Soils on Steep Slopes

In a hilly area in Lampung State, the southern end of Sumatra Island in Indonesia, coffee is commonly cultivated on hillsides with steep slopes and soil erosion affects sustainable coffee production. A field experiment on coffee cultivation was conducted for 4 years to evaluate the effects of alley cropping and no-tillage on the seed production of coffee and on erosion control in a steep slope area in this region. The cultivation of intercropped vegetables, red peppers, tomatoes, and long beans was introduced into the coffee fields when the coffee plants were small. No significant differences in the yields of either the coffee plants or the intercropped vegetables were noted among the treatments. Coffee shoot fresh weight, however, was slightly increased by no-tillage treatment. Soil erosion was reduced by 37% as a result of no tillage and by 64% with alley cropping. The amount of soil erosion for local farmers practice, tillage & no-alley, was more than four times that in no-tillage and alley treatment. These results indicate that alley cropping and no-tillage are effective for erosion control on coffee fields on steep slopes and that yield is not affected by these practices. The introduction of intercropped vegetables is beneficial in terms of farm economy, especially when the income from coffee cultivation is limited.

<p>Incised valleys or steep slopes in tectonic active mountain areas are normally in a critical equilibrium state which is highly fragile and prone to deviate under exotic disturbances (e.g., earthquake, heavy precipitation, or even human activities), inducing mass movements (e.g., landslides, avalanche, and/or debris flows). Mass movements have great impacts on fluvial processes and may even reshape valley morphology, hence are powerful drivers to river evolution in those environments. Unfortunately, compared to the mass movements themselves (e.g., occurrence time, volume, dynamics and underlying mechanisms), less attention has been paid to the fluvial processes (in a short/intermediate-term) and the long-term evolution of river morphology corresponding to (and after) those mass movements (especially catastrophic ones). This motivates the current work.</p><p>The southeast Tibet, located on the east Qinghai-Tibet Plateau, is one of the most active regions globally in terms of tectonic motion and rates of uplift. Rivers in the lower Yalung Tsangpo basin in this area are investigated to understand the morphodynamics influenced by modern and historical mass movements and examine the feedbacks of fluvial processes to mass movements. River reaches influenced by typical mass movements were chosen for detailed field surveys, including: (1) the upper part of the Yalung Tsangpo Grand Canyon which has been seriously impacted by avalanches and debris flows from tributary gullies originating at glacial mountains of Namcha Barwa and Gyala Peri; (2) the lower reach of the Yigong River covering the Yigong Landslide from the Zhamunong Gully; (3) the lower reach of the Palong River influenced by debris flows from Guxiang and Tianmo gullies; and (4)  the upper and middle reaches of the Palong River (extending roughly from Ranwu Lake to the upstream of Guxiang Lake) influenced by glacial processes and other induced mass movements since the last glacial maximum. Remote sensing images before and after the large-scale mass movements in recent decades were also used to track the corresponding river morphology variation.</p><p>Due to very high transport rate and volume of sediment incoming, mass movements have caused dramatic channel processes in east Tibet. Some even dammed the river, forming knickpoints and reshaping valley morphology. The morphology of the valleys in this area normally show alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. In recent decades, mass movements (mostly debris flows), occurred more frequently through gullies in the reaches of gorge sections than through gullies along the wide valley sections. Mass movements deviate river morphology and slope from (quasi-)equilibrium to non-equilibrium state, however, with attendant rapid sediment incoming, valley bottom siltation and erosion benchmark rising, it triggers a negative feedback which drives the river morphology to a new round of development towards equilibrium.</p>

Soil erosion is the main drivers in the world and Ethiopia in particular. This study has been conducted at Dijo watersheds in the Rift valley Basins of Ethiopia to estimate soil erosion rate and identify erosion hotspot areas for proper planning using Geographic Information System and Universal Soil Loss Equation adapted to Ethiopian condition. 64 years mean annual rainfall data for estimating erosivity factor, digital soil map for estimating soil erodibility factor, Digital Elevation Model for estimating topographic (LS) factor, Land use land cover for cover factor detection from Ethiopian ministry of water resources. The result reveals that the soil loss ranges from 0 ton/ha/year in flat slope to 38.09 ton/ha/year from steep slopes. The average soil loss rate is 2.2 tons per hectare per year and has been classified into three erosion severity classes as very low, low and moderate. The result also reveals that most of the watershed erosion severity evaluated under very low and low soil erosion severity classes covering 97.3% of the watershed areas which is due to the effect of mixed plantation of various tree and terraces. However, moderate soil erosion in the upper parts of the watershed could be due to the inherent characteristics of vertisols, lack of vegetation cover and terraces which should be given first priority for conservation interventions. From the gross soil erosion, 43,762 ton/year sediment yields have been estimated at watershed outlet. Policy aim at keeping land productivity will need to focus to reduce low and moderate soil erosion through terracing, inter-cropping, contour farming, strip cropping, conservation tillage, mulching and biological stabilizers based on their slope range, soil type and land use type. The current finding on erosion was evaluated based on the past 10 years land use land cover scenario; therefore, soil erosion might be reduced if the current land use land cover scenario considered. Finally, the integration of USLE and GIS is an effective tool in mapping the spatial distribution of soil erosion from the entire watershed. The moderate and low soil erosion severity areas should be managed through terracing, inter-cropping, contour farming, strip cropping, conservation tillage, mulching and biological stabilizers based on their slope range, soil type and land use type. Free grazing and cultivation of steep slope(Northern parts) contributed for moderate soil erosion in the watershed should be managed by cut–carry system, limiting the number of cattle units to be grazed in the specific plot of land and leaving the marginal steep slope areas with no ground covers for natural regeneration. Finally, the current finding on erosion was evaluated based on the past 10-year land use land cover scenario. Therefore, the soil erosion could be reduced if the current land use land cover scenario is considered.

Management of hillside cropland is a critical issue in the tropical world because of the extreme pressure on the land itself that results from the decision to farm what would be considered in many countries as marginal land. Practices such as contour hedgerows and other soil conservation techniques could be more effective if they are installed or aligned in such a way that they maximize the land capability potential in various sectors of typical soil catenas; and if biological control crops including trees, grasses and shrubs are spatially arranged to take advantage of their intrinsic biological potential to accommodate to the edaphic dissimilarities of steep hillsides. Spatial arrangements of annual and perennial crops in natural geosequences are discussed, and suggestions are given on how spatial considerations can be matched to preferred crop mixes of trees, shrubs and grasses, in an attempt to halt erosion and better protect the environment. Land use planning on a physiographic and soil capability basis is proposed, but acknowledges that effective implementation is subject to a determined campaign to extend both the theory of sound land management and the provision of technical assistance to peasants to demonstrate the concepts and to interpret the results of the practices. This paper explores certain aspects of physiographic and edaphic similarities and constraints of peasant farming practices on steep slopes, and offers some theoretical bases upon which hedgerow technology can be applied to improve water and plant relations, ameliorate environmental effects and be initiated by individual farmers at little cost. A range of other soil conservation or agroforestry techniques, as used in Haiti is described; and a simple monitoring or measurement model to determine the amount of soil saved is provided, and the possibility of teaching the methods to minimally trained field technicians is explored, pursuant to encouraging farmers to give greater attention to the value of soil conservation and proper land use planning.

Best management practices (BMPs) are the tools which are adopted to run any activity while inflicting least negative impacts on the surrounding environment. Since, water pollution is one of the most important issues in today's world; it is indispensable to discuss the activities which are deteriorating its quality. Although, a number of treatment technologies and methods are in place for treating the point sources of pollution, there is a need to address nonpoint sources of pollution. There are many successful practices which are capable of curtailing the impacts of nonpoint source pollution, if adopted. In this paper an attempt has been made to evaluate the performance and trade‐offs of various management practices to address the issues of agricultural nonpoint source pollution. Nevertheless, there is a dearth of guiding principles which can pave a way for adoption of these practices. Therefore, an attempt has also been made to explore the aspects of policy formulations along with emphasizing the factors which can lead to adoption/ non‐adoption of such practices.

Mass movements and floods triggered by rainstorms are considered some of the most serious environmental problems and are quite often able to cause great disasters in large tropical cities. This has been occurring due to anthropic activities which change natural drainage and stability of slope in urban areas. However, lower monthly rainfalls which occur with high frequency can also cause mass movements and floods. The direct and indirect effects of less intense but continuous rainfall mainly affect less privileged communities, which occupy areas more sensitive to mass movements and flooding, such as locations along river margins, coastal lagoons, mangroves, and steep slopes. This manuscript highlights the important contribution of the lower monthly rainfall totals in triggering mass movements and floods on the east side of Pedra Branca Massif in the city of Rio de Janeiro. Geoprocessing was used to estimate the total monthly rainfall in rain gauges managed by the local authority; create surface interpolation and choropleth maps; and conduct a comparative analysis of histograms of the total monthly rainfall and flooding and mass movement records provided by the City's Civil Defence. The results confirmed the direct relation between higher monthly rainfall totals and mass movements and floods, and also showed that lower monthly rainfall totals can trigger a significant occurrence of such events. Moreover, the monthly rainfall limit that could trigger mass movements and floods was confirmed on the east side of Pedra Branca Massif.

Soil erosion and related forms, now constitute serious problem in many part of Ethiopia. Particularly in Southern Nation, Nationalities and People Regional State (SNNPRS) situated on high and step-faulted western sides of the Ethiopian rift system. An attempt was made attempted, to identify the traditional and indigenous of soil conservation practices, to assess thesocio-cultural, economic system constraints for the implementation and maintenance of conservation practices and to evaluate the performance and identify problems and opportunities in the application of soil conservation practices. The study was conducted in Siliti woreda where on the basis sampling of four highland kebeles were selected and 120 farm households were purposively sampled. There was annual soil loss recorded 114.59 tons/ha/year on the steep slopes. The traditional and indigenous methods were applied and practiced as fallowing land 24.2%, contour ploughing 13.3%, structure of planted tress 7.5%, indigenous drainage ditches 8.3%, contour ploughing 13.3%, leaving crop residues 5% and Fanya juu bench-like terraces 4.2% terraces for the soil conservation and management in study area. Key words: Soil erosion, indigenous method, bio-physical factors, productivity, management.

Methods of agricultural development on steep slopes in Korea (contour farming, bench terracing and semi-bench terracing) are evaluated. Runoff and erosion plot results are discussed and a design criteria proposed for relating slope length to gradient so that annual soil loss will not be excessive.

Rapid assessments of landslides (including other mass movements of rock, snow and ice) as well as human impacts were conducted by many organizations immediately following the 25 April 2015 M7.8 Gorkha earthquake and its aftershock sequence. In particular, a NASA-led satellite mapping campaign identified over 4,300 coseismic and post-seismic landslides throughout Nepal, largely concentrated in the “down-dropped northern tectonic block” well north of Kathmandu in the Greater Himalaya (Kargel et al., 2016). The Solukhumbu District lies at the eastern margin of this zone, near the epicenter of the 12 May 2015 M7.3 aftershock. Given the enormous cultural and economic value of the Khumbu region to Nepal, we conducted two post-monsoon ground assessments of geomorphic and structural damage in the fall of 2015, and a third ground assessment of rebuilding efforts in May, 2016. While landslides and other mass movements were not as extensive as those to the west, numerous landslides and slumps were identified, mostly on steep, convex-up, east-facing slopes where the dip of metamorphic foliation (Namche orthogneiss and related rocks) is towards the Dudh Kosi River channel. Also, building damage was more extensive where villages were located on terraces of unconsolidated sand and gravel perched above the Dudh Kosi River (Nakchun Village). The area upstream from Phakding experienced several co-seismic mass movements on steep slopes that had clearly failed before (previous temblors?), as evidenced by old vegetated slump blocks and steep, unstable hummocky terrain. Particularly hard-hit was the Sherpa village of Thame northwest of Namche Bazaar, constructed on unconsolidated, water-saturated glacial outwash between two lateral moraines at the mouth of the Thame Khola Valley. Aside from Thame, one is struck by the randomness of structural damage in many Sherpa villages, reflecting micro-ground conditions beneath buildings and the style and/or age of construction (dry-stacked fieldstone versus the use of mud or cement mortar, the presence of wire mesh or gabion bands/spacers within stone walls, etc.). Fresh valley-flank slumps and landslides were markedly less obvious further north (towards Everest) where wide glacial valleys exist, although evidence of large rock falls and other mass movements in the past is clearly present.

The topographic condition of Tidore Island, where 50% of the area is on a steep slope, makes Tidore Island prone to landslides during the rainy season. This research aims to spatially identify landslide prone areas in Tidore Island using slope morphology method. SMORPH method is conducted by identifying and classifying potential landslide areas based on slope shape and slope angle matrix. The result of this study shows that high landslide potential area is 2,569.42 ha, medium potential area is 3,296.99 ha, low potential area is 4,778.46 ha, and very low potential area is 1,126.55 ha. Among the sub-districts in Tidore Island, North Tidore has the largest presentation area of 892.48 ha. It can be concluded that areas with steep slopes and convex or concave slope shapes have higher landslide potential. The findings of this research are expected to help local government in future spatial planning efforts for landslide mitigation.

Effects of slope angle on mass movement by tree uprooting

Erosion hotspots within a drainage basin refer to an area that erodes more rapidly than anticipated or more rapidly than adjacent portions. Or, areas having high erosion rate as compared to the adjacent places. Since erosion can adversely affect ecosystems on-site as well as off-site, the estimation of runoff and soil loss in catchments is becoming more important. The main objective of this work is to: (1) delineate the hotspot areas (areas of erosion/sediment source) within the Abbay/Blue Nile Basin, (2) generate vulnerability maps to assess the risk possibilities at these areas as well as to support the watershed management approaches for the whole basin, (3) determine the environmental impact, and (4) evaluate sediment and water resources. The area under consideration is located to the northwestern of Ethiopia and to the East of Sudan, directly on the political boundary separating the two countries. The basin area is about 314458 km² and is fully dissected by streams that form the Blue Nile River. The majority of mentioned area is considered one of the most important highlands feeding the River Nile with both water and sediment. Therefore, Assessment of the erosion hotspots within this basin is essential for the management of the whole system. The Splash and sheet erosion are most widely observed within the highlands of the Blue Nile basin in Ethiopia, which generate noticeable amounts of sediments that induce and increase the erosion rate when the rills and gullies start to form. The slope, runoff intensity, and soil types are the most factors that play an essential rule in the erosion hotspots. The Digital Elevation Model (DEM) was used to derive the slope angels, shapes (concavity and convexity), profile curvature, as well as the flow direction vector. Approximately 65% of the area has a slope gradient less than 15%. However, very steep slopes (up to 65%) are also present, increasing the risk of erosion in these mountainous areas. Climate maps, runoff maps, soil maps, land use maps as well as satellite images were also used in the spatial calculations and modeling. For the modeling phase, the Water Erosion Prediction Project (WEPP) Model along with the Geo-Spatial Interface for WEPP (GeoWEPP), integrated with the GIS, were used. The potential reading of the resulted maps showed that the most affected areas with erosion lie within the highlands of Ethiopia where there are very steep slopes, soft soil cover, and intensive runoff. Also, down from the highlands in Sudan, there are several hotspots formed due to the erosion by mass movement which due to the existence of specific soil types. Keywords: hotspot delineation, watershed management, Blue Nile Basin

Due to the importance of the study area for Erbil governorate and for it is practical and strategic implications, as it represents the only pass way that passes a high and complex structural ranges that linked the north part of the governorate with middle and south parts, and also for it is tourism importance and scientific value for the geologic purposes in particular, as it reveals rock formations at great depths in the valley area and for the lack of paying attention to this area from scientific point of view due to scarcity of geological and geomorphological studies about it, so the study aimed to study the landforms, perhaps its data and analyses contribute to development plans and projects that may include the study area in the future, as well as developing solutions for the geomorphological hazards taking places in the study area such as mass movements which are threatening architectures foundations, facilities and also people there. The main objectives of this study are to simplify and clarify the complex view about the area for the researchers and those interested in the field of geomorphology and other related disciplines, though the study found out the valley area is highly affected by its structural status. That represented by many folds which are subjected to main and giant faults; therefore, the structural factor was the dominants agents in developing most of the landforms in the area such steep slopes and landforms caused by mass movements, waterfalls, springs and the gorges …. etc., and also there is some geomorphic hazards in which some solutions have been proposed for.

The Himalayas as a whole is tectonically very active and geomorphologically very unstable. It is highly vulnerable to water induced disasters like soil erosion, landslides, floods, glacial lake outburst flood etc due to its high relief, steep slopes, active geology, and intense monsoon rainfall. Moreover, rapid growth of population and consequent changes in land use and land cover, development of infrastructures and man-induced changes in runoff are also responsible for increased events of landslide and flood hazards. The loss of life and properties from these hazards has been increasing. The livelihood options of the people have been threatening. There is urgent need to develop and implement disaster management activities in order to reduce the loss of life and properties and sustain development activities in this area. An assessment of hazard, risk and vulnerability and its mapping could provide basis for the development of effective disaster management activities. It is in this context, an attempt was made to identify different types of water induced disasters and map and assess its risk and vulnerability. Tinau watershed was selected for this study.Tinau watershed with the total area of 234 sq km lies in Palpa district in western Nepal. The elevation ranges from 330 m at the confluence of Tinau river and Jhumsa khola (stream) to 1893 m at Ghustung Lekh. Both the secondary and primary information have been used. Aerial photographs taken in 1996 were interpreted with field verification in order to identify the areas prone to different types of water induced disasters. Local people were consulted and interviewed to gather information for risk and vulnerability assessment. The field-work was carried out in September 2003. A total of eleven parameters like lithological units, lineaments, slope gradient, slope shape, slope aspects, relative relief, drainage density, water table and drainage condition, land use, vegetation cover, and distance from the road were used for landslide and flood hazard mapping. These information were derived from available analog maps such as toposheets, land system, land utilization, land capability prepared in the past with modification after field verification. GIS tool was used to analyse above mentioned parameters and prepare hazard, risk and vulnerability maps. Hazard areas were categorized into three groups according to the probability of occurrence of hazards such as high, moderate and low.

Soil erosion is the most challenging and continuous environmental problems resulting in both on-site and off-site effects in the world particularly in Ethiopia. Karesa watershed is one of the most erosion-prone watersheds which received little soil conservation attention. This study was conducted to estimate average annual soil loss rate using Geographic Information System and Universal Soil Loss Equation Model adapted to Ethiopian condition. The following datasets were obtained from different sources for estimating annual soil loss such as 15 years mean annual rainfall data for estimating erosivity factor, digital soil map for estimating soil erodibility factor, 30 m × 30 m resolution Digital Elevation Model for estimating slope length and slope steepness (LS) factor, Landsat6ETM+ images with 30 m × 30 m resolution for detecting vegetation cover and conservation practice factor. The result reveals that 42,413.72 ton per year soil loss from 9939 ha entire watershed or 4.27 tons per hectare per year average annual soil loss rate was observed. The mean annual soil loss rate was classified into four erosion severity classes as very less, less, moderate and high. The result also implies that 94.4% (9383.07 ha) of the watershed areas contributes 81.13% of the total soil loss which were observed from two slope classes (0-15% and 15-30%) and categorized under very less to less soil loss (0-6.25 tons ha-1yr-1). On the other hand, moderate to high soil loss (6.25-25 tons ha-1yr-1) was obtained on slope classes of >30% which covers 555.93 ha (5.6%) of the watershed areas and contributes 18.82% of the total soil loss indicating the maximum share of slope mainly due to cultivation of marginal land,intensive cultivation, poor vegetation cover during critical rainfall period. Moreover, about 2,184.93 ha of the watershed area requires integrated soil and water conservation measures. Key words: Conservation priority, soil erosion, Universal Soil Loss Equation Model (USLE), geographic information system (GIS), Karesa watershed   &nbsp