Since the passing of the Soil Conservation and Rivers Control Act, considerable progress has been made with river control throughout the country. Action has naturally been focused first on the major river valleys where there has been a history of severe flood damage and where the property owners have been able to meet their share of the cost. Schemes are now in hand, or planned, to deal with the lower reaches of most of the major problem rivers, and they range from channel clearing, training works, and bank protection with partial flood protection up to floods of 5–10-year frequency, to complete protection with stopbanks up to floods of 100-year frequency. Such schemes may involve expenditure up to £2,500,000, and Government subsidies vary generally from £1–£1 to £3–£1 or more depending on the economics of the proposed works and the capacity of the property owners to meet their share of the cost.
The policy of the Soil Conservation and Rivers Control Council is to encourage soil conservation work as complementary to river control. In the case of four large river schemes and several smaller schemes, planning has included the whole catchments. As farmers become aware of the benefits of soil conservation work, comprehensive planning for other river catchments will follow.
There are many rivers in New Zealand where major control schemes cannot be justified at the present time but where a great many smaller individual works covering clearing, training works, bank protection, minor stopbanking, and the like are being carried out. Such works primarily serve to hold the river in check and prevent serious deterioration until such time as more comprehensive planning can be justified. Type and cost of works have to be related to the financial capacity of the individual to pay. Subsidies are generally £2–£1 but may be up to £3–£1. Local share of the cost is generally met by individual cash payments.
As continuity of control and maintenance is of the greatest importance in river work, the Council therefore encourages the planning of comprehensive schemes where rating districts are established to ensure the meeting of capital charges and adequate future maintenance. Rating for works is based on benefits and with larger works it is usual to classify the land benefiting into six classes to conform to the degree of benefit estimated for defined areas. Rating is normally based on capital value, but there is also provision for rating on an acreage basis.
Since 1942 a total length of approximately 2,600 miles of river channel has been improved, 1,400 miles of banks protected, and 250 miles of diversions and 850 miles of stopbanks completed. The present annual expenditure on river works is approximately £1,500,000. On schemes that are well advanced there have already been not only substantial savings in flood losses but also major increases in production due to the protection afforded.