Kaituna Catchment

• 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

The Kaituna River has a total catchment of approximately 1250 km². The Upper Kaituna Catchment covers Lakes Rotorua and Rotoiti, and their tributaries - i.e. the Kaituna catchment above Okere where the Kaituna river begins. This is an area of approximately 626 km², of which 511 km² is land and the remainder, lake. The catchment includes rolling and steep hill country (including Mt Ngongotaha), the Mamaku Plateau and flat areas around the south of Lake Rotorua. 
The catchment area of the Kaituna River below the outlet of Lake Rotoiti is approximately 620 km² - approximately half of the total catchment.The flows from the upper catchment are reduced by the storage effect that the lakes have, in particular Lake Rotorua. Fluctuations in the lower river flow tend to be dominated by the lower tributaries. For example, even though the upper catchment makes up over half of the total area, the peak flow recorded at the Lake Rotoiti outlet at Okere is 56 m³/s, whereas it is 420 m³/s at Te Matai. The major tributary that contributes most to flood flows is the Mangorewa River, although the Kaituna River itself also contributes significantly. In the floodplain area, other tributaries include the Parawhenuamea, Waiari, Ohineangaanga, Raparapahoe and Kopuaroa Streams.

 "Severe convection storms of short duration are common around Rotorua and may cause flooding of the tributaries if their catchments have been previously wet" (BOPCC, 1969). Longer duration storms from the Pacific can also cause flooding.

Land use in the catchment

 The catchment land cover is a mixture of native and exotic forest, urban areas and pasture, see the table below for details. The main urban areas are Rotorua in the upper catchment, Te Puke and Papamoa in the lower catchment with a number of smaller communities on the edges of the lakes in the upper catchment. There are significant areas of horticulture (Kiwi fruit, Avocado) in the catchment in the foot hills around Te Puke. The Main land use in the Kaituna flood plain near the coast is dairy farming.

Flood risk management in the catchment

The Kaituna Catchment Control Scheme covers the catchments of Lakes Rotorua and Rotoiti as well as the catchment of Kaituna River, a total area of 1250 square kilometres (125 000 ha). The Scheme has in practice been split at Okere into two areas: an Upper Kaituna area and a Lower Kaituna area.

In the Upper Kaituna area, the scheme consists of:

• Significant areas of soil conservation works where streams have been fenced and planted with native or exotic vegetation or allowed to regenerate, and detention dams.
• Flood protection stopbanks on Waingaehe, Puarenga, Utuhina and Waiowhero Streams through the Rotorua urban area.
• Stream clearing, straightening and construction of floodways on Ngongotaha and Waiteti Streams to minimise flooding.
• Level control structures on Lakes Rotorua (Ohau Channel stop logs) and Rotoiti (Okere control gates).

In the Lower Kaituna area, the scheme consists of:

• 69 kilometres of stopbank.
• 88 kilometres of canals and drains.
• Six operative pump stations.
• Several major floodgate, culvert and weir structures.
• Riverbank protection - planting and rock riprap.
• A mole structure at the river mouth.

Prior to the construction of the Lower Kaituna River Scheme, the Kaituna basin was subject to a risk of extensive flooding as a result of overflow from high river flows or from restricted drainage. Various proposals for flood protection since 1907 had been partly implemented prior to the scheme, but none were sufficiently comprehensive to give the benefits achieved today. Sixteen floods are documented in the 1970 scheme report between 1907 and 1968 that caused extensive flooding to the surrounding areas.
The Kaituna River Major Scheme was designed by the then Bay of Plenty Catchment Commission during the 1960s to overcome these problems. Most of the works were undertaken over the period from 1981 to 1986, although capital works continued until 1992. Minor bank erosion protection works and other modifications have continued, hence new assets are still being created.

View map of Upper Kaituna catchment stopbanks (Rotorua area) pdf 18.3MB

View map of Lower Kaituna catchment stopbanks (Te Puke area) pdf 18.5MB

 More info on the Kaituna catchment control scheme and scheme liason group notes

Significant floods in the catchment