Flood zones - How do I avoid buying flood-prone properties?

In January a one in 200-year storm ravaged Auckland City.

Widespread flooding damaged homes, shut motorways, and caused significant landslides.

Two weeks later, Cyclone Gabrielle caused widespread devastation across the regions. It was described as the worst storm to hit New Zealand in a century,

With these extreme weather events fresh in our minds, many investors now worry about flood risk.

In this article, you’ll learn what tools are available to help you work out where the flood plains are. You’ll also learn what risk this poses to your property, and how to reduce flood risk when property hunting.

If you have any questions or thoughts, please leave them in the comments section below.

QUICK FACTS:

• A property in a known flood plain has a 1% chance of flooding in any year
• Existing properties are more likely to flood because they are lower to the ground
• Updated legislation states properties must be raised 1.5m off the ground, to avoid floodwater
• Underground water tanks are installed below a lot of new development to collect and siphon stormwater
• Property investors need to consider car parking in flood-prone areas

Is my property at risk of flooding?

There are a couple of ways to find out if your property is a potential flood hazard.

Auckland Council has released an interactive map called Flood Viewer.

The first thing you notice, when looking at Auckland City, is the blue veins.

These all represent flood plains throughout the entire city.

You can search for a specific address. If you go to the website and put in the address of your property, it will tell you if it’s in a flood zone area.

Not every council in NZ has this information available, although Invercargill and Christchurch do have something similar.

Here are the links for both. Invercargill, Christchurch.

Failing this, you can request a LIM (Land Information Memorandum) from the council. This is a comprehensive report of your property and will tell you if you’re buying in a flood-prone area. But the online tools make life a little simpler, and clearer.

What does it mean if I own a property in a flood plain?

A property in a flood plain is not an immediate cause for panic. Here us out.

Let’s say you type your address into Flood Viewer and you see your property is in the middle of a blue area (aka a flood plain).

This means you have a 1% chance in a given year that the area could get flooded.

For buy-and-hold investors, this risk increases to 14% during the 15 years of ownership.

A 14% chance is under 1 in 5.

Yes, I hear you: But we just saw it happen!

Now let’s talk about contributing factors.

What properties are at more risk of flooding?

Existing properties tend to have a higher flood risk.

Why? Because existing properties pre-date revised standards and are lower to the ground.

By contrast, updated building codes now specify how high off the land a property must be.

This means newer properties (not necessarily a New Build) are going to be built higher off the ground, aka above the flood water (hopefully).

For instance, Christchurch City District Plan has specific standards for building in a flood-prone area. (Bearing in mind that most of the city falls under this remit).

In the plan, it’s called “minimum floor levels”.

Here’s an example from the plan:

In Christchurch, you’ve got to build your property high enough off the ground so it can withstand:

• a one in 200-year rainfall event
• One-metre sea level rise

It’s not uncommon to see these differences side-by-side on flood-prone streets, and in Gloucester Street there are a few properties where we see this.

The newer front units are 3 steps up, which means they are 1.5 metres above street level.

But further down the street, the existing properties aren’t raised.

In this instance, if you own a low-riding existing property it’s more likely to flood, even though both properties are in a flood zone.

What is being done to protect New Build homes developed in flood zones?

As stated, “newer” builds (not necessarily New Builds) are often going to fare better in a flood.

This is true, even if you find your property in a flood plain.

This is because of the regulations around how these types of property are built.

#1 – Underwater water tank

New developments will often have a water tank installed underneath the unit.

It works as it sounds. It’s like a big bucket that collects all the rainwater running off the roof, driveways and walkways.

This is important for New Build developments.

Floods happen because stormwater systems get overwhelmed.

If you put a whole heap of New Build properties together, you’ve got a load of newly introduced water, with nowhere to go.

But the tanks stem the amount of collected water being discharged.

So, the stormwater system only gets fed water at a rate it can cope with.

#2 – Minimum floor level

As mentioned, councils state New Builds must be raised off the ground if prone to flooding.

For example, in suburbs like Bromley newer properties are built 1.5 metres off the ground.

This means that 2 properties, both in a flood zone, will have varying flood risks.

As a property investor, what else should I pay attention to?

It’s not enough to have a property that’s built off the ground.

Sure, it’s a good start, but there are a couple of other things you might need to consider, and both are to do with where you park your car.

#1 – Car parking

Yes, the contents of a raised property will most likely be OK in a flood … but most people also have a car.

An Opes investor once rented a property in Hurley Street, Christchurch.

It’s right next to the River Avon, which would often flood.

This rental was a newer property. This meant it was raised 1.5m off the ground, but the property did not have a garage, so the investor had to park on the road.

So, when the river banks broke the property was fine, but the car was a right-off. And unfortunately for this investor, it was his colleague’s Porsche.

The lesson to learn here is it’s not just enough to worry that the house is safe from flooding.

If you are buying in a flood-prone area, you need to ensure there won’t be damage to the car.

#2 – Check the garage

Similarly, you may not be off the car-parking hook entirely if your property comes with a garage.

While properties will be raised above ground level, often the garage won’t. A lot of new garages are lying at ground level too.

This is because a developer often isn’t going to lay the extra concrete to raise your car off the ground.

You can ask for it, of course. But it will be at an extra cost and this may put some people off.

It’s something to think about. If you’re newer property is in a flood-risk area, you still have to worry about your car.

#3 – Land flooding

Sometimes the flood risk is the susceptibility of water across land.

Often, because the focus is usually on how to keep water out of the house, we forget to think about how badly the land will get flooded.

You can get a building inspector to look at your property’s plans before you go unconditional.

For example, they will be able to tell if the water is going to pool on your land or run off somewhere else.

This can be an issue if you have to drive through the flood water to get to your property ... or get out.

Sure, it’s a small risk, but it’s something you want to think about when you’re making a purchasing decision.

Should I buy a property in a flood-prone area?

The reality is, you probably already do.

Flood zones are prevalent throughout Auckland, Christchurch and other major areas.

But it’s not so much about not buying a property in a flood zone.

It’s about knowing what risks you need to pay more attention to.

Some properties are more at risk than others. This is true, even for neighbouring properties.

Investors who deal in New Builds might be able to worry a bit less.

But there is some control you can exercise around flood risk when buying properties, especially when you know what properties are more susceptible than others.