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

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Land degradation and recurrent drought are the major threats to rain-fed agriculture in the semiarid Ethiopian highlands. To reduce the risk of crop failure induced by moisture stress and to bring food self sufficiency through irrigation, water harvesting has become a priority in theGebeyehu Taye, Poesen, J., Van Wesemael, B., Vanmaercke, M., Daniel Teka, Deckers, J., Goosse, T., Maetens, W., Nyssen, J., Hallet, V., Nigussie Haregeweyn, 2013. Effects of land use, slope gradient, and soil and water conservation structures on runoff and soil loss in semi-arid northern Ethiopia. Physical Geography, 34(3), 236-259.2

Soil erosion is often regarded as one of the main processes of desertification. This has lead 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, t km -2 y -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.

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.2 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 10 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 10 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.

Compared with surface soil erosion by water, subsurface erosion (piping) is generally less studied and harder to quantify. However, wherever piping occurs, it is often a significant or even the main sediment source. In this study, the significance of soil loss due to piping is demonstrated through an estimation of soil volume lost from pipes and pipe collapses (n = 560) in 137 parcels under pasture on loess-derived soils in a temperate humid climate (Belgium). Assuming a period of 5 to 10 years for pipe collapse to occur, mean soil loss rates of 2.3 and 4.6 t ha −1 yr −1 are obtained, which are at least one order of magnitude higher than surface erosion rates (0.01-0.29 t ha −1 yr −1 ) by sheet and rill erosion under a similar land use. The results obtained for the study area in the Flemish Ardennes correspond well to other measurements in temperate environments; they are, however, considerably smaller than soil loss rates due to subsurface erosion in semi-arid environments. Although local slope gradient and drainage area largely control the location of collapsed pipes in the study area, these topographic parameters do not explain differences in eroded volumes by piping. Hence, incorporation of subsurface erosion in erosion models is not straightforward.

The effectiveness of tropical grass species in strips of different length in trapping sediment from cropland was assessed, and the influence of filter length was determined. The assessment was made under natural rainfall which induced sheet and rill erosion in run‐off plots and then using simulated run‐off which caused concentrated erosion. The evaluated grasses were elephant grass, lemon grass, paspalum and sugarcane. Run‐off plots were on a 10% slope in a randomized complete block design replicated three times. Filter lengths were 2.5, 5 and 10 m against a 10‐m‐long sediment source area planted with maize on a clay loam soil. The results show that sediment trapping effectiveness (TE) increases nonlinearly with increasing filter length for all grasses. Under natural rainfall, more than 70% of sediment was trapped in the first 5 m, and lengthening the strip to 10 m only resulted in a marginal increase in TE. With concentrated run‐off, more than 70% of sediment was trapped in the first 5 m and lengthening the strip to 10 m resulted in a significant increase in TE. Paspalum and lemon grass performed significantly better than other grasses (P < 0.05), owing to their spreading growth pattern over the soil surface. Paspalum also has the highest root density in the upper 0.3‐m layer of the soil followed by lemon grass, hence offering the greatest resistance to erosion from concentrated flow. The results demonstrate that tropical grass filter strips provide a viable means for reducing the sediment flux from cropland.

&lt;p&gt;In recent years, research on drought risk has expanded to include multiple types of drought hazards, various exposed elements and a multitude of factors that determine the vulnerability of a given system or sector. This has resulted in a call from the scientific community to adopt a systemic risk perspective on drought. However, a thorough understanding of how drought risks manifest, cascade and interact across different systems and sectors is still lacking, and methodological guidance on how to analyse and represent these interdependencies does not yet exist.&amp;#160; In order to explore these gaps, we have developed conceptual models of drought risks for key selected systems and sectors in the European Union.&amp;#160;&lt;/p&gt; &lt;p&gt;For each system and sector considered (rain fed and irrigated agricultural systems, forest ecosystems, freshwater ecosystems, public water supply, inland water transport and the energy sector), a conceptual model was constructed to depict how drivers and root causes interact to create drought risk. The models are based on the impact chains methodology and are informed by literature review and multiple expert consultations (including a series of validation workshops). Subsequently, the system-specific models were used to build an overarching conceptual model of the critical interdependencies that exist between all the systems and sectors considered.&amp;#160;&lt;/p&gt; &lt;p&gt;The analysis has revealed that, in each system, drought risks manifest through a complex web of interactions between drivers of risk, which are in part system-specific and in part shared across the systems considered. From this, multiple considerations for drought risk assessment and management can be derived. In particular, special attention should be placed in defining and representing what drought risk is in each system, as the underlying characteristics might greatly differ. Additionally, the use of conceptual models can constitute an important first step for risk assessment, as they contribute to addressing the complexity of drought risks. Finally, the existence of commonalities and interdependencies between systems implies that interventions can and must be designed so as to consider multiple systems at once, thus avoiding maladaptive solutions. In this sense, the conceptual models can serve as entry points for the identification of risk reduction and adaptation measures which go beyond the single-risk and single-sector perspective, thus contributing to a more systemic view on drought risk management and adaptation, as well as highlighting persisting knowledge gaps.&lt;/p&gt;