The occurrence of consecutive positive IOD events is extremely rare with only two such events recorded, 1913–1914 and the three consecutive events from 2006 to 2008 which preceded the Black Saturday bushfires. Modelling suggests that consecutive positive events could be expected to occur twice over a 1,000-year period. The positive IOD in 2007 evolved together with La Niña, which is a very rare phenomenon that has happened only once in the available historical records (in 1967).[3][4][5][6] A strong negative IOD developed in October 2010,[7] which, coupled with a strong and concurrent La Niña, caused the 2010–2011 Queensland floods and the 2011 Victorian floods.