1. Eastern Uplands (EU)
1.3.1 Low relief landscapes at low elevation (Cann River south, Silvan, Templestowe)
1.3.2 Enclosed landscapes of low relief (Murmungee, Omeo, Dargo, Buldah)
1.3.3 Terraces, fans and floodplains (Kiewa Valley, Wonnangatta Valley)
1.3.4 Karst with depressions (Buchan)
|This Tier consists of alluvial terraces and floodplains, and the alluvial/colluvial fans that occur within the main valleys where the streams have reached a stable gradient, and are depositing the sediments that have been derived from the slow, natural (“geological”) erosion. This includes slope processes on the steeper valley sides, and the deepening and widening of the stream channels. However, in some stream systems, post-settlement erosion has added significant amounts of sediment to the floodplains. For example, extensive alluvial mining in the catchment of Yackandandah Creek in the 19th century resulted in deposition of about half a metre of orange sediment where it emerges onto the Kiewa River floodplain.
The major stream systems draining the northern slopes of the Eastern Uplands, the Goulburn, Broken, Ovens, Kiewa, Mitta Mitta and Upper Murray Rivers, emerge onto the Northern Riverine plain (Tier 4). The southern draining streams, the La Trobe, Thomson, Macalister, Avon, Mitchell, Tambo and Snowy Rivers, emerge onto the Eastern Riverine Plain (Tier 7).
Some highland streams have long, narrow, alluvial sectors where relatively softer sediments have been excavated or where streams have been temporarily dammed by alluvial fans from tributary valleys. The broad alluviated valley of the upper Wonnangatta River is of this type and may have originated by this mechanism or through damming by a hard rock barrier since breached.
Because the levels of alluviation and dissection in such stream systems on a regional scale are controlled by regional base levels, the most important being sea level, differences may be expected between the southern members of this Tier where the coast is only some 20-50 km away, and the northern members where the coast is over 2000km away at the mouth of the Murray River. The flood-plain of the Murray River at Wodonga at the northern edge of Tier 1.3.3 is about 150 m above sea level making the average gradient between Wodonga and the sea about 1m in 15 km, i.e. 1 in 15000.