Publications of Matthias Vanmaercke
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See detailSediment yield as a desertification risk indicator
Vanmaercke, Matthias ULiege; Poesen, J.; Maetens, W. et al

in Science of the Total Environment (2011), 409(9), 1715-1725

Soil erosion is often regarded as one of the main processes of desertification. This has led to the use of various desertification indicators that are related to soil erosion. Most of these indicators ... [more ▼]

Soil erosion is often regarded as one of the main processes of desertification. This has led to the use of various desertification indicators that are related to soil erosion. Most of these indicators focus, however, on small spatial units, while little attention has been given to the amount of sediment exported at the catchment scale. Such a small spatial unit approach neglects the transfer of sediment through catchments as well as the scale-dependency of erosion processes. Furthermore, this approach does not consider important off-site impacts of soil erosion, such as sediment deposition in reservoirs, flooding as well as ecological impacts.This study aims to illustrate the importance of also considering catchment sediment yield (SY, tkm-2y-1) in desertification assessment studies. Based on recently established databases of SY and soil loss rates in Europe and examples from previous studies, we illustrate that soil erosion rates at the plot scale are not representative for catchment SY, as they are often several orders of magnitude smaller. Also, the erosion response of catchments to changes in land use or climate often differs strongly from responses to those changes at the plot scale. We further discuss several of the impacts of SY and their link with desertification: i.e. the sedimentation of reservoirs, problems related to flooding, catchment hydrology, export of nutrients and ecological implications.Using earlier established criteria we evaluate the potential for using catchment SY as a desertification indicator and conclude that this could give an important added value to desertification studies. SY, used in combination with other indicators, allows the identification of other sediment sources than those considered at the plot scale and can reflect the results of desertification processes over longer time periods than periods over which assessments at the plot scale have been made. We argue therefore, that SY is a strong complementary indicator of desertification providing valuable information on the catchment response to changes in drivers of desertification. © 2011 Elsevier B.V. [less ▲]

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See detailAn exploratory study on the use of enzyme activities as sediment tracers: Biochemical fingerprints?
Nosrati, K.; Govers, G.; Ahmadi, H. et al

in International Journal of Sediment Research (2011), 26(2), 136-151

Little information exists on the potential of soil enzyme activities, which are sensitive to soil properties and management, for the characterization of sediment sources at the catchment scale. The ... [more ▼]

Little information exists on the potential of soil enzyme activities, which are sensitive to soil properties and management, for the characterization of sediment sources at the catchment scale. The objective of this study is to explore and evaluate enzyme activity as tracer for sediment fingerprinting in the Hiv catchment (55 km2), Iran. Therefore, four enzymes were measured from 42 different sampling sites, covering three sediment source areas (rangeland/surface erosion, orchard/surface erosion, and streambank erosion), as well as from 12 sediment samples from reservoir check dams (sediment sinks). The results indicate that, based upon backward mode discriminant analysis, β-glucosidase and dehydrogenase, allowed more than 95% of the samples to be correctly assigned to their source areas. These enzymes were selected as input data for a mixing-model to determine the relative contribution of the sampled sediment sources. The mean contributions from rangeland, orchard and streambank sources in the study area were estimated as 11.3%, 15.1% and 73.7%, respectively. Using geochemical tracers, the mean contribution from rangeland, orchard and streambank sources was estimated as 14.1%, 9.5% and 74.8%, respectively. Combined biochemical and geochemical tracers, similar values were obtained (18.7%, 10.7% and 70.7%, respectively). Our results indicate that soil enzyme activity allows for a good characterization of sediment sources, and can provide a complementary tool to currently existing sediment fingerprinting approaches. However, the method should be also tested in other regions. © 2011 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research. [less ▲]

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See detailSediment dynamics and the role of flash floods in sediment export from medium-sized catchments: A case study from the semi-arid tropical highlands in northern Ethiopia
Vanmaercke, Matthias ULiege; Zenebe, A.; Poesen, J. et al

in Journal of Soils and Sediments (2010), 10(4), 611-627

Purpose The Ethiopian highlands are a fragile environment characterized by steep slopes, intense rainfall, a sparse vegetation cover, and the occurrence of flash floods. Although important efforts have ... [more ▼]

Purpose The Ethiopian highlands are a fragile environment characterized by steep slopes, intense rainfall, a sparse vegetation cover, and the occurrence of flash floods. Although important efforts have been made to mitigate the ongoing soil erosion and land degradation problems, the sediment dynamics at medium-sized catchment scale (100-10,000 km2) are not fully understood. Therefore, this study aims to provide a better understanding of sediment export processes and the importance of flash flood events in semi-arid tropical catchments. Materials and methods Measuring campaigns were con ducted in ten sub-catchments of the Geba, a tributary of the Tekeze, representative of the northern Ethiopian highlands. During two to four rainy seasons, the rivers were sampled for their suspended sediment concentration (SSC) and runoff discharge. Results and discussion Variations in SSC and sediment grain size distribution indicate changes in sediment supply during the rainy season due to the depletion of readily available sediments and the development of a vegetation cover. Also, during flood events, changes in sediment supply are observed. Sediment yields (i.e., 497-6,543 t km-2 year-1) are higher than suggested by previous studies and correlate with rainfall depth. The majority of sediment export occurs during a few short but intense flash floods. No clear effect of implemented soil and water conservation measures could be detected in the sediment yields of the catchments. Conclusions Sediment export rates in the Ethiopian high-lands are high, are characterized by important changes in sediment supply, and are mainly controlled by the occurrence and magnitude of flash flood events. Mitigation measures to reduce sediment yield at the catchment scale should therefore not only focus on the reduction of hillslope erosion rates but also on the magnitude of these foods. © Springer-Verlag 2010. [less ▲]

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See detailRegional differences and scale dependency of sediment yield in Europe
Vanmaercke, Matthias ULiege; Poesen, Jean; Verstraeten, Gert et al

in Hydrology and Sedimentation for a Changing Future: Existing and Emerging Issues. Proc. of the Joint Federal Interagency Hydrologic Modelling and Sedimentation Conference (2010)

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See detailSediment yield in Europe: Regional differences in scale dependence
Vanmaercke, Matthias ULiege; Poesen, J.; Verstraeten, G. et al

in IAHS-AISH Publication (2010), 337

Current understanding of the regional variation in sediment yield (SY) and its scale dependence is limited for Europe. Based on an extensive literature review, a SY-database was assembled to bridge this ... [more ▼]

Current understanding of the regional variation in sediment yield (SY) and its scale dependence is limited for Europe. Based on an extensive literature review, a SY-database was assembled to bridge this gap. Measured SY-data from 1794 different locations throughout Europe were collected, representing a minimum of 29 203 catchment-years of records and comprising a wide range of catchment areas (0.01 km2 to 1 360 000 km2). Clear differences were observed between the temperate regions of Europe (low SY-values, i.e. <50 t km-2 year-1) and the Mediterranean and mountainous regions of Europe where SY-values are generally higher (i.e. >300 t km-2 year-1). Furthermore, for most temperate regions a negative relationship was found between catchment area and SY. For mountainous and Mediterranean regions, this was generally not the case. A comparison of catchment SY with rates of sheet and rill erosion also points to clear regional differences. Whereas soil erosion rates are generally higher than SY for temperate regions, this is not the case for the Mediterranean region. This indicates the importance of other erosion processes (i.e. landslides, riverbank erosion, and gullies). The results illustrate important regional differences in the scale dependence of SY and emphasize the need for an integrated modelling approach considering various types of sediment source and sink. Copyright © 2010 IAHS Press. [less ▲]

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See detailImpact of soil and water conservation measures on catchment hydrological response-a case in north Ethiopia
Nyssen, J.; Clymans, W.; Descheemaeker, K. et al

in Hydrological Processes (2010), 24(13), 1880-1895

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are ... [more ▼]

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post-harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre-implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5mm(RCD 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002-2003 (ΔT/WS D 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. © 2010 John Wiley & Sons, Ltd. [less ▲]

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See detailAssessment of the effectiveness of soil and water conservation measures in reducing runoff and soil loss: establishment of a European database
Maetens, Willem; Vanmaercke, Matthias ULiege; Poesen, Jean

in Romero Diaz, A.; Belmonte Serrato, F.; Alonso Sarriá, F. (Eds.) et al Advances in studies on desertification. Contributions to the international conference on desertification in memory of Professor John B. Thornes (2009)

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See detailGrootteorde en dynamiek van sedimentexport in het Geba Bekken, Noord Ethiopische Hoogland
Vanmaercke, Matthias ULiege; Poesen, Jean; Verstraeten, Gert et al

in Jaarboek ...: de Aardrijkskunde (2008), 32

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See detailMagnitude and Dynamics of Runoff and Sediment Transport in the Geba River Catchment, Northern Ethiopia
Vanmaercke, Matthias ULiege; Zenebe, Amanuel; Poesen, Jean et al

in Kertész, Adam (Ed.) Soil and water conservation, climatic change and environmental sensitivity. Proceedings of the International Congress of ISCO (2008)

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