MR. DOUSLIN AND THE HUTT RIVER.

Marlborough Express, Volume XIV, Issue 1121, 2 April 1879, Page 6

MR. DOUSLIN AND THE HUTT RIVER.

The following letter by Mr Doualin, of Blenheim, was read at a recent meeting of the Hutt County Council : Blenheim, 20th March, 1579. To the Chairman of the Hutt River Conservators Board. Sib, —In reply to your letters of the Ist and 14th ult., requesting information respecting the Wairau River and the floating dam, I have the honor to submit the following particulars : About three years ago I was over in Wellington for a few days, and went to the Lower Hutt expressly to see the river and the protective works. The river at this time was very low, and in consequence, it was an unfavorable time to judge of the comparative volume and velocity of the river with the Wairau River, but judging from the general appearance of its bed, and the waterway under the bridge, I -would venture to say the Wairau River in times of flood contains three times the volume of water. The Wairau takes its rise over' 100 miles from the sea, and receives many tributaries, both large and small, stretching out north and south. , One of its tributaries, the Waih’opai, is a large river. Below the confluence, the river in obedience to an infallible law, comes sweeping down with its power of change and destruction, and thus far this great river found no obstacle capable of coping with its united power until the floating dam was erected at Rock Ferry ; and there it is to-day, perfect'd!! all its parts. Not a shilling has been expended on it, but it has stood the test of this gigantic river for'three years, and in a position where the greatest inroads had been made. The Wairau River above the tidal influence slopes about 15ft in the mile. The average rise of the river in the upper reaches in the time of flood is about 6ft. 1 ! .&n February 4th, 1877, the river rose 6ft 1 9in, which was a very high flood. It is difficult to give a correct average of the width of the nver'in, times of flood, but I would venture to say it ! is from 500 ft to 1500 ft wide. About 16 miles from the sea the river divides. The branch ruUding/in fksouth-east direction through the townr rof'.rßlenhejm is the Opawa River, which ia navigable up to the town for vessels drawing sft of water. The volume of water in each stream below'the Breach in flood, is, in my opinion, six-tenths in the Wairau River, and four-tenths in,the Opawa River, and previous to the breach being closed at Rock Ferry by the floating .dam (two-tbirds of the whole volume swept down the Opawa River, amighty sedimentbearing river. The amplitude of the sections below the breach are much the same as those above, the diffusion of the water being the cause consequent on the loss of momentum, and except on the, north, bank; of the Wairau River there is no defined high banks to keep the river within

reasonable bounds—thus it runs riot until yon reach the tidal influence of each river. The banks of the river are of sucli a friable nature that they offer very little resistance to the river, and the consequence has been that the Opawa River for the last 14 years lias made great inroads on its south bank. About four miles from Blenheim, at a place known as Leary’s Beach, a cavin-in has been going on for 14 years —which has now worked to the south half-a-mile. It was evident the river intended to make a cut off, and prepare for itself a new bed, and shorten the distance to the sea. My opinion is most positive that, by this time, it would have been a realised fact if a large proportion of the water had not been forced down the Wairau Branch, and without some special comj bination of causes occur, this cut off is by no means out of the reach of danger, for the centre of effect is still working in a south east direction. (See Express of May 22nd, IS7S), T made an offer to she Board of 'Conservators to enter into a bond of LI 000, that I would entirely dry the old river bed at Leary’s on my being paid L3OO if I succeeded, and if I failed to forfeit my bond. I was of opinion the work would not have cost more than L6OO or L7OO Eleven years ago last month, about two miles below Leary’s, on the north side of the Opawa river, it cut off an elbow in the river, which reduced the length of the river three miles and live-eighths. It will be apparent from tills that the fall of the river would be very much increased, thus causing an increase of velocity and carrying power the river never previously attained, and the result has been that immense deposits of shingle have been carried miles below this cut off, raising the river bed and overflowing the bank, which has devastated some of the most valuable, land in the district, and endangered the town of Blenheim. About half-a-milc below the site of the Opawa railway bridge on the south side of the river, a large elbow will bo cut off this winter (Wratt’s bend), which will again shorten the river, and make a very material change. When the river breaks throng!), the whole of the river lied known as Wratt’s bend Mill fill up with fine sediment, and principally with sediment held in suspension. This erosion hai been going on for years, and in the apex of the bead in a high flood there is 20 feet of M'ater, and the neck which it will cut through is only 1(5 yards wide, so that it is almost reduceable to a mathematical calculation. The river bank is composed of loam, and supposing it was standing water 20 feet deep, the average pressure against the bank would be 6251bs to every foot; to add to this there is an impact, which is beyond my calculation. The proper course in such a case as this would be to make a cut, and Jet the river through before the winter floods set in, and not leave it to burst like a mighty dam ; but by letting it through it would gradually adapt itself to the new bed; for go through it will. Regarding the dam, I will forward you a number of articles that have been printed during the last three years. I may also inform you that I have not written any article on the dams except those to which my name has been signed. I am not an engineer, but have made shingle-bearing rivers a profound study for years, and what I know of them is from practical experience and observation, with such assistance as I could get from the best authorities on shingle-bearing rivers, and without exception my preconceived opinions are borne out in a most marked manner, and every article you see my name to I believe most emphatically. My belief is stronger to-day than ic was at the time I wrote them. Experience and results have so strengthened them that they cannot be shaken. On April sth, 1878, when 1 first submitted the plans to the Conservative Board, Mr Eyes, a member, said as follows;—“Ho had seen the river three times since Christmas, and every time he saw it the river looked worse. He quite agreed with the Spring Creek Conservators that there was never less probability of turning the water into the big river (Wairau River).” As there is no one in the district but will admit that there is a very much larger volume of water going down the -Wairau, and a decrease in quantity in the Opawa Iliuer, and as no other protective works have been erected in the Wairau River, it must be admitted that the great change has been caused by the protective works. It suits the settlers in one part of the district to get the water into the Wairau, hut, on the other hand, it suits those in another part to get the water back into the Opawa. The Spring Creek Board of Conservators have threatened the Wairau Board of Conservators with an action if they force any more water down the Wairau River. These are convincing proofs of there being more water going down the Wairau River now than formerly. (To he continued.)