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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 ULg 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 detailSpatial and temporal variability of river flows in the degraded semi-arid tropical mountains of northern Ethiopia
Zenebe, A.; Vanmaercke, Matthias ULg; 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 detailDecadal-scale analysis of ground movements in old landslides in western Belgium
Dewitte, Olivier ULg; Van Den Eeckhaut, M.; Poesen, J. et al

in Zeitschrift für Geomorphologie (2009), 53(1), 23-45

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See detailPolyphase karst system in Cretaceous chalk and calcarenite of the Belgian-Dutch border
Willems, Luc ULg; Rodet, Joël; Fournier, Matthieu et al

in Zeitschrift für Geomorphologie (2007), 51(3), 361-376

Along the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation ... [more ▼]

Along the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation allows the reconstruction of the genesis of an original karst system resulting from the merging of initially independent endokarsts and exokarsts. Deep weathering has developed within the Cretaceous formations, creating nodes of weathered chalk and closed cavities. These phenomena are expanded over time and can form interconnected voids. Near the surface, solution pipes are generated under the coarsest deposits of a fluvial terrace capping the Cretaceous formations. These pipes develop vertically and may be related to the progressive lowering of the water table in connection with the incision of the Meuse valley. Some of these phenomena cut up the older endokarsts and organize complex systems of out-flow within the chalk. [less ▲]

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See detailAnalyse de la variabilité spatio-temporelle de la morphologie du chenal de la Warche en amont du barrage de Butgenbach (Belgique).
Assani, A. A.; Petit, François ULg; Buffin-Belanger, T. et al

in Zeitschrift für Geomorphologie (2003)

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See detailStudy of siliceous karst genesis in eastern Niger : microscopy and X ray microanalysis of speleothems
Willems, Luc; Compère, Philippe ULg; Sponholz, Barbara

in Zeitschrift für Geomorphologie (1998), 42

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See detailStudy of siliceous karst genesis in Eastern Niger. Microscopy and analysis of speleothems
Willems, Luc ULg; Compère, Philippe ULg; Sponholz, Barbara

in Zeitschrift für Geomorphologie (1998), 42(2), 129-142

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See detailPhénomènes karstiques en milieux non carbonatés. Etudes de cavités et problématique de leur développement au Niger Occidental
Willems, Luc ULg; Pouclet, André; Lenoir, François et al

in Zeitschrift für Geomorphologie (1996)

The study of several caves in siliceous formations belonging to the Precambrian basement and its Cenozoic sedimentary cover brings to the fore the importante of an underground drainage network in relation ... [more ▼]

The study of several caves in siliceous formations belonging to the Precambrian basement and its Cenozoic sedimentary cover brings to the fore the importante of an underground drainage network in relation with crustal fracturation. This network guides the waler transfer from the land surface to the depth and generates géomorphologic phenomena similar to those in calcareous areas. The study of caves in a siliceous environmemts shows the importance of solution phenomena in their formation and also in that of West Niger landscapes. Therfore, a general model of topographic evolution îs proposed. [less ▲]

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See detailPhénomène influençant la mise en mouvement et le transport des particules en rivières naturelles
Petit, François ULg

in Zeitschrift für Geomorphologie (1988)

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See detailLes surfaces d'érosion crétacique et paléogènes du nord de l'Ardenne-Eifel
Demoulin, Alain ULg

in Zeitschrift für Geomorphologie (1986), 30

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See detailSome analyses of the CO2 content of the air in five Polish caves
Ek, Camille ULg; Gilewska, S.; Kaszowski, L. et al

in Zeitschrift für Geomorphologie (1969), Neue Folge 13(3), 267-286

It is in a cave of the Silesian Upland and in four caves of the Polish Tatra Mts that some fourty analyses of CO2 in air were carried out between the 7 and the 12.4.67. CO2 content is generally very low ... [more ▼]

It is in a cave of the Silesian Upland and in four caves of the Polish Tatra Mts that some fourty analyses of CO2 in air were carried out between the 7 and the 12.4.67. CO2 content is generally very low in the studied caves, sometimes lower than in open air. The lowest figures seem related with low temperatures. [less ▲]

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