Ohinemuri Regional History Journal 55, September 2011
(This is an address "Waihou and Ohinemuri Rivers and Goldmining" given by Mr H. R. Thorp, Deputy-Chairman of the Hauraki Catchment Board to the annual conference of the New Zealand Catchment Boards' Association, held in Te Aroha in 1955.)
In November, 1769, Captain James Cook sailed into the Hauraki Gulf and anchored off the mouth of the Waihou River, which he named The Thames. He went by rowing boat up the river a considerable distance and was impressed by the fine stand of timber. This was kahikatea pine and was probably the first export from this district.
Captain Cook noted a particularly large kahikatea tree, which his men marked. Many years afterwards this tree was felled and found to be hollow. The first recorded export of any commodity from the Thames Valley was in 1794 when a ship loaded kahikatea (white pine) timber in the vicinity of Thames. Presumably kauri spars were taken about this time from the vicinity of Thames. The fame of kauri spars may have led to the first exploration of this part of the country by Europeans.
The first settler arrived about 1840 and, after negotiating with the native chiefs for some land, settled on the Waihou River, near Paeroa. Other settlers arrived some years later, but it was not until the discovery of gold that much interest was taken in the district, which consisted mainly of forest clad hills and swamps covered with kahikatea bush, flax and raupo.
There were of course several Maori tribes in occupation and tribal wars were still going in the early part of the 19th century. One notable chief named Taraiha [Taraia - E] is reputed to have held the last cannibal feast near to Thames.
Gold was discovered at Coromandel in 1852 but, after the first rush nothing much was done. In 1862 Coromandel was declared a gold field and few a years later gold was found at Thames. The Thames field proved to be very rich and most of the ore first taken out was easily worked and gold was obtained by simple processing.
The Ohinemuri goldfield was opening in 1875 after protracted negotiations with the Maori for the sale of the land. On this field the original claim holders were disappointed because the ore was mostly of a refractory nature and the then known methods of treatment saved only a small portion of the gold.
This proved the case at both Karangahake and Waihi and it was not until the discovery of the cyanide process that it became economical to work the vast quantities of low grade ore which constituted the bulk of the material taken from these mines.
Waitekauri was one of the earlier fields in the Ohinemuri but it had not a very long life, though, while it lasted, it was merry and the township, which sprang up in the narrow valley, had a civic pride which was hard to equal. The same applied to the township of Karangahake but in this case its life was a little longer and perhaps a little livelier.
Waihi was of course a very large field and supported a town with a population of 6000 for many years and it is only recently that the great Martha mine closed down after producing about £30 million worth of gold and silver.
It is interesting to note that the machinery used in the reduction plants, which treated the ore from most of the goldfields was run by water power and in many cases all the water available was trapped and in some cases twice over.
At Waitekauri the plant was run by a large water wheel. The wheel was 32 feet in diameter with a bucket width of 6 feet. The wheel and plant was constructed by the late E. M. Corbett, the father of our chairman (Mr H. M. Corbett). The Victoria battery was built at Waikino, five miles from Waihi, so as to be in a position to use all the water in the streams of the Ohinemuri basin.
At Karangahake the waters of these streams were picked up again and put through pelton wheels and turbines to supply power and processing water in the various batteries. If all the data collected by the mining companies about the water run-off in the Ohinemuri catchment was available today it would be very interesting reading.
The Waihou River basin and the goldfields area was also noted for its timber. Several timber mills were situated on the river and cut the kahikatea from the river flats and the kauri from the hills. The cutting and milling of this timber would be a story in itself. The ingenuity of the men working out the timber in some of this difficult country was only equalled by some of the mining men in the use of the water to produce power.
Now during all the rush and excitement of mining areas farming was slowly progressing all along the Waihou Valley from Thames to Matamata. One of the early ventures in the agricultural field was undertaken by the late J. C. Firth, who purchased the Matamata estate of 55,000 acres in 1886. To give access to this large area of land he cleared the Waihou River from Paeroa to the Stanley Landing to make a waterway from the mouth for about 50 miles, which was navigable for boats drawing five feet.
All types of farming were carried out in the valley but, with the advent of refrigeration, the dairy industry became predominant and has grown to its present state of prosperity. In the earlier years of this district most of the wealth came from under the ground in the form of gold and silver, but today much more wealth is taken from the surface through agricultural and pastoral pursuits.
An example of this is the wonderful developments of the Waihi Plains where farm production now equals the annual production of the mines. As in New Zealand the earlier settlement took place on the rich flats close to water transport. Later the lighter land in the upper parts of the valley was brought into a high state of production when it was found that phosphate fertiliser solved the fertility problem.
Drainage operations were started in the vast swamps of the valley from very early times. Some of these operations were started on a fairly large scale in the early 1900s and where there was plenty of fall to the rivers. Where the swamps were near the clay and without much timber the drainage schemes were highly successful. This drainage was undertaken by county councils and by large land holders and estates. Later drainage boards were formed to control areas on certain streams and development blocks.
In many cases these boards were amalgamated and today we have several large drainage boards controlling the various areas. The men who commenced and carried forward this work are to be admired for their foresight and their fortitude. Their faith and fortune of this valley has been amply justified even though their work has not received the recognition which it deserves.
It is hard to realise today that the many miles of drainage construction and stream improvement were done by hand. The best machine in those days was a man, who generally wielded a round mouth shovel.
In giving an account of the life and history of the valley one must not forget the hardships of the pioneers. Where there were rivers, boats were used for transport, but where the navigable waters ceased or there were no rivers, the early settlers and gold prospectors had to pack their goods on their backs or they used horses. A tremendous amount of goods and material was shipped as far as Paeroa and Te Aroha and it is amazing to consider the difficulties which had to be overcome to transport the machinery to the many mines which were situated in the hills and gorges of the goldfields.
So prior to the advent of the railways, the Waihou River was the only means of transporting heavy material. Many thousands of tons of mining machinery and material were carried by boat up this river. The river was the highway for rowing boats, cutters, ketches, scows, tugboats and barges and river steamers. From the river to the mines and mining townships it was a case of horse power. Live horse power attached to buggies, coaches, carts and wagons of all descriptions.
But alas for our river, it was found by mining companies that water power was a wonderful thing so they sought legislation to give them the right to get rid of mining debris. So in 1895 the Waihou, along with other streams in the goldfields was declared a sludge channel. This act gravely jeopardised the farming lands in the lower part of the valley. This brought about the advent of the Waihou and Ohinemuri Rivers Improvement Scheme.
Farming development in the Thames Valley originated with the Waihou River as the main communication. A series of floods between 1907 and 1910 culminating in that of March, 1910, indicated increased flooding in the Waihou and Ohinemuri Rivers. This was attributed to silting from mining tailings in the Ohinemuri and lower Waihou also to the heavy willow growth in both rivers. The Ohinemuri was declared a sludge channel in 1895 and at 1910 it was estimated that at least 3,000,000 tons of tailings had been discharged into the river.
The position was investigated by a Royal Commission in 1910 and this recommended:
- Removal of willows from river banks on the Waihou from Te Aroha to the sea and on the Ohinemuri up to the mouth of the Karangahake Gorge.
- Stopbanking the same length of the river with stopbanks, six feet wide on top and four feet above the highest known flood.
- The cutting of Ngarahi and Kouto diversion canals in the Waihou River just south of Ngahina and the crossing of a diversion canal at Pereniki end in the Ohinemuri River.
- Two-thirds of the total cost, then estimated at £150,000, be placed on mining interests.
The 1910 Waihou and Ohinemuri Rivers Improvement Act provided the necessary authority to put the recommendations of the Commission into effect. The Public Works Department, later named the Ministry of Works, commenced an investigation in 1911 and construction commenced in 1916.
The main river system is composed of two rivers, namely the Waihou River which rises in the Kaimai Ranges flowing in a northerly direction towards Thames and the Ohinemuri River which rises in the Waihi basin cutting its way through the main range to the Karangahake Gorge and joining the Waihou below Paeroa. Three important tributaries flow into the lower Waihou, namely the Komata, Hikutaia and Omahu Streams. These enter at distances roughly one mile, nine miles and 13 miles below Ngahina Bridge.
The shape of the watershed of the rivers involved played a very important part of the economy of the scheme. The Waihou watershed is narrow and long, roughly 80 miles by nine miles, aggregating 700 square miles in area.
As a result, when flood conditions prevail, the Waihou rises very slowly and subsidies slowly, whereas the Ohinemuri rises to a peak in from nine to 12 hours at Paeroa and subsides as quickly.
In consequence the combination of these two ensures that the Ohinemuri is past its peak before any serious flooding is occurring in the Waihou. The watersheds lie in relation to one another in such a way that it would be impossible for the flood storms (which come from east to south east) to bring up the Waihou before the Ohinemuri, and so nullify the above.
The protective works by the Public Works Department generally consisted of the killing off and subsequent removal of all willows, the straightening of the river by canals, the enlargement of the river channel by dredging and widening, and the formation of a complete system of stopbanks from Mangaiti to Mackaytown to the Omahu Stream.
Willows were ring-barked in the summer months while the sap was up, a process which usually ensured destruction in two years. Later the stumps were completely removed and the banks cleared of all high growth by a log hauler. This later machine consisted of boiler and with a winch mounted to haul out all the stumps within reach. It then travelled along by hauling itself along on skids.
The main straightening affected Koutu and Ngarahi Cuts. These cuts, aggregated 110 chains in length, shortening the Waihou by two and three-quarters miles and also cut out five bends. Two others, namely the Pereniki cut on the Ohinemuri and the Waimarie cut on the lower Waihou, were found to be unsound, and were not proceeded with. The only other cuts were those for straightening of the Hikutaia and Komata Streams.
The river channel itself was dredged and widened by plant putting the spoil to stopbanks. Suction dredges were employed to remove the sand in the bed of the river, and the channels were enlarged by draglines working on the berm. This served the dual purpose of giving the river an increased area of flow and also of the construction of the stopbanks.
The stopbank system was built to a level to give two feet of freeboard above computed high flood level, and was constructed where required from Mangaiti to Hikutaia on the Waihou and from about Mackaytown to the new junction at Puke on the Ohinemuri. The combined length is about 59 miles involving 5,000,000 cubic yards of excavation and dredging.
All stopbanks built of sand or silt were given a coat of soil, one foot in thickness and sown with grass. This provided a very effective and sufficient protection of the sand from scour in times of flood.
The stopbank system crosses a considerable number of drains and in order to obviate the necessity of numerous floodgates, large internal cut-off drains were excavated, to lead all small drains to one floodgate. In most instances this resulted in greatly improved internal drainage apart from the economy of floodgate construction. Floodgates of standard design were of re-enforced concrete with barrels of oval section five feet by five feet, and fitted with hand-operated sluice gates at the inlet and hinged gates at the outlet.
Some 163 floodgates, varying in size from 4ins to 5 feet square, have been installed. Until the rivers were controlled and confined to their channels adjoining farm lands were deteriorated by floods and silting which caused high stock mortality and a consequent falling of production.
Completion of the Waihou and Ohinemuri Rivers Improvement Scheme works, which terminated near the Hikutaia Stream produced the following results:
- Approximately 46,100 acres of good land has been made secure from floods and has been drained, varying degrees of betterment having been conferred.
- Floodwaters from the Waihou River, which used to sweep across the Hauraki Plains to the Piako River basin have been confined to their own channel. Only a very small portion of the above 46,000 acres is in the Piako basin, the drainage of which was carried by the Land Drainage Department.
- The confinement of floodwaters between stopbanks, combined with the removal of willows and river shortening by cuts, has induced velocity flow which now tends to keep the Waihou and Ohinemuri Rivers reasonably clear of mining tailing and silt.
- Bars, which originally existed in the Waihou River, were dredged to an even grade to provide better navigation and flow channel. Their elimination, together with dredging for stopbank spoil, has so lowered the normal river level that some of the first floodgates installed were left high and dry.
The work was done as a national undertaking at no cost to the local settlers. The 1910 Commission suggested a loan to cover river improvement works, but this was not adopted. Maintenance costs are at present met out of Government funds and are in the order of £4000 to £5000 per annum. This figure relates to the main channel, its stopbanks and floodgates.
The recommendations of the 1910 Commission, which were modified as a result of subsequent detailed engineering investigation, were well founded. Work as completed has been worthwhile, and has contributed in a large measure to district development. These general statements could no doubt be substantiated by comparing present day land values and production with 1910 levels.
The control of these rivers is now to be the responsibility of the Hauraki Catchment Board. The future development and drainage of lands in the upper reaches and the protection of the lands in the lower reaches, together with the safety of the towns on the banks of the rivers, is a grave responsibility and will tax the ability of the board and its engineering staff for many years to come.
It is over 100 years since the first settlement in this valley. How far have we gone? On this side of the valley we have still a long way to go.