Relative Proliferation of Gullies on Three Geological Sediments: The Influence of Soil Consistency Limits and Shear Strength (original) (raw)
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Relative Vulnerability to Gully Erosion of Three Geological Sediments: A Texture-Based Assessment
This study was carried out to evaluate the particle size distributions and erodibility indices at two soil depth ranges, 0 -60 cm and 60 -90 cm, of the three geological sediments underlying 100% of the landscape of the Idah-Ankpa Plateau of the Anambra Basin, Nigeria. The aim was to explain why the three geological sediments, namely, the Upper Coal Measures (UCM, 36%), the Ajalli Sandstones (AS, 44%) and the Lower Coal Measures (LCM, 20%) are exposed to varying degrees of vulnerability to gully (soil) erosion. The depth range 0 -60 cm was considered the topsoil most prone to rill erosion, the range 60 -90 cm (and above) was the subsoil, the normal depth of a formed gully. The particle size distributions were determined by the hydrometer method plus NAOH for dispersion, and the erodibility indices were computed in decimal units using the clay ratio method. Data were analyzed using descriptive statistics. In the top and subsoils, the LCM was observed to have the highest mean clay contents (39% and 41% respectively). This was followed by the UCM (20% and 36%), while the As had the least (5% and 18%). Nevertheless, the mean erodibility indices of the AS in both the top-and sub-soils were respectively the highest (0.244 and 0.084), followed by the UCM (0.041 and 0.022), whereas the LCM was the least (0.016 and 0.016). The results show that the AS is the most erodible both in the top and subsoils, followed by the UCM. The LCM is the least. The relative vulnerability to soil (gully) erosion of the three sediments can, therefore, be ranked as AS>UCM>LCM. The ranking agrees with the observed order of proliferation of gullies on the IAP. Expenditure on gully erosion control on the IAP should be concentrated on the areas covered by the underlying sediments in the descending order of their vulnerability to gully formation: AS > UCM > LCM.
Advances in Environmental Biology, 2012
Gully erosion is an important form of soil erosion in arid and semi arid lands of Iran. This form of erosion is an key procecces of land degradation. This paper focuses on the some basic aspects of role of soil physical properties upon gully erosion in semi aride region of 210 km 2 . For this case, Abgendi watershed which has the largest amount of gully erosion was selected. In this area 35 gullies were studied. From main water way of each gully, soil sampling from head-cut & two walls in two depths (0-30 cm & 30 cm to bottom of gully) were carried out. To compare the soil physical properties in different sizes of gullies, the gullies were classified based on gully volume in four sizes big, medium, small and very small gully. To identify the role of gully soil texture as the important physical characteristic on the gully erosion development the gullies were also classified and compared based on soil texture. Moreover, to compare the soil physical characteristics of gully to the control (the area without gully), using the gullies scattering map and field survey the study area, three control areas with at least 5 hectares were chosen randomly as the control in the study area. In each control area five samples of the depth 0 -30 cm were taken and mixed then one of them was taken. For depth 30 -60 cm, was done the same process. For both gully and control samples, soil physical characteristics such as clay, sand, silt, soil texture, AS (aggregate stability) and MWD (main weighted diameter) were determined. In addition these factors, gully volume and gully length as independent variables and two important indexes of gully erosion development were measured. The result of the comparison between the gully volume groups showed that MWD in deeper layer and AS in both deeper and surface layer were increased from big gully to very small gully. The results of soil texture comparison in soil texture groups showed that the gully length and volume were increased from loam to clay loam. The gullies frequency were also showed that gullies have silt loam and silt clay loam texture in their surface and deeper layer respectively had the most frequency, while, the gullies with silt loam in their surface layer and loam in deeper layer have the least number of gullies. Moreover, comparison of the gully and control indicated that there is a significant difference between both two areas in terms of sand and silt, as the amount of sand and silt the control areas are higher than the gully erosion areas.
Nigerian Journal of Technology
Gully erosion is an environmental problem that confronts the international community. This study was undertaken to investigate the relationships between gully length and average gully width on two geological sediments of varying resistance to erosion. Thirty-seven and five gully samples formed respectively on two homogenous geological sediments (the Ajalli Sandstones (AS) and the Upper Coal Measures (UCM)) underlying the Idah-Ankpa Plateau of the North Central Nigeria were measured and their lengths (L) and average widths (W) were subjected to correlation analyses and the sample bivariate regression to examine and compare their relationships on the two formations. Results show that on the highly erodible AS, L is positively, poorly, and not significantly correlated with W (R = 0.201, R 2 = 0.040), whereas the correlation is stronger, significant, but negative at the 0.05 level on the UCM (R =-0.930, R 2 = 0.865). The regression equations show that L is a poor predictor of W on the AS (W1 = 6.387 + 0.03L1, R 2 = 0.040), and a very good predictor of the parameter (W) on the UCM (W2=18.135-0.033L2, R 2 = 0.865), which appears as a negative value. And the valid range of gully lengths for the prediction of the average width on the AS can be ranked as 0 = L < (infinity), whereas the ranking is of the form 0 ≤ L ≤ 549.55 m on the UCM. The study suggests that the correlation of W with L becomes stronger, negative and significant as the resistance to erosion of the geological sediments increases. It also suggests that the predictability of W using L as a tool improves and transforms to a negative value as the resistance to erosion of the formation increases.
Soil aggregate stability and erodibility in different gully sites in parts of Kaduna State, Nigeria
Ethiopian Journal of Environmental Studies and Management, 2014
This paper assesses soil aggregate stability and erodibility in different gully sites in parts of Zaria, Kaduna State, Nigeria with the aim to provide quantitative information on the variation of some soil properties and their interaction with eroding agents and how this affects soil erosion on the sites. The gullies selected are found at the headwaters of river Saye, Yashi, Guga and Kubanni basins with leached ferruginous tropical soils developed from the basement complex and quaternary deposits drained by River Galma whose pattern is basically dentritic. Soil samples collected from the headscarps, sidewalls and floor of each gully length at 5-10 cm depth were analysed using standard laboratory methods. Particle size distribution data was used to compute clay ratio index. The result shows that based on aggregate stability the most susceptible to water erosion is the Yashi gully site. Soil particle size distribution in all the gully sites show soil textural classes of silt loam, sandy loam, sandy loam and sandy clay loam at Guga, Saye, Kubanni and Yashi gully sites respectively. Based on clay ratio index (3.58) Yashi show more resistant to erosion followed by Saye with a mean clay ratio index of 4.02, then Kubanni with a mean clay ratio of 10.89 and lastly Guga with a mean clay ratio of 13.06. Results show there is a significant variation of clay, silt, sand, clay ratio and aggregate stability with gully sites at 0.05 levels of significance. A linear multiple regression analysis was used to check the contribution or influence of each independent variable on the dependent variable. Clay ratio index was also derived. The Research concludes that though all sites exhibit gully erosion the reaction of soil properties to environmental conditions varies. Slightly different efforts will be required to turn around the gullies.
Due to sediment production and tremendous damages resulted by land destruction, roads and construction factors in Fars province, gully erosion is considered of high priority. One of the studied thresholds in gully erosion is topographic threshold. This threshold is given as exponential relation between area and slope above the point of gully. The current research is to compare topographic threshold in gully creation in various land use in Fars province, south west of I.R.Iran. Six most important gully regions were chosen and in each region, 30 active gullies were selected for detailed study and sampling. At the first stage, watershed and gully erosion boundary, and their land uses were determined on the topographic map with a scale of 1:25000. Area and slope above the point of gully outlet were measured in the field, land physical properties and soil chemico-physical properties in each gully were determined by lab measurement. Area and slope relationships of gullies were determined ...
Gully Erosion-Induced Land Degradation on the Idah-Ankpa Plateau of the Anambra Basin, Nigeria
Forty three gullies were sampled and measured on the three geological formations underlying the Idah-Ankpa Plateau of the Anambra Basin, Nigeria, to define their morphometry as well as their roles in the degradation of the plateau lands. The three geological formations comprise the Ajalli Sandstones (AS), the Upper Coal Measures (UCM), and the Lower Coal Measures (LCM). Of the forty three gullies studied, 37, 5, and 1 were located on the AS, UCM, and LCM respectively. Descriptive statistics of mean, standard deviation, and coefficient of variation were used to describe their morphometric characteristics such as length (L), average depth (D), average width (W), average volume (V), average cross sectional area (A), and the form factor (W/D). Findings indicate that the mean L = 452.27, 361.66, and 400.00 m; mean D = 6.49, 5.96, and 5.00m; and mean W = 7.95, 6.23, and 3.00 m on the AS, UCM, and LCM respectively. These translate to standard deviation values of L = 322.12 and 200.52; D = 3.47 and 4.91; and W = 5.53 and 0.87 with a coefficient of variation of L = 71.22 and 55.44; D = 532.47 and 82.38; and W = 69.56 and 13.97 on the AS and UCM respectively. The respective W/D ratios on the AS, UCM and LCM were 1.46, 0.91, and 0.60. The size and population of the gullies on the AS show that the greatest amount of sediment pollution occurs on this formation. In addition, a W/D ratio of 1.46 indicates that the surface soils are degraded (eroded) more than the sub-soils on the AS. On the other hand, a W/D ratio of 0.91 on the UCM shows that the sub-soils are slightly more degraded and degradable than the surface soils. Furthermore, a W/D of 0.60 of the only existing gully on the LCM reveals that the sub-soils are more erodible than the surface soils. Whereas land management practices shall be geared towards preventing accelerated erosion on the UCM and LCM, government shall intensify more efforts in the control of gullies on the AS.
Gully erosion: Impacts, factors and control
CATENA, 2005
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.
The topographic threshold of gully erosion and contributing factors
Natural Hazards, 2022
The topographic threshold is based on the power relationship between area and slope and is widely applied in gully-erosion research; however, this relationship requires further testing. Accordingly, the Alamarvdasht Lamerd and Fadagh Larestan regions in Fars Province, Iran, were selected as case studies to explore the topographic threshold for gullies. Thirty active gullies were identi ed in each study area during eld surveys, and data describing land use and land cover, drainage areas, slope, and the physical and chemical properties of the soils were assembled. Multivariate analysis was conducted using SPSS to determine the effects of these factors. Using the power relationship between the catchment area and slope for each gully, the analyses explored critical controls for gully development. The results showed that surface runoff was the most signi cant effective factor for gullies in the study areas. Sparse ground cover, ne-textured soils, and inappropriate land use all contribute to gully development. The results suggest that the relationship between slope and drainage area in the Fadagh Larestan case study is S = 0.0192 A − 0.159 for gully headcut areas and S = 0.0181 A − 0.258 at gully outlets. The corresponding values of the exponent β at the gully headcuts and outlets at Fadagh were − 0.15, and-0.25, respectively. The corresponding relationships for gullies in the Alamarvdasht Lamerd area for the gully headcuts and outlets were S = 0.0143 A − 0.061 and S = 0.0073 A − 0. 18 , respectively, with β values of-0.06 and −-0.18. This study provides a basis for determining the thresholds for the initiation of gully development. Analyses of the effective factors provide clues to improve the management of bare lands to prevent the initiation of gully erosion. Highlights Considering among topographic threshold of gully erosion and contributing factors; Multivariate analysis was conducted to determine the effects of contributing factors; Determining the thresholds for the initiation of gully development; Using the power relationship between the catchment area and slope for each gully
International journal of advanced geosciences, 2016
The evaluation of geotechnical properties of rock materials is used to ascertain the environmental factor that necessitated gully erosion in Orlu and its environs, Imo State, Nigeria. The study is aimed at geotechnically defining the characteristics, causes and formation of the gully erosion with particular emphasis on the current land degradation in the study area. Data used in the study were derived from field measurements, and laboratory analysis. Gully variables such as length, depth and widths were also determined. The result of the geological mapping revealed that there are three geologic formations encountered in the study area namely; Ameki, Ogwashi Asaba, and Benin Formations. The result of the field studies shows that 27% of the gullies observed occur in Ameki Formation while no gully was discovered in Ogwashi Asaba formation. The grain size distribution curves interpretation revealed that 80% (by weight) of the soils are medium to coarse grained sand and fine gravels, while the remaining 18% and 2% are for fine grained sand and coarse grained silt. The Atterberg Limit Test interpretation shows that the plasticity index of the formations ranges from 24.83% to 48.42%. Based on the results of the geotechnical properties of rock materials in the study area, the factors responsible for gullies occurrence in the study area were identified as topography, rainfall, geology, and anthropogenic factors. The devastating effects of gully erosion in the study area were observed to include loss of about 22km2 of arable lands; 2 major and 6 minor road failures; loss of many houses and other infrastructures; pollution of surface and underground water. Finally, it is recommended that the appropriate authorities, individuals and all stakeholders in the environmental protection agency should develop ideas in environment watch towards gully erosion control.
The evaluation of geotechnical properties of rock materials is used to ascertain the environmental factor that necessitated gully erosion in Orlu and its environs, Imo State, Nigeria. The study is aimed at geotechnically defining the characteristics, causes and formation of the gully erosion with particular emphasis on the current land degradation in the study area. Data used in the study were derived from field measurements, and laboratory analysis. Gully variables such as length, depth and widths were also determined. The result of the geological mapping revealed that there are three geologic formations encountered in the study area namely; Ameki, Ogwashi Asaba, and Benin Formations. The result of the field studies shows that 27% of the gullies observed occur in Ameki Formation while no gully was discovered in Ogwashi Asaba formation. The grain size distribution curves interpretation revealed that 80% (by weight) of the soils are medium to coarse grained sand and fine gravels, while the remaining 18% and 2% are for fine grained sand and coarse grained silt. The Atterberg Limit Test interpretation shows that the plasticity index of the formations ranges from 24.83% to 48.42%. Based on the results of the geotechnical properties of rock materials in the study area, the factors responsible for gullies occurrence in the study area were identified as topography, rainfall, geology, and anthropogenic factors. The devastating effects of gully erosion in the study area were observed to include loss of about 22km2 of arable lands; 2 major and 6 minor road failures; loss of many houses and other infrastructures; pollution of surface and underground water. Finally, it is recommended that the appropriate authorities, individuals and all stakeholders in the environmental protection agency should develop ideas in environment watch towards gully erosion control.