The great Roper river flood of 1940

Probably because of its sparse population, floods in the tropical north of Australia (apart from eastern Queensland) tend to have less impact, and receive less attention, than floods in the more densely populated areas. Nevertheless, severe floods do occur, one of the most exceptional
being the flooding that took place on the Roper River in early January 1940. This event was all the more remarkable because preceding conditions over the Roper River catchment had been very dry; in fact the river had stopped running for the first time in living memory during December 1939. Despite this, old local Aborigines predicted a heavy wet season, and early in the new year the rains began falling. A tropical depression developed over Arnhem Land and gradually intensified, eventually moving into the Gulf of Carpentaria. This system generated masses of rain: Borroloola reported 312 mm in one 24-hour period, while several places reported up to 700mm in six days. At the Roper River mission, about 120km from the river's mouth, inhabitants were evacuated as the flood waters rose into the trees. The mission lugger “Holly” was lost in the raging river during the evacuation, and many people were forced into the upper branches of a large tree for one night, before being rescued.

About 40 km upstream of the mission the resident police constable organised a similar evacuation from the Police Station. Here the river rose about 25 metres above its normal level, destroying most of the buildings. The mission was subsequently rebuilt on higher ground about 10 km upstream of the original site.

Although the Roper Valley was the worst-hit area, the whole northern half of the Northern Territory reported big floods. Katherine was inundated, and the Katherine River was reportedly 16 km wide. An aircraft arriving in Darwin on 12 January reported that the area between Daly Waters and Newcastle Waters had become “a vast expanse of water as far as the eye can see”.