Management of Sediment in New South Wales, Australia
ABSTRACT The amount of sediment in major New South Wales rivers and reservoirs is relatively low compared to world averages. This is a result of relatively low erosion rates, the sediment coarseness and numerous sediment sinks between the erodingparts of catchments and the rivers and reservoirs. However, in some locations several problems have required attention. These include: sediment blockage of roads and culverts; sedimentation of small reservoirs and recreational lakes; sedimentation on large alluvial fans; river channel damage casued by low sediment supply; and lack of effective government control over soil erosion and sedimentation in the past. Strategies to overcome these problems start with information collection to pinpoint major problems. This enables the preparation of total catchment management plans. These require proper land-use policies, legislation and education of the public for effective implementation.
Denudational history of the south‐central uplands of New South Wales
Summary K‐Ar age determinations on Tertiary basalts provide the basis of a new chronology for part of the south‐central uplands of N.S.W. A master planation surface which truncates a very diverse lithology was formed before Tertiary times, probably during the Triassic. There is evidence neither of the early Tertiary nor mid‐Tertiary planations which figured so prominently in many accounts of the N.S.W. uplands. By the beginning of Miocene times the Lachlan and Wollondilly Rivers had cut to within 80 metres of their present beds. Basalts in headwater valleys show that this part of the Great Divide was well‐established by Eocene times. The sequence of events in this region is strikingly similar to that proposed for the southern part of the Sydney Basin.
Evolutionary geomorphology of Australia and Papua-New Guinea
By means of examples it is demonstrated that much of the geomorphology of Australia dates back to early Cenozoic, Mesozoic and even Palaeozoic times. Papua-New Guinea is built of several fragments that had different histories before they collided with the Australian plate, and it is meaningless to construct a geomorphic history on the present map of the country. Despite signs of geomorphic youth, such as Pleistocene granite and gneiss domes, even Papua-New Guinea has many relic landforms. Conventional models of geomorphic evolution are evaluated and it is considered that process studies, dynamic equilibrium, and even cyclic theory and uniformitarianism, are inadequate for the time-scale involved and the many unique events recorded in landscape history. Evolutionary geomorphology, a branch of evolutionary earth science, is suggested as a more appropriate concept. IT is well known that Australia is an old continent, worn down over a long period of continental erosion to become the flattest continent. Over the past few years the development and application of absolute dating techniques has put the geomorphic history on a firm basis with a large number of accurate dates. It has been found that the development of the Australian landscape that we see today started before the break-up of Gondwanaland, which created the present continents of the southern hemisphere, and that there are significant relationships between landforms and continental drift. But even more important than the decipherment of this long geomorphic history is the light it throws on geomorphic concepts. Many of the ruling theories of today seem to be inadequate on the long time-scale, and a new view of the evolution of ancient landscapes is required that can accommodate the many unique events that occur in such long spans of time. PALAEOGEOGRAPHY