Chas Keys, a former deputy director general of the NSW SES and honorary associate of Risk Frontiers (Macquarie University), prepared a series of articles about Maitland and its ability to deal with flooding.

In part 4 he looks at flood evacuation.

Maitland's long history of floods has often seen people having to leave their homes.

During the second half of the 19th century the evacuation of hundreds or even small numbers of thousands of people occurred frequently, and the numerous floods of 1949 to 1956 also saw many having to flee.

In 1955 more than 8000 people, of a total of about 25,000 in the area of the present City of Maitland, had to leave.

Since 1955, thanks to the modern mitigation system, evacuation has been mercifully infrequent, though 1971 saw 450 people leave their homes and in  2007 about 3000 did so.

Evacuation is never fun. Nobody ever wants to do it. At the very least it is hugely inconvenient. Many people leave when advised to, but resistance to the call to evacuate is also common.

In 2007, a woman shouted "It's crap!" at a TV camera as she left her Lorn home. She went, though, unlike some on the farms and in the levee-protected built-up areas who refused to leave for higher ground in East Maitland, Telarah or elsewhere.

A survey carried out shortly after the 2007 flood indicated that about 75 per cent of those who had been asked to evacuate actually did so.

This was a smaller proportion than the 95 per cent of residents who left Nyngan in 1990, but in that case almost all the town's houses had taken in floodwater before evacuation began.

It was, though, more than the 30 per cent who left their homes in Hay, on the Murrumbidgee River, in 2012.

Hay's mayor opposed the State Emergency Service's call to evacuate, saying that the levee (which had required augmentation as the flood approached) would withstand the floodwaters.

He turned out to be right, or lucky, though it was a close-run thing. The shored-up levee, not well compacted and without binding grass cover, only just kept the flood out.

Since Maitland's modern flood mitigation scheme was built, evacuation has been for the most part averted.

In the 1950s, by contrast, several people had to leave home time and time again. Some did so about eight times, and had to clean up the mud and mess as often on returning.

In 2007, the flood failed to meet the predictions of the Bureau of Meteorology and in hindsight the large-scale evacuation seemed unnecessary. That people were inconvenienced was regrettable, but the scientifically based forecasts justified the call for people to leave.

Had the forecasts been precisely accurate - and these days about 80 per cent of them in NSW are accurate to within 0.3 metres, whereas the 2007 flood peaked 0.5 metres below what was forecast more than 24 hours earlier - water would probably have flowed over the ring levee and into streets and houses in South Maitland, central Maitland and perhaps Horseshoe Bend. It might also have got into Lorn from the east.

Fortunately, none of this happened, although several houses outside the town-protecting levees took in water.

The emergency services, noting the Bureau's prediction, adopted the precautionary principle - which in the case of floods is taken virtually world-wide to mean that urban areas potentially threatened with flooding should if possible be evacuated before inundation occurs.

For people to stay at home when water could enter their houses is to risk health and even lives.

Maitland's flood history contains several instances of people who died because they failed to evacuate.

Had they accepted the temporary inconvenience of evacuation, they would have survived.

Flood special part 1

Flood special part 2

Flood special part 3