Rise Of Groundwater Table Research Articles

Cracking Modeling In Partially Saturated Media With Phase-Field Method And Application To Rainfall-Induced Landslides

Cracking is the principal mechanics of failure in engineering structures and geo-logical systems. Complex cracking patterns are observed in rock-like materials under compressive stresses. On the other hand, rainfall is one of the main triggering factors of landslides. Therefore, the rainfall induced landslides should be investigated by considering complex relationships between rainfall and rising groundwater table and related reduction of shear strength. In this paper, we present a new phase-field method for modeling the transition from diffuse damage to localized cracks. The damage variable is assumed to be driven by the deviatoric strain and positive (or dilatant) volumetric strain. This allows the description of tensile, shear and mixed cracks. The phase-field method is extended to partially saturated porous media by considering hydromechanical and phase-field coupling mechanisms. The proposed phase-field method is then applied to the analysis of rainfall-induced landslides in partially saturated conditions. The evolutions of pore water pressure, displacement and damage fields are predicted. Different failure mechanisms are discussed.

Quantification of resilience metrics as affected by conservation agriculture at a watershed scale

It is suggested that conventional tillage operations exacerbate global environmental changes and affect the sustainability of our food production systems. Therefore, no-till has been introduced as one of the conservation agriculture practices to counteract these challenges. No-till has been adopted by a substantial number of farmers in major cropping regions; however, its resilience from large scale implementation has been overlooked. The majority of the studies have reported only a few aspects of the no-till practice (e.g., yield, soil properties, etc.), often with contradicting observations. To fill this gap, we present an approach that integrates long-term field experimental data and modeling to quantify resilience at a watershed scale. The study was conducted in the Kalamazoo River watershed located in Michigan, USA. Recharge, groundwater table, soil moisture, yield, and net return were used as resilience metrics. The DSSAT sequence crop model was developed for a corn-soybean-wheat rotation and calibrated using the yield and soil moisture data from a long-term (1993–2019) experiment for the conventional and the no-till treatment conducted within the study area. Soil moisture, recharge and yield were simulated, and the recharge was fed into a calibrated groundwater model to analyze changes in groundwater heads. The results illustrate clear evidence of higher recharge and net return under the no-till treatment, which were statistically significant for all crops at the watershed scale. Moreover, the no-till treatment consistently retained greater soil moisture than the conventional treatment, thereby helping to mitigate the impacts of droughts. The rise in groundwater table as affected by the adoption of no-till practices in this watershed has ranged between 0.1 and 0.5 m, depending on the underlying groundwater system, and has the potential to beneficially affect the aquifers and groundwater-dependent ecosystems. Therefore, the conservation agriculture could improve the overall resilience of the row crop system.

Shallow Landslides Physically Based Susceptibility Assessment Improvement Using InSAR. Case Study: Carpathian and Subcarpathian Prahova Valley, Romania

A multi-temporal satellite radar interferometry technique is used for deriving the actual surface displacement patterns in a slope environment in Romania, in order to validate and improve a landslide susceptibility map. The probability the occurrence of future events is established using a deterministic approach based on a classical one-dimension infinite slope stability model. The most important geotechnical parameters for slope failure in the proposed study area are cohesion, unit weight and friction angle, and the triggering factor is a rapid rise in groundwater table under wetting conditions. Employing a susceptibility analysis using the physically based model under completely saturated conditions proved to be the most suitable scenario for identifying unstable areas. The kinematic characteristics are assessed by the Small BAseline Subsets (SBAS) interferometry technique applied to C-band synthetic aperture radar (SAR) Sentinel-1 imagery. The analysis was carried out mainly for inhabited areas which present a better backscatter return. The validation revealed that more than 22% of the active landslides identified by InSAR were predicted as unstable areas by the infinite slope model. We propose a refinement of the susceptibility map using the InSAR results for unravelling the danger of the worst-case scenario.

Effect of reservoir geometry on functionality of recharge dams influenced by sedimentation: case study of the Meymand recharge dam

In the present study, influence of reservoir geometry on sedimentation pattern and functionality of the Meymand recharge dam, located in a semi-arid region in southern Iran, is studied. After 7 years of dam operation and sedimentation, the reservoir functionality was evaluated during 2018–2019 water year, which discharged ~ 813700 m3 of floodwater into the reservoir. Field measurements supported by isotope and hydro-chemical tracing indicated that most of inflow floodwater (94%) recharged the aquifer through the reservoir bed, resulting in ~ 33.63-m groundwater table rise in the downstream aquifer. Based on field mapping, accumulated sediments on reservoir bed covered only ~ 9.3% of reservoir surface area. Numerical simulation using Seep2D revealed that due to very low permeability, accumulated sediments acted as a barrier against recharge from reservoir bed. Therefore, only permeability of ~ 9.3% of the Meymand reservoir surface area was influenced by sedimentation and the rest of the reservoir surface area (~ 90.7%) was not influenced by sedimentation. The V-shaped cross-sectional of the Meymand reservoir was instrumental in the formation of the minimal sedimentation coverage area, which consequently resulted in increased reservoir recharge efficiency. Because during dry periods, accumulated sediments on slopping sidewalls of reservoir bed are easily washed out and transported to the lowest area in reservoir bed for settlement. So, V-shaped alluvial valleys are suggested as suitable sites for recharge dams, which should be considered in new artificial recharge projects.

Impacts of Soil Salinity/Sodicity on Soil-Water Relations and Plant Growth in Dry Land Areas: A Review

Soil salinity/sodicity is the major problem in irrigated and rain-fed areas and are a continuous threat for the sustainability of agricultural production. The presence of salt affected soils has been identified as a major process of land degradation and the greatest cause of declining productivity by causing a detrimental effect on biological, physical and chemical properties of the soil system. Therefore, the objective of this topic is to review the impacts of salinity/sodicity on soil- water relations and plant growth in dry land areas in relation to their extent, distribution and development so as to manage and efficiently utilize the limited natural resources under irrigation and rain-fed farm lands. Land degradation by salinization is often found in Arid and Semi-Arid lands where irrigation of unsuitable soils or with poor quality water is a common practice. Moreover, dry land salinity is also mainly a function of rising groundwater tables, caused by increased recharges. Soils having soluble salts in solution and/or Na + ions or both on exchange sites exceeding certain limits that can adversely affect soil plant health by disturbing the biological , physical and chemical properties of the soil to the lower limit are classified as saline, sodic and saline sodic by taking into consideration of their pH, ECe and ESP. High levels of salinity have negative impact and potentially lethal effects on plants growth. On the other hand, high sodium concentration causes sodium-induced dispersion like reduced infiltration, reduced hydraulic conductivity and surface crusting while salts like calcium and magnesium, do not have this effect because they are smaller and tend to cluster clay particles and keep the soil to be flocculated since they compete for the same spaces as sodium to bind clay particles and reduce the amount of sodium-induced dispersion. High salt levels in the soil affects the nutrient balance in the plant or interfere with the uptake of some nutrients. Salt affected soils restricts plant growth and nutrient uptake due to osmotic forces. Keywords: Salt Afected Soils, Dry land, Soil-Water, Soil Properties DOI: 10.7176/JNSR/12-3-01 Publication date: February 28 th 2021

Danger from beneath: groundwater–sea-level interactions and implications for coastal archaeological sites in the southeast US

ABSTRACT Coastal low-lying archaeological sites are known to be at risk due to sea-level rise associated with climate change. However, not all of the potential impacts of sea-level rise on these sites have been documented. In this interdisciplinary study we set out to document the effects of rising groundwater tables induced by rising sea level on middens located on barrier islands in southeastern Florida. After excavating two sites, we collected sediment samples that were analyzed for grain size and moisture content. We found that even though these sites are not yet submerged below the groundwater table significant increases in moisture content indicate a subterranean source of the moisture, most likely the capillary fringe above the water table. Increased moisture content of the sediment in which the artifacts are entrained can increase artifact deterioration. Therefore, current and future groundwater water table elevations should be considered when prioritizing sites for excavation and preservation.

Long-Term Changes in Moisture Circulation Processes by Data of Water Balance Stations in the Central Don Basin

The materials of long-term observations at water balance stations in the Don basin confirm the existence of climate changes, which have led to changes in water runoff formation and other water balance elements. It is shown that the major changes in the hydrological regime of water bodies have been induced by the weakening of the effect of cryogenic regulation of water exchange in the basin. This can be seen in two processes: an increase in the infiltration of atmospheric precipitation into aeration zone and groundwater and better drainage of groundwater by the hydrographic network. The first process dominates in the initial period, leading to an increase in the share of surface runoff, a rise in groundwater table, i.e., an increase in groundwater inflow into rivers. Later, the contribution of the second process increases, resulting in a decrease in groundwater reserves in the basin and a drop of groundwater table and river runoff in the dry season. The budget of the processes of replenishment and drawdown of groundwater recovers after the cessation of the formation of cryogenic phenomena in the river basin caused by phase transitions in water–ice (snow)–water system. It is very likely that the transformation of these processes is now coming to an end.

Reactivation mechanism of a large-scale ancient landslide

This paper presents details of the recently reactivated landslide in Wushan Town, Chongqing, China. The landslide was reactivated on July 17, 2019, by slope cutting, and thereafter, entered a state of imminent sliding. The landslide involved 4 million m3 of rock and soil masses, thereby threatening National Road G348 and the safety of 588 residents in 136 households in Xiping Village and over 1000 residents in the Jinke Community. Field investigations, drilling, and in situ monitoring were performed to determine the landslide deformation characteristics and reactivation mechanism. The results show that the regional abundant rainfall, formation lithology, and tectonic effects were responsible for the formation of the ancient Baiyangwan landslide. Moreover, the building load on the rear and middle parts increased the sliding force. Open excavation at the toe decreased the anti-sliding force and directly promoted landslide reactivation. In particular, the groundwater table rise caused by gully filling in recent years also played a key role in the reactivation of the ancient landslide.

Salinity risk assessment of an irrigation development using treated coal seam gas water in the Condamine River catchment

All irrigation developments inherently carry a salinity risk, due to an unavoidable change in the water and salt balance. The time frame in which either land or water salinity will develop is driven by the ability of the landscape to absorb the change of water and salt supplied. Factors that influence this are landscape attributes, such as the size of the unsaturated zone and its properties (permeability and drainage), management considerations (land-use changes, water application rate and crop water use) and climate variability (temperature and rainfall). This study assessed the risk of secondary salinity expression occurring in an irrigation area in the Condamine-Balonne catchment in southern inland Queensland, Australia. The objectives were to (1) define the depth, size and properties of the unsaturated zone and regolith, (2) define deep drainage rates for past, present and future land uses and (3) assess this information to calculate the risk that groundwater table rise may result in surface salinity expression. Data collected during field investigations was used to conceptualise the regolith architecture, undertake hydrogeological modelling, estimate the available moisture storage capacity of the unsaturated zone and model paddock deep drainage characteristics. The work identified that irrigation-induced deep drainage had started to mobilise salt stores in the unsaturated zone. It also identified connectivity between land management and salt discharges into the Condamine River. As the water supply for the scheme is scheduled to continue until 2030, there is a clear risk of the unsaturated zone moisture storage capacity being exceeded, leading to both land and surface water salt expressions.

Rising groundwater and sea-level rise

The response of coastal groundwater to sea-level rise is largely unknown. Groundwater modelling along the California coast — accounting for complex topography and its interaction with rivers, streams and tributaries — shows that the area at risk from rising groundwater tables extends beyond that inundated by sea-level rise alone.

Multivariate Analysis of Soil Salinity in a Semi-Humid Irrigated District of China: Concern about a Recent Water Project

The Chaobai River (CBR) basin in northern China is experiencing an unprecedented continuous inflow of external water via the South–North Water Diversion Project, which has channeled water from the southern part of the country to the north. Consequently, the steady rise of groundwater table in recent years is threatening soil salinity regulation. The purpose of this study was to describe the status of salinity of the surface soil in the CBR basin and to evaluate the impact of environmental factors including groundwater table on the spatial distribution of soil salinity using multivariate analysis (MVA) technique. In this study, 10 chemical variables of soil samples collected in 204 sites along CBR were analyzed, considering their interaction with three environmental factors: the density of irrigation canals, groundwater depth and topography. Statistical analysis mainly consisted of principal component analysis (PCA), redundancy analysis (RDA) and clustering analysis (CA). The results allow defining the surface soil in the CBR basin as a slightly saline and moderately alkaline media. The first two axes of multivariate model approximately explains 51% of the observed variability and allows distinguishing two main domains: the saline and the alkaline. The variability of the saline domain, defined by major cations and anions, is obviously controlled by macro environmental factors, of which the density of irrigation canals and groundwater depth contributes 71% and 28%, respectively, while that of the alkaline domain, related to pH and bicarbonate, mainly manifests as singular behaviors of soil groups like rice cultivation or sewage irrigation. The results suggests that more attention should be paid to the ongoing water table rise to help inform future land management decisions and to prevent a double threat of both groundwater and surface water on soil salinization. Meanwhile, this study shows the enormous potential of MVA technique, specifically the complementary duo of RDA and CA, for integrating both global and local information of soil salinity and environmental factors.

Water logging problems in Egypt’s Deserts: Case study Abu Mena archaeological site using geospatial techniques

Groundwater table rise below cultivated, industrial and urban areas, and archaeological sites is a worldwide environmental phenomenon. Groundwater level rise can cause damages to the foundations of the archaeological monuments due to water logging and salt accumulation. Several factors contribute to the groundwater rise. Important factors are those related to hydrological and hydrogeological conditions as well as the inadequate sewerage, excessive irrigation and poor drainage systems. Reclamation projects in West Al-Nubaria area, including Abu Mena archaeological site in Burg Al-Arab to the southwest of Alexandria lead to urban and agricultural sprawl. The groundwater table has risen remarkably and reached mostly the ground surface causing the problems of water logging. Intense groundwater exploitation carried out without careful planning has however brought about a severe deterioration of land and water resources. Water logging, salt accumulation and the deterioration of land and water resources can be prevented, or at least mitigated, through implementation of some guidelines that control irrigation, drainage and sewage processes. The current work aims at investigating the groundwater table rise and its related problems at the Abu Mena archaeological and cultural site and to explore the reason(s) behind this problem. According to the results of study, some measures for the management of water irrigation, drainage and sewage systems will be recommended.

Sea Level Rise Effect on Groundwater Rise and Stormwater Retention Pond Reliability

The coastal areas of Florida, United States, are exposed to increasing risk of flooding due to sea level rise as well as severe hurricanes. Florida regulations suggest constructing stormwater retention ponds as an option to retain excess runoff generated by the increased impervious area and to protect the environment by reducing pollutants from new developments. Groundwater level rise can significantly lower the soil storage capacity and infiltration at retention ponds, in turn, reducing the pond’s capacity to capture consecutive storms due to longer pond volume recovery time. Partial groundwater inundation can affect retention ponds’ ability to decrease peak flow rates and keep the post-development outflow lower than or equal to pre-development conditions. In this paper, the reliability and performance of a retention pond near Tampa Bay, Florida, was evaluated under sea level rise conditions. An integrated surface water and groundwater model was developed, and the groundwater table was projected for future conditions as a function of sea level rise. The results showed that sea level rise could increase the seasonal high water elevation of the retention pond up to 40 cm by mid-21st century. This increase lowered the reliability of the retention pond by about 45%. The pond failed to recover the designed treatment volume within required 72 h because of the high groundwater table, increasing the risk of pollutant discharge. Furthermore, the peak flow and volume of runoff significantly increased under sea level rise and associated groundwater table rise conditions. The study results suggest that it is imperative to consider future sea level rise conditions in stormwater design in low-lying coastal areas of Florida and around the world to prevent poor pond performance and increased risk of flooding in the future.

South African peatlands: A review of Late-Pleistocene-Holocene dvelopments using radiocarbon dating

South Africa has a limited number of peatlands and most of them are relatively small compared to those in cooler temperate regions in the northern hemisphere. We gathered 40 basal peat samples representative of South Africa’s peatlands to explore their development during the Late Pleistocene and Holocene. Depth profiles of nine of them were also investigated using radiocarbon dating, which yielded information on past environmental changes affecting South African peatlands. The data showed three peaks in the frequency of peatland initiation, which are consistent with available climatic and sea level fluctuation data: one after the Last Glacial Maximum (LGM) and two during the Mid to Late Holocene. Inland peatlands in mountain valleys showed optimal growing conditions during the glacial-interglacial transition, continuing until the Early-Holocene. This is due to the switch to the wet and warm interglacial climate. In contrast, coastal peatlands showed optimal initiation conditions over two phases during the Holocene, which is consistent with sea level rise peaks that led to optimal moist conditions occurring ca. 6,000–3,000 and 1,000 years ago. Sea level rise reduced groundwater drainage, which led to a rise in the primary groundwater table. However, data from some of the coastal peatlands indicate independence from the sea level fluctuation, and that they are rather controlled by climatic conditions and their local hydrogeomorphic setting, e.g. perched groundwater aquifers. Some peatland complexes show a pattern of phased initiation with peat initiation consistent with altitude difference, which could be due to a positive feedback of blocking caused by peat accumulation in lower reaches, reducing groundwater drainage to the sea.

Assessing methyl tertiary butyl ether residual contamination in groundwater using radon

About 15 years ago, a fuelling station in Roma (Italy) was dismissed. When underground tanks were removed, a subsoil NAPL (Non-Aqueous Phase Liquid) contamination came out, showing gasoline leakage from the reservoirs. Monitoring actions took place next and only recently radon dissolved in groundwater was measured for a year and used as tracer of NAPLs in view of its high solubility in these substances. The relative deficit of radon in polluted groundwater compared to radon in background “clean” water allowed us to detect areas where residual gasoline is still located. The source of pollution was identified in correspondence of former gasoline tanks, in agreement with direct measurements of dissolved NAPLs, mainly Methyl Tertiary Butyl Ether (MTBE), a resistant and water-soluble additive introduced in gasoline in place of lead. A short and transient plume of MTBE was occasionally recognized. We hypothesize that the rise of groundwater table enhances removal of MTBE, likely adsorbed onto soil minerals such as zeolites, thus increasing its concentration in water. MTBE levels are then progressively reduced by natural attenuation processes, with half-life of about 23 days. Estimates of MTBE saturation from radon-deficit equations were not reliable because the aquifer is not homogeneous in terms of 226Ra distribution, porosity and emanation power and no equilibrium is reached for radon partitioning between NAPL and water.

Assessing the impact of spatial allocation of bioretention cells on shallow groundwater – An integrated surface-subsurface catchment-scale analysis with SWMM-MODFLOW

Well-designed and implemented green infrastructure (GI) can help to recover the natural hydrologic regime of urban areas. A large-scale GI planning requires a good understanding of the impact of GI spatial allocation on surface-subsurface hydrologic dynamics. This study, firstly, developed a coupled surface-subsurface hydrological model (SWMM-MODFLOW) that can simulate fine-temporal-scale two-way interactions between GI and groundwater at catchment scale. The model was calibrated and validated using the monitoring data at one urban catchment within Kitsap County, WA, US. Based on the validated model, a series of hypothetical simulations was then performed to evaluate how spatial allocation of bioretention cells (BCs), one type of GI, influences and correlates with surface runoff and groundwater table dynamics. The spatial allocation was represented by implementation ratio (i.e., area), aggregation level (i.e., density) and location of BCs. The hydrologic dynamics were quantified by peak and volume reductions of surface runoff, as well as groundwater table rise and standard deviation of groundwater levels. A small number of BCs can raise groundwater table locally and regionally. However, it may not affect the spatial uniformity of groundwater levels (represented as the standard deviation of groundwater levels) if being properly allocated. Although the impact of aggregation level of BCs was relatively low compared to the implementation ratio and relative location of BCs, more-distributed BCs resulted in lower peak groundwater table rises but higher temporally-averaged groundwater table rises. Allocating BCs upstream resulted in higher groundwater table rises regionally, which is recommended for areas of deeper groundwater tables. While, allocating BCs downstream is more recommended for areas of shallower groundwater tables. BCs of greater surface runoff control efficiencies lead to higher groundwater table rises, which highlights the importance of considering the tradeoff between surface runoff control and groundwater protection in GI planning.

Sustainability problems of the Giza pyramids

The Pyramids complex in Giza consists of three main pyramids in addition to the famous Sphinx and small queen’s pyramids. Recently, the pyramids of Cheops (Khufu), Chephren (Khafre) and Mykerinos (Menkaure) on the Giza plateau have been threatened by a rising groundwater table resulting from water leakage from the suburbs irrigation canals, and mass urbanization surrounding the Giza pyramids. The pyramids at Giza suffer from a lot of Geo-environmental and structural problems. The main objectives of this study are (1) to assess the current status of the preservation of this unique and high valuable archaeological site, (2) to analyze the various actions that cause the destruction of the pyramid complex, in particular the weathering activities and strong seismic event, and (3) to determine the geochemical and engineering properties for construction materials using different types of tools and advanced analytical and diagnostic techniques. Structural stability analysis requires good assessment of present conditions of major materials used such as stones and structural mortar. The paper shows a thorough analysis of the current condition of the Great Pyramids at Giza. The work includes a discussion and analysis of the natural character and source of the pyramids building stones, geological context, damage survey, petrographic investigation, and physical and mechanical characterization of the stones and structural mortars, by means of laboratory and in situ testing. The results are displayed, described and analyzed in the paper in the context of potential threats to the monuments. The experimental study indicates the dependence of mechanical geological properties on the physical properties and the mineral composition of the studied building materials. The physical and petrographic characteristic of the stones are related. The modeling of properties indicates a reliable relationship between the various visible pores and uniaxial compression force parameters that can be applied to predict and characterize limestone elsewhere.

High-Resolution, Integrated Hydrological Modeling of Climate Change Impacts on a Semi-Arid Urban Watershed in Niamey, Niger

This study evaluates the impact of climate change on water resources in a large, semi-arid urban watershed located in the Niamey Republic of Niger, West Africa. The watershed was modeled using the fully integrated surface–subsurface HydroGeoSphere model at a high spatial resolution. Historical (1980–2005) and projected (2020–2050) climate scenarios, derived from the outputs of three regional climate models (RCMs) under the regional climate projection (RCP) 4.5 scenario, were statistically downscaled using the multiscale quantile mapping bias correction method. Results show that the bias correction method is optimum at daily and monthly scales, and increased RCM resolution does not improve the performance of the model. The three RCMs predicted increases of up to 1.6% in annual rainfall and of 1.58 °C for mean annual temperatures between the historical and projected periods. The durations of the minimum environmental flow (MEF) conditions, required to supply drinking and agricultural water, were found to be sensitive to changes in runoff resulting from climate change. MEF occurrences and durations are likely to be greater from 2020–2030, and then they will be reduced for the 2030–2050 statistical periods. All three RCMs consistently project a rise in groundwater table of more than 10 m in topographically high zones, where the groundwater table is deep, and an increase of 2 m in the shallow groundwater table.

3D Effects of permeability and strength anisotropy on the stability of weakly cemented rock slopes subjected to rainfall infiltration

Weakly cemented sedimentary rocks with pronounced stratification exhibit permeability and strength anisotropy. The influence of permeability and strength anisotropy on the groundwater flow and slope stability depends on the orientation of the bedding planes. The stability of slopes with different orientations of bedding planes under rainfall infiltration was evaluated in this study using three-dimensional finite element modeling. The groundwater table and pore water pressure in slopes before and after rainfall were simulated, and the calculated pore pressure corresponding to the initial and highest groundwater tables was used for slope stability analyses. The results showed that in comparison with gently dipping bedding planes, a slope with steeply dipping bedding planes exhibits a greater rise of the groundwater table and a greater increase of pore pressure, leading to a larger reduction in the factor of safety. Also, a shorter time is required to reach the highest groundwater table and the maximum pore pressure at a certain position. In consideration of the anisotropic behavior and the groundwater table rise during rainfall, unfavorable conditions were identified for the slope stability. The four unfavorable conditions, where the bedding planes and the slope face approximately strike in the same direction are: (1) the daylight condition of the bedding planes, (2) the coincidence of the bedding planes and the slope face, and (3) steep bedding planes dipping out or (4) into the slope. Slopes with the unfavorable orientations of bedding planes need additional attention in order to ensure a safe land development in the mountainous areas.

Numerical Analysis of Soil Slope Stabilization by Soil Nailing Technique

Slope instability may be a result of change in stress conditions, rise in groundwater table and rainfall. Similarly, many slopes that have been stable for several years can abruptly fail due to changes in geometry, weak soil shear strength or as the effect of an external force. Debris flows (i.e. slope failures) take place without any warning and can have devastating results. So, it is vital to understand the slope failure mechanism and adopt safety prevention measures. Soil nailing is one of the widely used stabilization techniques for soil slopes. In this study, soil nail technique is proposed to upgrade the existing slope in clay. A parametric study was conducted to understand the effects of different nail diameter (i.e. 25mm and 40mm) and nail inclination (i.e. 200, 250, 300, 350 and 400) on slope stability. Morgenstern-Price (i.e. limit equilibrium) method was used to determine the factor of safety of the slope. It was found that the factor of safety of the existing slope improved significantly with three rows of 40mm diameter nail at an inclination of 400.