Brisbane flood prediction map, 1933

Brisbane flood prediction map, 1933. Drawn by the Survey Office, this map was prepared by the Bureau of Industry in 1933. At the time it provided information on which areas of Brisbane were likely to be inundated under various flood scenarios: 10, 15, 20, 25 and 30 feet. These areas were shaded blue, pink, yellow, green and plum respectively. Because ‘improvements’ (dredging and channel widening) had been made in the lower river, flood heights were expected to be at least four feet lower from the Victoria Bridge downstream, however, no appreciable effects were expected upstream. The map contained a list of major floods since 1841 as well as a table estimating the probable duration of floods at different heights. The last major flood was on 7 February 1931 which rose just below 15 feet. Its approximate extent can be inferred from the areas shaded red. According to the map, 15 feet at the Port Office gauge was the ‘critical level’ where ‘no serious damage need be anticipated by a flood which does not exceed that height.’ A flood around 15 feet or below would not be treated as lightly. The cost of this map was three shillings. Collection of the Museum of Lands, Surveying and Mapping