Once again, Lismore is on high alert for flooding of the Wilson River as another low pressure trough makes its way down the NSW coast. Analysis by Aon indicates that current flood protection in Lismore only reduces flood risk in the LGA by less than 10 per cent compared to if it were left completely undefended, which is significantly below the national average where flood mitigation reduces flood risk by 25 per cent.

The existing levee system in Lismore was built in 1999 to protect the CBD and South Lismore from a 1-in-10-year flood event (top 10 per cent of flood events in any one year). This levee was first breached in the March 2017 floods, causing widespread property damage. The relatively low standard of flood protection means the benefit of the Lismore flood defences is significantly less than the national average.

While past its peak, the La Niña that started last year and has already caused extremely wet conditions over east Australia is dissolving only very slowly. As long as the La Niña event is still underway, the stronger westerly winds it causes and then warmer ocean surface push more moist air to the east coast. Therefore we are likely to see more heavy rainfall events hitting the already affected communities and the rest of the Australian east coast.

The repeated flood risk to key parts of towns like Lismore highlights the grave risks of rebuilding in harm’s way. No amount of house raising or flood resilient materials will adequately reduce flood risks in places like the low-lying parts of Lismore that have experienced a 14m high flood.

Now is the time for federal and state governments to help local councils plan to relocate the most flood prone town centres and towns to higher ground. It has been done before in Australia. Land swaps and buyouts are among the options needed. It may be expensive but it is time to increase the 3% that our government spends on mitigation, preparedness and resilience as opposed to 97% on recovery. Relocating people to high ground is a key long-term investment that Australia needs.

People think floods like those that occurred in Lismore last month are isolated instances but they are not, as today’s flood warnings prove. But this flood repetition is not unprecedented. In February 1893 Brisbane’s Port Office Gauge recorded an 8.35m flood, a fortnight later a flood of 8.09 metres. In the middle, there was a 2 metre flood. A month of floods. But we often think of these floods as happening once in our lifetime or maybe once in 100 years. In La Nina years (like this one) a cluster of floods can occur.

Offering hollow comfort after Brisbane’s repeated 1893 floods a Townsville newspaper stated 'it is not likely that the flood will do serious damage, for there is scarcely any left for it to do' after the last floods. But they do cause more damage. With repeating floods the problems compound: the damage increases, the costs mount up, the clean-up is impeded and the emotional and psychological toll grows. This is what is happening in northern NSW and why we need to consider climate adaptation.

Given the saturated catchments and forecast heavy rainfalls there remains a high risk of major flooding in northeast NSW and southeast Queensland. What we are seeing is a compound disaster where the previous flood event exacerbates vulnerabilities to the current flood threat adding further complexities to flood recovery efforts. We have seen repeat major flooding before. At Lismore, two major floods occurred in 1987, inundating the CBD twice in the space of two months. Such repeat flooding highlights the need for mitigation investments.
 
Tragically, we have seen further loss of life. Most flood deaths have occurred where motorists have entered or been engulfed by floodwaters. Our research has shown that driving through floodwater is largely an entrenched behavior. Only a small error in judgement can result in tragedy. There is a need to not only invest in education campaigns, but to implement improved warning systems, enforcement measures and engineering interventions as part of a holistic approach aimed at improving the safety of road users.

The ongoing wet conditions which unfortunately have led to more flooding are consistent with the lingering La Nina in the Pacific Ocean.

Significant cooling persists over the central Pacific, with warm ocean temperatures surrounding Australia.  Such a pattern is indicative of a La Nina.  Warm waters over the Australian east coast provide moisture for rainfall.

Like El Nino, which is associated with drought conditions in Australia, La Nina peaks in summer and peters out in autumn.  However, La Nina's persistence is typically longer than that of El Nino.  In fact, the trade winds over the central Pacific have strengthened recently, supporting the La Nina.

It is possible that this La Nina will persist through autumn, and even towards the end of the year.  End-of-year forecast would be more reliable in June after the El Nino-La Nina 'autumn predictability barrier' is over.  

There are other factors that come into play.  The Southern Annular Mode (SAM) has been in its positive phase recently.  Positive SAM allows more inflow of moisture offshore towards eastern Australia.  The Atlantic and Indian Oceans are warmer than normal.  Such conditions tend to enhance the Pacific Trade Winds which are in turn conducive for La Nina.  

The flooding has been exacerbated by the fact that we have had La Nina two years in a row.  There is not enough time for soil and catchments to dry, to soak up more rain.

Queensland and NSW have recently been repeatedly impacted by floods. Just over a month ago there was massive flooding and while clean-up is still ongoing in some places, flooding has begun again in parts of Queensland and there are flood warnings for northern NSW.

The SES has been highly proactive this time, enabling the evacuation of many at-risk people and keeping them out of harm’s way. Lessons from the past seem to have been learnt and such proactive measures will define the pathway for future resilience.

What are the options for people living in these areas that are and possibly will again be exposed to floods? Does it make sense for them to return to their existing homes and businesses, carry out extensive and expensive clean-up and repair operations, only to face the same predicament again? The idea of relocation will need to be assessed carefully in consultation with the affected and at-risk communities. The importance of relocation from areas with high disaster risk is widely acknowledged globally, but mixed outcomes are also evident. A holistic systems approach is required - relocation where feasible combined with in-situ upgrading of buildings for flood-resilience, backed by mitigation measures such as improving levees.

This flooding has exposed something we already knew, but had chosen to ignore. That Australia, one of the most prone countries to secondary disasters from climate change, like flood and bushfire, is also one of the most under-insured of comparable economies.

Many Australians are uninsured or underinsured for flood because each time it floods, their premiums go up. At a certain level that becomes unaffordable so they take the risk of going without insurance. That’s not a risk that they as individuals can afford. How do you continue to pay the mortgage on a property you cannot rebuild because you have no insurance? Neither is it a risk we as a society can afford to keep pushing back onto individual homeowners.

Floods are not rare. They are becoming all too commonplace. Each time an uninsured property floods, society has to pay to help those people make good. At the same time, the wealth and viability of those owners to contribute economically to society is reduced. There are very sound reasons to start pooling these risks across society - and using the data developed in the pool, to inform better disaster resilience of properties. There are other models worldwide we can learn from about successful risk pooling and resilience. We need to act now.

A tsunami of mental health problems may be expected from the northern NSW floods – but government can take immediate steps to minimise these. We know this because we have the data.

The University of Sydney’s University Centre for Rural Health (UCRH), based in Lismore, is the first centre in the world to have undertaken a study of a flood-affected community five years before the community was inundated by an even more major flood event. UCRH has so far published six journal articles from studies of the 2017 northern NSW floods.

The biggest predictor of mental health problems was displacement from home for more than six months – there are an estimated 15,000-25,000 northern NSW residents currently displaced. Federal and State Governments can play a key role in minimising these impacts. The first most important task is to restore hope to these traumatised communities.  How can government restore hope? Rapid commitment and financial support to resolving the northern NSW housing crisis and financial support for flood-affected businesses are key first steps.

The residents of NSW/QLD and the SES, Police and medical personnel are weary and at risk. It is time to examine the past decisions and move forward in this new world with new policies. Engineers and others can advise on the risks in this climate change affected world, and in conjunction with governance professionals, lawyers and others, rework existing policies.

Clearly, we need a scheme devised to trade land and preserve communities and the social bonds that are essential. We also need ways to engage communities in this drastic process in full awareness of the upheaval and with supports to alleviate the stresses.

The obligations in [the UN's] Sustainable development goal 16 in part look at effective, accountable and inclusive institutions for all. I would suggest a Commission be formed to examine flood and fire risk towns and parts of cities and come up with a set of criteria to be used.

Drowning is the leading cause of death during times of flood, and these predominately occur due to driving into floodwaters. We have already seen tragic loss of life associated with the current floods, with many losing their lives due to driving into or being swept into floodwaters while in their vehicle.

Research indicates there are many pressures which lead people to drive into floodwaters. These include pressure from other motorists (and/or having nowhere to turn around), pressure to get home to family or pets, or to work or school.

Drivers may have seen other cars successfully go through or have passed through the location successfully themselves previously. We have seen several instances of drivers entering floodwaters at night, highlighting the dangers of arriving upon flooded roadways at night with no opportunity to avoid entering the water or being swept away.

Despite warnings, this behaviour continues to cause loss of life among motorists and their rescuers. Entering floodwaters should be avoided at all costs, and this includes playing in floodwaters or taking selfies for social media.