DIVERSION OF THE RIVER

Manawatu Herald, 20 June 1895, Page 3

DIVERSION OF THE RIVER

tO THE EDITOR OF THE MANAWATU HERAIi)

Sir, — Your article oh the flood channel in the Manawatu Herald of the 11th June, seemed to me certainly not to encourage the scheme. You say that if the water that rises 70 feet at the Gorge were confined to a channel the same width all the way to the sea, that the height of the water at the George would be the height all the way down.

The absutdity of such a statement will be apparent to nearly every one. Suppose it is as you state, then at the sea line there will be a wall of water 70 feet high which is absurd. Again suppose we have a channel 100 yards long with parallel banks and the height of the water at one end is 10 feet above the height at the other, we will have a fall of ten feet in 100 yards. Take a point 80 yards down, and you tell us that the water will be still ten feet high, that means from that point to the mouth we will have a fall of ten feet in 20 yards, so that the velocity of the water must be no greater with a fall of ten in twenty than ten in 100. Which is absurd. Now if you draw a right angled triangle and let the perpendicular represent the height of youi 1 column of water at the Gorge, given no obstructions the hypotenuse will represent the line of height of the river to the sea. Now if you shorten the base which is equivalent to shortening the river your line of height will be lower all the way down.

Now if the river at Moutoa is on the sea level as it must be if the tide runs up there, then Ihe river must rise ten feet to get a fall of ten feet in about 24 miles to Foxton. Now if a cut were made from Moutoa to Foxton about five miles we would get a fall of 10ft in five miles or nearly five times the fall, and therefore an increase of velocity. And every modern school boy knows that a straight pipe will discharge more water than a bent one with the same pressure, so a straight river will discharge more water thnn a crooked one in the same time for every bend acts as a check, so that by making a straight cut from Moutoa to Foxton the discharging capability of the river is increased from two different causes.

Suppose for argument sake the increase is a third, then a third more water will have to come down the river than at present to cause the same rise.

Hoping you can find space for these few remarks. I am, &c, Oswald Gakdneb.

[Note.— We regret our correspondent writes in such a " cocksure " manner, as the proposal is one that demands most careful consideration, and simple assertions will not convince the ratepayers. Our contention, which Mr Gardner carefully avoids, was, that the cost of river deviation would probably be greater than the value received by such work, and that no deviation would be justifiable unless all lands were assured from flooding. Our statements may appear " absurd " to our correspondent, but the fact remains as stated by us that the volume of water rising at the Gorge is the volume to be removed to avoid lands being flooded. We mentioned that professional men should be engaged, and until such a report is to hand all statements must be of little value. Ed. M.H.]