Leading the Muddy Horse to High Ground – Flood

Following on from my post about cyclones, it makes sense to follow up by talking about floods since the two often go together. I’ve previously written on this site about my personal experience of floods.  I won’t rehash that here, but I want to talk about flooding more broadly.

While we have always had floods here in Australia, climate change is making them worse.  For every extra degree of atmospheric temperature, the air can hold 7% more water vapour.  This means that as the water cools and condenses the rain is more intense.  In addition, changes to the movement of weather systems mean that the low-pressure systems that bring rain will hover in one place for longer, dropping heavy rain over a number of days.  We saw this in 2022 in South-East Queensland and in North Queensland earlier this year.

What this means is that other things being equal, floods are likely to be bigger (that is, higher) than in the past.  However, each flood event is different, and there can be more or less rain, so a flood event can be anything from minor to catastrophic.  It’s also complicated – overall, average rainfall is declining in the southern part of Australia and increasing in the north, but there is great variability year to year.  How do you prepare for this?

Flood Information

The first thing you need to know is the flood risk on your property.  Depending on where you are, this may be easier or harder to find.  Local governments with a history of flooding, alongside State governments, have generally done flood studies which they use for planning purposes.  These are published in various ways – the best are interactive maps like the ones linked below for Brisbane and the Hawkesbury-Nepean.  Some have just published PDF maps, like the Cairns ones linked below.  In other cases, you can access the full study via either the State or Local Governments but this may be more or less helpful depending on your capacity to wade through the technical information involved.  In such cases, it’s probably better to consult your local Council planning department. 

It’s helpful to know what some of the terms mean in flood prediction.  The most common term used in flood risk mapping is the Annual Exceedance Probability (AEP).  This is the probability of a location being flood effected in any particular year.  For instance, a 1% AEP indicates that during any year there is an average possibility of 1% that the location will be flooded. This is often loosely referred to as a ‘one in one hundred year flood’ but this is misleading – there is nothing to prevent such a flood happening two years in a row, it’s just a question of statistical probability.

When there is  flood event, the Bureau of Meteorology will report and/or predict flooding in a particular way, as explained in the link provided below.  They will report on expected river heights at particular points on the river, and also will warn about ‘minor’, ‘moderate’ or ‘major’ flooding.  It is important to know what these terms mean. 

Minor flooding

If the water level reaches the minor flood level, it causes inconvenience. Low-lying areas next to water courses are inundated. Minor roads may be closed and low-level bridges submerged. In urban areas flooding may affect some backyards and buildings below floor level as well as bicycle and pedestrian paths. In rural areas removal of livestock and equipment may be required.

Moderate flooding

If the water level reaches the moderate flood level, the area of inundation is larger. Main traffic routes may be affected. Some buildings may be affected above floor level. Evacuation may be required. In rural areas removal of livestock is necessary.

Major flooding

If the water level reaches the major flood level large areas are inundated. Many buildings may be affected above floor level. Properties and towns are likely to be isolated and major rail and traffic routes closed. Evacuation may be required. Utility services may be affected.

If you’re familiar with the flood history of your property, this information can help you assess your risk in any particular event.  The precautionary principle applies here – a flood could end up being either higher or lower than predictions as weather forecasting is not an exact science, so it’s handy to plan for it to be worse than predictions. 

Planning Ahead

Once you know that your property is at risk of flooding, you need to plan how to respond.  Some key questions guide this.  For instance:

• What is the nature of the potential flooding – how high is it likely to be?

• How well placed is your property to withstand a flood?  For instance, how high off the ground is it?  How water-resistant are the materials it is built from?  Is there a higher area (upper floor, attic etc) to which tenants can move their property as a flood approaches?

It’s then worth considering how to make at-risk properties more flood resilient.  There’s a whole set of work that has been done around this, focusing on raising floor levels where possible, retrofitting (or building) with water-resistant materials, locating electrical fittings above potential flood levels, and of course drainage on the property.  I’ve included links to some technical information about this in the Resources section.  As with some other extreme events, with some properties you may decide that the risk is too great to mitigate and it’s best to exit.

Both the Queensland and NSW Reconstruction Authorities have funding (matched with the Commonwealth) to retrofit homes.  Unfortunately, to date this funding has only kicked in after a major flood event – how much better would it be to fund such upgrades before a flood comes?

The other thing to consider is insurance.  You need to make sure that your property insurance covers both overland and riverine flood damage.  Insurance premiums for flood-affected properties have increased astronomically in recent years, and retrofitting for flood resilience provides you with an opportunity to negotiate these premiums down. 

Of course, when there is a flood, even if the home is quite resilient the tenants are likely to need to evacuate – the house can still be inundated even if it is built to withstand this, and flood waters present serious health risks.  In addition, electricity is often cut off during a flood so it can be difficult to stay in a house for any length of time even if it’s not flooded.

During and after a flood

A lot of the comments made in the previous article on cyclones are also relevant to responding to flooding.  Just briefly, some of the key elements are:

• Making sure your staff and tenants are aware of the progress of the flood and are able to keep informed and up-to-date – this can be especially important for tenants who experience various forms of disadvantage.

• Ensuring ‘at risk’ tenants have an evacuation plan.  This would include where they can go (including knowledge of emergency shelters nearby) and how they are going to get there, particularly for tenants who are elderly or have disabilities.  If they don’t have someone nearby who can help them (family/friends/neighbours) you may be able to link them with local support organisations.

As with cyclones, following the immediate emergency and urgent cleanup, the process of recovery can stretch over years as insurance is negotiated and houses are repaired.  You need to also be aware that even if the physical toll for a tenant or property is not great, the psychological toll can mean the tenant doesn’t want to return to the property, and you may need to consider transfer options.

It’s also worth being aware that after a major disaster governments will often put resources in to try to mitigate the effect of similar disasters in the future.  This is when you may have the opportunity to access significant funds to make your housing more resilient, or else negotiate a buy-back to so you can replace the property with one in a less risky location.

Resources

To get a general picture of the impact of climate change on rainfall, here’s some basic information from Climate Change Australia, the Australian government’s climate change body. 

By way of example, here’s some mapping and information about flooding in the Hawkesbury-Nepean Valley in NSW.    Here’s the Brisbane version. Here’s the Cairns version. 

The BOM explains its flood warning system and terminology here. 

The Queensland Reconstruction Authority has detailed Flood Resilient Building Guidance to cover a range of building types and resilience strategies.  The NSW Reconstruction Authority has a similar guide.   For a handy, accessible starting point, here’s an ABC report on flood retrofitting.

It's also worth just linking once again to some of the resources on disaster preparation highlighted in the cyclone article. There are lots of great resources for individuals to prepare for disaster.  Here’s one from the Red Cross - while the National Emergency Management Agency has published a set of links to each State and Territory planning resources.

For organisations, ACOSS has a good disaster resilience framework you can apply to help you prepare.  For community level planning for vulnerable people, Collaborating4Inclusion has a great set of resources focused on homelessness and other vulnerable community members, which you can use across the community.