Flooding, storms and slips in Palmerston North: What you need to know

Find out how best to prepare for, stay safe and informed during flooding in Palmerston North. 

Flooding, storms, earthquakes and landslips are the most frequent and damaging natural hazards in Palmerston North and wider Manawatū. 

With several waterways, including the Mangaone Stream and the Manawatū River, our city is  susceptible to flooding, especially during periods of heavy rainfall or large storms. Street ponding /flooding and small landslips are also common. Understanding the risks and being prepared can help protect you, your family, pets,  property and the wider environment.

Causes of flooding

Flooding in Palmerston North can occur for the following reasons:

• Storms or heavy rainfall: Severe weather systems can bring intense and prolonged rainfall along with strong winds. This can cause rivers, streams and streets to overflow, increasing the risk of floods and landslips. The Manawatū River catchment begins in the Ruahine Ranges, meaning the river can flood in Palmerston North even when it’s not raining in the city.
• Stormwater capacity: Our city streets can pond or flood when drainage systems reach capacity. This doesn’t mean the drainage systems are broken, it is because the amount of rainfall has exceeded the design capacity, and will take time for water to get through the system and get back to normal. 
• Blocked drains: Unexpected failures, such as blocked drains or damaged stormwater systems, can also contribute to flooding. You can help avoid this by clearing any leaves, branches or debris blocking the stormwater drains both inside and outside your property. 

For more information and resources on flood preparedness, check out the handy tips below or visit the Horizons Regional Council website and the Get Ready website

You can also check Horizons website for flood plain mapping of the wider Manawatū

Understanding surface ponding and flooding in Palmerston North 

Surface ponding or flooding often occurs on city streets and parks during heavy rainfall. 

While it may seem like a sign of stormwater system failure, it’s actually an indication the system is functioning as designed. Palmerston North’s stormwater system is an extensive network of streams, sumps, more than 300 kilometres of pipes and drains, and a few pump stations, most of which are located beneath the roads, collecting rainwater from both streets and private properties.

The stormwater system has three levels of function to handle varying levels of rainfall

• Primary: In normal conditions, the majority of stormwater is kept within the underground pipe systems, and there is no visible ponding or flooding.
• Secondary: As rainwater volume increases, the piped systems and drains can become full, causing water to pond on roads and in low-lying areas. This is still normal—there’s simply more water than the piped systems can process.
• Tertiary: In heavy rain, some areas across the city are designed to act as secondary flow paths (for overland flow) and as stormwater detention reserves to temporarily hold excess water. Example are Rangitāne Park on Maxwell’s Line and Norton Park on Featherston Street. These areas are designed as overflow zones to help prevent flooding in nearby homes. This ponding is a crucial part of the stormwater system's function.

Check out our stormwater page for more information. 

Palmerston North is especially prone to surface flooding due to its geography

Palmerston North is built on a relatively flat area that is a historic flood-plain. The Manawatū River is the ultimate discharge point for stormwater runoff, which means high river levels severely impact on the ability for stormwater to drain from the city.  The surrounding areas have predominantly clay-based soils, which don’t absorb much stormwater. These facts significantly contribute to making the Manawatū landscape susceptible to ponding and flooding during significant rainfall.

When to call for help 

If surface flooding threatens to enter your home call us immediately on 06 35 6 8199. Note this does not include for garages or sleepouts, which may have lower floor levels. Properties near streams or rivers are at higher risk, so keep an eye on water levels and report any concerns or when water levels are rising fast.

Monitoring and alerts

Horizons actively monitors waterways across the Manawatū. Alert systems are in place to provide early warnings of rising water levels and potential flood risks in critical catchments.

Sign up for Horizons’ alert system to receive real-time notifications of potential flooding.

Staying safe during flooding 

Flooding can happen quickly, so it’s important to be prepared, stay informed and act quickly. 

Remember, it’s important to stay away from floodwater, drains, and gutters during flooding. Floodwater can be contaminated and may conceal hazards like displaced manholes or strong currents that could pull you or your pets under water. Never lift manhole covers or grates during flooding. Avoid driving or walking through floodwater, and always follow evacuation orders from emergency services.

Don’t let your dog enter waterways less than 48 hours after heavy rain

It’s good to know how to help your dog, but you should never risk your life for a pet. Instead, you should guide your dog to a safe location.

Do not go into dangerous water (such as fast running river water or any water where you don’t know the depth) to rescue your dog.

The best response is to remain calm and guide your dog by to a location where you can get them out of the water safely. This includes walking along the riverbank or waterway while calling your dog’s name. Stay ahead of your dog’s float path so they are not fighting against the current of the water, but paddling with it towards the edge of the waterway.

Medium to big dogs that panic in the water can easily drown a human, especially those who are small or poor swimmers.

Jumping into deep river water to swim alongside your dog puts you at serious risk. You can provide more help by attempting a land rescue. Dogs are very buoyant, which can make them great swimmers.