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Sedimentation in the Fly River Delta |
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Report: PDF (2671kB)
Author: Dr G. Pickup
Date: February 2007
It is generally assumed that sediment disposed from the Ok Tedi Mine into the Ok Tedi has little or no effect on the South Fly (below Everill Junction) and the Fly Delta. As this assumption has never been tested directly, this report examines recent changes in the South Fly and the Delta as observed on satellite imagery. It covers the period 1972-2006 and so includes a significant period of pre-mine behaviour. The aim is to identify changes, determine if there are any trends, and to compare pre-mining behaviour with changes that have occurred during mine operation. Recommendations are then made for further investigation through sampling of river bed sediments in selected areas. Satellite imagery has been processed to identify coastal boundaries, river and island edges, and large exposed bars. Changes below water level cannot be identified with certainty because of variations in water colour due to tidal and flood conditions, both of which affect the suspended sediment content. In spite of this limitation, clear trends can be identified in some parts of the river system and these give a good indication of long-term changes.
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Uncertainty Analysis for the Null Scenario - 2003 Sediment Transport Modelling |
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Report: PDF (2441kB)
Author: Dr G. Pickup
Date: December 2003
This report describes the main uncertainties in the 2003 sediment transport modellling, concentrating on the null scenario. However, many of the conclusions of this uncertainty analysis would apply to the other scenarios considered in the 2003 modelling.
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2003 Sediment Trasport Modelling by G. Parker and Y. Cui |
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Report: PDF (5746kB)
Author: Drs G. Pickup and Y. Cui
Date: December 2003
This sediment transport modelling study examines possible effects of disposal of additional waste rock and tailings on sedimentation processes and water levels in the Ok Tedi and Middle Fly River, adopting the 'null scenario' of 2010 as the end of mine life (with continuation of dredging to mine closure) but also examining scenarios for 2015 and 2020. It also evaluates the likely impact of changing dredging rates to 25%, 50%, 75% and 125% of current rates as well as stopping dredging from mid-2003. Two sediment transport models were used. Runs with OkGrav6 covered effects in the Mine Area Creeks and the Upper and Middle Ok Tedi. Runs with HEC-6 examined likely changes in the Lower Ok Tedi and Middle Fly. OkGrav was updated in this process and recalibrated using new data on flow durations, sediment characteristics, sidewall erosion and deposition. HEC-6 was calibrated using observed water levels and patterns of deposition from cross section surveys. Floodplain deposition could not be modelled with available data and technology. However, some estimates of future patterns of levee growth and floodplain inundation were obtained from cross-section data and HEC-6 water surface profiles.
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Geomorphic Impacts on the Fly River of Extending Mine Life |
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Report: PDF (3498kb)
Author: Dr G. Pickup
Date: October 2001
This study was commissioned to provide an independent assessment of: the current state of Fly River geomorphology and sedimentation processes; the likely impact of a further 10 years of mining; expected changes in river system behaviour after mining ceases; and possible interventions to reduce mining impact and to accelerate the rate of recovery of the river system.
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Sediment Transport Workshop, February 2000, Minutes |
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Author: OTML
Date: February 2000
These minutes record the major issues and discussion at a workshop convened at Tabubil, PNG, to review the information available at that time on river surveys and sediment transport modelling. It also includes a sediment budget for the years 1985 to 1999.
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1998/99 Sediment Transport Modelling |
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Report: PDF 654 kb
Author: Y. Cui and G. Parker
Date: July 1999
This model predicts the fate of mine-derived waste material throughout the Ok Tedi and Fly River systems. The predictive period was to 2055 and the model extended to the junction of the Strickland and Fly rivers. The model was developed specifically for this purpose to account for movement and abrasion of gravels, sands and silts. Outputs from this model include: bed aggradation and recovery, floodplain flooding and aggradation, and silt loads. The silt loads are used in the dissolved copper model and the flooding data are used in the dieback model. Aggradation data are used for predicting the navigability of the Fly River and for the assessment of acid rock drainage potential.
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