Public urged to stay away from region's waterways

Greater Wellington Regional Council is urging public to stay away from the region's waterways even though rainfall and high water levels have receded. Banks and tracks may have become unstable following high river levels even if there is no visible erosion. A Severe Weather Watch is still in place and more rain is expected. Land is sodden and quakes continue - a recipe for land slips and erosion.

Yesterday's events were significant for the region's western river systems. Whilst this was a large flood event, affecting people, property and roads, levels remained well within GWRC flood management design lines. In the Wairarapa, east of the Tararua Ranges, rivers remained at average annual flood flow levels.

Greater Wellington Regional Council (GWRC) teams were across the region yesterday visually assessing our waterways, monitoring river flow data gathered electronically through telemetry systems and feeding into emergency response intelligence gathering. While GWRC's main Wellington office has been closed due to quake damage, operations continued across the region.

"The heavy rain compounded the impact of the severe and moderate quakes in the region. However Greater Wellington Regional Council has an efficient 24-hour flood assessment and warning system in place. Our data is directly fed into the Wellington Regional Emergency Management Office during emergency events such as the one we have just experienced. GWRC regularly works alongside communities and our flood hazard warning systems have been operational," says Cllr Chris Laidlaw GWRC Chairman.

"The heavy rainfall after exceptionally wet weather in recent weeks has meant rivers rose quickly. River levels are receding and we are pleased to see river water staying largely where we expected it. Our operational teams will continue to monitor the situation and assess impacts."

ENDS

For more information: 021 914-266 or comms@gw.govt.nz

Notes to Editors 

• The Porirua area was hardest hit again with the Pauatahanui Stream getting up to around a 30-year return period flow, the largest recorded flood since records began in 1975. The Porirua Stream reached an 8 year return period magnitude. This was smaller than the May 2015 flood event of 20-year return period.
• The Waiwhetu Stream reached its largest flow since the January 2005 flood, a 5-year return period. River flooding affected twenty-five riverside properties. Residents were advised to evacuate and protect belongings from flood damage but have since returned. Some sewage was discharged to the Waiwhetu Stream due to storm water volumes in the Hutt City Council system.
• Elsewhere across the region most of the disruption is a consequence of urban storm water systems being overloaded and landslips.
• A return period, also known as a recurrence interval, is an estimate of the likelihood of an event, such as an earthquake, flood or a river discharge flow to occur. It is a statistical measurement typically based on historic data denoting the average recurrence interval over an extended period of time, and is usually used for risk analysis.