Ohinemuri Regional History Journal 22, June 1978

by H. A. THORP

To realise the full potential of this great river valley it is necessary briefly to tell of the past 200 years. Captain Cook called it the Thames. Hence the name Thames Valley but the river has taken the old Maori name of Waihou. How was this valley formed? Geologists tell us that much more water was flowing down this valley in the distant past, than is flowing down the Waihou channel to-day. Possibly all the waters of the central plateau and Lake Taupo, flowed into the Hauraki Gulf. There is much evidence to support this theory in the nature of the soil structure right through the valley and the mouth of the river, which appears to have been made by a very large river; much larger than the Waihou, but that must have been thousands of years before human habitation.

The finding of gold at Coromandel and Thames and later Ohinemuri gave the few early settlers in the district brighter hopes for the future. These hopes were dashed when the gold faded out in the early part of this century. A fairly large population of mining men and all those connected with them turned to the land. What a land! A land of swamps and hills. Swamps which appeared undrainable and hills covered with forest which mostly grew on ground so poor that the best farming practices of those days brought very poor returns.

There were men of vision in those days who saw what could happen in the future if the job was tackled with determination perseverance. Those men of vision met with many frustrations and lack of money was one of them. The returns from much effort and expenditure brought no return for many years. The exploitation of the goldfields brought quick returns but left a land desolated with scarred hills and blocked river channels. The first necessity was to clear and improve these rivers. This work was started in 1912 by the Public Works Department but took over 20 years to complete and then only covered the middle area of the river. This was because the future was obscure and in those circumstances economics ruled the situation.

It was not until the Soil Conservation and Rivers Control Act was passed in 1941 that hope for a solution to the problems of the Waihou river valley appeared possible. The Hauraki Catchment Board was formed in 1945 and took responsibility for the whole catchment district from the Mamaku and Putaruru in the south and the Hauraki gulf in the north. This board was first occupied with the Piako river which it immediately took over from the Lands Department; but did not take over the Waihou until late 1960.

It was found that the works completed by the Public Works Department and later maintained by the Ministry of Works were not of adequate capacity to meet the needs of future land use and development in the valley. In fact this was proved by the floods which occurred in 1936, 1954, and 1960.

Up to this time the rivers of New Zealand had been improved and the land protected where necessity arose. The consequence was that an incomplete job was achieved. The Hauraki Board took the bold step of including the whole catchment in the scheme proposal, which meant that besides river and land drainage works, soil conservation works were included. This put the responsibility on the whole district.

The necessity of combining soil conservation and river control is obvious and received the approval of local authorities and the Government. With co-operation from local authorities and government, the scheme was declared one of Local and National importance. This meant that work could start immediately. The first sod was turned at the site of the Hikutaia cut in 1972. Plans for this scheme took many years to complete because it covered a catchment area of 500,000 acres which included: river works, land drainage, flood protection, soil conservation, water quality and the environment.

River Works:-

Work covered all rivers and streams from the source to the sea. Waihou River work was complicated by earlier works which were completed in the 1930's, later proving totally inadequate. A river channel originally constructed to carry 30,000 cusecs of water has to be doubled in capacity to a channel to carry 60,000 cusecs of water, a very complicated and sometimes dangerous practice. Old stopbanks are retained until new ones are built, joining up the new with the old at the end of the completion of each portion of the work. This means the moving of millions of yards of spoil in more than one operation and increases the cost considerably. Along with river work come roading and bridging involving the Ministry of Works, the Railway Department, Lands Department and all local authorities in the area. Requirements of these departments and authorities have to be met and co-ordinated with the works as they proceed.

Land Drainage:-

Much work has already been done in this valley and it is estimated that about 1,000 miles of communal drains are controlled by the various drainage authorities. This does not include private farm drainage and other local body drains. Co-ordination and in some cases re-design of many of these drainage systems to connect them to the river system is a major part of the whole valley scheme.

Flood Protection:-

Besides construction of stop banks on the main rivers much work has also to be done on the smaller streams, including bank protection and erosion control, along with any other necessary soil conservation.

Soil Conservation:-

At the northern end of this Waihou catchment including the Ohinemuri River catchment from Te Aroha northwards, there is very little need for any soil conservation practices but to the south there is much unstable country which must be protected. Much of this area is highly productive farm land but there is also a range of very steep hills stretching away to the Mamaku plateau. From this area comes the main flow of water in the Waihou, consequently the management of this area is of grave concern to the Hauraki Catchment Board and the Regional Water Board.

Water Quality and the Environment:-

The Waihou catchment is very fortunate in having water of good quality in these streams of the area and this must be preserved from pollution right from its source to the sea. All these proposals are within the policy of the Hauraki Catchment and Regional Water Boards so that the visions of the early settlers and engineers of those days, can be brought to fruition.