In the 16th Century, the Lea was apparently still tidal as far as Lockbridge.
To the north-east, there is a record summarizing what the Victorian County History (1973) has to say on a wooden causeway, consisting of twelve bridges, built or perhaps repaired in 1544, and although ruinous by the end of the 17th Century, were apparently still visible in the 19th Century (see further below).
There was also a causeway of some twelve bridges across the marsh, extending from Blackbridge to Lockbridge, built or repaired in 1544, repaired in 1580, and in a dangerous state in 1611.
It is reported that Lockbridge was broken down and that Lord Wentworth, lord of the manor of Hackney, 'ought to repair it sufficiently for foot traffic'. In 1594 it is described as being among the most useful bridges in Middlesex.
The City of London sponsored legislation to construct a canal from the Lea to London. Parliamentary opposition thwarted the original ambitious scheme.
‘Commission of Sewers’ appointed in 1575 to carry out works to the River Lea. (Commissions were usually appointed for period of up to ten years). Commissions of Sewers for the marshlands were primarily concerned with the problems of flooding and drainage, but also the navigable river with the task of maintaining the navigation. Commission of Sewers for the levels of Havering and Dagenham had responsibility for the Lea from the mouth of the Fleet and the head stream of Walthamstow Mills, to the Thames, and supervised the levels of Walthamstow, Leyton and West Ham in Essex and the level of Bromley in Middlesex. Such boundaries meant that the commission supervised the tidal stretches of the Lea and all tidal mills fed by the river.
The Saxton’s county map of Essex from 1576 shows schematic details of several crossings that may be bridges, causeways, flashlocks, fords or ferries.
Following the abandonment of the canal scheme of 1571, new surveys by the City of London considered two cheaper routes for a water supply channel: A shorter route between Lea Bridge and Moorgate and a route from Tottenham; which was subsequently preferred but not implemented. Instead an ambitious and unique river improvement scheme was successfully implemented. This experimental navigation (reducing reliance on flashes to a minimum) survived 20 years, before persistent and violent opposition from land carriers closed it in about 1594.
A wooden causeway comprising 12 footbridges led from Blackbridge (which crossed the Shortlands Sewer west of Hemstall Green) on the Leyton side over the marsh to Lockbridge. In the 16th Century, this causeway was built or repaired by Sir George Monoux (d. 1544) and repaired again by Lady Laxton, probably about 1580 when it was reported in ruins. They did this 'of charity', having no lands in Leyton themselves.
The more modest scheme included dredging, removal of fishing and mill weirs, blocking up of smaller streams, which drained off water into the surrounding marshes and meadows, and the construction of raised river banks where needed. Towing bridges were built over mill-streams so that horses pulling barges could pass unimpeded. Footbridges were either removed or raised and a range of road bridges, including those at Higham Hill in Walthamstow and at Hackney, were raised to give a clearance of at least four feet.
By 1588, barges capable of carrying three to five tons were navigating the Lea. These boats were single masted and had a towline attached at the mast. They had a crew of three or four, one steerer and three haulers. Sails and oars would have been used on the tidal section of the river south of Hackney. It took twelve hours to travel from Bow Bridge to Ware. Besides grain, barges carried beer, coal and salt.
In 1592, works to the navigation were deliberately destroyed (at Waltham) after the authority of the 1571 Act was questioned, whilst the authority of the Commissioners of Sewers expired in 1585 and was not renewed. All this led to the abandonment of the improvements and reversion to the traditional system of pens and flashes from locks, fishing weirs and mills along the river. Major navigational improvement of the Lea was not attempted again until the 18th Century.
Disputes between barge owners, who wanted locks, and millers, who needed water to power their mill wheels, delayed negotiations over improvements (planned since the 1425 Act) until 1594, when the barge owners won. In 1594, Sir Thomas Fanshawe, representing Ware and the bargemen of that town and Amwell, together with the City of London brought a case in the Court of Star Chamber. Their complaints were many and, if all true, there must have been a state of near anarchy on the river.
The Star Chamber case upheld the rights of the bargemen, but the experimental navigation was not restored. Instead the traditional flash-lock navigation re-appeared, and was to last, with only minor improvement, until 1767.
 The River Lea 1571-1767: A River Navigation prior to canalisation. Keith Roland Fairclough, University of London. 1986
 The Navigation Of The River Lee (1190 – 1790). Occasional Paper New Series No. 36 J.G.L.Burnby and M.Parker. Edmonton Hundred Historical Society. 1978
 The River Lea 1571-1767:A River Navigation prior to canalisation. Keith Roland Fairclough. University of London. 1986
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