Pittock, Barry, Abbs, Debbie, Suppiah, Ramasamy and Jones, Roger ORCID: 0000-0001-6970-2797 (2006) Climatic background to past and future floods in Australia. Advances in Ecological Research, 39. pp. 13-39. ISSN 0065-2504

Abstract

Rainfall variability in Australia is generally among the highest in the world, largely due to the dominant influence of the El Nin˜o–Southern Oscillation. Australian climate has been characterized by wet and dry periods with sometimes sudden transitions from one mode to the other. Synoptic explanations and teleconnections are discussed, with an emphasis on the Murray–Darling Basin (MDB). Floods in Australia are generally of two types: local ‘‘flash floods’’ and widespread basin flooding. The latter often start in the upper reaches of the MDB due to tropical low‐pressure systems, and slowly move downstream. Floods in smaller subcatchments can be rapid and intense due to heavy thunderstorms or other instability exacerbated by topography. Global warming due to human activities is occurring. Observed rainfall trends may be partly natural but partly of human origin. Possible changes to rain‐bearing systems associated with tropical and midlatitude systems will be discussed, along with land cover change and possible effects on runoff, erosion, and sediment loading. The general picture for the MDB, despite significant uncertainties, is that the frequency of small catchment flash flooding is likely to increase, especially in autumn and winter and in summer over the northern and southern (but not central) areas of the MDB. Large catchment floods may increase in magnitude in summer in the northern parts of the Basin, but are less likely to do so in the south, where average rainfall is likely to decrease. Increased fire risk and decreased ground cover may lead to greater sediment loading and erosion during floods, although reforestation could slow runoff and decrease magnitudes of floods, especially in the upper catchments.

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