A new method of Robert Colepepyr, Gent., for speedy and effectual preservation of the navigation on the River Thames and to repair the water-breach in to Havering and Dagenham levels in Essex ...

A New Method of ROBERT COLEPEPYR, Gent. For speedy and effectual Preservation of the Navigation on the River THAMES; and to Repair the WATER-BREACH in to Havering and Dagenham Levels, in Essex.

This Proponent having many Years spent Thoughts on the Tendancies of Tides, Ebbs, and Sands, for the Benefit of Navigation: Humbly proposes (To the Right Honourable the BRITISH HOUSE of COMMONS in Parliament Assembled, that some New Cutts be made in the Thames Bank, as the cheapest and speedyest Way to perform the Works aforesaid, which if approved of as the best Method, he hopes to be enabled by Your Authority, to proceed on the same, notwithstanding any Statute to the contrary.

Gentlemen,

THE Damages to the said Navigation, Your Pro∣ponent apprehends are these following,

First, The Water received by the Inundation or Bason, is thereby cut off from the upper Part of the same River; this makes some abatement in Water-depth there, but it must be inconsiderable; since taken from so many Miles of Length, and the Breadth of Water that flows above the Bason.

Secondly, That Sand from the Bason damnifies Navigation, by subsiding in the Thames, near the Breach.

And it is true, the Thames first entered this Bason by Failure of a Sluice, and in time, enlarged that Passage to 100 Yards broad; and also to the Thames depth, (viz. where the Bason's Water falls into that River.) But as it was impossible the Tides could ever make high Water in the Bason, before it was so in the Thames, they could not do it till long after that Time; before the Breach was much widened, because the Bason was al∣ways the same to receive Tides; but soon after the Innundation, the Breach gave far less Passage into the Bason than afterwards the Water made; therefore we may conclude, that soon after the Inundation, the Water remained flowing into the Bason, a good part of the time the Thames was Ebbing; before those Waters could come to a Par, and that the Thames must be the lower, before any Water could ebb out of the Bason.

From the Reasons above, a great quantity of Water must remain in the Bason, after the next Tide began to flow in the Thames: Yet this quantity did abate as the Breach grew wider, however may not all be abated; therefore the Time that remaining Water ebbs out of the Bason, and meets the first part of the next Tide; those Waters stop, and swell up one against the other, and drop Sullage, till the Tide prevails, and gives them a new Motion. For whatever doth cause Loss of Motion in Water, gives it a Tendency to drop Sullage; and the Sand of this Sul∣lage will subside where it drops, and will encrease till want of Room for Tides and Ebbs, will suffer it to rise no higher. For Storms there can disperse little, if any Sand, though very useful at the Mouths of our Rivers, where Winds have more Power. Yet to provide against this

Second, and much greater Damage to the Thames Navigation; the Pro∣ponent prays leave to observe as follows, to wit, that

Four Miles of Bank were maintained, to keep the Thames from drown∣ing the same Levell, therefore while not Imbanked, the flowing Water had four Miles to enter this Levell; whereon it rose in heighth slowly, as the Thames Water did, and so abated at Ebb; therefore it must then be high Water at the same time in the Thames, and on that then un-imbank∣ed Land; and all Water would go off from the latter, long before Low-Ebb: Therefore no Sand could then drop through long Contests between Tides and Ebbs, when no Contest was. When at Ebb, the Water was a Foot deep on the un-imbanked Marsh, that small quantity of Water was as long in Ebbing off through its four Miles Passage, as the Thames was in abating a Foot in heighth; therefore the little Speed the Water made to drown and drain the Land last mentioned, bore a very small Propor∣tion, with the Running of Tides and Ebbs in the Thames; but if a Bank had been made gradually on that four Miles Passage, it would as gradu∣ally have given more Motion to the Water that flowed on, and ebbed off from that Land, to bring them to the same Swiftness of running they had in the Thames; and since Low-VVater at the same time in the Deep VVater-frett of the Bason and Thames, is necessary to prevent Subsidence of Sand in the latter; therefore your Proponent would now make four new Cutts in the Thames Bank for that benefit, and each of them as wide as the Breach, though only cut down as low as Marsh Surface.

If the same Cutts, and the Breach, give as much room in proportion to the Bason's Water, as the Thames Channel gives to the Water that flows above the Bason, then we must have high and low. Water in the Thames, and deep Water frett of the Bason at the same times; and little, if any part of an Ebb will be lest in the Bason to meet the next Tide. So this Cutting of Banks is an effectual Way to obviate such subsiding of Sand in the Thames, for it takes away the Cause thereof. The Proponent would not cutt so much Bank if less will serve. However, these or wider Cutts he hopes appear able to answer his End aforesaid, in few Days, to pre∣serve the Navigation, and also abate Rapture in the main Water-frett, that Materials for Reparation may be kept there, and Benefits obtain∣able by cutting of Banks, are without Risque of Failure, since Water builds no Banks.

The Proponent would raise Stops of small Wood in the new Cutts a Foot high; and when Tides rise to the Marsh Surface, the Water will run in through these Stops, and when risen a Foot higher, it will flow freely in over the same Stops, till high Water, and much help the Breach to fill the Bason He can also make a strong Wood Pile, and place the same about 40 Rods within the Mouth of the Breach, to stand in all the deep Water there; and the shallower Water, between the Wood Pile and Shoars, he can fill with sinking Faggots, to be made as long as the Wood Pile shall be broad.

Over the said Wood Pile and Faggots, the Water shall flow several Foot more or less, every Tide. And when it is Ebbed down to the Head of the Wood Pile, the Water to the Thames, ward will have nothing in it's Way, so will run as fast as the Thames Ebbs; but the Water to Landwards of the Wood Pile, &c. will have the same to get through, and notwith∣standing the Water hath a Thousand Millions of small Passages out, through, and by the Wood Pile, and other Stops, yet those Stops will make Sullage subside within them every Tide; for all Sullage that sinks

below the Heads of the Stops, must go down to the Ground, and sub∣side there, for want of Water strength, to drive it through, or to the Stops; and the same Sullage will in reasonable Time, fill all Water-fretts, and raise the same fit for Imbankment, as has been done elsewhere by this Proponent's means; and where all the difficult Parts of that Work were avoided: The said Precedent was about 200 Acres, being the deep∣est part of a Water-frett, had been made by a Bason of 3000 Acres, and was given for Lost by those who regained the rest of it, by Fighting against the Tendency of Tides and Ebbs.

No cutting of Banks was wanted for the Work above, for the Breach remained 500 Yards wide, with the Bason but 200 Acres; but if a Wood Pile be set in Dagenham Water-fret, without Cutts, the Water will fret Soyl from bottom and sides of the Water-frett, where the Wood Pile shall stand, to make good the room it stands in, because that Bason is 2000 Acres, or thereabouts, and but 100 Yards wide.

The Cutts are also extreamly serviceable for Repair of the Breach, and by the last Quarter of a Tide, the Water may rise as high within the Bason, against the back part of the Work, as it shall rise against the Front thereof, by entering at the Breach. And after these two Parts of a Tide come to a Par, by rising within and without the Wood Pile in the Wa∣ter-fret, the Wood Pile has no Water-weight against it, during the rest of the Tide; and it is the latter part of a Tide (as highest) that presses hardest against Works that contend with it.

The Ebbs far exceed Tides, in being Destructive to Works that fight against them; however their Waters on each side the Wood Pile ebb to∣gether, and keep to a Parr, so as one Ounce of Water-weight lies not against the Wood Pile all the Ebb, and thus the Works in Dagenham be∣come less liable to Risque, than the Precedent, or Work before-men∣tioned; for Preservation whereof, no Cutts were made; but any great Water Passages may be left in this Wood Pile, or between the same and the Earth, yet they cannot wear wider, while the Water is on a Par on both Sides, as aforesaid.

Till Dagenham Breach is well repaired, the VVorks there shall lie under the said Guard and Protection of Tides and Ebbs, for Wood-stops in the Cutts shall be raised a little slower than that in the Breach, and the ma∣king of new Banks in the Cutts, on a good Foundation, shall be the last work for Draining the same Levels.

Gentlemen, your Proponent is unwilling good Inventions should die as idle Projects, and hopes he has explained his Methods for Preserva∣tion of the Navigation, and Repair of the Breach aforesaid, so far as may shew him able to perform both, and much Cheaper than in the old Way of fighting against VVater Powers. If this Method succeed, as well in Essex as elsewhere, the same will be an Established Way for all great Water-Breaches for the future, and many Work-Men will be made able to do it, whence no more Families will be ruined by Water-Breaches: Besides, the Security to all Marsh-Land hereby, will considerably raise their Value; and the less Money shall be spent on Repair of your VVater-Breach, the more Serviceable will this New Method be to the Kingdom.

Gentlemen, The Cutts do appear as necessary to do the said Services with∣out any excessive Charge, as the Loss of a Leg to save a Life, which Ope∣ration is often ventur'd by those who only hope to survive it on a Wooden Leg, but here shall be good Banks again, when the Cutts have done their Service.

Some Objections will be made against the Cutts, which are proposed in this manner, and answered as follows.

Objection I. That the new Cuts will become as deep as the Breach.

For Answer, the Proponent says, That the Breach did gain neither Depth nor Breadth, for some Years before the last Stop failed, because it had gained Passage enough, to fill and empty the Bason, by the moderate running Marsh-Channels will bear, without enlargement.

For a further Precedent, when West Thorack Level was under Inundation, the West∣erly Winds that cause the highest Tides in the Thames, did destroy and carry off several Parts of the Easterly Bank of the Level last mentioned, but made those new Breaches little, if any lower than that Marsh Surface; because all the Breaches there abated the Water's Restraint and Tendency to carry out more Earth for a wider Passage. This Precedent is on the Thames, but few Miles lower than Dagenham, and well in Memory.

In each new Cutt may be two Rows of Boards driven into the Ground edge-way, till only the upper edge appears, and these Rows to stand 8 Foot asunder; the Water will run over the edges of these Boards without fretting them lower; nor can it in running 8 Foot frett a Boards breadth into the Ground, because there it must mount again, to pass over the second Row of Boards. These Boards may ease doubtful Minds, but other∣wise they seem needless.

A further Objection against Cutts is, That the Water entering only at the Breach, did, at, and since the first Inundation, break a Bank three Times, and drown a large adjoin∣ing Level, because Soil fit for Banks is wanting there, and the Breach with Cutts may raise Tides a little higher against that feeble Bank, and destroy the same.

Answer, The Bason has four Mile of Bank against the Thames, whose Repair has been much neglected since the Inundation, and the Westerly Winds blow the highest Tides from the feeble Bank, full against the Easterly Bank of the Bason: however no new Breach is yet made quite through any part of that Easterly Bank; and the Feeble Bank ought to have the Heighth and Strength of the Thames Bank, since Tides flow as high against it; and then the Cutts may make high Water in the Bason, just when it is so in the Thames, and damage no Man thereby.

As to want of good Soile for the feeble Bank; the Earth, or rather Mudd used for it, is much soaked every Tide, the same being taken out of the Bason: So the said Bank when new repaired, is at least one third Part of it Water, as the Proponent apprehends: For Water swells the Particles of Earth according to the Quantity of Water that is in them. And as such a Bank dries, the Water is Exhaled by Sun and Wind; and the Parts of Earth shrink one from the other in drying, till the Bank cleaves and parts, or cones in many places, and receives as much Air, as it formerly contained Water. A few Months after the last Repair of this Bank, the Proponent was thereon, and sound very many Cones in it, some of which Cones lying cross the Bank and Deep: And when a Tide rises high enough to enter through these Cones, a Breach is soon made in such Bank. And beyond Michaelmas Winds the same Bank will hardly stand, if not better repaired than Mudd will do it.

Near the new Cutts, (and the better to repair the same,) the Proponent intends to lay some of the Earth which comes out of the Old Banks and Forelands in high Heaps, that the Sun and Wind may make it as dry and fit to be well Rammed, as the upper two Foot of an Old Bank is. And the same way ought to be taken to Secure the Level now in danger; either by its Owners, or the Government, otherwise that Land will probably be added to the Inundation. Note, the Work last mentioned will answer the Objection against Bank-cutting last made; viz. That there is no Earth fit to repair the same Cutts. Therefore when the said feeble Bank is well repaired, and Cutts in the Thames Bank made lawful as aforesaid; then this Proponent hopes Water may faster, or in a greater quantity be let into the Bason, without Danger to himself, or any Person.

FINIS.