In 2014, I was appointed as senior lecturer in the Geography Department of the University of the Free State (UFS), however, my research career started in 2005 at the Agricultural Research Council – Institute for Soil Climate and Water (ARC-ISCW). I was project leader of several national projects in the fields of soil erosion and sediment modelling using GIS. In my role as project leader at the ARC I successfully completed several medium to long-term externally funded projects, all within budget.

 

My MSc focussed on soil erosion modelling under land use changes in Mauritius - obtained with distinction at the University of Pretoria (UP) in April 2005 (funded by UP’s International Study Abroad Programme). My A paper was published in the South African Geographical Journal. I am still involved with erosion research in Mauritius, co-author of a book chapter in 2016 as well as a review paper in 2021. In my PhD thesis titled “Water erosion risk assessment in South Africa: towards a methodological framework” I assessed soil erosion risk in South Africa (SA) using a multi-process and multi-scale approach. Findings were published in 5 peer-reviewed journals (e.g. Land Degradation and Development), presented at 1 international (e.g. Highland Symposium in Ethiopia) and 4 national conferences. The erosion maps I produced are frequently requested by several researchers from across the world (e.g. Friedrich-Schiller-University Jena, KU Leuven).

 

During my PhD, I also contributed to fieldwork at the SA Antarctic Base SANAE IV in 2009 participating in the SA National Antarctic Programme and NRF-funded projects on Marion Island (3 relief voyages). Outcomes included 2 papers in international peer-reviewed journals along with other team members. Although interested in cold geomorphology, my research focus is modelling soil erosion in a GIS. After my PhD, I was appointed as acting manager of the Soil Health and Remediation Programme at the ARC-ISCW responsible for human resource and financial delegations. Although this managerial position sharpened my leadership skills, it greatly limited time available for research (see absence from research section). To strategically shift my focus back to soil erosion research, I applied successfully in 2013 for a lecturing position in the Geography Department at UFS. I moved to UFS in July 2014 which has rejuvenated my research. With the retirement of our Head of Department in June 2020, I was requested to assist as acting HoD during the Covid19 pandemic.

 

I am currently in collaboration with Friedrich-Schiller-University Jena, KU Leuven, Manchester Metropolitan University, University of Mauritius, Northwest Agricultural and Forestry University in China; whereas local includes Rhodes University, University of Fort Hare, University of Pretoria, University of South Africa, and the Agricultural Research Council, as well as the Department of Environmental Affairs, Forestry and Fisheries; co-supervising 4 PhD and 7 MSc programmes, around 3 Honours projects per annum and also external examiner for 8 universities (16 MSc and 1 PhD). I have acted as reviewer for 23 journals and 9 proposals for the Water Research Commission (WRC), and reference group member of 3 projects. I also served as a reviewer for the NRF including applications for rating (3), project funding (3) and support for Doctoral students (2). I am registered as a professional Geographer at the South African Council for Natural Scientific Professions (reviewed 2 applications). I was President of and co-organized the Southern African Association of Geomorphologists Conference at the University of Swaziland in 2017. I am also member of the Soil Science Society of South Africa, Society of South African Geographers, and the EGU (co-convener for 2 sessions: 2020 and 2021).

Current research efforts/outputs focus on 3 aspects:

The first is sediment yield contribution from gully erosion including connectivity between source and sink areas. An article (Le Roux, 2018) was published in Land Degradation and Development 29(3): 765-775, titled: “Sediment yield potential in South Africa’s only large river network without a dam: implications for water resource management.” Results were presented at the EGU General Assembly 2016 in Vienna. The main feature that distinguishes my approach from others is that my model estimates sediment yield contribution from gully erosion at large catchment scale. The model is currently refined using UAV technology.

The second is establishing a national input database to run the SWAT model (in a GIS) that will be made available as an “open-source” baseline, to standardize SWAT modelling efforts in SA. The WRC-funded study will provide well-structured and geo-spatial input datasets in “cloud storage”, including digital elevation data, drainage networks, land cover codes, soil map and attribute table, and weather statistics required as input by SWAT.

The third is mapping (vegetated and/or gully-free) areas that are susceptible to gully development in SA, as well as estimated the sediment yield potential from the susceptible areas if gully development occurs. An article (Le Roux and van der Waal, 2020) was published in the South African Geographical Journal 102(3): 406-420, titled: Gully erosion susceptibility modelling to support avoided degradation planning. Results were also presented online at the EGU General Assembly 2020. 

Hedding DW, Hansen CD, Nel W, Loubser M, Le Roux JJ, Sumner PD, Meiklejohn KI (2016) Rock mass loss on a nunatak in Western Dronning Maud Land, Antarctica: implications for periglacial landform development and habitat facilitation. Arctic, Antarctic and Alpine Research, 48(1):1-8. https://doi.org/10.1657/AAAR0015-005.

 

Hedding DW, Meiklejohn KI, Le Roux JJ, Loubser M, Davis JK (2010) Short communication – Some observations on the formation of an active pronival rampart at Grunehogna Peaks, Western Dronning Maud Land, Antarctica. Permafrost and Periglacial Processes 21(4): 355–361. https://doi.org/10.1002/ppp.698.

 

Le Roux JJ (2018) Sediment yield potential in South Africa’s only large river network without a dam: implications for water resource management. Land Degradation and Development 29(3): 765-775. https://doi.org/10.1002/ldr.2753.

 

Le Roux JJ, Morgenthal TL, Malherbe J, Sumner PD, Pretorius DJ (2008) Water erosion prediction at a national scale for South Africa. Water SA 34(3): 305-314. ISSN 1816-7950.

 

Le Roux JJ, Newby TS, Sumner PD (2007) Monitoring soil erosion in South Africa at a regional scale: Review and recommendations. South African Journal of Science 103: 329-335. ISSN 1996-7489.

 

Le Roux JJ, Sumner PD (2012) Factors controlling gully development: Comparing continuous and discontinuous gullies. Land Degradation and Development 23(5): 440–449. https://doi.org/10.1002/ldr.1083.

 

Le Roux JJ, Sumner PD (2013) Soil erosion risk assessment in South Africa: towards a methodological framework. Geografiska Annaler: Series A, Physical Geography 95(4): 323–336. https://www.jstor.org/stable/43870696.

 

Le Roux JJ, Sumner PD, Lorentz SA, Germishuyse T (2013) Connectivity aspects in sediment migration modelling using SWAT. Geosciences 3(1): 1-12. https://doi.org/10.5923/j.geo.20130301.01.

 

Le Roux JJ, Sumner PD, Rughooputh SDDV (2005) Erosion modelling and soil loss prediction under changing land use for a catchment on Mauritius. South African Geographical Journal 87(2): 129-140. https://doi.org/10.1080/03736245.2005.9713836.

 

Le Roux JJ, van der Waal B (2020) Gully erosion susceptibility modelling to support avoided degradation planning, South African Geographical Journal 102(3): 406-420. https://doi.org/10.1080/03736245.2020.1786444.

 

Malherbe H, Le Maitre D, Le Roux JJ, Pauleit S, Lorz C (2019) A simplified method to assess the impact of sediment and nutrient inputs on river water quality in two regions of the southern coast of South Africa. Environmental Management 63(5): https://doi.org/10.1007/s00267-019-01147-w.

 

Mararakanye N, Le Roux JJ, Franke AC (in press) Using satellite-based weather data as input to SWAT in a data poor catchment. Physics and Chemistry of the Earth 117. https://doi.org/10.1016/j.pce.2020.102871.

 

Mararakanye N, Le Roux JJ (2012) Gully erosion mapping at a national scale for South Africa. South African Geographical Journal 94(2): 208-218. https://doi.org/10.1080/03736245.2012.742786.

 

Stander MH, Le Roux JJ, Abd Elbasit MAM, Liu G (in press): A review of sediment fingerprinting for erosion hotspot assessment in southern Africa, South African Geographical Journal. https://doi.org/10.1080/03736245.2020.1791240.

 

Sumner PD, Rughooputh SDDV, Boojhawon R, Dhurmea K, Hedding DW, Le Roux JJ, Pasnin O, Tatayah V, Zaynab A, Nel W (in press): Erosion studies on Mauritius: overview and research opportunities, South African Geographical Journal. https://doi.org/10.1080/03736245.2020.1795915.

 

Theron SN, Weepener HL, Le Roux JJ, Engelbrecht CJ. (2021) Modelling potential climate change impacts on sediment yield in the Tsitsa River catchment, South Africa. Water SA 47(1): 67–75 https://doi.org.10.17159/wsa/2021.v47.i1.9446.

 

Le Roux JJ (2018) Sediment yield potential in South Africa’s only large river network without a dam: implications for water resource management. Land Degradation and Development 29(3): 765-775. https://doi.org/10.1002/ldr.2753.

 

Le Roux JJ, Morgenthal TL, Malherbe J, Sumner PD, Pretorius DJ (2008) Water erosion prediction at a national scale for South Africa. Water SA 34(3): 305-314. ISSN 1816-7950.

 

Le Roux JJ, Newby TS, Sumner PD (2007) Monitoring soil erosion in South Africa at a regional scale: Review and recommendations. South African Journal of Science 103: 329-335. ISSN 1996-7489.

 

Le Roux JJ, Sumner PD (2012) Factors controlling gully development: Comparing continuous and discontinuous gullies. Land Degradation and Development 23(5): 440–449. https://doi.org/10.1002/ldr.1083.

 

Le Roux JJ, Sumner PD (2013) Soil erosion risk assessment in South Africa: towards a methodological framework. Geografiska Annaler: Series A, Physical Geography 95(4): 323–336. https://www.jstor.org/stable/43870696.

 

Le Roux JJ, Sumner PD, Lorentz SA, Germishuyse T (2013) Connectivity aspects in sediment migration modelling using SWAT. Geosciences 3(1): 1-12. https://doi.org/10.5923/j.geo.20130301.01.

 

Le Roux JJ, Sumner PD, Rughooputh SDDV (2005) Erosion modelling and soil loss prediction under changing land use for a catchment on Mauritius. South African Geographical Journal 87(2): 129-140. https://doi.org/10.1080/03736245.2005.9713836.

 

Le Roux JJ, van der Waal B (2020) Gully erosion susceptibility modelling to support avoided degradation planning, South African Geographical Journal 102(3): 406-420. https://doi.org/10.1080/03736245.2020.1786444.

Introduction

Soil erosion is an important form of land degradation and is among South Africa’s most critical environmental issues.  Land degradation may get worse in the future due to population growth and potential climatic changes.  Loss of fertile topsoil and reduction of soil productivity is coupled with serious off-site impacts related to increased mobilization of sediment and delivery to rivers.  One of the main concerns of the Department of Water Affairs of South Africa is the mobilization of eroded soil and its delivery to rivers and dams. Given the increasing threat of the sedimentation/siltation of reservoirs, it is important to identify source areas and key processes of sediment transport from field to stream. 

 

Research interests

Dr Le Roux’s main interests and research focus areas includes the following:

• Land degradation assessment, mapping and monitoring;
• Specifically in spatial modelling of soil erosion risk, as well as;
• Sediment transport and hydrological connectivity;
• Using hydrological models such as the Soil and Water Assessment Tool; and
• GIS and UAV technologies;
• From a catchment to national scale.

Dr Le Roux also has experience in the mapping of other geomorphological landforms including:

• The distribution of periglacial and mass-wasting landforms in South Africa, Marion Island and the (Sub)Antarctic (which are used as diagnostic indicators for climatic conditions).