Your search found 7 records
1 Addisie, M. B.; Ayele, G. K.; Gessesse, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M.; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2015. Reducing surface and subsurface water flow effect on gullies through low cost measures [Abstract only] Paper presented at the 10th Alexander von Humboldt Conference 2015 on Water-Food-Energy River and Society in the Tropics. EGU Topical Conference Series, Addis Ababa, Ethiopia, 18-20 November 2015. 1p.
Surface water ; Groundwater ; Flow discharge ; Gully erosion ; Erosion control ; Watersheds ; Water table ; Cost analysis ; Soil properties ; Case studies / Ethiopia / Amhara State / Birr Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H047331)
(0.04 MB)
Gully erosion in the humid Ethiopian highlands intensified in recent decades. The study was conducted in the Birr watershed located south west of Bahir Dar the capital of Amhara regional state, Ethiopia. We studied 14 gullies having similar morphology at three sub watersheds. The watershed covers a total area of 414 ha. The monitoring continued over the 2013 to 2014 monsoon season to better understand the factors controlling gully erosion and the effectiveness of erosion control structures. Perched ground water table was measured at the gully heads and erosion pins were installed to monitor the rate of recession from uncontrolled heads. Though soil properties, ground cover, gully morphology had small contribution for the gully development; water fall effect at the head of the gully and elevated water table depth at both heads and banks played the key role. Therefore the study focused on reducing the water fall and elevated water table effect by applying two low cost gully control approaches. The first approach was regrading the gully heads and banks at 45o and the second approach follows regrading the gully heads at 45o and putting a graded type of stone rip rap. Large stones were anchored at the toe of the head maintaining the stable gully bed slope. The result shows that unprotected gully heads retreat an average of 4m which is equivalent to 37m3 volume of soil loss. The maximum and minimum head cut retreat was between 0 and 22.5m. The total area damaged by annual gully head retreat was 240m2 and total volume of soil lost was 444m3. The treated gully heads did not show any retreat during the monitoring period. Compared with simple reshaping of gully heads, integration with Stone rip rap was an effective and low cost measure in the study watershed. Plantation could not stop the upslope migration of heads though it had the potential to trap sediments down slope. Heads with stone rip rap allows fast re vegetation whereas unprotected reshaped heads and banks took longer time to re vegetate and stabilized. Time of reshaping was important for the stability of banks and heads.
2 Addisie, M. B.; Ayele, G. K.; Gessess, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M. M. [NARS]; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2015. Hydrological and morphological factors at gully heads in the humid northern Ethiopian Highlands, Birr watershed [Abstract only] In Nyssen J., Enyew A., Poesen J et al. (Eds.). International Conference on Tropical Lakes in a Changing Environment: Water, Land, Biology, Climate and Humans (TropiLakes), Bahir Dar, Ethiopia, 23-29 September 2015. Book of Abstracts. Bahir Dar, Ethiopia: Bahir Dar University. pp.72.
Hydrological factors ; Gully erosion ; Humid climate ; Water table ; Watersheds ; Highlands ; Soils / Ethiopia / Birr Watershed / Ethiopian Highlands
(Location: IWMI HQ Call no: e-copy only Record No: H047416)
(0.10 MB)
In the Ethiopian highlands, gully erosion is severe. Although attempts to prevent gullying, it remains a challenge. Our objectives are to understand better the processes that control gully head cut retreat. The study was conducted in Birr watershed located at South West of Bahir Dar, Ethiopia. Twelve gully heads were selected and monitored from July to October, 2014. We measured gully head morphology, length of recession via pegging technique, soil analysis to determine soil shear strength, physical and chemical properties, water table elevations and catchment physical characteristics. Two active gully head cuts were arrested with stone riprap after regarding at 450. The result shows that the maximum rate of head cut retreat was between 0 to 22.5m. There was no head retreat observed from the protected heads compared with unprotected heads. The average short term head cut retreat was much greater than that observed in semiarid highlands of northern Ethiopia. The greater gulley rate of recession in the humid monsoon climate is likely caused by the water table that was above the gully bottom. In August when the soil became saturated, about 45% of head cut migration occurred. Thus the water table contributed to the slumping of gully heads and weakened the strength of the soil cohesion. The soil shear strength test result shows, angle of internal friction was by far greater than the slope of gully heads where heads are located in the periodically saturated flat lands. The width depth ratio showed that the shallow depth heads were controlled by fluvial erosion whereas for the deep gully heads both fluvial and mass wasting due to tension cracks was the main driving force. Both the water table control and protecting the head cuts of shallow gullies plays a key role in reducing the sediment contribution of gully in the humid Ethiopian highlands.
3 Addisie, M. B.; Ayele, G. K.; Gessesse, A. A.; Tilahun, S. A.; Moges, M. M.; Zegeye, A. D.; Mekuria, Wolde; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2016. Rehabilitating gullies with low cost methods, in the sub humid Ethiopian highlands. Paper presented at the International Conference of the Advancement of Science and Technology, Bahir Dar, Ethiopia, 17-18 July 2016. 10p.
Gully erosion ; Humid zones ; Highlands ; Environmental degradation ; Ecosystems ; Watersheds ; Riverbank protection ; Vegetation ; Plantations ; Sedimentation
(Location: IWMI HQ Call no: e-copy only Record No: H047636)
(691 KB)
Gully erosion in the highlands of Ethiopia has reduced agricultural productivity and degraded ecosystem services. To better understand the processes controlling gully erosion and design effective control measures, a study was conducted in the headwaters of the Birr watershed for three consecutive years (2013-2015). Fourteen gullies with similar morphology were studied in three adjacent sub-watersheds. Stabilization measures were applied to 5 of the 14 gully heads. Three gully control measures were compared: a) reshaping gully banks and head to a 45 degree slope with stone rip rap on the gully heads, b) controlling gully bed grade, and c) planting grasses and trees on shallow gullies (i.e., < 3 m deep). Results demonstrated that gully control measures were effective in controlling the expansion of gullies as no further retreat was observed for the 5 treated gully heads, whereas the average retreat was 3 meters with a maximum of 22.5 m for the 9 untreated gullies. The migration of untreated gully heads produced an average soil loss of 38 tons per gully. Compared with simple reshaping of gully heads, the additional integration with stone rip rap was an effective and low cost measure. Vegetative treatment by itself could not stop the upslope migration of gully heads, though it had the potential to trap sediments. Re-vegetation at gully heads stabilized with stone rip rap occurred faster than at unprotected, reshaped heads and banks. From the fourteen rehabilitation treatments, gully head protection integrated with plantation showed the largest potential in decreasing gully development in terms of labor, time and material it requires.
4 Addisie, M. B.; Ayele, G. K.; Gessess, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M. M.; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2017. Gully head retreat in the sub-humid Ethiopian Highlands: the Ene-Chilala Catchment. Land Degradation and Development, 28(5):1579-1588. [doi: https://doi.org/10.1002/ldr.2688]
Gully erosion ; Erosion control ; Humid zones ; Highlands ; Catchment areas ; Sedimentation ; Wet season ; Monitoring ; Soil texture / East Africa / Ethiopia / Ene-Chilala Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H048152)
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° 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.
5 Addisie, M. B.; Langendoen, E. J.; Aynalem, D. W.; Ayele, G. K.; Tilahun, S. A.; Schmitter, Petra; Mekuria, Wolde; Moges, M. M.; Steenhuis, T. S. 2018. Assessment of practices for controlling shallow valley-bottom gullies in the sub-humid Ethiopian Highlands. Water, 10(4):1-15.
Gully erosion ; Assessment ; Best practices ; Rehabilitation ; Sediment ; Highlands ; Valleys ; Vegetation ; Slope ; Farmers ; Watersheds ; Dams ; Grasses ; Soil conservation ; Water conservation / Africa / Ethiopia / Ethiopian Highlands
(Location: IWMI HQ Call no: e-copy only Record No: H048964)
Rehabilitation of large valley bottom gullies in developing countries is hampered by high cost. Stopping head cuts at the time of initiation will prevent large gullies from forming and is affordable. However, research on practices to control shallow gully heads with local materials is limited. The objective of this research was therefore to identify cost-effective shallow gully head stabilization practices. The four-year study was conducted on 14 shallow gullies (<3 m deep) in the central Ethiopian highlands. Six gullies were used as a control. Heads in the remaining eight gullies were regraded to a 1:1 slope. Additional practices implemented were adding either riprap or vegetation or both on the regraded heads and stabilizing the gully bed downstream. Gully heads were enclosed by fencing to prohibit cattle access to the planted vegetation. The median yearly head retreat of the control gullies was 3.6 m a-1 with a maximum of 23 m a-1. Vegetative treatments without riprap prevented gully incision by trapping sediments but did not stop the upslope retreat. The gully heads protected by riprap did not erode. Regrading the slope and adding riprap was most effective in controlling gully head retreat, and with hay grown on the fenced-in areas around the practice, it was profitable for farmers.
6 Zegeye, A. D.; Langendoen, E. J.; Steenhuis, T. S.; Mekuria, Wolde; Tilahun, S. A. 2020. Bank stability and toe erosion model as a decision tool for gully bank stabilization in sub humid Ethiopian highlands. Ecohydrology and Hydrobiology, 20(2):301-311. [doi: https://doi.org/10.1016/j.ecohyd.2020.02.003]
Gully erosion ; Erosion control ; Models ; Soil loss ; Soil stabilization ; Subhumid zones ; Highlands ; Watersheds ; Groundwater table ; Runoff ; Vegetation / Ethiopia / Blue Nile Basin / Debre Mawi Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H049936)
(2.29 MB)
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.
7 Addisie, M. B.; Ayele, G. K.; Hailu, N.; Langendoen, E. J.; Tilahun, S. A.; Schmitter, Petra; Parlange, J.-Y.; Steenhuis, T. S. 2020. Connecting hillslope and runoff generation processes in the Ethiopian highlands: the Ene-Chilala Watershed. Journal of Hydrology and Hydromechanics, 68(4):313-327. [doi: https://doi.org/10.2478/johh-2020-0015]
Highlands ; Watersheds ; Hydrology ; Sloping land ; Rain ; Groundwater table ; Infiltration ; Stream flow ; Discharges ; Forecasting ; Observation ; Monsoon climate ; Saturation ; Piezometers ; Models / Ethiopia / Ene-Chilala Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H050129)
https://content.sciendo.com/downloadpdf/journals/johh/68/4/article-p313.xml
https://vlibrary.iwmi.org/pdf/H050129.pdf
https://vlibrary.iwmi.org/pdf/H050129.pdf
(2.85 MB) (2.85 MB)
Effective watershed planning requires an understanding of the hydrology. In the humid tropical monsoon climates and especially in volcanic highland regions such as the Ethiopian Highlands, the understanding of watershed processes is incomplete. The objective is to better understand the hydrology of the volcanic regions in the humid highlands by linking the hillslope processes with the discharge at the outlet. The Ene-Chilala watershed was selected for this study. The infiltration rate, piezometric water levels and discharge from two nested sub watersheds and at the watershed outlet were measured during a four-year period. Infiltration rates on the hillsides exceeded the rainfall intensity most of the time. The excess rain recharged a perched hillside aquifer. Water flowed through the perched aquifer as interflow to rivers and outlet. In addition, saturation excess overland flow was generated in the valley bottoms. Perched water tables heights were predicted by summing up the recharge over the travel time from the watershed divide. Travel times ranged from a few days for piezometers close to the divide to 40 days near the outlet. River discharge was simulated by adding the interflow from the upland to overland flow from the saturated valley bottom lands. Overland flow accounted only for one-fourth of the total flow. There was good agreement between predicted and observed discharge during the rain phase therefore the hillslope hydrologically processes were successfully linked with the discharge at the outlet.
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