Sunday, March 28, 2010

Floods from space

NASA's Earth Observatory has been posting some great pictures of the Queensland floods. East-Central Australia's ephemeral rivers have very low gradients, so floods can be tens of kilometers wide while being only a few meters deep. Using the correct spectral band, this standing water is easily visible from space. The flooded rivers in the above picture are (from West to East) The Georgina and Diamantina rivers, which flow together in Northern South Australia before entering Lake Eyre; Coopers Creek, which independently enters Lake Eyre, The Bulloo River, which is a closed drainage all of its own; and the various tributaries of the Darling, which runs south into the Murray river and eventually into the Great Australian Bight.

The Earth Observatory has a page showing a series of images from both this and previous floods.

When I was in exploration, we had a few tenements in Western Queensland. We were lucky enough to work some areas after moderate rain events, and got to see what happens when these places fill up with water. The following images are from the Georgina basin, and show how the Eastern Simpson desert changes with rain.

The characteristic longitudinal dunes are present in all
images, as low lines of orange sand (often overgrown).

When dry, there isn't much there aside from spinifex, mallee scrub, and arid animals (which are interesting in their own right).

When it rains, though, the waterbirds are spectacular. These are brolgas, but we also saw ducks, herons, gulls, and all sorts of other things which I can't identify.

The Real Dirt has this report on flooding of the Mulligan river, a Georgina tributary near where the above "dry" photo was taken (We had the uranium exploration rights to parts of their nature reserves). It is well worth reading.

Update: The most recent image is here.

No comments: