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Tammo S Steenhuis - One of the best experts on this subject based on the ideXlab platform.
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bank stability and toe erosion model as a decision tool for Gully bank stabilization in sub humid ethiopian highlands
2020Co-Authors: Assefa D. Zegeye, Tammo S Steenhuis, Eddy J Langendoen, Wolde Mekuria, Seifu A. TilahunAbstract:Abstract Gullies that are expanding at alarming rate are responsible for the majority of soil losses in the (sub) humid highlands of Ethiopia. Few affordable and effective methods for Gully erosion control are available in the highlands. The objective of the study was to develop cost-effective measures to halt Gully expansion by determining stable-bank conditions under a variety of environmental situations using the Bank Stability and Toe Erosion Model (BSTEM). The study was carried out in the sub humid Debre Mawi watershed, located 30 km south of Lake Tana. Input data for the BSTEM model were collected using field surveys and soil sampling. After the BSTEM was tested on actual measured soil data, soil cohesion and internal friction angle were calibrated against observed Gully bank retreat. Using the calibrated parameters, the model evaluated the stabilization of the existing Gully bank under different scenarios in which groundwater table, bank angle and bank height, tension crack depth, vegetation, and toe protection were varied. Finally, the head-cut of the study Gully was treated based on the model recommendation. The simulated results showed that a 5 m deep Gully was stable under fully saturated conditions when the bank toe is protected, its upper surface is vegetated, and its bank angles do not exceed 45°. If the depth of the Gully is less than 5 m or if its water table is deeper than 0.5 m, only regrading the Gully bank to an angle of 45° can stabilize the Gully. BSTEM showed to be an effective tool that can be used to evaluate Gully control measures.
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Gully head retreat in the sub humid ethiopian highlands the ene chilala catchment
2017Co-Authors: Meseret B Addisie, Seifu A. Tilahun, Assefa D. Zegeye, Tammo S Steenhuis, Eddy J Langendoen, Getaneh K Ayele, Azalu A Gessess, M M Moges, Petra SchmitterAbstract:In the northern highlands of Ethiopia, Gully erosion is severe. Despite many efforts to implement Gully prevention measures, controlling Gully erosion remains a challenge. The objective is to better understand the regional Gully erosion processes and to prevent Gully head retreat. The study was conducted in the Ene-Chilala catchment in the sub-humid headwaters of the Birr River located southwest of Bahir Dar, Ethiopia. Twelve Gully heads were monitored during the 2014 and 2015 rainy monsoon phase. We measured Gully head morphology and retreat length, soil shear strength, ground water table levels and catchment physical characteristics. Two active Gully head cuts were treated in 2014 and an additional three head cuts in 2015 by regrading their slope to 45 degrees and covering them with stone riprap. These treatments halted the Gully head advance. The untreated gullies were actively eroding due to groundwater at shallow depths. The largest head retreat was 22.5 m, of which about half occurred in August of the first year when the surrounding soil was fully saturated. Lowering both the water table and protecting the Gully heads can play a key role in reducing Gully expansion and soil loss due to Gully erosion in the Ethiopian highlands.
Verstraete H. - One of the best experts on this subject based on the ideXlab platform.
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Monitoring van kustbroedvogels in de SBZ-V ‘Kustbroedvogels te Zeebrugge-Heist’ en de westelijke voorhaven van Zeebrugge tijdens het broedseizoen 2018
2019Co-Authors: Stienen E., Courtens W., Van De Walle, M., Vanermen N., Verstraete H.Abstract:This report describes the fluctuations in the numbers of breeding pairs in the Special Protected Area under the Bird Directive ‘Kustbroedvogels te Zeebrugge-Heist’ and in the adjacent western port of Zeebrugge during the period 1985-2017. Until recently, this was by far the most important breeding site for coastal breeders in Belgium and of high importance (> 1% of the biogeographic population) for the European tern populations as a whole. The conservation targets that were set in 2004 (being 22 ha of suitable nesting habitat without significant impact by land predators) for terns breeding in the Special Protected Area were never met since. The populations of the 3 tern species (Sandwich, Common and Little Tern) and of Black-headed Gulls breeding in the Special Protected Area have strongly declined after 2008 and the reproductive output has been extremely poor ever since. The decline is due to the presence of land predators, initially cats and rats, and from 2009 onwards also fox. The maximum number of breeding pairs amounted to respectively 4,067, 3,052 and 425 for Sandwich, Common and Little Tern,, but in 2016 these species no longer bred in the SPA. In 2017, fox was not present and the area again attracted Common Terns, although in lower numbers than before. In 2018, the SPA hosted 560 pairs of Common Tern, 23 pairs of Little Tern, 52 pairs of Black-headed Gull and 2 pairs of Mediterranean Gull, next to 60 pairs of Herring Gull and 354 pairs of Lesser Black-backed Gull. Considering the SPA conservation targets, the nests of the latter two species were systematically cleared. About 60% of the tern population chose to breed in the areas that were electrically fenced to prevent fox predation and disturbance. Eventually almost all tern chicks outside the fence were predated by fox, leading to a poor breeding success of Common Terns of 0.2 fledglings per pair. Inside the electric fence breeding success was not measured, but seemed somewhat higher. Also, in the non-protected western part of the Zeebrugge port, breeding numbers are in strong decline due to fox disturbance and predation and deterioration of the habitat. This area used to host large numbers of Herring Gulls (max 2,433 pairs in 2010) and Lesser Black-backed Gulls (max 4,760 pairs in 2011), but after 2013 both species strongly decreased in numbers as foxes frequented the breeding site. In 2018, 375 pairs of Herring Gull and 852 pairs of Lesser Black-backed Gull bred in the western part of the port, all on fox-free rooftops or in electrically fenced areas. The total population in Zeebrugge (SBZ-V included) amounted to 472 and 1,390 pairs, respectively. After 2013 the numbers of Herring and Lesser Black-backed Gull have increased elsewhere in Flanders and especially along the coast the number of breeding sites is rapidly growing. This suggests that part of the Zeebrugge colony has moved to both new and existing breeding sites. Indeed, recoveries of colour-ringed individuals revealed that there is a strong connection between Zeebrugge and other breeding sites along the Flemish coast. Other ringed gulls moved to existing colonies in the north of France, the south of the Netherlands and the south-east of the UK. Colour ring sightings further suggest that the gulls that colonised the SBZ-V most likely originate from the western part of the Zeebrugge port
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Monitoring van kustbroedvogels in de SBZ-V ‘Kustbroedvogels te Zeebrugge-Heist’en de westelijke voorhaven van Zeebrugge tijdens het broedseizoen 2017
2018Co-Authors: Stienen E., Courtens W., Van De Walle, M., Vanermen N., Daelemans R., Verstraete H.Abstract:This report describes the fluctuations in the numbers of breeding pairs in the Special Protected Area under the Bird Directive ‘Kustbroedvogels te Zeebrugge‐Heist’ and in the adjacent western port of Zeebrugge during the period 1985‐2017. Until recently, this was by far the most important breeding site for coastal breeders in Belgium and of high importance for the European tern populations as a whole. The conservation targets that were set in 2004 (being 22 ha of suitable nesting habitat without significant impact by land predators) for terns breeding in the Special Protected Area were never met since.The populations of the 3 tern species (Sandwich, Common and Little Tern) and of Black‐headed Gulls breeding in the Special Protected Area have strongly declined after 2008 and the reproductive output was extremely poor. The decline is due to the presence of land predators, initially cats and rats, and from 2009 onwards also fox. The maximum number of breeding pairs amounted to 4,067, 3,052 and 425 for Sandwich, Common and Little Tern, respectively, but in 2016 these species no longer bred in the SPA. In 2017 fox was no longer present and the area again hosted 576 pairs of Common Tern, 21 pairs of Lesser Black‐backed Gull, 1 pair of Mediterranean Gull, 2 pairs of Kentish Plover , 12 pairs of Ringed Plover and 16 pairs of Oystercatcher. The SPA also attracted 114 pairs of Lesser Black‐backed and 44 pairs of Herring Gulls that were actively chased away in the nearby western part of the Zeebrugge port. Some of them developed into specialised predators of Common Tern leading to a reproductive output of only 0.1 fledged chick per pair.Also in the non‐protected western part of the Zeebrugge port, breeding numbers are in strong decline due to fox disturbance and predation, and loss of breeding grounds and deterioration of the habitat. Crested Lark, Northern Wheatear, Mediterranean Gull and Yellow‐legged Gull used to breed in small numbers, but these species were no longer present in 2016. This area used to host large numbers of Herring Gulls (max 2,433 pairs in 2010) and Lesser Black‐backed Gulls (max 4,760 pairs in 2011), but both species strongly decreased in numbers as fox frequented the breeding site after 2013. In 2017, 516 pairs of Herring Gull and 1.326 pairs of Lesser Black‐backed Gull bred in Zeebrugge, the majority (65.9%) on fox‐free rooftops. After 2013 the numbers of Herring and Lesser Black‐backed Gull have increased elsewhere in Flanders and especially along the coast the number of breeding sites is rapidly growing. This suggests that part of the Zeebrugge colony has moved to both new and existing breeding sites. Indeed, recoveries of colour‐ringed individuals revealed that there is a strong connection between Zeebrugge and other breeding sites along the Flemish coast. Other ringed gulls originating from Zeebrugge moved to existing colonies in the north of France, the south of the Netherlands and the south‐east of the UK
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Monitoring van kustbroedvogels in de SBZ-V ‘Kustbroedvogels te Zeebrugge-Heist’ en de westelijke voorhaven van Zeebrugge tijdens het broedseizoen 2014
2015Co-Authors: Stienen E.w.m., Courtens W., Van De Walle, M., Vanermen N., Verstraete H.Abstract:This report describes the fluctuations in the number of breeding pairs in the Special Protected Area under the Bird Directive ‘Kustbroedvogels te Zeebrugge-Heist’ and in the western port of Zeebrugge. These are by far the most important breeding sites for coastal breeders in Belgium and used to be of high importance for the biogeographical population as a whole. The quality of the breeding sites and the foraging areas is discussed and advice is given for a better management of the Special Protected Area.The populations of terns (Sandwich, Common and Little Tern) and Black-headed Gulls have decreased strongly since 2008 and the breeding success was insufficient for a stable population size. In Zeebrugge all 3 tern species used to exceed the threshold of 1% of their respective biogeographic population considerably. In 2014 none of the tern species reached this threshold. The decrease is due to persistent problems with land predators. Food availability seemed to play no role in this.Also some scarce species strongly declined in Zeebrugge. Crested Lark, Northern Wheatear, Mediterranean Gull and Yellow-legged Gull used to breed in the Zeebrugge port but in 2014 these species were no longer recorded. The numbers of Oystercatchers and Common Gull seem to have stabilised at a level much lower than before. Only the population of Common Ringed Plover is rather stable at about 8 pairs.Following a slight reduction in 2013, the populations of Herring and Lesser Black-backed Gulls further and strongly declined in 2014. Both species used to exceed the 1% level (maxima of 1.2 and 2.8%, respectively for Herring and Lesser Black-backed Gull), the number of Herring Gulls dropped to 0.2% of the total biogeographic population while that of Lesser Black-backed Gull dropped to 0.6%. This decline is due to disturbance by foxes and a decreased availability of suitable nesting areas
Mingan Shao - One of the best experts on this subject based on the ideXlab platform.
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controlling Gully and revegetation induced dried soil layers across a slope Gully system
2021Co-Authors: Chencheng Zhang, Yunqiang Wang, Mingan ShaoAbstract:Abstract The introduction of exotic plants and improper management strategies with regard to plant species can change the soil-water balance of deep soils, which in turn results in the formation of a dried soil layer (DSL) within the soil profile. The Loess Plateau (LP) of China has a complex terrain; however, only a few studies have evaluated the effects of the Gully-induced DSL patterns, especially in hilly and Gully regions of the northern LP. In this study, we collected soil-water content data to a depth of 5 m at 40 sampling sites in a slope–Gully system to investigate and characterize DSLs and their spatial patterns. Results show that the DSL indices vary greatly in different slope positions. The thickness of DSLs (DSLT) and quantitative index (QI) in the Gully were significantly (p
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permanent Gully increases the heterogeneity of soil water retention capacity across a slope Gully system
2019Co-Authors: Miao Gan, Yuhua Jia, Mingan Shao, Chengjiu GuoAbstract:Abstract The coexistence of permanent Gully and slope farmland in the northern Loess Plateau catchment has experienced great changes since the implementation of the Grain for Green project in 1999. This program swaps agricultural production in the slope land for soil and water conservation measures. To date, the slope-Gully system soil water retention capacity are poorly understood. In our study, undisturbed soil samples at 0–25 cm depth were taken from three transects along a Gully bottom, bank and nearby slope, and the effects of Gully terrain and slope position on the soil water retention curves (WRC) in two soil layers (surface layer: 0–12 cm; sub-surface layer: 12–25 cm) were evaluated. The results showed that: (1) with the increasing suction, soil water retention capacity within the vertical direction of the Gully bottom was constant and increased on the nearby slope. For all the slope positions on the Gully bank, the WRC shapes of surface soil differed from those of sub-surface soil; (2) The capillary rupture moisture in the surface soil at the lower (L-) slope of the Gully bank occurred at low suction pressure. The available water content of the L-slope was lower than the upper (U-) slope in the Gully bank; (3) The Gully increased the complexity of soil pore distribution across the slope-Gully system. The Gully bank reduced the water retention capacity of surface soil. In conclusion, the permanent Gully enhanced the heterogeneity of soil water retention capacity. These results provide specific information about hydrological functioning in gullied areas and improves our understanding of soil hydrology in the post-farmland environment in the northern Loess Plateau.
Jean Poesen - One of the best experts on this subject based on the ideXlab platform.
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how fast do Gully headcuts retreat
2016Co-Authors: Jean Poesen, Matthias Vanmaercke, Bert Van Mele, Matthias Demuzere, Amber Bruynseels, Valentin Golosov, Jose Fernando Rodrigues Bezerra, Sergey BolysovAbstract:Abstract Gully erosion has important on and off site effects. Therefore, several studies have been conducted over the past decades to quantify Gully headcut retreat (GHR) in different environments. Although these led to important site-specific and regional insights, the overall importance of this erosion process or the factors that control it at a global scale remain poorly understood. This study aims to bridge this gap by reviewing research on GHR and conducting a meta-analysis of measured GHR rates worldwide. Through an extensive literature review, GHR rates for 933 individual and actively retreating gullies have been compiled from more than 70 study areas worldwide (comprising a total measuring period of > 19 600 years). Each GHR rate was measured through repeated field surveys and/or analyses of aerial photographs over a period of at least one year (maximum: 97 years, median: 17 years). The data show a very large variability, both in terms of Gully dimensions (cross-sectional areas ranging between 0.11 and 816 m 2 with a median of 4 m 2 ) and volumetric GHR rates (ranging between 0.002 and 47 430 m 3 year − 1 with a median of 2.2 m 3 year − 1 ). Linear GHR rates vary between 0.01 and 135 m year − 1 (median: 0.89 m year − 1 ), while areal GHR rates vary between 0.01 and 3628 m 2 year − 1 (median: 3.12 m 2 year − 1 ). An empirical relationship allows estimating volumetric retreat rates from areal retreat rates with acceptable uncertainties. By means of statistical analyses for a subset of 724 gullies with a known contributing area, we explored the factors most relevant in explaining the observed 7 orders of magnitudes of variation in volumetric GHR rates. Results show that measured GHR rates are significantly correlated to the runoff contributing area of the Gully (r 2 = 0.15) and the rainy day normal (RDN; i.e. the long-term average annual rainfall depth divided by the average number of rainy days; r 2 = 0.47). Other factors (e.g. land use or soil type) showed no significant correlation with the observed GHR rates. This may be attributed to the uncertainties associated with accurately quantifying these factors. In addition, available time series data demonstrate that GHR rates are subject to very large year-to-year variations. As a result, average GHR rates measured over short ( 100%) uncertainties. We integrated our findings into a weighted regression model that simulates the volumetric retreat rate of a Gully headcut as a function of upstream drainage area and RDN. When weighing each GHR observation proportional to its measuring period, this model explains 68% of the observed variance in GHR rates at a global scale. For 76% of the monitored gullies, the simulated GHR values deviate less than one order of magnitude from their corresponding observed value. Our model clearly indicates that GHR rates are very sensitive to rainfall intensity. Since these intensities are expected to increase in most areas as a result of climate change, our results suggest that Gully erosion worldwide will become more intense and widespread in the following decades. Finally, we discuss research topics that will help to address these challenges.
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challenges in Gully erosion research
2011Co-Authors: Jean PoesenAbstract:Although the number of publications on Gully erosion has increased over the last decade, there are still various as- pects of Gully erosion that deserve more research efforts. Some of these, discussed in this contribution, are Gully erosion in historical times, measuring techniques, processes of Gully initiation, development and infilling, the interaction between Gully erosion with hydrological and other soil degradation processes (e.g. piping, landsliding, tillage erosion and erosion induced by land levelling), Gully erosion models, effective and efficient Gully prevention and control measures. A better understand- ing of these aspects would allow one to better predict the impact of environmental change, Gully prevention and control mea- sures on Gully erosion and Gully infilling rates at a range of temporal and spatial scales and for various types of environments, and the effects of Gully erosion on sediment yield, hydrological process intensities and landscape evolution.
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the potential of 3d Gully monitoring with gis using high resolution aerial photography and a digital photogrammetry system
2009Co-Authors: Irene Marzolff, Jean PoesenAbstract:Although Gully erosion is generally considered a major process of land degradation, its contribution to total soil loss by erosion has recently been a subject of much discussion. The lack of adequate methods for the documentation and monitoring of gullies resulted in the shortage of quantitative data. Therefore, a high-resolution remote sensing system for aerial surveys by blimp or kite has been developed which meets spatial and temporal image resolutions required for short-term Gully monitoring. The objective of this paper is to examine the potential of a method using non-metric digital photogrammetry and GIS for Gully surface modelling and monitoring. Two bank gullies representing different morphological types of gullies (V-shaped and U-shaped) were chosen from a dataset of Gully systems in semi-arid Spain. The considerable relief energy and complex topography of the gullies in a natural, vegetated landscape were found to be a challenge to digital photogrammetric techniques, introducing errors which inhibit fully automated DEM generation. Using a hybrid method combining stereomatching for mass-point extraction with manual 3D editing and digitizing, high-resolution DEMs (5 and 7.5 cm pixel size) were created for the study sites. GIS analysis of the DEMs for different monitoring periods (2 to 4 years) allowed the computation of Gully area and volume, as well as their changes with an accuracy and detail sufficient to represent the geomorphological forms and processes involved. Furthermore, the spatially continuous survey of the entire form offered the possibility of distinguishing different zones of activity both at the Gully rim and within the Gully interior, identifying patterns of erosion and deposition which indicate the limited use of headcut retreat rates for the assessment of sediment production on a short-term basis.
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Gully erosion impacts factors and control
2005Co-Authors: Jean Poesen, Yong LiAbstract:Gully erosion attracts increasing attention from scientists as reflected by two recent international meetings [Poesen and Valentin (Eds.), Catena 50 (2–4), 87–564; Li et al., 2004. Gully Erosion Under Global Change. Sichuan Science Technology Press, Chengu, China, 354 pp.]. This growing interest is associated with the increasing concern over off-site impacts caused by soil erosion at larger spatial scales than the cultivated plots. The objective of this paper is to review recent studies on impacts, factors and control of Gully erosion and update the review on dGully erosion and environmental change: importance and research needsT [Poesen et al., 2003. Catena 50 (2–4), 91–134.]. For the farmers, the development of gullies leads to a loss of crop yields and available land as well as an increase of workload (i.e. labour necessary to cultivate the land). Gullies can also change the mosaic patterns between fallow and cultivated fields, enhancing hillslope erosion in a feedback loop. In addition, gullies tend to enhance drainage and accelerate aridification processes in the semi-arid zones. Fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion. In this respect, tracers such as carbon, nitrogen, the nuclear bomb-derived radionuclide 137 Cs, magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment. Recent studies conducted in Australia, China, Ethiopia and USA showed that the major part of the sediment in reservoirs might have come from Gully erosion. Gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess (European belt, Chinese Loess Plateau, North America) and sandy soils (Sahelian zone, north-east Thailand) or in soils prone to piping and tunnelling such as dispersive soils. Most of the time, the Gullying processes are triggered by
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Gully erosion importance and model implications
1998Co-Authors: Karel Vandaele, Jean Poesen, Bas Van WesemaelAbstract:This paper deals with Gully erosion in agricultural environments and concentrates in particular on types of gullies, importance of Gully erosion with respect to sediment production in agricultural environments and modelling needs. Two major Gully types can be often observed in agricultural lands: ephemeral gullies and bank gullies. Field measurements combined with aerial photo analysis in three contrasting European environments indicate that ephemeral Gully erosion rates represent 44 per cent of total sediment production in central Belgium and up to 80–83 per cent of total sediment production in Mediterranean conditions (Portugal and Spain). In contrast, bank Gully erosion rates are about one order of magnitude less than ephemeral Gully erosion rates in central Belgium. Nevertheless, there is a need to model these erosion features, which are complementary to interrill and rill erosion. More particularly, there is a need for more detailed monitoring, experimenting and modelling of the development and infilling of both ephemeral gullies and bank gullies in a variety of agricultural environments. In other words, there is a need to better predict the location, the total length and the cross-section of gullies. The threshold concept could be a useful tool to help locate ephemeral gullies in the landscape. However, threshold conditions for incipient Gullying in a variety of climatological, topographic, pedological and land-use conditions first need to be established. Existing erosion models need to be refined to incorporate the effects of the resistance of various soil horizons to concentrated flow erosion and the effects of other soil detaching mechanisms in gullies such as soil fall, slumping and headcutting. Improved Gully models are needed to predict more accurately the effects of environmental change on the intensity of this soil degradation process.
Seifu A. Tilahun - One of the best experts on this subject based on the ideXlab platform.
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bank stability and toe erosion model as a decision tool for Gully bank stabilization in sub humid ethiopian highlands
2020Co-Authors: Assefa D. Zegeye, Tammo S Steenhuis, Eddy J Langendoen, Wolde Mekuria, Seifu A. TilahunAbstract:Abstract Gullies that are expanding at alarming rate are responsible for the majority of soil losses in the (sub) humid highlands of Ethiopia. Few affordable and effective methods for Gully erosion control are available in the highlands. The objective of the study was to develop cost-effective measures to halt Gully expansion by determining stable-bank conditions under a variety of environmental situations using the Bank Stability and Toe Erosion Model (BSTEM). The study was carried out in the sub humid Debre Mawi watershed, located 30 km south of Lake Tana. Input data for the BSTEM model were collected using field surveys and soil sampling. After the BSTEM was tested on actual measured soil data, soil cohesion and internal friction angle were calibrated against observed Gully bank retreat. Using the calibrated parameters, the model evaluated the stabilization of the existing Gully bank under different scenarios in which groundwater table, bank angle and bank height, tension crack depth, vegetation, and toe protection were varied. Finally, the head-cut of the study Gully was treated based on the model recommendation. The simulated results showed that a 5 m deep Gully was stable under fully saturated conditions when the bank toe is protected, its upper surface is vegetated, and its bank angles do not exceed 45°. If the depth of the Gully is less than 5 m or if its water table is deeper than 0.5 m, only regrading the Gully bank to an angle of 45° can stabilize the Gully. BSTEM showed to be an effective tool that can be used to evaluate Gully control measures.
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Gully head retreat in the sub humid ethiopian highlands the ene chilala catchment
2017Co-Authors: Meseret B Addisie, Seifu A. Tilahun, Assefa D. Zegeye, Tammo S Steenhuis, Eddy J Langendoen, Getaneh K Ayele, Azalu A Gessess, M M Moges, Petra SchmitterAbstract:In the northern highlands of Ethiopia, Gully erosion is severe. Despite many efforts to implement Gully prevention measures, controlling Gully erosion remains a challenge. The objective is to better understand the regional Gully erosion processes and to prevent Gully head retreat. The study was conducted in the Ene-Chilala catchment in the sub-humid headwaters of the Birr River located southwest of Bahir Dar, Ethiopia. Twelve Gully heads were monitored during the 2014 and 2015 rainy monsoon phase. We measured Gully head morphology and retreat length, soil shear strength, ground water table levels and catchment physical characteristics. Two active Gully head cuts were treated in 2014 and an additional three head cuts in 2015 by regrading their slope to 45 degrees and covering them with stone riprap. These treatments halted the Gully head advance. The untreated gullies were actively eroding due to groundwater at shallow depths. The largest head retreat was 22.5 m, of which about half occurred in August of the first year when the surrounding soil was fully saturated. Lowering both the water table and protecting the Gully heads can play a key role in reducing Gully expansion and soil loss due to Gully erosion in the Ethiopian highlands.