh (this cut would be about half a mile long), and blocking up the old channel immediately above it, which was about half a mile wide. These two works would shorten the navigation quite half a mile, and admit and discharge the tidal and fresh waters more readily, and thus produce a corresponding scour and lowering of the low-water line and bed of the river all the way up to the Grand Sluice above Boston.

The Corporation adopted my recommendation, and entered into a contract with Jolliffe and Banks for that purpose. Although a small work, it was attended with considerable difficulty, particularly in closing the old channel, on account of its great width and the great body of tidal water which passed through it. The effect of this work exceeded my most sanguine expectations; in a short time it improved the channel upwards to Boston to such an extent that spring tides rose at Boston Bridge 14 feet, and neaps 10 feet, and the bed of the river was deepened from 3 to 4 feet below low water of springs, so that vessels drawing 15 feet and 16 feet could come up to the town at springs, and vessels drawing 12 to 13 feet could come up at neaps; moreover, all the silt was scoured away from the front of the Maudfoster Sluice, so that it discharged the highland water from the fens, which it had not done for years before, and improved also the discharge of the waters from the Grand and Black sluices. I must confess that I was not a little elated at this successful result, as it most completely established the correctness of my father’s opinion as well as my own, and demonstrated the fallacy of my friend Telford’s judgment. The cost of the above works was 33,000l., which was very small compared to the advantage obtained. The Corporation of Boston were so much pleased with the success that they determined to carry into effect the remainder of the improvement in the old channel to Boston, which was afterwards done by confining the channel by degrees to a proper width by means of fascines and loose stone and clay properly combined together up to the level of half tide, so that the flood and ebb always acted to the greatest advantage in one and the same channel without materially diminishing the quantity of tidal water.

The effect of these additional works was to still further deepen the bed of the river and increase the flow of the tide by lowering the low-water mark, which improved the navigation and drainage still further, so that the trade of Boston revived and increased in prosperity, and all this was effected by the resources of Boston alone; and it is only to be regretted that the drainage interests, who derived so much benefit, were not compelled to contribute their just proportion.

In 1852 a Bill was obtained to carry into effect my plan for improving the mouths of the Witham below Hobhole, and the Welland below Fosdike Bridge, and reclaiming 35,000 acres of land from the Great Wash, as formerly described, but the Bill was clogged with so many restrictions, and neither the drainage or navigation interests would contribute anything towards it, although they would have been greatly benefited, that it was found impossible to carry it into effect so as to remunerate the shareholders, and therefore it was abandoned.

I about this time finished some minor works which had been designed and partly executed for the improvement of the Witham near Lincoln. This was part of a great plan of my father for improving the river Witham, so as to make it navigable for the Yorkshire coasting vessels, drawing 6 feet and carrying about 70 tons. From Lincoln they proceeded to the Trent by the Old Foss navigation, which entered the Trent at Torksey, and from thence to the Humber and the adjacent coasts. This improved navigation of the Witham answered very well as a commercial speculation, and in the year 1847 was sold to the Great Northern Railway Company, who established a railway on its banks, which now forms part of their loop line between Peterborough and Lincoln, which has in a great measure superseded the navigation.