Bird's-eye view of a flooded city
The chopper flight makes an hour go fast.
It reduces the city to a compact framework of roads, hills, rivers, reserves, coastline, houses and factories, most of which look soggy but appear to have escaped flooding.
The neatness is broken by rashes of clay-brown water, spreading mainly from the contained arteries.
From the air the flooded houses and factories are easy to spot.
The houses, usually about 10 to 20 of them, are surrounded by water, about a metre below the window sills in the worst areas.
The bird's-eye view shows just how unlucky these pockets are. A little further down the road other houses or factories are high and dry.
The helicopter takes off about midday, buffeted by wind and with rain running in rivers across the windscreen.
We head north and are soon flying over watery paddocks and following the Avon River through Avondale, Burwood and New Brighton.
Large swathes of water in the red-zoned suburbs show how many houses have already been cleared. Some on the edges have been hit by disaster again. It looks a good place to leave behind today.
The water appears relatively well behaved in New Brighton and, then, as the sun comes out, the flight heads towards Sumner.
The water is lapping at the doorsteps of houses not far from the Mt Pleasant Yacht Club and another troubled area emerges inland from Sumner beach at the head of the valley.
Everywhere the sea is running different shades of brown, depending on the sort of sediment and debris that is coming down the streams and drainage channels.
The chopper flies over Evans Pass to reveal rock and mud slips on the disused Evans Pass Road and the bulk fuel tanks, better known as the tank farm, on the west side of Lyttelton, are encircled by water.
The water cascading down Voelas Rd earlier in the day, threatening houses, appears to have abated. Below Tunnel Rd, some of the worst of the residential flooding emerges. The Heathcote has overflowed into small, unfortunate pockets with water nearly up to house window sills and the odd car looking as though it is taking a bath.
Some blocks of factories are also marooned. Following the twists and turns of the Heathcote reveals more houses inundated in Opawa, Waltham and St Martins. In Halswell, a dead horse is under water in a paddock.
Viewing a disaster from the air does not necessarily give an accurate idea of what it's like on the ground.
It does not show what it's like to have water in your living room or to see your house threatened by a raging torrent coming off the hills behind.
It fails to capture the feeling of wading across a flooded street or driving through what appears to be a bottomless puddle.
But up there you get an idea of scale.
And compared to the earthquakes, this disaster looks manageable.