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.
Preliminary Evaluation of Lithofacies Models for Meandering Alluvial Streams
Abstract Recently completed and ongoing studies of meandering streams disclose a complexity of sedimentary facies not found in standard fining-upward models and later models from the Endrick and Wabash Rivers. The following features are usually deemed diagnostic of low-sinuosity undivided or braided streams but typify many meandering streams: negligible mud, large facies changes over short distances laterally, vertical sequences that do not denote an upward decrease in flow regime, predominance of gravel (sometimes quite coarse), scarcity of cross-stratification, absence of natural levees, and sheetlike geometry of channel facies. Many other widely used criteria for meandering streams do not occur in all meandering streams or else can exist in non-meandering streams. The ubiquitous assumption of a close correspondence between channel pattern and lithofacies in rivers presents additional complications to fluvial facies models. The morphology of many streams varies greatly from one short reach to another, can be drastically modified by great floods, or can be transitional between recognized types of channel pattern. Five lithofacies classes of meandering streams are identified tentatively: muddy fine-grained streams, sand-bed streams with modest fine member, sand-bed streams without mud, graveliferous sand-bed streams, and streams with coarse gravel and little sand. The last three classes include vital features ordinarily deemed typical of non-meandering streams. These considerations imply that the reconstruction of depositional environment of ancient fluvial sediments requires detailed knowledge of the three-dimensional lithofacies. Failure to appreciate this fact may be one reason why environmental interpretations of ancient fluvial sediments commonly are equivocal. A second important factor may be the present ignorance of the manner and potential of preservation of individual fluvial units when stacked upon one another.