Ohiwa Harbour / Waiotahi Catchments

• Geology and geography of the catchment
• Land use in the catchment
• Flood risk management in the catchment
• Significant floods in the catchment

Geology and geography of the catchment

Ohiwa Harbour Catchment 

Ohiwa harbour has a land catchment area of 172 km² and an estuary area of 26 km² with56 km of margin length. There are 17 major streams draining the catchment, with the Nukuhou river being the largest and draining 60% of the Harbour catchment. The catchment starts around 35km inland of the harbour and about 5km south of Waimana. The majority of the catchment is rolling to steep hill county with many small valleys, the one larger being the Nukuhou River Valley. Due to the nature of the soils the hills are prone to slip and many old and new slip scars can be seen throughout the catchment.
The harbour itself was formed around 6,000 years ago and is protected by two sand spits, Ohope, 6km long on the west, and Ohiwa, less than 1km on the east. There a number of significant wetlands within the catchment. The harbour contains a number of islands, Ohakana, Uretara, Hokianga and Pataua. Ohakana Island is large enough to support a small number of residents on rural lifestyle blocks.
3,500 people live in the Ohiwa harbour catchment area, of these 2,000 live in the three main residential areas of the Harbour, Ohope, Kutarere and Ohiwa. Ohiwa is an ancestral taonga of significance to many Iwi groups such as Ngati Awa, Upokorehe, Whakatohea and Tuhoe.
The Harbour is a rich source of kai moana (sea food), Maori knowledge of the abundant food resources at Ohiwa has endured for many centuries. The earliest names of the harbour reflected this, including "Te Kete Kai a Tairongo" (the food basket of Tairongo) and 'Te Umu Taonoa a Tairongo' or the place where Tairongo found an abundance of food ready to eat.
The table below outlines the geology and soils of the catchment.

Link to more information about Ohiwa Harbour

Waiotahi catchment

Land use in the catchment

The table below give a good overall sumary of the current land use in these two catchments.

Ohiwa Harbour catchment

The Ohiwa Harbour catchment has a diversity of land uses ranging from protection and production forestry, through dry stock and dairy farming, to horticulture and lifestyle blocks.

download Ohiwa Harbour Sediment and Mangrove Management Plan (also outlines land use) (4.7 MB pdf)

Waiotahi catchment

The table below outlines the land use cover for the Waiotahi Catchment.

Areas of indigenous (native) forest are primarily in the upper half of the catchment with pockets lower down, a band in the centre of the catchment contains most of the exotic forest. Further down the catchment as the land flattens out onto the flood plain the land use becomes primarily pasture and farm lands with a few pockets of horticultural land.

 download Waiotahi Catchment Management Plan (4.1 MB pdf)

Flood Risk Management in the Catchment

Ohiwa Catchment

The Ohiwa Harbour Catchment does not have a formal flood management scheme within it. Farmer and land owners have private drains to maintain adequite drainage of their land.

Waiotahi Catchment

The Waiotahi catchment has both a small river scheme and a drainage scheme.
The river scheme known as the Waiatahi River District, was established in around 1972 after the local land owners petitioned the then East Cape Catchment Board to see it established. Their key priorities were to have a programme to clear live plant growth and debris obstructing the flow of the river, construction of light bank protection for stabalising river banks and the restoration of areas damaged by floods. These key objectives are still relevant to the current river district, it is primarily a river maintanance scheme and has no solid structures such as stopbanks. Maintenance of the channel and stabalisation of river banks are the primary tasks. Willow plantings are used to help maintain river banks where needed. Some stopbanks exist within the Waiotahi river district, these are privately owned and maintained separate from the river scheme.
The drainage scheme was originally established by the Waiotahi Dranage Board in 1922 with the view of improving and maintaining the two main drains, however not much was done due to limited staff and money. In 1967 the Waiotahi Drainage Board was dissolved and control of the drainage scheme was handed over to the East Cape Catchment Board and from then on to the Bay of Plenty Regional Council who still maintain the scheme.
Flowing into the Waiotahi River about 2km upstream from where the river joins the Waiotahi eastury the drainage district covers and area of around 990 acres of flat land, much of this is very low lying land. The total catchment of 4,200 acres feeds water into this drainage district. There are two main drains that operate in this scheme, the Waiotahi Drain and Gabriel's Gully Drain. Beacuse of the large catchment and the flat nature of the valley floor farming the flats is only possible only by maintaining the drains so water can drain away. The scheme is tasked with maintaining and clearing drainage channels, de weeding as well as the maintanance of the stopbanks that line the two main drains.

Significant floods in the Catchment