Next Article in Journal
Slaughterhouse Wastewater Treatment: A Review on Recycling and Reuse Possibilities
Previous Article in Journal
Detailed Trend Analysis of Extreme Climate Indices in the Upper Geum River Basin
Article

Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia

1
Research Institute for Environment & Livelihoods, Charles Darwin University, Ellengowan Drive, Casuarina, NT 0810, Australia
2
College of Engineering, IT & Environment, Charles Darwin University, Ellengowan Drive, Casuarina, NT 0810, Australia
3
Surface Water & Erosion Solutions, Lakes Crescent, Marrara, NT 0812, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: David Post
Water 2021, 13(22), 3172; https://doi.org/10.3390/w13223172
Received: 20 October 2021 / Revised: 2 November 2021 / Accepted: 8 November 2021 / Published: 10 November 2021
(This article belongs to the Section Water Erosion and Sediment Transport)
Mining can cause environmental disturbances and thus mined lands must be managed properly to avoid detrimental impacts in the future. They should be rehabilitated in such a way that post mining landforms behave similarly as the surrounding stable undisturbed areas. A challenge for government regulators and mine operators is setting closure criteria for assessment of the stability of the elevated post-mining landforms. Stability of a landform is often measured by the number and incision depth of gullies. This can assess mass stability and bulk movement of coarse material. However, there is a need for a more sensitive approach to assess catchment disturbances using the concept of waves of fine suspended sediment and thus determine the dynamics of recovery of a post mining landform. A more environmentally meaningful approach would be to assess the fine suspended sediment (FSS, silt + clay (0.45 µm < diameter < 63 µm)) leaving the system and entering downstream waterways. We propose assessing stability through relationships between rainfall event loads of FSS and event discharge (Q) in receiving streams. This study used an innovative approach where, instead of using instantaneous FSS concentration, it used total FSS load in waves of sediment driven through the system by rainfall runoff events. High resolution stream monitoring data from 2004 to 2015 in Gulungul and Magela Creeks, Northern Territory, Australia, were used to develop a relationship between sediment wave and event discharge, ∑FSS α f(Q). These creeks are adjacent to and receive runoff from Ranger Mine. In 2008, a 10 ha elevated waste rock landform was constructed and instrumented in the Gulungul Creek catchment. The earthworks required to build the landform created a considerable disturbance in the catchment, making a large volume of disturbed soil and substrate material available for erosion. Between 2008 and 2010, in the first two wet seasons immediately after construction, the downstream monitoring site on Gulungul Creek showed elevated FSS wave loads relative to discharge, compared with the upstream site. From 2010 onwards, the FSS loads relative to Q were no longer elevated. This was due to the establishment of vegetation on the site and loose fine sediment being trapped by vegetation. Large scale disturbance associated with mining and rehabilitation of elevated landforms causes elevated FSS loads in receiving streams. The predicted FSS loads for the stream as per the relationships between FSS and event discharge may not show a 1:1 relation with the observed loads for respective gauging stations. When downstream monitoring shows that FSS wave loads relative to rainfall runoff event discharge reduce back to pre-construction catchment levels, it will indicate that the landform is approaching equilibrium. This approach to assess landform stability will increase the sensitivity of assessing post-mining landform recovery and assist rehabilitation engineers to heal the land and benefit owners of the land to whom it is bestowed after rehabilitation. View Full-Text
Keywords: catchment disturbance; fine suspended sediment; event discharge; closure criteria catchment disturbance; fine suspended sediment; event discharge; closure criteria
Show Figures

Figure 1

MDPI and ACS Style

Nair, D.; Evans, K.G.; Bellairs, S.; Narayan, M.R. Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia. Water 2021, 13, 3172. https://doi.org/10.3390/w13223172

AMA Style

Nair D, Evans KG, Bellairs S, Narayan MR. Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia. Water. 2021; 13(22):3172. https://doi.org/10.3390/w13223172

Chicago/Turabian Style

Nair, Devika, K. G. Evans, Sean Bellairs, and M. R. Narayan. 2021. "Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia" Water 13, no. 22: 3172. https://doi.org/10.3390/w13223172

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop