6.1.5 Alluvium, terraces, floodplains, swamps and lunettes of the Volcanic Western Plains

Alluvium terraces and floodplains are associated with the lake and swamp systems within the volcanic terrain as well as drainage systems such as the Barwon, Yarrowee/Leigh and Woady Yaloak rivers. Lakes and swamps, both permanent and ephemeral dominate the volcanic plains north and west of Colac. Hydrologically, the lakes vary from hypersaline groundwater discharge lakes (e.g. Lake Beeac) to groundwater throughflow lakes with surface water input (e.g. Lake Murdeduke) (Coram 1996). In the Lough Calvert region (east of Beeac), climate changes during the Pleistocene and Holocene have resulted in a complex landscape, as lunettes and alluvium deposits trace the changes in lake levels. Alluvial terraces and lunettes have been formed and partially destroyed by oscillating lake levels (Edwards et al. 1996). Associated soil types include black and grey self-mulching and cracking clays, black (and some red) sodic texture contrast and dark loam soils.