Gully Head Retreat in the Sub‐Humid Ethiopian Highlands: The Ene‐Chilala Catchment

Addisie, Meseret B.; Ayele, Getaneh K.; Gessess, Azalu A.; Tilahun, Seifu A.; Zegeye, Assefa D.; Moges, M. M.; Schmitter, Petra; Langendoen, Eddy J.; Steenhuis, Tammo S.

doi:10.1002/ldr.2688

Cited by 36 publications

(38 citation statements)

References 64 publications

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“…Although the root distribution with depth was not studied in this research, our physical observation showed that the number of plant roots decreased with soil depth, indicating that in the case of high banks, like those along larger rivers or deeply incised gully channels, potential slip surfaces are located below the root zone, and vegetation probably has little effect on soil strength (Abernethy & Rutherford, 2001). This finding is in line with Langendoen et al (2013) (Addisie et al, 2017;Ayele et al, 2015).…”

Section: Mechanical and Hydrologic Effect Of Plant Roots On Soil Shsupporting

confidence: 93%

“…Deep rooted shrubs, such as J . shimperiana , V. auriculata, and trees such as A. abyssinica , can be used to stabilize gully walls as they provide an added cohesion exceeding soil depths of 1 m. Grasses, such as D. abyssinica , E. floccifolia , C. zizanioides , Hechynomene dregeana , or P. purpureum (in the order of decreasing additional cohesion from 10.6–2.6 kPa), can be planted on small gullies to stabilize the 0–0.30 m of topsoil (Addisie et al, ; Ayele et al, ). These species have also other benefits.…”

Section: Resultsmentioning

confidence: 99%

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Root reinforcement to soils provided by common Ethiopian highland plants for gully erosion control

et al. 2018

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Grasses and trees are often used to stabilize gully banks. However, the effectiveness of such biological conservation measures has not been investigated for the Ethiopian highlands. This study investigates the reinforcement that plant roots may provide to strengthen gully banks in Ethiopia. The root systems of 26 indigenous and exotic plant species of 3 plant life forms (grasses, shrubs, and trees) were sampled, and root tensile strength and distribution were determined. The RipRoot model was used to quantify the additional cohesion derived from the plant roots. Among all tested roots, Eleusine floccifolia (grass), Tephrosia vogelii (tree), and Rosa abyssinica (shrub) had the strongest roots for each life form. The root volumetric ratio (root volume divided by soil volume) in the top 0.6 m of soil ranged from 0.03% to 0.46%. Roots of Digitaria abyssinica provided the maximum added cohesion (10.6 kPa) over this depth. For a given plant species, root volumetric ratio had a greater effect on additional cohesion than root tensile strength. Plant species with a fibrous root system provided greater additional cohesion values in the top 0.6 m (on average 3.4 vs. 1.7 kPa for tap root systems) and could potentially enhance gully bank stability for shallow gullies more than plants having a tap root system. To effectively rehabilitate larger gullies, plants should be integrated with other gully rehabilitation measures, such as regrading of gully banks and structural measures such as check dams to trap sediments, thereby reducing the effective gully bank height relative to rooting depth.

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Section: Mechanical and Hydrologic Effect Of Plant Roots On Soil Shsupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Root reinforcement to soils provided by common Ethiopian highland plants for gully erosion control

et al. 2018

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“…Check dams reduce the effective slope of the channel, thereby reducing the velocity of flowing water, allowing sediment to settle and reducing channel erosion. Check dams require maintenance to be effective [32,33]. The infiltration furrows with bunds were built along the contour across the sloping lands to decrease runoff by reducing or stopping the overland flow and increasing the infiltration of rainwater into the soil in the furrows.…”

Section: Description Of the Study Areamentioning

confidence: 99%

Section: Description Of the Study Areamentioning

confidence: 99%

Impact of Soil Depth and Topography on the Effectiveness of Conservation Practices on Discharge and Soil Loss in the Ethiopian Highlands

Akale

Dagnew

Belete

et al. 2017

Land

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Abstract:Restoration of degraded landscapes through the implementation of soil and water conservation practices is considered a viable option to increase agricultural production by enhancing ecosystems. However, in the humid Ethiopian highlands, little information is available on the impact of conservation practices despite wide scale implementation. The objective of this research was to document the effect of conservation practices on discharge and sediment concentration and load in watersheds that have different soil depths and topography. Precipitation, discharge, and sediment concentration were measured from 2010 to 2012 in two watersheds in close proximity and located in the Lake Tana basin, Ethiopia: Tikur-Wuha and Guale watersheds. The Tikur-Wuha watershed has deep soils and a gentle slope stream channel. The Guale watershed has shallow soils and a steep slope stream channel. In early 2011, the local community installed upland conservation measures consisting of stone and soil bunds, waterways, cutoff drains, infiltration furrows, gully rehabilitation, and enclosures. The results show that conservation practices marginally decreased direct runoff in both watersheds and increased base flow in the Tikur-Wuha watershed. Average sediment concentration decreased by 81% in Tikur-Wuha and 45% in Guale. The practices intended to increase infiltration were most effective in the Tikur-Wuha watershed because the deep soil could store the infiltrated water and release it over a longer period of time after the rainy season than the steeper Guale watershed with shallow soils.

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“…The construction of roads in mountainous regions can also contribute to the expansion of gully channels (Nyssen et al, 2002;Frankl et al, 2012). Unlike in sub-humid areas where seasonal rising of the groundwater table may be important for the initiation and expansion of gullies (Tebebu et al, 2010;Zegeye et al, 2016;Addisie et al, 2017), the occurrence of high runoff discharges in semi-arid areas due to degraded vegetation and soil crusting explains the expansion of gullies (Poesen and Vandekerckhove, 2004;Valentin et al, 2005;Frankl et al, 2011Frankl et al, , 2012. Dispersive soils such as sodic soil and clay rich soils (Vertisols) are vulnerable to gully initiation and expansion as these materials are prone to soil piping that causes internal erosion and eventually gully erosion when the soil pipe roof collapses (Faulkner et al, 2004(Faulkner et al, , 2013Nyssen et al, 2004a;Valentin et al, 2005;Wilson, 2011;Frankl et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Gully and soil and water conservation structure densities in semi‐arid northern Ethiopia over the last 80 years

Guyassa

Frankl

Zenebe

et al. 2018

Earth Surf Processes Landf

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Gullies have been a common phenomenon in semi‐arid northern Ethiopia for the last centuries. However, soil and water conservation (SWC) structures have been implemented for a long time to curb soil erosion. Though, like most of the affected areas worldwide, density and distribution of gullies and SWC structures, their causes and interrelations are poorly understood. The aims of this study were to develop a technique for mapping these densities of gullies and SWC structures, to explain their spatial distribution and to analyze changes over the period 1935–2014. Aerial photographs from 1935 to 1936 and Google Earth images from 2014 of the 5142 km2 Geba catchment were used. Transect lines were established to count gullies and SWC structures in order to calculate densities. On average, a gully density of 1.14 km km−2 was measured in 1935–1936 of which the larger portion (75%) were vegetated, indicating they were not very active. Over 80 years, gully density has significantly increased to 1.59 km km−2 with less vegetation growing in their channel, but 66% of these gullies were treated with check dams. There was c. 3 km km−2 of indigenous SWC structures (daget or lynchets) in 1935–1936 whereas a high density (20 km km−2) of introduced SWC structures (mainly stone bunds and terraces) were observed in 2014. The density of gullies is positively correlated with slope gradient and shrubland cover and negatively with cropland cover, whereas the density of SWC structures significantly increased with increasing cropland cover. Density maps of gullies and SWC structures indicate sensitive areas to gully formation and priority areas for the implementation of SWC structures in Geba catchment. The obtained results illustrate the feasibility of the methods applied to map the density of gullies and SWC structures in mountainous areas. Copyright © 2018 John Wiley & Sons, Ltd.

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Gully Head Retreat in the Sub‐Humid Ethiopian Highlands: The Ene‐Chilala Catchment

Cited by 36 publications

References 64 publications

Root reinforcement to soils provided by common Ethiopian highland plants for gully erosion control

Root reinforcement to soils provided by common Ethiopian highland plants for gully erosion control

Impact of Soil Depth and Topography on the Effectiveness of Conservation Practices on Discharge and Soil Loss in the Ethiopian Highlands

Gully and soil and water conservation structure densities in semi‐arid northern Ethiopia over the last 80 years

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