Cooper's Creek is a large, ephemeral, multi-channel fluvial system in the Lake Eyre Basin of arid Central Australia. The large extent and aggradational regime of the system make it a suitable model for interpreting ancient successions formed under similar environmental conditions. The dominant channel pattern in the Cooper is a combination of relict braids and active anastomosing channels. The braids are the partly buried surface expression of a sand sheet attributed to a pluvial episode about 5,000 years ago, whereas the anastomosing pattern is interpreted as an adjustment to the present arid climate. Tectonism and eolian processes are minor, localized influences. The anastomosing channels accumulate sand but they occupy a small part of the floodplain, on which overbank mud is blanketing the relict braids. A preliminary depositional model for arid-zone anastomosing fluvial systems comprises a mud-dominated succession, with minor isolated channel sands. Other features are deep desiccation cracks, minor carbonaceous horizons, duricrusts, and evaporite horizons.