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

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 regulat...

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Autores principales:	Devika Nair, K. G. Evans, Sean Bellairs, M. R. Narayan
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	catchment disturbance fine suspended sediment event discharge closure criteria Hydraulic engineering TC1-978 Water supply for domestic and industrial purposes TD201-500
Acceso en línea:	https://doaj.org/article/a5f0e818946f44f698dfd87a6d3cce07
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spelling	oai:doaj.org-article:a5f0e818946f44f698dfd87a6d3cce072021-11-25T19:15:01ZStream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia10.3390/w132231722073-4441https://doaj.org/article/a5f0e818946f44f698dfd87a6d3cce072021-11-01T00:00:00Zhttps://www.mdpi.com/2073-4441/13/22/3172https://doaj.org/toc/2073-4441Mining 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.Devika NairK. G. EvansSean BellairsM. R. NarayanMDPI AGarticlecatchment disturbancefine suspended sedimentevent dischargeclosure criteriaHydraulic engineeringTC1-978Water supply for domestic and industrial purposesTD201-500ENWater, Vol 13, Iss 3172, p 3172 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	catchment disturbance fine suspended sediment event discharge closure criteria Hydraulic engineering TC1-978 Water supply for domestic and industrial purposes TD201-500
spellingShingle	catchment disturbance fine suspended sediment event discharge closure criteria Hydraulic engineering TC1-978 Water supply for domestic and industrial purposes TD201-500 Devika Nair K. G. Evans Sean Bellairs M. R. Narayan Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia
description	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.
format	article
author	Devika Nair K. G. Evans Sean Bellairs M. R. Narayan
author_facet	Devika Nair K. G. Evans Sean Bellairs M. R. Narayan
author_sort	Devika Nair
title	Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia
title_short	Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia
title_full	Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia
title_fullStr	Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia
title_full_unstemmed	Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia
title_sort	stream suspended mud as an indicator of post-mining landform stability in tropical northern australia
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/a5f0e818946f44f698dfd87a6d3cce07
work_keys_str_mv	AT devikanair streamsuspendedmudasanindicatorofpostmininglandformstabilityintropicalnorthernaustralia AT kgevans streamsuspendedmudasanindicatorofpostmininglandformstabilityintropicalnorthernaustralia AT seanbellairs streamsuspendedmudasanindicatorofpostmininglandformstabilityintropicalnorthernaustralia AT mrnarayan streamsuspendedmudasanindicatorofpostmininglandformstabilityintropicalnorthernaustralia
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Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia

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