Editing River Witham (section)

===Canalisation===
Following meetings of Landowners held in 1752 and 1753, they asked John Grundy Jr, as his father had died in 1748, to re-evaluate his plans from 1744 and consider a plan for a "Grand Sluice" that had been produced by Daniel Coppin in 1745. Grundy suggested that the 1744 cut should be extended by a further {{convert|2|mi|km}} into Boston, and that the sluice could then be built on the extension. The landowners moved the location of the sluice nearer to Boston, but otherwise approved his report, although no action was taken. John Grundy was again consulted in 1757, and Langley Edwards of King's Lynn was asked to review the positioning of the sluice in 1760. The landowners then asked [[John Smeaton]] to liaise with Grundy and Edwards, and the three engineers produced a joint report in 1761, with estimates of £38,000 for drainage works and £7,400 for improvements to navigation. The report was approved, although a meeting held in January 1762 decided that the new cut should revert to the alignment suggested by Grundy in 1753. The location of the Grand Sluice would be as suggested by Edwards in 1760. Grundy produced another engraved map, and parliamentary approval for the works was obtained in June 1762.<ref name=skempton280>{{harvnb |Skempton |2002 |p=280}}</ref>

Once the Act of Parliament was obtained, Edwards became the engineer for the project, and drew up the detailed plans, which Grundy and Smeaton checked and altered slightly, after which they had no further involvement with the scheme. Construction was started in April 1763, and the drainage element of the project, which included the sluice, was finished in 1768, having cost £42,000. Work on three locks and other work connected with navigation cost £6,000 and continued until 1771.<ref name=skempton280/> The locks were located at Stamp End, Kirkstead and Barlings.{{sfn |Boyes |Russell |1977 |p=259}} The Grand Sluice was a major construction which maintained the height of water above Boston to near normal high tide level and had massive flood gates to cope with any tides above this. It was completed in 1766<ref name=labrum66>{{harvnb |Labrum |1994 |p=66}}</ref> and was effective in scouring the Haven below it and increasing silting of the river above it.

The 1762 act created the Witham Navigation Commissioners and the Witham Drainage General Commissioners,{{sfn |Boyes |Russell |1977 |p=258}} who continued to promote drainage schemes actively,<ref>{{cite web |url=http://witham-1st-idb.gov.uk/?page_id=30 |archive-url=https://web.archive.org/web/20201126011624/http://witham-1st-idb.gov.uk/?page_id=30 |archive-date=26 November 2020 |url-status=live |publisher=Witham First Drainage Board |title=History |access-date=14 July 2018}}</ref> creating a drainage network known as the [[Witham Navigable Drains]] that transformed much of northern Lincolnshire from fen to farming land. Today many of these channels are managed by the Witham [[Witham First District IDB|First]], [[Witham Third District IDB|Third]] and Fourth District Internal Drainage Boards and Upper Witham Internal Drainage Board. These four [[internal drainage board]]s reduce the flood risk to the surrounding properties, land and environment.

In 1791, as part of the campaign to promote the construction of the [[Horncastle Canal]], the Commissioners of the River Witham asked the engineer [[William Jessop]] to assess the state of the [[Fossdyke Navigation]] and the Witham, with particular reference to the problems of navigating through Lincoln, where the channel was restricted by a medieval bridge. He proposed two solutions; the first avoided the route through the city entirely, by utilising the course of the Sincil Dyke to the south, while the second involved lowering the bottom of the channel through the Glory Hole bridge, which was only {{convert|18|in|cm}} deep at normal water levels. The Commissioners had imposed a toll on all traffic passing under the bridge, but decided that a channel bypassing the city would have grave financial consequences. They opted for improving the existing channel<ref name=boyes261>{{harvnb |Boyes |Russell |1977 |p=261}}</ref> and the work to remove the wooden floor, to lower the river bed under the bridge and to underpin its foundations was completed in 1795.<ref name=labrum60>{{harvnb |Labrum |1994 |pp=60–61}}</ref> The Commissioners dropped the collection of tolls at the bridge, but the amount they received from traffic passing through the locks increased as the volume of traffic grew in response to the easier passage through the bridge.<ref name=boyes261/>