River flooding

On this page: Photograph of the Waikato River in flood, Huntly, June 2002 Flooding in our region, What we are doing, Risk Mitigation, Thames-Coromandel river flooding, Taupo District flooding reports, Useful links

The Waikato region has 20 large rivers and about 1400 small river systems. A lot of the region's river systems are constantly prone to flooding and flooding is frequent because of steep terrain, low lying flood plains and areas of high rainfall.

Extensive flooding occured in the Waikato region in 1958. More recently, back-to-back storms in July 1998 and the Leap Day flood event in 2004 caused widespread flooding. The most recent flood events occured in 2008, 2011 and 2014 (Northern Coromandel).

River flooding can threaten people’s lives and property and damage our environment. ‘Lifeline’ services such as water, power, telecommunication and transportation networks can also be damaged.

Waikato Regional Council has developed a strategy for river flood risk management which will assist all stakeholders (including district and regional councils) to integrate their respective responsibilities under different pieces of legislation.

Our flood warning and information pamphlets can be downloaded here:

Flooding in our region

River flooding is a risk in the Waikato region because:

it is susceptible to storms of tropical origin
many steep river catchments get intense, localised rainfall that is difficult to predict
it has large river systems
it has large areas of low-lying flood plains near sea-level that are intensely farmed or developed
large areas of land lack vegetation cover, increasing runoff and erosion.

Risk factors

River flooding is more likely to occur when:

heavy rain runs off already saturated soils
a river channel is no longer able to hold the volume of water
damaged or poorly constructed stop banks fail to hold floodwaters back
drains (such as storm water drains) are blocked by debris.

High tides can also affect river flooding, increasing water levels in a river where it flows into the sea.

Risk areas

Map of the Waikato region's main river flooding risk areas

Coromandel - due to its short steep catchments (where rain quickly runs into the rivers) and susceptibility to tropical storms. The Coromandel has frequent severe flooding when water levels rise very quickly, with little time for warning and preparation.

Hauraki Plains - low lying farmland and towns are vulnerable to flooding along the Waihou and Piako river systems.

Farmland adjacent to the Waipa River – vulnerable to flooding, especially since the river is uncontrolled by dams.

Lower Waikato River (from Ngaruawahia north) - properties on low lying land near the Waikato River are at risk. The River carries large volumes of water where the Waipa River joins the Waikato River.

Flooding at the southern end of Lake Taupo - where the Tongariro and Tauranga-Taupo rivers enter the Lake.

The costs of flood control mean it is more appropriate to avoid development in at-risk areas.

Flood management

Impacts can be avoided or reduced through sensible planning by locating development away from flood pathways.
Control structures - such as flood gates, which divert water to be held until it can be released when water levels fall and pumps which pump ponded water back over the stopbanks.
Stopbanks - which keep water within the channel.
Dams on the Waikato River - which allow flood peaks to be held back so they don’t coincide with the Waipa River peak flow where the two rivers join at Ngaruawahia.
Catchment management - through soil conservation and pest control. Uncontrolled pests can damage vegetation, increasing the chance of soil erosion and flash flooding. Adequate vegetation cover stabilises the ground and absorbs water, controlling water and sediment running off sloping land.
Land drainage - which helps keep the water table low.

What we are doing

Waikato Regional Council is involved in a number of strategies for managing flood risk. The following links provide you with more information on these strategies.

Flood Risk Management Strategy- A strategy which provides guidance on how river flood risks will be managed across the region in the future. The strategy encourages better integration between the stakeholders involved in flood risk management and the work that the Waikato Regional Council does.

Flood Risk Mitigation Plan- A plan which sets out efficient and effective flood risk management for the Waikato region, aiming to prevent floods from happening, or lessen their effects by planning for response and recovery.

Natural Hazards in the Hauraki district- Information and publications on the natural hazards in the Hauraki District.

What are we doing? - An overview of all the Waikato Regional Councils strategies for managing flood risk.

Risk Mitigation

As part of Waikato Regional Councils mangement of flood risks, we provide several means of flood information to help residents plan, prepare for and monitor flood events.

Information on river levels and rainfall- Maps and graphs showing river levels, flow and rainfall at monitored sites around the region.

Broadscale flood hazard information- Broadscale maps of flood hazards areas in the Waikato region, useful for identifying potential flooding issues that require further discussion and investigation.

Flood Hazard Information- Request a flood hazard report for a particular property or site.

Preventing floods on your property- Information on how to prevent flood risk on you property, and steps to take when developing.

Waikato Regional Council’s flood warning system

Waikato Regional Council operates a flood warning system, with staff dealing with system alerts activated by heavy rainfall and rising river levels. Waikato Regional Council uses the system to:

Photograph of Waikato River flood waters, Mercer, June 2002

monitor River Levels and Rainfall at over 50 automated recording sites
warn landowners and communities about a flood
collect data to improve our accuracy of flood prediction
co-ordinate flood response
maintain flood protection works, such as stopbanks, in low lying catchments.

To sign up for the flood warning service email regionalhazards@waikatoregion.govt.nz or free call 0800 800 401 and ask for the Senior Emergency Management Officer (SEMO).

Early warning: flood level and rainfall

When river levels at a site reach a set level or rain is very heavy, our early warning system is activated.

The early warning flood level indicates that a river’s level should be more closely watched. Our 0832 Infolines service provides telephone information about the various sites we monitor. This information varies between sites but can include:

river level
rainfall
barometric pressure
wind speed
wind direction
air temperature
river flow.

Thames-Coromandel river flooding

The Thames Coast Project is just one part of Waikato Regional Council's wider Peninsula Project. The Peninsula Project aims to deal with soil erosion, river management and flooding management issues throughout the Thames Coromandel District.

You can check out the following Thames Coast Project information in PDF format:

Find out more about river and catchment management in the Waikato region.