Publications of Matthias Vanmaercke
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See detailEvolution of the effectiveness of stone bunds and trenches in reducing runoff and soil loss in the semi-arid Ethiopian highlands
Taye, G.; Poesen, J.; Vanmaercke, Matthias ULiege et al

in Zeitschrift für Geomorphologie (2015), 59(4), 477-493

Soil and Water Conservation (SWC) structures, in particular stone bunds and conservation trenches, have been extensively installed in Tigray since the 1980's. As the effectiveness of stone bunds and ... [more ▼]

Soil and Water Conservation (SWC) structures, in particular stone bunds and conservation trenches, have been extensively installed in Tigray since the 1980's. As the effectiveness of stone bunds and trenches in reducing runoff and soil loss depends on their retention capacities, it can be expected that this effectiveness declines over time due to infilling with sediment. However, little is known about the rate of this decline during subsequent years. We therefore assessed the effectiveness of SWC structures for two land use types, three slope classes and during three consecutive rainy seasons. Rainfall, runoff and soil loss were measured using 21 large (600-1,000m2) runoff plots at Mayleba catchment. Results show that all studied SWC structures are more effective in reducing soil loss than runoff. Conservation trenches are generally more effective in reducing runoff and soil loss than stone bunds. However, due to their infilling with sediment, their effectiveness quickly declines over time. By the end of the third rainy season, their effectiveness was reduced to about one third of their initial effectiveness. The effectiveness of stone bunds remained fairly constant during three consecutive rainy seasons. These findings have important implications, as they demonstrate that many of the installed SWC structures (especially in rangelands) are only very effective for short periods (one to two years). Regular sediment removal from conservation trenches is therefore crucial to preserve their effectiveness over longer periods. © 2014 Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany. [less ▲]

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See detailSeismic controls on contemporary sediment export in the Siret river catchment, Romania
Vanmaercke, Matthias ULiege; Obreja, F.; Poesen, J.

in Geomorphology (2014), 216

While differences in catchment sediment yield (SY, [tkm-2y-1]) are generally attributed to topography, lithology, climate and land use, recent studies have highlighted that also seismic activity may have ... [more ▼]

While differences in catchment sediment yield (SY, [tkm-2y-1]) are generally attributed to topography, lithology, climate and land use, recent studies have highlighted that also seismic activity may have an important impact on SY. Nonetheless, relatively little is known about the importance of this factor and the processes and mechanisms explaining its influence. Therefore, this study explores the role of seismic activity in explaining spatial and temporal variation in sediment export within the Siret Basin (Romania, 45,000km2), a catchment with a large variability in seismic activity. Based on previously unpublished long-term (>30years) SY measurements for 38 subcatchments of the Siret, we analyze the correlation between average SY, seismic activity and various other catchment characteristics. Our results showed that spatial variation in average SY was indeed strongly correlated with the degree of seismic activity in each catchment (R2=0.74). Also catchment lithology explained an important part of the differences in SY (R2=0.67). The combination of these two factors accounted for about 80% of the observed variation in SY, while other factors (e.g. topography, land use, climate, and runoff) did not significantly contribute to the explained variance in average SY. To explore the impact of a specific earthquake event on sediment export, we analyzed daily variations in suspended sediment concentrations of 10 subcatchments, five years before and after an earthquake of Mw= 7.4 that affected the Vrancea region in 1977 and triggered a substantial number of landslides. Only one catchment showed a clear (3-fold) increase in sediment concentrations at unit discharge. For the other nine catchments, no consistent increase could be observed. This indicates that the impact of seismic activity on average SY is mainly indirect and not associated with sudden pulses of sediments, caused by earthquake-triggered landslides. Potential mechanisms that could explain such indirect responses are discussed. © 2014 Elsevier B.V. [less ▲]

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See detailSediment yield in Africa
Vanmaercke, Matthias ULiege; Poesen, J.; Broeckx, J. et al

in Earth-Science Reviews (2014), 136

Several studies have compiled and analysed measured contemporary catchment sediment yield (SY, [tkm-2 y-1]) values for various regions of the world. Although this has significantly contributed to our ... [more ▼]

Several studies have compiled and analysed measured contemporary catchment sediment yield (SY, [tkm-2 y-1]) values for various regions of the world. Although this has significantly contributed to our understanding of SY, Africa remains severely underrepresented in these studies. The objective of this article is therefore: (1) to review and compile available SY data for Africa; (2) to explore the spatial variability of these SY data; and (3) to examine which environmental factors explain this spatial variability. A literature review resulted in a dataset of SY measurements for 682 African catchments from 84 publications and reports, representing more than 8340 catchment-years of observations. These catchments span eight orders of magnitude in size and are relatively well spread across the continent. A description of this dataset and comparison with other SY datasets in terms of spatial and temporal distribution and measurement quality is provided. SY values vary between 0.2 and 15,699tkm-2y-1 (median: 160tkm-2y-1, average: 634tkm-2y-1). The highest SY values occur in the Atlas region with SY values frequently exceeding 1000tkm-2y-1. Also the Rift region is generally characterised by relatively high SY values, while rivers in Western and Central Africa have generally low SY values. Spatial variation in SY at the continental scale is mainly explained by differences in seismic activity, topography, vegetation cover and annual runoff depth. Other factors such as lithology, catchment area or reservoir impacts showed less clear correlations. The results of these analyses are discussed and compared with findings from other studies. Based on our results, we propose a simple regression model to simulate SY in Africa. Although this model has a relatively low predictive accuracy (40%), it simulates the overall patterns of the observed SY values well. Potential explanations for the unexplained variance are discussed and suggestions for further research that may contribute to a better understanding of SY in Africa are made. © 2013 Elsevier B.V. [less ▲]

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See detailCorrigendum to "Scale-dependency of sediment yield from badland areas in Mediterranean environments" (Progress in Physical Geography 35 (3) (2011) 297-332)
Nadal-Romero, E.; Martínez-Murillo, J. F.; Vanmaercke, Matthias ULiege et al

in Progress in Physical Geography (2014), 38(3), 381-386

[No abstract available]

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See detailCorrigendum to "Predicting soil erosion and sediment yield at regional scales: Where do we stand?" [Earth-Sci. Rev. 127 (2013) 16-29]
De Vente, J.; Poesen, J.; Verstraeten, G. et al

in Earth-Science Reviews (2014), 133

[No abstract available]

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See detailModerate seismic activity affects contemporary sediment yields
Vanmaercke, Matthias ULiege; Kettner, A. J.; van Den Eeckhaut, M. et al

in Progress in Physical Geography (2014), 38(2), 145-172

Current models aiming to simulate contemporary sediment yield (SY) implicitly assume that tectonic effects are either irrelevant or are reflected by catchment topography. In this study we analyse the ... [more ▼]

Current models aiming to simulate contemporary sediment yield (SY) implicitly assume that tectonic effects are either irrelevant or are reflected by catchment topography. In this study we analyse the relation between SY and seismic activity, a component of tectonic processes. Results show a spatial correlation between SY and seismic activity expressed as the estimated peak ground acceleration (PGA) with a 10% exceedance probability in 50 years. PGA has a significant impact on the spatial variation of SY, even after correcting for cross-correlations with topography, lithology or other factors that may influence SY. Based on three distinct data sets, we demonstrate that this effect is significant both for small catchments in Europe (0.3-3940 km2) and for large river systems worldwide (1580-6.15×106 km2) and that seismic activity may be even more important for explaining regional variation in SY than land use or many other commonly considered factors (e.g. catchment area, climate). We show that explicitly considering seismic activity may lead to SY-estimates that easily deviate a factor 2 or more compared to estimates that do not consider seismic activity. This is not only the case for highly seismically active regions: also in regions with a weak to moderate seismic regime seismic activity helps explaining regional patterns in SY. We argue that these findings have important implications for a better understanding of SY and its sensitivity to human impacts, as well as for our comprehension of sediment fluxes at longer timescales. © The Author(s) 2014. [less ▲]

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See detailImpact of earthquake-triggered landslides on catchment sediment yield
Vanmaercke, Matthias ULiege; Obreja, F.; Poesen, J. et al

in IAHS-AISH Proceedings and Reports (2014), 367

This study explores the role of seismic activity in explaining spatial and temporal variation in sediment export from the Siret basin in Romania. Based on long-term (>30 years) sediment export ... [more ▼]

This study explores the role of seismic activity in explaining spatial and temporal variation in sediment export from the Siret basin in Romania. Based on long-term (>30 years) sediment export measurements for 38 subcatchments, we found that spatial variation in sediment yield (SY) is strongly correlated to the degree of seismic activity and catchment lithology. Combined, these factors explain 80% of the variation in SY. To investigate the role of earthquake-triggered landslides in explaining these correlations, we studied the temporal variability in sediment concentrations before and after the 7.4 Mw earthquake of 1977 for ten subcatchments. Despite the fact that this earthquake triggered many landslides, only one subcatchment showed a clear (3-fold) increase in sediment concentration per unit discharge after the earthquake. This shows that, although prolonged seismic activity strongly controls average SY, individual earthquakes do not necessarily affect sediment export at short timescales. Copyright © 2014 IAHS Press. [less ▲]

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See detailSpatial and temporal variability of river flows in the degraded semi-arid tropical mountains of northern Ethiopia
Zenebe, A.; Vanmaercke, Matthias ULiege; Poesen, J. et al

in Zeitschrift für Geomorphologie (2013), 57(2), 143-169

Water availability has for long been a critical issue in many developing countries. Despite its enormous potential of water resources, Ethiopia is suffering from a lack of water availability and ... [more ▼]

Water availability has for long been a critical issue in many developing countries. Despite its enormous potential of water resources, Ethiopia is suffering from a lack of water availability and threatened by the consequences of climate change. Well-considered planning to develop these resources is crucial. However, very few observational runoff data exist for this type of environments. Especially runoff data for catchments at the intermediate scale (100- 10,000 km2) are lacking. This study assesses the runoff from 10 medium-sized catchments in the Geba river basin, a subcatchment of the Nile in the semi-arid degraded northern Ethiopian highlands. Flow depth records were automatically obtained every 10 minutes during the rainy seasons (July-September) of 2004-2007 and converted to continuous runoff discharge records. Cumulative annual runoff depths (46-395 mm) are mainly correlated with rainfall depth. Estimated runoff coefficients (9-47%) and are negatively correlated with the areal fraction of limestone outcrops in the catchments, indicating runoff transmission losses. Throughout the rainy season, increases in runoff depth and runoff coefficient were observed, which is partly attributed to an increase in baseflow throughout the season. The majority of the runoff occurs during flash floods, i. e. relatively short runoff events with often very high peak discharges. Characteristics of these floods are discussed with some examples, including an exceptionally large flood. Taking into account the difficult conditions for river discharge measurements, this study provides one of the most comprehensive analyses so far of the magnitude and dynamics of river discharges in Ethiopia. © 2012 Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany. [less ▲]

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See detailPredicting soil erosion and sediment yield at regional scales: Where do we stand?
De Vente, J.; Poesen, J.; Verstraeten, G. et al

in Earth-Science Reviews (2013), 127

Assessments of the implications of soil erosion require quantification of soil erosion rates (SE) and sediment yield (SSY) at regional scales under present and future climate and land use scenarios. A ... [more ▼]

Assessments of the implications of soil erosion require quantification of soil erosion rates (SE) and sediment yield (SSY) at regional scales under present and future climate and land use scenarios. A range of models is available to predict SE and SSY, but a critical evaluation of these models is lacking. Here, we evaluate 14 models based on 32 published studies and over 700 selected catchments. Evaluation criteria include: (1) prediction accuracy, (2) knowledge gain on dominant soil erosion processes, (3) data and calibration requirements, and (4) applicability in global change scenario studies. Results indicate that modelling of SE and SSY strongly depends on the spatial and temporal scales considered. In large catchments (>10,000km2), most accurate predictions of suspended sediment yield are obtained by nonlinear regression models like BQART, WBMsed, or Pelletier's model. For medium-sized catchments, best results are obtained by factorial scoring models like PSIAC, FSM and SSY Index, which also support identification of dominant erosion processes. Most other models (e.g., WATEM-SEDEM, AGNPS, LISEM, PESERA, and SWAT) represent only a selection of erosion and sediment transport processes. Consequently, these models only provide reliable results where the considered processes are indeed dominant. Identification of sediment sources and sinks requires spatially distributed models, which, on average, have lower model accuracy and require more input data and calibration efforts than spatially lumped models. Of these models, most accurate predictions with least data requirements were provided by SPADS and WATEM-SEDEM. Priorities for model development include: (1) simulation of point sources of sediment, (2) balancing model complexity and the quality of input data, (3) simulation of the impact of soil and water conservation measures, and (4) incorporation of dynamic land use and climate scenarios. Prediction of the impact of global change on SE and SSY in medium sized catchments is one of the main challenges in future model development. No single model fulfils all modelling objectives; a further integration of field observations and different model concepts is needed to obtain better contemporary and future predictions of SE and SSY. © 2013 Elsevier B.V. [less ▲]

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See detailEffects of land use, slope gradient, and soil and water conservation structures on runoff and soil loss in semi-arid Northern Ethiopia
Taye, G.; Poesen, J.; Wesemael, B. V. et al

in Physical Geography (2013), 34(3), 236-259

Land degradation and recurrent drought are the major threats to rain-fed agriculture in the semi-arid Ethiopian highlands. Water harvesting has become a priority in the Tigray region since 1990. However ... [more ▼]

Land degradation and recurrent drought are the major threats to rain-fed agriculture in the semi-arid Ethiopian highlands. Water harvesting has become a priority in the Tigray region since 1990. However, the success of water harvesting in reservoirs is limited due to reduced inflow. The aim of this study was to investigate the effects of typical land-use types, slope gradients, and different soil and water conservation (SWC) structures on runoff and soil loss at the runoff-plot scale. Six runoff measuring sites, corresponding to three slope gradients, were established for cropland (cultivated land for annual crop production) and rangeland (heavily grazed land on hillslopes with high rock-fragment cover) at Mayleba catchment in Tigray, Ethiopia. SWC structures tested were stone bunds, trenches, and stone bunds with trenches, in addition to control plots. In total, 21 large runoff plots (with lengths of 60 to 100 m) were monitored daily for runoff production and soil loss during the main rainy season (July-September) in 2010. The results show that the seasonal runoff coefficient (RCs) representing the fraction of rainfall measured as runoff was much higher for rangeland (0.38 < RCs < 0.50) compared to that for cropland (0.11 < RCS < 0.15). Seasonal soil loss (SLs) values were five to six times larger on rangeland (28.6 < SLs < 50.0 ton ha-1) compared to that for cropland (4.6 < SLs < 11.4 ton ha-1). Stone bunds with trenches were the most effective SWC structures in reducing runoff and soil loss. With the same SWC structures installed, RCs and SLs for both rangeland and cropland tend to decrease with increasing slope gradient mainly due to a corresponding increase in rock-fragment cover. The effects of SWC structures on runoff production and soil loss are considerable; hence, it is crucial to consider these effects for optimal design of water-harvesting schemes such as micro-dams that collect and store surface runoff for irrigation development in the Ethiopian highlands. © 2013 Taylor & Francis Group, LLC. [less ▲]

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See detailHow effective are soil conservation techniques in reducing plot runoff and soil loss in Europe and the Mediterranean?
Maetens, W.; Poesen, J.; Vanmaercke, Matthias ULiege

in Earth-Science Reviews (2012), 115(1-2), 21-36

The effects of soil and water conservation techniques (SWCTs) on annual runoff (R a), runoff coefficients (RC a) and annual soil loss (SL a) at the plot scale have been extensively tested on field runoff ... [more ▼]

The effects of soil and water conservation techniques (SWCTs) on annual runoff (R a), runoff coefficients (RC a) and annual soil loss (SL a) at the plot scale have been extensively tested on field runoff plots in Europe and the Mediterranean. Nevertheless, a comprehensive overview of these effects and the factors controlling the effectiveness of SWCTs is lacking. Especially the effectiveness of SWCT in reducing R a is poorly understood. Therefore, an extensive literature review is presented that compiles the results of 101 earlier studies. In each of these studies, R a and SL a was measured on field runoff plots where various SWCTs were tested. In total, 353 runoff plots (corresponding to 2093 plot-years of data) for 103 plot-measuring stations throughout Europe and the Mediterranean were considered. SWCTs include (1) crop and vegetation management (i.e. cover crops, mulching, grass buffer strips, strip cropping and exclosure), (2) soil management (i.e. no-tillage, reduced tillage, contour tillage, deep tillage, drainage and soil amendment) and (3) mechanical methods (i.e. terraces, contour bunds and geotextiles). Comparison of the frequency distributions of SL a rates on cropland without and with the application of SWCTs shows that the exceedance probability of tolerable SL a rates is ca. 20% lower when SWCT are applied. However, no notable effect of SWCTs on the frequency distribution of RC a is observed. For 224 runoff plots (corresponding to 1567 plot-year data), SWCT effectiveness in reducing R a and/or SL a could be directly calculated by comparing measured R a and/or SL a with values measured on a reference plot with conventional management. Crop and vegetation management techniques (i.e. buffer strips, mulching and cover crops) and mechanical techniques (i.e. geotextiles, contour bunds and terraces) are generally more effective than soil management techniques (i.e. no-tillage, reduced tillage and contour tillage). Despite being generally less effective, no-tillage, reduced tillage and contour tillage have received substantially more attention in the literature than the other SWCTs. Soil and water conservation techniques are generally less effective in reducing R a than in reducing SL a, which is an important consideration in areas where water is a key resource and in regions susceptible to flooding. Furthermore, all SWCTs show a more consistent and effective reduction of both R a and SL a with increasing R a and SL a magnitude, which is attributed to the reduced influence of measurement uncertainties. Although some significantly negative correlations between SWCT effectiveness and plot slope length, slope gradient or annual precipitation were found, the importance of these factors in explaining the observed variability in effectiveness seems limited. Time-series analyses of R a during multiple years of SWCT application strongly indicate that no-tillage and conservation tillage become less effective in reducing R a over time. Such an effect is not observed for SL a. © 2012 Elsevier B.V. [less ▲]

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See detailHow long should we measure? An exploration of factors controlling the inter-annual variation of catchment sediment yield
Vanmaercke, Matthias ULiege; Poesen, J.; Radoane, M. et al

in Journal of Soils and Sediments (2012), 12(4), 603-619

Purpose: Although it is well-known that catchment suspended sediment yields (SY; tons per square kilometre per year) can vary significantly from year to year, little information exists on the magnitude ... [more ▼]

Purpose: Although it is well-known that catchment suspended sediment yields (SY; tons per square kilometre per year) can vary significantly from year to year, little information exists on the magnitude and factors controlling this variability. This is crucial to assess the reliability of average SY values for a given measuring period (MP) and is of great geomorphic significance. This paper aims to bridge this research gap. Materials and methods: A worldwide database was compiled with time series of measured SY values. Data from 726 rivers (mostly located in Europe, the Middle East and the USA) were collected, covering 15,025 annual SY observations. The MPs ranged between 7 and 58 years, while catchment areas (A) ranged between 0.07 and 1.84 × 106 km2. For 558 catchments, the annual runoff depths corresponding to the SY observations were also available. Based on this database, inter-annual variability was assessed for each catchment, and relationships with factors potentially explaining this variability were explored. Results and discussion: Coefficients of variation of SY varied between 6% and 313% (median 75%). Annual SY data were generally not normally distributed but positively skewed. Inter-annual variability generally increased with increasing average SY. No significant relationship was found between the inter-annual variability of SY and A, while weak but significant relationships were noted with the variability in annual runoff and rainfall depths. Detailed analyses of a sub-dataset corresponding to 63 catchments in Romania revealed no clear relationships between inter-annual variability of SY and land-use or topographic characteristics. Nevertheless, indications were found that variability was larger for catchments with erosion-prone land-use conditions. Using a Monte Carlo simulation approach, the effect of inter-annual variability on the reliability of average SY data was assessed. Results indicate that uncertainties are very large when the MP is short, with median relative errors ranging between -60% and 83% after 5 years of monitoring. Furthermore, average SY values based on short MPs have a large probability to underestimate, rather than to overestimate, the long-term mean. For instance, the SY value of a median catchment after a 1-year MP has a 50% probability of underestimating the long-term mean by about 22%. Uncertainties quickly decrease after the first few years of measurement but can remain considerable, even after 50 years of monitoring. Conclusions: It is important to consider uncertainties associated with average SY values due to inter-annual variability, for example when attempting to predict long-term average SY values using a steady-state model, as such uncertainties put fundamental limits to the predictive capabilities of such models. © 2012 Springer-Verlag. [less ▲]

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See detailA comparison of measured catchment sediment yields with measured and predicted hillslope erosion rates in Europe
Vanmaercke, Matthias ULiege; Maetens, W.; Poesen, J. et al

in Journal of Soils and Sediments (2012), 12(4), 586-602

Purpose: This study aims to understand better the relationship between measured soil loss rates due to sheet and rill erosion (SL), predicted SL rates and measured catchment sediment yields (SY) in Europe ... [more ▼]

Purpose: This study aims to understand better the relationship between measured soil loss rates due to sheet and rill erosion (SL), predicted SL rates and measured catchment sediment yields (SY) in Europe. Materials and methods: Analyses were based on a recently established database of measured annual SY for 1794 catchments, a database of 777 annual SL rates measured on runoff plots and two recent maps of predicted sheet and rill erosion rates in Europe (i. e. one based on empirical extrapolations of measured SL data and one based on the PESERA model). To identify regional trends, all data were grouped into eight climatic zones. Results and discussion: Measured SL rates are generally a factor of five to ten times larger than predicted SL rates and are strongly biased towards erosion-prone situations in terms of land use. Also measured SY are generally higher than predicted SL rates, especially in the Mediterranean and Alpine regions where SY is generally ten times higher than predicted SL rates. This illustrates the importance of other erosion processes contributing to SY. Regional differences in the importance of these processes and their implications are discussed. Conclusions: This study confirms previous findings indicating the relatively low sheet and rill erosion rates compared to SY in the Mediterranean region and illustrates the importance of other erosion processes contributing to SY in most regions of Europe. This indicates that hillslope erosion rates cannot be used directly to estimate SY, and consequently soil conservation programmes should focus more on the dominant erosion processes in each catchment. © 2012 Springer-Verlag. [less ▲]

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See detailEffects of land use on annual runoff and soil loss in Europe and the Mediterranean: A meta-analysis of plot data
Maetens, W.; Vanmaercke, Matthias ULiege; Poesen, J. et al

in Progress in Physical Geography (2012), 36(5), 599-653

The largest currently compiled database of plot runoff and soil loss data in Europe and the Mediterranean was analysed to investigate effects of land use on annual soil loss (SL), annual runoff (R) and ... [more ▼]

The largest currently compiled database of plot runoff and soil loss data in Europe and the Mediterranean was analysed to investigate effects of land use on annual soil loss (SL), annual runoff (R) and annual runoff coefficient (RC). This database comprises 227 plot-measuring sites in Europe and the Mediterranean, with SL for 1056 plots (PL) representing 7024 plot-years (PY) and R for 804 PL representing 5327 PY. Despite large data variability, continental-wide trends are observed. Construction sites have the highest mean annual RC (57%) and SL (325 Mg.ha -1.yr -1). Bare soil, vineyards and tree crops have high mean annual RC (5-10%) and SL (10-20 Mg.ha -1.yr -1). Cropland and fallow show similar mean annual RC (8.0 and 7.3%), but lower SL (6.5 and 5.8 Mg.ha -1.yr -1). Plots with (semi-)natural vegetation cover show lowest mean annual RC (<5%) and SL (<1 Mg.ha -1.yr -1). Plot length and slope gradient correlations with R and SL depend on land-use type and are not concurrent for R and SL. Most land-use types show positive correlations between annual R and SL. Plots in cold climates have higher annual RC than plots in temperate and pan-Mediterranean climates. Annual SL in the pan-Mediterranean is less than in temperate zones, due to stony or clayey soils having a low erodibility. Annual RC in the pan-Mediterranean was higher than in temperate zones. Annual R increases strongly with increasing annual precipitation (P) above 500 mm.yr -1, while annual SL was found to stabilize at P > 500 mm.yr -1. For shrubland, annual SL was found to decrease for P > 250-500 mm.yr -1, which is attributed to an accompanying increase in vegetation cover. However, no such trend was found for R. The results allow a rapid assessment of the impact of land-use changes on annual R, RC and SL, based on field-measured plot data. © The Author(s) 2012. [less ▲]

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See detailSeismic activity controls spatial variability of contemporary sediment yields
Vanmaercke, Matthias ULiege; Kettner, Albert; Van Den Eeckhaut, Miet et al

in Morphoevolution of tectonically active belts (Proceedings of the IAG 16th Geomorphological Meeting, Rome, Italy, July 1-5 2012) (2012)

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See detailImpacto local y regional de la degradación del suelo sobre los recursos de suelo y agua: importancia de la escala y modelos de predicción
de Vente, Joris; Govers, Gerard; Vanmaercke, Matthias ULiege et al

in Ortiz Silla, R.; Sánchez Navarro, A. (Eds.) Control de la degradación y uso sostenible del suelo. V Simposio nacional sobre control de la degradación y uso sostenible del suelo (2011)

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See detailScale effects on sediment yield from badland areas in Mediterranean environments
Martínez-Murillo, Juan Francisco; Nadal-Romero, Estela; Vanmaercke, Matthias ULiege et al

in Landform Analysis (2011), 17

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See detailFactors controlling sediment yield at the catchment scale in NW Mediterranean geoecosystems
de Vente, J.; Verduyn, R.; Verstraeten, G. et al

in Journal of Soils and Sediments (2011), 11(4), 690-707

Purpose: This study aimed to (1) increase understanding of the relation between sediment yield and environmental variables at the catchment scale; (2) test and validate existing and newly developed ... [more ▼]

Purpose: This study aimed to (1) increase understanding of the relation between sediment yield and environmental variables at the catchment scale; (2) test and validate existing and newly developed regression equations for prediction of sediment yield; and (3) identify how better predictions may be obtained. Materials and methods: A correlation and regression analysis was performed between sediment yield and over 40 environmental variables for 61 Spanish catchments. Variables were selected based on availability and expected relation with diverse soil erosion and sediment transport processes. For comparison, the Area Relief Temperature (ART) sediment delivery model was applied to the same catchments. Sediment yield estimates obtained from reservoir surveys were used for model calibration and validation. Results and discussion: Catchment area, catchment perimeter, stream length, relief ratio, Modified Fournier Index, the RUSLE's R factor, and catchments percentage with poor vegetation cover showed highest correlations with sediment yield. Stepwise linear regression revealed that variables representing topography, climate, vegetation, lithology, and soil characteristics are required for the best prediction equation. Although calibration results were relatively good, validation showed that the models were unstable and not suitable for extrapolation to other catchments. Reasons for this unstable model performance include (1) lack of detail and quality of the data sources; (2) large variation in catchment characteristics; (3) insufficient representation of all relevant erosion and sediment transport processes; and (4) the presence of nonlinear relations between sediment yield and environmental variables. The nonlinear ART model performed relatively well but systematically overpredicted sediment yield. A model reflecting human impacts, including dams and conservation measures, is expected to provide better results. This, however, requires significantly more input data. Conclusions: Although important insight is obtained into the relation between sediment yield and environmental factors, prediction of sediment yield at the catchment scale requires alternative approaches. More detailed information is required on land cover (change), and the effect of soil conservation measures. Validation of regression equations is a necessity, and better predictions are obtained by nonlinear models. © 2011 Springer-Verlag. [less ▲]

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See detailSediment yield in Europe: Spatial patterns and scale dependency
Vanmaercke, Matthias ULiege; Poesen, J.; Verstraeten, G. et al

in Geomorphology (2011), 130(3-4), 142-161

Our understanding about the regional variation of Sediment Yield (SY) in Europe and its scale dependency currently relies on a limited number of data for mainly larger river systems. SY is the integrated ... [more ▼]

Our understanding about the regional variation of Sediment Yield (SY) in Europe and its scale dependency currently relies on a limited number of data for mainly larger river systems. SY is the integrated result of all erosion and sediment transporting processes operating in a catchment and is therefore of high value for environmental studies and monitoring purposes. Most global assessments of SY consider catchment area (A), climate and topography as the main explanatory variables. However, it is still unclear if these factors also control regional variations of SY within Europe. This paper aims at bridging this gap. Therefore, we i) present a large database of SY-values which was constructed through an extensive literature review; ii) describe the spatial patterns of SY across Europe; and iii) explore its relation with A, climate, and topography.In total, sediment yield data from 1794 different locations throughout Europe were collected (507 reservoirs and 1287 gauging stations), representing a minimum of 29,203 catchment-year data. Only SY-data measured at gauging stations or derived from reservoir siltation rates over a period of a minimum of one year were included in the database. This database comprises a large range of catchment areas (A): i.e from small upland catchments (≥ 0.01. km2) to major European river basins (≤1,360,000. km2). An overview of the collected SY-data is provided and sources of uncertainty on the available data are discussed.Despite potentially large uncertainties on several of the individual SY-values, analysis of this database indicates clear spatial patterns of SY in Europe. The temperate and relatively flat regions of Western, Northern and Central Europe generally have relatively low SY-values (with ca. 50% of the SY<40tkm-2yr-1 and ca. 80% of the data <200tkm-2yr-1), while Mediterranean and Mountainous regions generally have higher SY-values (with around 85% of the SY-data >40tkm-2yr-1 and more than 50% of the data >200tkm-2yr-1). These differences are attributed to a combination of factors, such as differences in climate, topography, lithology and land use. Although larger differences in SY were found between the climatic regions than between topographic zones, it is currently difficult to identify the individual importance of the various controlling factors of SY. SY-A relationships were calculated for the entire dataset and for subgroups stratified according to the measurement method (gauging stations or reservoir surveys), range of the catchment area, climatic region, topographic zone of the river outlet, and major European river system. Although typically a negative relationship between SY and A is expected due to a decrease in topsoil erosion rates on more gentle slopes and an increase in sediment deposition with an increase in catchment size, this relationship was found to be generally very weak and subject to a lot of scatter. Furthermore, results illustrate important differences in scale dependency: whereas a weak but significant negative trend is generally observed for the temperate and relatively flat regions, no significant or even positive trends were observed in mountain regions and Mediterranean Europe. When only larger river catchments (i.e. > 100. km2 and especially >10,000. km2) are considered, catchment area exerted a larger control on SY. These findings confirm previous studies and indicate that the relationship between SY, spatial scale and other controlling factors is often complex and non-linear. © 2011 Elsevier B.V. [less ▲]

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See detailScale-dependency of sediment yield from badland areas in Mediterranean environments
Nadal-Romero, E.; Martínez-Murillo, J. F.; Vanmaercke, Matthias ULiege et al

in Progress in Physical Geography (2011), 35(3), 297-332

While much attention has been given to erosion processes in badlands, an integrated analysis of sediment production and export rates in badland areas at various spatial scales is currently lacking. This ... [more ▼]

While much attention has been given to erosion processes in badlands, an integrated analysis of sediment production and export rates in badland areas at various spatial scales is currently lacking. This study reviews area-specific sediment yield (SY) from badlands in the Mediterranean measured at different spatial scales, using various measuring techniques, in order to investigate the relationship between size of study area (A) and SY. A database representing 16 571 plot-year and catchment-year data on SY at 87 Mediterranean study sites was compiled. The most commonly reported lithologies associated with badlands are marls, clay rocks and mudstones, and to a lesser extent shales. A high variability of SY from badlands in the Mediterranean region is observed. The relation between A and SY for Mediterranean environments with badlands is significantly different from that reported for Mediterranean environments without badlands. A complex A-SY relationship is identified: for areas < 10 ha, SY is very high (mean SY=475 t ha-1 y-1), whereas for areas > 10 ha, SY decreases non-linearly (power law) with increasing A (mean SY=75 t ha-1 y-1 and drops from 164.5 t ha-1 y-1 for 10 ha <A<200 ha to 9.3 t ha-1 y-1 for A > 100 000 ha). This difference is explained by several factors. For A < 10 ha there is little or no sediment storage within badland areas, while for A > 10 ha progressively more sediment can be trapped in different sinks. Further, for A > 10 ha, area-specific erosion rates do not increase (or even decrease) due to decreasing average hillslope gradients and a decreasing fraction of erosion-prone (bare/badland) area. No significant relationships between SY, lithology, and mean air temperature nor mean annual precipitation were observed. © The Author(s) 2011. [less ▲]

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