The Pamphlet Collection of Sir Robert Stout: Volume 64
Art. IV.—Notes upon the great Floods of February, 1868
Art. IV.—Notes upon the great Floods of February, 1868.
In February, 1868, the northern part of the South Island was visited by an extraordinary rainfall, which did a large amount of damage and left indelible marks of its occurrence wherever the waters of the main rivers rose above the height of ordinary floods. The general steepness of the mountains within this area necessarily causes a rapid superficial drainage, and, as a consequence, a rapid erosion and displacement of the materials of their surface, so that during heavy rains the channels of all the draining streams are not only quickly filled but their waters become heavily charged with silt and gravel, which is carried into the main watercourses, converting them into huge muddy torrents. Almost all the main rivers in this part of the South Island are, in effect, torrents even to their mouths, the average slope of their beds being little less than 85 feet to the mile. There was, moreover, this peculiarity in the rainfall in question, namely, that the quantity which fell within the first few hours was so great as to fill every stream bank high, and as the rain continued to fall almost as heavily for many hours after that had occurred, the main rivers not only became enormously flooded within a singularly short period, but maintained their flooded condition for an unprecedented length of time. Many causes, too, resulting from man's foolish and wanton interference with natural operations, had contributed to bring about a rapid accumulation of the rainfall in the main rivers. In the first place, the forest had been cleared by fires and otherwise but principally by fires, from a large extent of the eastern slopes of the mountains in the very localities in which the ordinary rainfall is usually page 77 heaviest. In the next place, the surface vegetation of all those portions of the country in question, which could be used for depasturing purposes, had ken systematically burnt over, year after year, in order to encourage a fresh growth for the use of the stock. And, moreover, the treading of the surface by depastured animals tended still further to harden it, and cause it to contract and crack in under the combined influence of the sun and wind. It is easy, therefore, to conceive that after any exceptionally great rainfall the main rivers which drain the districts referred to must become powerful engines for mischief, and are well calculated to make and leave indelible marks of their action, especially where their waters overspread a cultivated country.
Some years ago, I brought under the notice of the members of the New Zealand Institute (in a series of lectures) the desolating effects of torrents such as those which rise in and flow from our great mountain districts, owing to destructive changes occasioned by man's agency; but, although the evils I pointed out have been recognized and publicly commented upon, both in and out of Parliament, no attempt has been made to check the continuance of the acts which have brought them about. It is, no doubt, true that legislation has proved ineffectual to prevent the progress of such evils in older countries, but this is chiefly owing to the facts that the entire soil is vested in private persons, and that every proprietor will, as a rule, insist upon his right to fell his woods, and otherwise deal with his property in such manner as he thinks most consistent with his pecuniary interest, and that whether the result be injurious to others or not. But in a country like this, where the State has the possession and control of nearly all the forests which clothe the mountain sides, it is its imperative duty to retain that possession and control, and to provide severe punishment for acts calculated to produce evils of the kind referred to. The revenue derived from the demise of the great tracts of beech forest, which are frequently included within the limits of depasturage areas, is as nought when compared with the enormous damage which must result to the State from its destruction, destruction, moreover, which is rarely confined to the tracts comprised within the demise itself. I have seen thousands of acres of such forest wantonly burnt, and within a very short period afterwards nearly the whole of the loose soil has been washed from the cleared surface, leaving nothing behind but bald mountain ridges, rocky declivities, and steep earthy banks, furrowed by deep ravines usually filled, during rains, with torrents of mud and gravel. In Europe and America, the desolation produced by such causes has already been very great, and, in the older continent, millions of money have been spent in the regions of the Alps, the Pyrenees, and the Apennines, in attempts to prevent a continuance of the physical page 78 deterioration already produced in tracts of country which had formerly presented the uniform aspect of luxuriant pasture grounds and abundant cornfields and vineyards.
I have digressed somewhat from the immediate subject of my paper, but a recollection of the destructive results of the great floods of February, 1868, brought vividly before me the amount of injury which has already occurred, and which is likely to follow, from continued improper interference with natural operations; and I could not resist the opportunity of once again urging the necessity for checking such interferences, before it is altogether too late to do so with effect.
To return to my immediate subject. I have added by way of Appendix to this paper, a table (compiled for me by Mr. Gore), containing the meteorological notices recorded in both Islands during the month in which they occurred, from a perusal of which, independently of what I am about to state in this paper, you would doubtless conclude that the floods in question were of an unprecedented character. From observations made by myself during two or three journeys overland between Christchurch and Nelson, and, therefore, through the heart of the country in which these floods attained their maximum intensity, I was led to the startling conclusion, not only that they were the greatest which had occurred for a very long period of time, but that that period might properly be reckoned by thousands of years. Such a statement is, I admit, easily made, and must primarily be treated as being incapable of proof; but, whether I succeed or not in establishing my proposition to your satisfaction, I feel pretty well assured of its truth, and will, in due course, state my reasons for advancing it. In order, however, that you may be able to appreciate those reasons, it is necessary that I should give a somewhat detailed description of the features of the country in which my observations were made.
My first journey took place within a fortnight after the floods had subsided, and was from Christchurch to Nelson, visiting on my way a cattle-station which I then held, in the heart of the Spenser Mountains. My route, after leaving the Canterbury Plains, lay through the Weka Pass to the Hurunui and Waiau-ua Plains; from thence through the second gorge of the Waiau-ua, to the Hanmer Plain; across that plain to Jack's Pass; and over the pass into the Valley of the Clarence; and then into my station on the Upper Waiau-ua, by Fowler's Pass. From my station to Nelson, I crossed Maling's Pass to the head of Lake Tennyson; thence over the Island Saddle to the head waters of the Wairau, and through the Wairau Gorge, and the upper valley of that river, to the Top House; and thence through the Big Bush, to Nelson.page 79
The Hurunui and Waiau-ua Plains form together a long oval tract of practically level country, lying nearly east and west in its longest diameter, surrounded by mountains, and occupying the centre of the Amuri District, in the Province of Nelson. The eastern and larger portion of this oval is called the Hurunui Plain, and is traversed diagonally from north-west to south-east by the river of that name. The western and smaller part of the oval is called the Waiau-ua Plain, and is also traversed from north-west to southeast by the river of that name. This latter portion lies at a lower level than the Hurunui Plain, for reasons to which I will shortly refer. The whole area presents the appearance of an ancient lake basin, the bed of which had been filled with gravels brought down by its various feeders before the waters had been drawn off through the channels cut from its southern side to the sea, by the rivers which now traverse its bed. These rivers are the Hurunui and the Waiau-ua, the first of which, after debouching from the mountains at the north-western end of the oval, flows diagonally across its upper part to about the middle of its southern side, where it enters a gorge and passes on to the sea; and the second of which, debouching from its own gorge above referred to, at a point a little below the middle of the northern side of the oval, also flows across it diagonally (on a line nearly parallel to the course of the Hurunui) to the south-eastern end of the oval, where it also enters a gorge through which it flows to the sea. Each of these rivers has removed in its course from its debouchure onto the plane to the gorge which it enters on the southern side, an immense quantity of the materials of which the lake bed was originally composed, leaving that part of the latter which lies between their courses as an undisturbed level tract, some twelve miles long, standing considerably above the general level of those portions of the oval which have been acted upon by the two rivers. Moreover, each of these rivers occupies a more or less defined channel in the lower ground through which it now flows, that of the Hurunui gradually widening to about three-fourths of a mile until it reaches the point at which it enters the gorge, where it again contracts, while that of the Waiau-ua rapidly spreads until it attains a width of from one to two miles, and as rapidly contracts again towards the point at which it enters its own lower gorge at the south-eastern end of the oval.
A stream called the Pahau, which in its ordinary state is most insignificant, flows from the mountains on the northern side of the oval about midway between the debouchures of the Hurunui and Waiau-ua, running in a shallow depression across the higher ground between these two rivers, until it joins the Hurunui close to its entrance into the gorge on the south side of the plain.page 80
The Hurunui and Waiau-ua are both, and especially the latter, very large rivers, each draining an immense area of the steep mountain masses which form the northern extension of the Southern Alps, and each is subject to heavy floods, especially during north-west summer rains. The Pahau, though ordinarily an insignificant stream, is also liable to heavy floods, not only because it drains a large mountain tract, but also because in the area which it drains the mountains are exceptionally steep, and the rainfall necessarily finds its way very rapidly into the minor watercourses which supply it. The Weka Pass road debouches on to the Hurunui Plain at a point where there is yet an undisturbed level portion of the old lake bed, from the top of which it descends into the channel of the Waikari, a small tributary of the Hurunui, which flows along the base of the mountains on the south side of the oval. This tributary has also cut its channel through the old lake bed, and has a small terrace on its northern side, between which and the channel of the Hurunui the ground rises gradually to the westward. On arrival near the latter channel we find a terrace similar to that on the north side of the Waikari, below which lies the main bed of the Hurunui river. Crossing this bed, which is here upwards of half a mile broad, we come to a high terrace, on ascending which we reach the level ground which I have referred to as lying between the two main rivers. The surface of that portion of the plain which lies between the Waikari and Hurunui rivers is, as already stated, a good deal lower than that of the original lake bed, as both rivers have been engaged, ever since the lake basin was emptied, in removing the sands and gravels of which it was composed, but this surface rises gradually towards the western end of the oval, where it lies at the same level as the upper surface of the plain between the two main rivers.
On reaching the point at which the second gorge of the Waiau-ua opens out to view, the road leads downwards over a succession of small terraces to a main one bounding the high flood-channel of the river, the whole of the gravels and sands below the original surface-level of the lake bed having been removed from this part of the oval, besides which the river, in its course through the gorge, has cut through the solid rock, underlying these gravels, to a depth of from twenty to thirty feet. The gorge itself between the Waiau-ua and Hanmer Plains is about eleven miles long, and rarely more than a quarter of a mile in width, from the foot of the hills on the one side to that of the hills on the other, the greater part of the river channel being in solid rock overlaid by gravels disposed in terraces, corresponding with those above described. The road through the gorge runs along the surface of a main terrace on its western side, the gravels of which immediately overlie the rocky walls between which the waters now flow.page 81
A number of small valleys, lying generally at right angles to the course of the main river, occur amongst the spurs of the mountains on each side of the gorge, each of which has its own stream, whose size is proportionate to the extent of the valley in which it flows. Every one of these lateral valleys is filled with gravels to about the same height as the level of the higher part of the Hurunui Plain, and its front towards the main river, between the extremities of the spurs which bound it, is a terrace face equal in height to the difference between that of the upper surface of the Hurunui Plain and the surface of the gravels of the terrace at its foot. From this foot to the edge of the bank of the main river the width varies from fifty to three or four hundred yards, and it is along this terrace that the road runs.
Now each of the streams which occupy these lateral valleys has cut a channel, more or less deep, through the gravels with which its own valley is filled, and, in some instances, through the rock which underlies them, and debouches on to the terrace of the main river, over which it flows in a manner having special relation to its magnitude and the force of its current. In every instance, however, these lateral streams have formed, at their debouchures on to the main terrace, what are geologically termed half-cones, more or less extensive, composed of the gravel and other detritus which they have removed in their courses through their own respective valleys. In some cases, where the streams are small, they become lost after debouching from their own valleys in the gravels of these half-cones, their waters then finding their way by subterranean courses to the main river.
In flood times the waters of these smaller streams spread over the surfaces of their several half-cones, and after flowing beyond them for short distances lose themselves in the gravels of the main terrace. In other cases, where the streams are larger, each of them has cut a channel through the upper surface, but not to the full depth of its own half-cone, and after discharging its waters beyond the edge of the half-cone, also loses itself, except in flood time, in the gravels of the main terrace, whilst in flood time it finds its way by a number of shallow surface-channels to points beyond its ordinary place of disappearance, and then loses itself in the same manner.
But there are several of these lateral streams which, after having formed their half-cones, in times long past, have not only cut through the gravels of their own valleys and through the rock below them to a level below that of the surface of the main terrace, but also through their half-cones and the gravels of the main terrace and the rock below them, running into the main river in narrow ravines, varying from ten to thirty feet in depth.
In flood times streams of this class are raging torrents, bearing into the main river immense quantities of silt and gravel which are carried forward by the larger stream. As may be supposed, however, the beds of all these page 82 lateral streams contain considerable quantities of boulders and gravels which floods of ordinary magnitude are incapable of moving, the larger rocks and boulders serving as dams or buttresses for supporting smaller matter above them. But, whatever the relative size and force of these lateral streams may have been, there was one character which they all had in common before the occurrence of the great floods of 1868, namely, that they had evidently never changed their courses, at all events for some distance upwards from their debouchures onto the main terrace, since this had been left permanently above water by the cutting down of the present main river-channel. This is a point of great importance, and to be carefully borne in mind in connection with the observations referred to in the sequel. The hills and mountains on each side of the gorge are steep and hummocky, generally bare of forest, but covered with tussock grass and fern, and with the other vegetation characteristic of such localities in the South Island.
The valley of the main river rises from about 800 feet at the mouth of the gorge to about 1200 at its upper end in the Hanmer Plain, Mount Tekoa, on its western side, attaining an elevation of upwards of 5000 feet on a base of less than ten miles from the bank of the river. I am bound to be thus particular in describing the physical features of this gorge, and, indeed, of all the country in which I noticed extraordinary marks of the flood in question, because the changes effected by it in those physical features afford the chief proofs in support of my proposition. To these changes I will refer after completing my general sketch of the country affected, so far as this is necessary for the purposes of this paper. The gorge I have been describing terminates at the Hanmer Plain, which, like that of the Hurunui, lies nearly east and west, and is also surrounded by mountains. The main river flows into the plain from a gorge at its western end, and after flowing along its southern side to about the middle of the plain, turns abruptly into the one which I have lately described. At the point where this occurs it is met by two small rivers, one called the Percival, flowing directly across the plain from the northward, and the other called the Hanmer, flowing from the westward in a course directly opposite to that of the main river.
These rivers are very insignificant in size compared to the Waiau-ua, but in times of flood each of them brings down, to the latter a large quantity of silt and gravel, partly derived from the shingle of the plain and partly carried into it by the innumerable rivulets which drain the surrounding mountain slopes. When, however, the whole of the rivers are in flood, the waters of the Percival and Hanmer are banked up at the confluence, and form a large expanse of practically still water, the effect being that, as in the case of the Pahau and the Hurunui hereafter referred to, a considerable quantity of silt page 83 is precipitated, which, upon the subsidence of the waters, presents the appearance of a bed of soft sandy mud. The Hanmer Plain appears also to be the bed of a former lake which had been gradually emptied by reason of the erosion of the rock in the gorge below it.
Crossing this plain the road leads up a long spur to Jack's Pass, a depression in the mountain ridge on the north side of the plain, through which the valley of the Clarence is reached. I need scarcely say, that the scenery in the gorge, and upon the lines of road over the passes into the Clarence and the Upper Waiau-ua, is very beautiful, but I am compelled to omit any notice of it in this paper as foreign to the subject in hand, although I should like to dwell upon it. It is a curious circumstance that the valley of the Clarence lies but little below the upper level of Jack's Pass, and that from the outlet of Lake Tennyson, for upwards of sixty miles of its course, it lies at an average altitude of 1,400 feet above, though parallel with the valley of the Waiau-ua, the level of Jack's Pass being little less than 3,000 feet above that of the sea. Fowler's Pass, through which the Upper Waiau-ua is reached from the Clarence, is about twenty miles up the valley from Jack's Pass, the saddle being from seven to eight hundred feet above the level of the valley, making the summit of the pass nearly 4,400 feet above sea-level. It is in these localities that the remarkable Alpine vegetation of New Zealand is found in its greatest luxuriance and in its most quaint and striking forms, whilst the air is not only delicious from its mere purity, but is always filled, and especially so in midsummer, with the perfume of many exquisitely scented mountain plants.
The descent from Fowler's Pass to Lake Guyon is extremely rapid, the track leading through broken rocky gorges, above which the mountains, rugged and bare, rise to an additional height of several thousand feet, the more sheltered spots in their northern aspect being rarely free from snow. The valley of the upper Waiau-ua lies below Lake Guyon, and was formerly filled by a huge glacier, formed and fed from the snows of the Spenser Mountains, the highest points of which, the Faery Queen, Mount Una, and the Pyramid, attain to the elevation of nearly 10,000 feet above sea-level. Maling's Pass is about eight miles above the outlet of Lake Guyon, and leads to Lake Tennyson, a very beautiful sheet of water now occupying the bed of a great glacier, which formerly descended from the skirts of the Princess Mountain. This lake receives the head waters of the Clarence River. From the eastern side of the lake the track lies over a low saddle to the head of the Wairau, the river which, after passing close to the town of Blenheim, flows into Cloudy Bay. Between the northern side of the saddle and the Rainbow River, the Wairau runs for several miles through a narrow rocky gorge, on each side of which the mountains rise in steep and page 84 rugged masses to the height of three or four thousand feet; numerous torrents flow into it from lateral gorges and ravines, helping to swell the volume of the main river, and they bring down, even in ordinary floods, great quantities of angular detritus. But the beds of these lateral streams were, as a rule, prior to the floods of February, 1868, much encumbered with loose rock and other material not liable to be removed even by the heaviest ordinary floods. The bed of the main river, in its course through the gorge, was filled with huge smooth boulders, which made it difficult to ford it even when low, and dangerous even when moderately swollen, its waters then rushing over their rough bed with great force and impetuosity. In this gorge, also, the marks left by the great flood of 1868 were most singular and instructive, and I will now proceed to mention such of those marks along the line of country which I have described as appear to me to afford evidence of the unprecedented character of that flood.
The first thing which struck me was the enormous quantity of water-borne timber which was lodged upon the surface of the Hurunui Plain, every part of it which had been reached by the flood-waters being strewed with such timber in the most extraordinary manner. The waters of the various rivers which ran through it appeared to have risen to an incredible height, so much so indeed that a very large part of it must, when the waters were at their highest, have presented the appearance of a vast lake. I was told, moreover, by a person who stood on the terrace above the Hurunui, so as to command a view of the line of the ordinary channel of the river, that the waters in that line appeared to run at a height of from three to four feet greater than the general level of the water spread over the plain, and that the roar of the shingle which was being carried down was like that of distant thunder. As the waters subsided enormous quantities of timber were left upon the level ground over which they had spread, and it was curious to see the singular regularity with which the drifted logs were piled up, often to the height of several feet, giving to the whole an absolutely artificial appearance. The Pahau, which in its ordinary flow is scarcely more than a brook, and which even in ordinary floods is rarely more than two or three hundred yards broad, must, during the flood in question, have been upwards of two miles wide. Like the Hurunui, and upon a scarcely less scale, it deposited upon the surface of the upper plain immense quantities of timber built up in precisely the same manner. I was informed by shepherds and stockmen well acquainted with the forest tracts on the surrounding mountains, that every atom of fallen timber had been washed out of the innumerable gullies and ravines by which their slopes are furrowed, and that the beds of all the streams which flowed in them appeared to have been cleaned out to the very rock, few of them retaining page 85 even the slightest trace of the shingle and other materials which had previously lain in them. It is impossible to convey an idea of the extraordinary quantity of timber piled upon the surface of the plains, and that, too, in positions which had not, before this flood, presented any trace of having been covered with water since that of the lake had been drained from it. It must be borne in mind, moreover, that the timber thus left on the surface of the plain could only have been a mere fraction of the total quantity brought down by the rivers, the greater proportion having been carried out to sea.
At the point where the waters of the Pahau joined those of the Hurunui, they were banked up to the height of upwards of thirty-five feet, and a bed of silt was deposited varying in depth from a few inches to upwards of ten or twelve feet (according, of course, to the depth of the banked-up water), and covering an area of several hundred acres. This silt-bed remained so soft for many months after the subsidence of the waters, immediately below the dry crust which formed on its surface, that cattle which got on to it from the bank above, attracted by the young grass which soon grew upon it, sank into it and were smothered. A similar but smaller bed of silt was formed at the confluence of the Hanmer with the Waiau-ua, and several months after it had been uncovered, a pack-horse, which I was driving, was very nearly bogged in attempting to cross it. The larger part of the great bed of silt, formed at the confluence of the Pahau and the Hurunui, remains to this day, and is not exposed to removal by the ordinary action of those rivers, but no such bed existed prior to the occurrence of the flood of February, 1868.
The next striking result of this flood was one which especially affected the surfaces of the hills in the Waiau-ua Gorge, and was indeed noticeable, though in a less remarkable degree, all over the surrounding country. These hills were scarred by innumerable small isolated slips, evidently caused by the sudden bursting from points on their sides of accumulations of water which had suddenly found its way between the surface-soil and the solid ground below. An occasional scar of the same kind is seen on the mountain sides all over New Zealand, but the extent to which this process bad taken place as the result of the great flood in question, was such as to create a marked and by no means agreeable feature in the landscape. I believe I am not exaggerating when I say that, to the eye at all events, not less than one-twentieth part of the surface of a large proportion of the bills had been rendered useless by these peculiar slips, for as the surfaces exposed by them consist almost exclusively of the underlying rock, they are, and are likely to remain for ages to come, completely destitute of vegetation.page 86
A still more remarkable result of the flood was presented in connection with the lateral valleys which opened on to the terrace of the main river. You will remember that I described the front line of each of these valleys, drawn from the extremities of the bounding spurs, as presenting the appearance of an ordinary river terrace, more or less deeply cut through by its own particular stream, and I mentioned that each of these streams had formed, at its debouchure on to the surface of the main terrace, a half-cone of detritus over which it continued to flow, or through which it had cut a channel more or less deep as the case might be. Now, before the flood of 1868, there was not, in any instance, more than one such half-cone in connection with any one valley, the stream from each valley having unquestionably debouched from the same channel on to the main terrace ever since the waters of the main river had ceased to run at the level of the upper surface of that ten-ace. But in the case of several of these larger lateral valleys, the channels of their streams, though wide and deep, bad proved to be entirely insufficient to carry off the enormous quantity of water which had suddenly poured into them during this flood, the consequence being that the surplus water overflowed the valley and found its way along one or more lower lines on its surface over the edge of its frontal-terrace on to the main terrace below. These valley-terraces are, as I think I have before observed, composed of loose gravels and silt. Now the quantity of surplus water was so great in some instances, that wide fresh channels were cut through the fronts of the valley-terraces, and fresh half-cones deposited on the main terrace below, some of them being actually larger than the old half-cones which had accumulated in front of the original debouchures during the immense time which had elapsed since they began to be deposited. There could be no mistake about this operation. There were the large open gaps freshly cut through the front terraces, in some instances extending in depth to the solid rock below. There were the great new half-cones, some of them covering several acres of the previously level surface of the main terrace, and formed out of the materials which had filled these gaps. But no water has ever since flowed through these new gaps. The streams of the lateral valleys are again flowing in their old channels, and the latter have, in almost every instance, been emptied of every atom of the loose material which had previously lain in their beds, thus giving largely increased room for the flow of the water. Chasms along the line of these streams, in their course across the main terrace, in some instances ten and twelve feet deep, the bottoms and sides of which are clean solid rock, have taken the place of beds of shingle which had formerly filled them up to the general level of the ground, the consequence being that a considerable number of bridges have had to be constructed on page 87 the line of road along the main terrace, in order to permit the wool-drays to pass over across the beds of these streams in places which had previously been forded without the slightest trouble. In several places, moreover, where the old channels had proved insufficient to carry the enormous quantity of flood-waters suddenly poured into them, these had burst over their banks and cut subsidiary channels through the gravels of the main terrace down to the solid rock on which they rest, and had then fallen in cascades into the great river below. Now I submit, that if any such flood as that of February, 1868, had occurred in this locality since these several gravel terraces had been formed, it must have left marks similar to those which I have described, marks which, looked upon from a geological point of view, are practically indelible; and the non-existence of such marks in any part of the gorge prior to the occurrence of the flood in question, is sufficient to indicate that no such flood had taken place since the river had flowed at the foot of the terraces fronting the lateral valleys.
It is not necessary that I should specially notice the effects of the flood in the valley of the Clarence on the Upper Waiau-ua. Though palpable enough, they were not of a class to afford strong evidence of its being unprecedented in extent, for both these localities are high above sea-level, are very rugged and bare, and the marks left were not sufficiently distinctive to require special notice.
In the gorge of the Wairau the case was different. There, as before observed, the river flowed for miles over a bed filled with huge boulders, but the immediate effect of the tremendous rainfall referred to had been, that all the loose angular detritus previously lying in the beds of the lateral torrents was washed out of them, forming, in some instances, enormous mounds, the bases of which were cut away by the waters of the main river, the effect being that the interstices between the boulders in its bed were filled up, for many miles of its course, changing the surface of this bed from one of great ruggedness to the smoothness of a macadamized road, and giving to the river the appearance of a beautiful purling stream instead of that of an impetuous brawling torrent. In process of time the major portion of the small stuff thus distributed over the bed of the river will be removed, but when I last passed through the gorge, eight years after the occurrence of the flood in question, the places where I forded the river still retained the even smoothness which had followed from the great flood.
Such are the principal grounds upon which I have based the opinion expressed in the earlier part of this paper, and I have little doubt that, had I been able to devote time to a more extended examination of the district in which my observations were made, I should have found abundant additional evidence in support of it, I am aware of the danger of drawing general page 88 conclusions from isolated facts, but instances sometimes occur—footprints on the sand—so pregnant as to justify such a course, and I still believe, after long thought, that the remarkable results of the flood in question, which I had the opportunity of observing in the gorge of the Waiau-ua, are of that character. It must be remembered that whilst all the great observers of physical phenomena have rightly concluded that the changes which have taken place upon the surface of the earth have not been suddenly brought about, but result from the slow though continuous operation of natural causes, none of them can or do deny that there are, or have been, catastrophes or cataclysms, though these are usually limited in extent at any one period, when compared with the whole terrestrial surface. The downfall of nearly thirteen inches of rain, in the course of three days, over an area of thousands of square miles of steep mountain country, was unquestionably calculated to produce a catastrophe in the level areas through which their drainage passed to sea, for even the water which would thus be carried into the river of a valley whose drainage area did not much exceed eight square miles (which is about that of the Kaiwarra stream), would reach the astounding quantity of sixteen hundred millions of gallons, a quantity equal to the entire measured ordinary flow of that stream for a period of three years, or to the estimated ordinary flow of the river from which the city of Wellington is about to derive its new supply of eight millions of gallons a day, for a period of nearly eight months. Whilst I have not hesitated in setting forth the views contained in this paper, I feel that they may not deserve acceptance; but, even then, I trust that the observations I have brought under your notice will not be without their use to those who take an interest in the history of remarkable physical occurrences.
Extracts from the Official Meteorological Reports for February, 1868.
The rainfall, especially in the earlier part of the month, was excessive in some districts. A storm, which commenced on the 3rd, appears to have backed round from north, through east, when the rainfall from this unusual quarter was productive of the most disastrous floods which have been recorded in the colony, and which devastated the eastern districts of the South Island.
Taranaki—On 2nd, barometer 29-628, wind S.E.; but scud coming from E. and N.E., threatening rain and wind; at 3 p.m. barometer falling, wind S.E. and rising, evening wild looking, with heavy rain; at 10 p.m. barometer 28 80. On 3rd, gale from S.E., with thunder and lightning; about two inches of rain fell during night; wind changed to S.W., and violent gale blew, breaking the anemometer; a maximum pressure of 18 lbs. to square foot was registered; barometer commenced to rise; at 4 p.m. gale continued, but veered back to N.W., at 9 p.m. barometer 29 20. On 4th gale continued, with heavy squalls of rain, hail, thunder, and lightning, but moderated towards morning. It continued stormy up to 8th.page 89
Wellington—On 3rd, very low barometer, strong wind from E.; at 3 p.m. barometer 28.754; at 4.15 p.m. rose rapidly, wind shifting round to S., through E.; no rain to speak of at this period.
Nelson—A storm commenced on 3rd, wind S.E.; on 4th, wind N.E.; and on 5th, N.; the rainfall on the 5th, for 24 hours previous, was 7′03 inches; from 3rd to 5th the rainfall was 12.88 inches; barometer down to 28.83 inches.
Christchurch—Disastrous and unparalleled floods oecurred throughout the eastern portion of the Province of Canterbury on 2nd, 3rd, and 4th. The rainfall at Mount Peel was 808 inches in 24 hours, ending at 12 p.m. on the 3rd. In Christchurch the rain was heavy, but not so severe as the above.
Hokitika—On the 3rd a heavy S.E. gale experienced, but no great rain.
Dunedin—On 3rd, a storm from S.E.; 1.37 inches rain, recorded on 4th, for previous 24 hours. There were great floods all over the Province, doing much damage.
Southland—Gale occurred on 3rd and 4th from E.S.E., but no rain.
|Same Month Previous Years.||Feb., 1868.|