Big floods in the Wellington region

The Wellington region is home to a number of large river systems that have a long history of flooding.

Wairarapa

	Flooding in the Upper Ruamahanga River

The most recent severe flooding in the Wairarapa occurred in February 2004. At Angle Knob in the Tararua Ranges 394.5mm of rain was recorded in 24 hours causing the Ruamahanga, Waipoua and most other Wairarapa river systems to flood. Heavy rains also caused numerous slips and road closures.

October 2000 also brought heavy rain to the Wairarapa region with 300mm of rain recorded in the Tararua Ranges in 24 hours on the 10th. Severe flooding occurred in Eketahuna and Pahiatua causing slips and road closures including SH2. Some homes were also flooded. Record river flows in most Wairarapa rivers caused damage to roads, bridges and heavy stock losses. Flood repairs in the Wairarapa region were estimated at $1.1million.

Heavy rain fell in the Wairarapa region in October 1998. Approximately 300mm of rain fell in the Tararuas which led to many road closures due to swollen rivers including the Ruamahanga River which reached a 50 year record near Masterton. The Ruamahanga River peaked at 4.4m at the Martinborough Bridge.

In April 1991 the Tinui flood event made national news headlines with huge stock losses and property damage. Damage to the area was estimated at $2.84 million.

One of the most destructive floods to occur in the Wairarapa Valley happened in June 1947. Floodwaters entered Masterton and many other Wairarapa towns and one person drowned. The flow in the Ruamahanga River measured 2580 cumecs which is a 100 year event. Every stopbank in the upper Lake Wairarapa area was overtopped and 10,000 acres of farmland was flooded resulting in serious stock losses for farmers.

On the 24 ^th of March 1880, the region’s biggest flood recorded since European settlement occurred in the Wairarapa. Its flow wasmeasured at 2830 cumecs which is larger than a 100 year event.

Hutt River

	Hutt River in flood October 1998. View from Moonshine Bridge

The Hutt River also has a long history of flooding.

On the 5 ^th and 6 ^th of January 2005 heavy rain fell in the Wellington region with the majority falling on the Kapiti Coast. The Hutt River recorded a 25 year event and peaked at a higher level in some parts than during the October 1998 flood. Water entered 10 homes in Lower Hutt and there was severe erosion damage to golf courses along the Hutt River.

The flood damage in February 2004 was estimated to be the most expensive in recent history at $200 million. The Hutt River reached high flow levels while the Waiwhetu Stream nearly reached its 50 year flood level causing property damage and forcing people to evacuate their homes. There was severe erosion damage to the Te Marua golf course partly caused by a major slip blocking the Hutt River.

In 1998 two floods within a week of each other (1305 and 1540 cumecs) caused extensive bank edge damage and serious slips in the Hutt Valley.  The Hutt River reached a 12 year peak with the lower Hutt River reaching the highest level not seen since 1939 (a 26 year return period).  250 square metres of the Manor Park golf course was washed away.  Overall the flood protection system coped very well considering the size of the events.

The historical 1939 flood in the Hutt Valley is the most devastating flood in living memory.  Flood waters swept areas north of Boulcott covering hundreds of acres of land, isolating houses and blocking roads.  The entire valley flood from Silverstream at the southern-most point to the Upper Hutt basin was flooded wall to wall.  The Hutt River recorded a flow of 2130 cumecs with the river rising 6.5m at Maoribank and 4.5m on the lower reaches of the river.

In 1931 a 1400 cumec flood tested the stopbanks and structural works put in place to protect people from flooding. The Hutt River rose 5.2 metres to within 600mm of the crest of the stopbank at Moera. The Manor Park Bridge and Haywards suspension bridge were swept away.

The largest flood on record occurred in 1898 and covered the entire valley floor. It was recorded at 2000 cumecs and was followed by another flood of 1500 cumecs that almost filled the valley again. These floods led to the construction of the first major stopbanks to protect Hutt residents.

Kapiti Coast

Waikanae River in flood October 1998

On the Kapiti Coast there have been at least 13 events recorded in history where the Otaki and Waikanae and other local rivers have flooded. The biggest floods in both rivers were in 1955, 1998, 2004 and 2005.

In the early hours of January the 6th 2005 the Waikanae River experienced an 80-year flood, the biggest in recorded history. Campers were evacuated from the EL Rancho Holiday Park in Waikanae and properties were flooded in Otaihanga.

February 2004 saw both the Otaki and Waikanae Rivers reach flood levels and many properties flooded with some residents evacuated from their homes.  The Upper Hutt to Waikanae road was closed.

In October 2003 an unexpected and extreme storm hit the Paekakariki area, one expected once every 125 years.  It dumped 82mm of rain in just 4 hours and caused extensive damage in Paekakariki with many homes and businesses flooded.

The Otaki and Waikanae rivers flooded in October 1998.  A Civil Defence emergency was declared in Kapiti and Horowhenua.  This flood was of a size expected once in 30 years.   The Waikanae River flooded homes and properties and 40 homes were evacuated.  SH1 was closed north of Otaki and part of the Waitohu Bridge was washed out.  Roads and golf courses were inundated.  The Akatarawa River reached its highest level in 75 years.  The 1998 floods cost over $2 million for repairs to bank edge protection and houses. 

In 1955 the Otaki River flooded once and the Waikanae River twice. The floods caused major damage to the riverbanks and many homes were flooded especially in Waikanae. It is estimated that these floods were 1 in 50 year events.