The Okana River, formerly called the Ohiriri River, is a river on Banks Peninsula

Banks Peninsula

Banks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately and encompasses two large harbours and many smaller bays and coves...

 in the Canterbury Region of New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

's South Island

South Island

The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...

. It flows southwest past the settlement of Little River

Little River, New Zealand

Little River is a town in New Zealand on Banks Peninsula in the Canterbury district.-Location:Little River is approximately 30 minutes drive from Akaroa on Banks Peninsula, a major South Island tourist destination, and 45 minutes drive from Christchurch. It is on State Highway 75, which links...

 where it meets the Okuti River

Okuti River

The Okuti River is a river of Banks Peninsula, in the Canterbury Region of New Zealand's South Island. It flows west to meet the Okana River. The combined waters form the Takiritawai River, a short stream which flows into the eastern end of Lake Forsyth two kilometres south of the settlement of...

, the two rivers forming the short Takiritawai River

Takiritawai River

The Takiritawai River is a river of the Canterbury Region of New Zealand's South Island. A short river of approximately , it flows from the confluence of the Okana and Okuti Rivers to feed the top of Lake Forsyth, at the southwest of Banks Peninsula....

 which flows into the northern end of Lake Forsyth

Lake Forsyth

Lake Forsyth is a lake in the Canterbury region of New Zealand.It is fed by the Takiritawai River, a short arm of the Okuti River, and exits via a gravel bank into the sea in the vicinity of the small community of Birdling's Flat.State Highway 75 leading to Akaroa and part of the Little River Rail...

.

On 19 October 2011, the Okana River caused the worst flooding in Little River for many years, with State Highway 75

New Zealand State Highway 75

State Highway 75 is a State Highway in New Zealand servicing the Banks Peninsula region, connecting Christchurch on the northwestern part of the peninsula with Akaroa towards the east coast. It is wholly two lane , but partially functions as a major arterial corridor of Christchurch...

 closed. Long term residents believe that the flooding was the worst since the Wahine storm

Wahine disaster

The Wahine disaster occurred on 10 April 1968 when the TEV Wahine, a New Zealand inter-island ferry of the Union Company, foundered on Barrett Reef at the entrance to Wellington Harbour and capsized near Steeple Rock...

on 10 April 1968.