Sediment/contaminant delivery from mine sites to stream systems

An important step in the design or assessment of mine site rehabilitation is to determine how much sediment eroded from the mine site is delivered through the catchments linking the rehabilitated landforms to the receiving stream systems. It is also important to understand where sediment may be deposited and stored in these catchments. When erosive forces detach a particle it is generally not transported directly to the watercourse from a rehabilitated landform. The particle goes through repeated cycles of detachment, transport and deposition until, after a considerable time period, it enters the stream system. The amount of sediment entering a stream is only a fraction of the total sediment eroded from upland areas. This fraction is the 'sediment delivery ratio', which is defined as the percentage of the sediment delivered at a location in the stream system to the total amount of erosion occurring throughout a stream catchment. Total erosion is the sum of all forms of erosion in the contributing catchment including gully, rill, and sheet erosion.

Erosion survey equipment (photo: M Saynor)

Earlier work by ERISS has provided information on the transport and distribution of sediment in areas downstream of ERA Ranger mine in Magela Creek and on the Magela Creek Flood Plain. Present research on landform evolution modelling will provide information on sediment transport from the mine sites. Movement of mine-derived sediment in small catchments connecting mine sites and creeks should be evaluated using sediment transport models, an account of the alluvial history and sediment budgeting. The modelling skills are being developed but detail of sediment storage and transport in small catchments in the Alligator Rivers Region is not well known.

Until recently, much of the eriss research focused on the Ngarradj catchment, which contains the ERA Jabiluka project site. Ngarradj is a major downstream right-bank tributary of the Magela Creek that flows directly into the Magela Creek floodplain and wetlands. To be able to manage the catchment responsibly and control any adverse affect of mining it is necessary to have a good baseline data set. There is a need to update baseline data to quantify temporal and spatial change that may occur in the catchment. This information can be used to predict future catchment changes given various scenarios of disturbance thereby enabling proactive management at a catchment scale. Good baseline hydrology, sediment transport and stream channel stability data are now available for Ngarradj. Recently the focus of eriss research has switched to the Gulungul Creek catchment, which contains part of the Ranger mine. Similar to Ngarradj, we are currently establishing the hydrological, sediment transport and channel stability characteristics of the catchment which could be used to assess rehabilitation success.

Research projects

  • Jabiluka catchment studies
  • Baseline data collection Gulungul Creek – sediment movement, hydrology and morphology
  • Development of a GIS on sediment movement, hydrology and morphology
  • Development and application of GIS-based modelling technology for 'total catchment' management

Relevant Supervising Scientist reports

SSR156
Erskine WD & Saynor MJ 2000. Assessment of the off-site geomorphic impacts of uranium mining on Magela Creek, Northern Territory, Australia. Supervising Scientist Report 156, Supervising Scientist, Darwin.

SSR158
Erskine WD, Saynor MJ, Evans KG & Boggs GS 2001. Geomorphic research to determine the off-site impacts of the Jabiluka Mine on Swift (Ngarradj) Creek, Northern Territory. Supervising Scientist Report 158, Supervising Scientist, Darwin.

SSR159

Boggs GS, Devonport CC, Evans KG, Saynor MJ & Moliere DR 2001. Development of a GIS based approach to mining risk assessment. Supervising Scientist Report 159, Supervising Scientist, Darwin.

SSR176
Saynor MJ, Erskine WD & Evans KG 2003. Bank erosion in the Ngarradj catchment: Results of erosion pin measurements between 1998 and 2001. Supervising Scientist Report 176, Supervising Scientist, Darwin NT.

SSR179
Evans KG, Moliere DR, Saynor MJ, Erskine WD & Bellio MG 2004. Baseline suspended-sediment, solute, EC and turbidity characteristics for the Ngarradj catchment, Northern Territory, and the impact of mine construction. Supervising Scientist Report 179, Supervising Scientist, Darwin NT.

SSR181
Saynor MJ, Erskine WD & Evans KG 2004. Cross-sectional and scour and fill changes in the Ngarradj catchment between 1998 and 2003. Supervising Scientist Report 181, Supervising Scientist, Darwin NT.

SSR183

Moliere D 2005. Analysis of historical streamflow data to assist sampling design in Gulungul Creek, Kakadu National Park, Australia. Supervising Scientist Report 183, Supervising Scientist, Darwin NT.

SSR188
Saynor MJ, Erskine WD & Evans KG 2006. Bed-material grain size changes in the Ngarradj Creek catchment between 1998 and 2003. Supervising Scientist Report 188, Supervising Scientist, Darwin NT.

Relevant Journal Papers

Boggs G, Evans K, Devonport C, Moliere D & Saynor M 2000. Assessing Catchment-wide, Mining Related Impacts on Sediment Movement in the Swift Creek Catchment, Northern Territory, Australia, Using GIS and Landform Evolution Modelling Techniques. Journal of Environmental Management, Special Issue 59(4), 321–334.

Boggs GS, Evans KG & Devonport CC 2004. Rugged plateaus and extensive floodplains – modelling landform evolution in a northern Australian catchment. Australian Geographic Studies 42(2), 260–273.

Boggs GS, Moliere DR, Evans KG & Devonport CC 2003. Long-term hydrology modelling and analysis in a data limited small catchment in the wet-dry tropics of Australia. Australian Journal of Water Resources 7 (2), 71–85.

Erskine WD, Saynor MJ, Erskine L, Evans KG & Moliere DR 2005. A preliminary typology of Australian tropical rivers and implications for fish community ecology. Marine and Freshwater Research 56(3), 253–267.

Evans KG 2000. Methods for assessing mine site rehabilitation design for erosion impact. Australian Journal of Soil Research 38(2), 231–248.

Evans KG, Martin P, Moliere DR, Saynor MJ, Prendergast JB & Erskine WD 2004. Erosion risk assessment of the Jabiluka mine site, Northern Territory, Australia. Journal of Hydrologic Engineering 9(6), 512–522.

Evans KG, Saynor MJ & Willgoose GR 1999. Changes in hydrology, sediment loss and microtopography of a vegetated mine waste rock dump impacted by fire. Land Degradation and Development 10, 507-522.

Evans K, Saynor M, Willgoose G & Riley SJ 2000. Post-mining landform evolution modelling. I. Derivation of sediment transport model and rainfall-runoff model parameters. Earth Surface Processes and Landforms 25(7), 743–763.

Evans KG & Willgoose GR 2000. Post-mining landform evolution modelling. II. Effects of vegetation and surface ripping. Earth Surface Processes and Landforms 25(8), 803–823.

Moliere DR, Evans KG, Saynor MJ & Erskine WD 2002. Estimation of suspended sediment loads downstream of the Jabiluka mine, Northern Territory, Australia. Hydrological Processes 18 (3), 531–544.

Moliere DR, Saynor MJ & Evans KG 2005. Suspended sediment concentration-turbidity relationships for Ngarradj – a seasonal stream in the wet-dry tropics. Australian Journal of Water Resources 9(1), 37–48.

Saynor MJ & Erskine WD 2006. Spatial and temporal variations in bank erosion on sand-bed streams in the seasonally wet tropics of northern Australia. Earth Surface Processes and Landforms Journal 31, 1080–1099.

Saynor MJ, Erskine WD, Evans KG & Eliot I 2004. Gully initiation and implications for management of scour holes in the vicinity of the Jabiluka Mine, Northern Territory, Australia. Geografiska Annaler 86 (2), 191–203.

Saynor MJ & Evans KG 2001. Sediment loss from a waste rock dump, ERA Ranger Mine, northern Australia. Australian Geographical Studies 39 (1), 34–51.