Disasters usually a temporary setback for population

TO what extent does a natural disaster affect the propensity of people to live in a particular area?

TO what extent does a natural disaster affect the propensity of people to live in a particular area?

Or, more correctly, of people to continue to live in a particular area? After all, a natural disaster is often associated with a local geographical feature, such as a river, a coast, a geological faultline, a volcano or a site near tinder-dry bushland.

If an area is proven inherently dangerous, perhaps locals may not be keen to resettle there. Will flooding of the Brisbane River dissuade Brisbanites in the coming decade from living along the riverfront? And will the fact of two cyclones, Larry in 2006 and now Yasi, affect population levels on the coast south of Cairns?

Perhaps the best example of the demographic impact of a natural disaster is Hurricane Katrina, which made landfall over New Orleans in August 2005 and claimed 1800 lives.

Before Katrina, New Orleans was a city of 1.3 million, about the same size as Adelaide.

Nine months after the hurricane, the city's population had dropped by 300,000, or 22 per cent, according to US small area population estimates.

By the middle of last year, the city's population had recovered to within 5 per cent of its pre-impact level. The demographic impact of Katrina has therefore lasted six years.

New Orleans and the whole of Louisiana are a series of parishes not unlike English counties or Australian local government areas. The worst-affected area was the central New Orleans Parish, where the population dropped from 455,000 in 2005 to 209,000 in 2006. About 250,000 people were displaced from one parish by Katrina.

In neighbouring St Bernard's Parish, the population dropped from 65,000 to 15,000 over the same period. However, in the nearby city of Baton Rouge (130km northwest of New Orleans) the population of East Baton Rouge Parish jumped from an historically flat 411,000 in 2005 to 431,000 in 2006.

About 20,000 people moved from New Orleans into Baton Rouge because of Katrina.

But here's the lesson: whereas the population of New Orleans recovered gradually over six years, the hurricane-inspired population boost to East Baton Rouge Parish has not dissipated.

Many people fled New Orleans, re-established their lives in Baton Rouge and ended up staying there.

Closer to home, there are other lessons from Cyclone Larry (which caused one death). This storm affected Innisfail in 2006, which was then part of the Shire of Johnstone. It is now part of the Cassowary Regional Council.

In 2005, Johnstone Shire had 19,863 residents. A year later, and three months after Larry, the population had dropped by 400, or 2 per cent. A year after that, the number had recovered to 19,731 and within two years the shire had more people than it had prior to Larry.

What about bushfire?

The Victorian fires of February 2009 claimed 173 lives and brought devastation to several towns, but perhaps the best known example is Marysville, in the Shire of Murrindindi. Between 2007 and 08, that shire recorded population growth of 1.5 per cent to 14,405. This level of growth is consistent with what would normally be expected from a lifestyle and tree-change community close to Melbourne.

Within four months of the Black Saturday fire, the shire's population had dropped 7 per cent, or by 1000 residents. I suspect that, not unlike Larry's impact, the Victorian bushfire's demographic impact will stretch over two or three years.

New population estimates to be released in March will confirm the extent to which population is recovering in Murrindindi.

There are several lessons in this evidence.

There seems to be a time division between people deciding to return or to stay in the new location. For disasters in which reconstruction can be achieved within two or three years, there is every likelihood that disaster evacuees will return to the affected area.

At least, that was the evidence from Larry. The Victorian bushfire experience is likely to be the same.

If, however, recovery from the devastation takes four to six years -- as in New Orleans -- there is scope for evacuees to "go native". They put down roots in their new location and do not return. This was the evidence of New Orleans residents ensconced in East Baton Rouge.

On this evidence, I would expect both Yasi and the Brisbane River flood damage to fall within the former category.

The local population might be depleted by up to 10 per cent initially, but within two or three years full demographic recovery could be expected.

In the short term, however, and in both areas, there is likely to be heightened demand for specific construction skills such as plumbing, carpentry, electrical, plastering and the like. In some cases, demand for skills could be such that they are attracted out of nearby towns such as Townsville and Cairns.

From a broader perspective, this exercise also shows that people generally, and not Australians uniquely, are remarkably resilient. Local communities, town planners and businesses should plan on a two or three-year schedule for full demographic recovery from the disasters in Queensland over the past month. The psychological impact of these events will last a lifetime for many survivors.

KPMG partner Bernard Salt is now on Facebook BernardSaltDemographer and twitter.com/bernardsalt   [e-mail]