Waikato Regional Hazards Portal - Supporting information
Drainage Differential classes and benefits
This information supports the 'Flood management' map in the Waikato Regional Hazards Portal.
Waikato Regional Council owns and maintains land drainage schemes. The level of service for the open drains and culverts of these schemes is generally to drain water from a 10% AEP rainfall event within 3 days. This is intended to remove ponding from rural areas prior to pasture damage occurring, rather than to prevent inundation.
Different Drainage Differentials receive different levels of benefit. This table provides the benefit description for each class type.
Class |
Drainage differential benefit description |
A |
High direct benefit as it is land that would not be capable of significant production without the Council maintained system, high indirect benefit, and contribution, as it is land in pasture. One category of land assigned to this type is gully systems where the area of land drained is a narrow band, which is drained by the Council system. Without a drainage system the soil water levels would be so high as to prevent the establishment of productive use within the gully. It is likely that the unproductive use would extend to the top of the gully banks, which generally results in weeds and plant pests becoming established. Another category is floodplains alongside streams/drains where regular flooding causing inundation, erosion, pasture damage, debris, stock losses and fence damage would be likely to occur if the waterway were not maintained by Council. |
B |
Direct benefit as it is land that requires drainage for maximum production and is adjacent to a Council maintained drain, high indirect benefit, and contribution, as it is land in pasture. This is generally a ribbon of land either side of council maintained drains that receive direct benefit from the drain. |
C |
Low direct benefit as it is land that requires drainage for maximum production but is removed from the Council maintained system, high indirect benefit, and contribution, as it is land in pasture. This is generally land beyond the B Group land that requires drainage, and the drainage is provided privately but the drains discharge into Council system. |
D |
No direct benefit as the land is elevated and free draining, high indirect benefit as it is surrounded by land that requires drainage and contribution, as it is land in pasture. This is generally hilly land that occurs within areas that are drained, but does not require drainage in itself. |
E |
No direct benefit as the land is elevated and free draining, low indirect benefit as the land is removed from land that requires drainage, and contribution, as it is land in pasture. This is generally rolling and hilly pasture that drains to the Council maintained system. |
F |
No direct benefit as the land is all elevated and free draining, low indirect benefit as the land is removed from land that requires drainage by the Council system and no contribution as the land drains away from the area where the Council works are located. This is generally land that is within the drainage area but does not benefit directly from the Council work, as it does not drain to the Council maintained system. |
G |
Land that derives no direct or indirect benefit from Council maintained system and does not contribute to the need for Council's work. This land is non-rateable. This is generally land such as lakes, or other land that has no productive potential. It includes land that drains to the Council maintained system that is fenced to exclude stock, and is maintained in trees or bush. It also includes land within the drainage area that drains away from the Council maintained system and has no community of interest with the balance of the drainage area, and land which is excluded from rating by the RPA such as roads, schools, churces or reserves. |