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Time-lapse resistivity measurements and groundwater geochemistry were used to study salinity effect on groundwater aquifer at the ex-promontory-land of Carey Island in Malaysia. Resistivity was measured by ABEM Terrameter SAS4000 and ES10-64 electrode selector. Relationship between earth resistivity and total dissolved solids (TDS) was derived, and with resistivity images, used to identify water types: fresh (ρ e > 6.5 m), brackish (3 m < ρ e < 6.5 m), or saline (ρ e < 3 m). Long-term monitoring of the studied area's groundwater quality via measurements of its time-lapse resistivity showed salinity changes in the island's groundwater aquifers not conforming to seawater-freshwater hydraulic gradient. In some aquifers far from the coast, saline water was dominant, while in some others, freshwater 30 m thick showed groundwater potential. Land transformation is believed to have changed the island's hydrogeology, which receives saltwater pressure all the time, limiting freshwater recharge to the groundwater system. The time-lapse resistivity measurements showed active salinity changes at resistivity-image bottom moving up the image for two seasons' (wet and dry) conditions. The salinity changes are believed to have been caused by incremental tide passing through highly porous material in the active-salinity-change area. The study's results were used to plan a strategy for sustainable groundwater exploration of the island.

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From years to years, the construction of residential buildings at hill-site in Malaysia will lead to various fatalities event. Cutting down of trees can vanish the reinforcement provided by the root of tree to the soil by means of weakening the soil shear strength due to the increasing value of pore water pressure and decreasing value of effective stress. Root of a tree plays an important part in preventing landslides event to occur either it is by modifying the soil moisture regime via evapotranspiration or providing root reinforcement within the soils. Water uptake by plant roots is fundamental in many applications agriculture. This study is conducted to explores the vegetation approach by using tropical mature tree and monitors the activeness of the root zone of a tree that lies at the top of the slope by which the data of the matric suction generated within this section of the slope is recorded by using Tensiometer and applied to the slope stability problem to increase the value of factor of safety (FOS). Based on the research conducted, it is proven that by using tree water uptake method can increase the FOS of the slope up to 57%. In retrospect, the method used in preventing the landslides event to occur at the slope is economical and eco-friendly which can be implemented globally as this is the most nature method to prevent landslide and required low cost compared to other methods.

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Analysis of slope stability is very important as many structures in hilly areas failed due to instability of slope. The aim of this study is to determine the factor of safety (FOS) of slopes located at Pahang Matriculation College by using limit equilibrium method. Two methods known as modified Fellenius’s method and modified Bishop’s method are used in this study. Laboratory testing involving index and engineering properties are conducted to determine the properties of soil within the study area. The soil at Pahang Matriculation College can be classified as sandy SILT with high plasticity. From the analysis, the FOS values for two slopes in saturated soil conditions (0 kPa suction) are between 1.262-2.885 when using Bishop’s method which are higher compare to 1.199-2.688 when using Fellenius’s method. The percentage differences of FOS between these two methods are between 5.25% to 7.33%. For slopes in unsaturated conditions (20 kPa suctions), the FOS are between 1.550-3.702 when using modified Bishop’s method which always higher compare to 1.492-3.507 when using modified Fellenius’s method. The percentage differences of FOS are between 3.89% to 5.56%. The relative accuracy of Bishop’s method is due to it consider only the vertical equilibrium of each slices and there is no need to consider the horizontal components of the interslice forces without introducing serious error in the FOS value.

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