Malaysian Journal of Geosciences (MJG)

The gneissic rocks of Oka-Akoko area form part of the Migmatite-Gneiss-Quartzite Complex of the southwestern Nigerian Basement Complex. The petrologic units in the study area include grey gneiss, granite gneiss, Older granite, charnockite and minor felsic and basic rocks. Twelve gneissic rock samples comprising six granite gneiss and six grey gneiss from the area were collected for petrographic and geochemical analyses. Petrographic analysis revealed that the granite gneiss is more enriched in quartz and alkali feldspar than the grey gneiss. The grey gneiss is richer in plagioclase, hornblende and opaques compared to the granite gneiss. Interpretation of petrographic and geochemical analyses results revealed that Oka-Akoko granite gneiss and grey gneiss were derived from igneous protoliths of granitic and granodioritic compositions respectively. The grey gneiss is ferroan, alkalic to alkali-calc and metaluminous suggesting that its igneous protolith(s) is a M-type granitoid derived from melting of rocks from upper mantle or lower crustal region under conditions of limited availability of H2O and low oxygen fugacity while the granite gneiss is magnesian, alkali-calc and slightly peraluminous suggesting that its igneous protolith(s) is an I-type granitoid derived from the partial melting of crustal igneous rocks.

Excessive rain pattern has been the major cause contributing to flooding of low land due to excess water release from affected dams. This deliberate measure has to be taken to prevent the catastrophic effect of a dam break scenario. Therefore, this kind of disaster is considered as a local phenomenon. The local communities are the vulnerable population to face the immediate impact of such disaster. Needless to mention that they are also first emergency responders which is crucial for saving lives. It is therefore imperative for the involved stakeholders to improve local communities’ resilience to dam related disasters. This resonates well with the Hyogo Framework for Action, which identify local communities as integral cornerstone for saving lives and livelihoods. In the case of communities living near main hydropower dams owned by Tenaga Nasional Berhad, an initiative known as Integrated Community Based Disaster Management (ICBDM) has been launched in May 2015. This initiative adopts the concept of 3Es; embrace, educate and empower. The priority is to ensure the vulnerable communities embrace the reality, being educated to face any upcoming situation as well as being empowered to take charge of immediate live saving efforts in the future. The initiative involves five key scopes encompassing technical and non-technical areas and promotes the strategic partnerships between dam owner, authority and the community. It is anticipated that this initiative will build the resilience of communities to dam related disaster.

Drought is a phenomenon of water shortage that will impact the wellbeing of human life. The hydrological drought is a situation of water shortage compared to normal conditions. The degree of severity of drought events can be explained via duration and water deficits of drought events. The duration is an important parameter in understanding the event of drought. Duration refers to a period in which the value of river discharge remains below a certain threshold level. This study attempts to identify the severity of drought based on two drought duration parameters namely the duration of drought event (DE) and the inter arrival time (IAT). In the context of this study, the Q90 percentile value was obtained from the flow duration curve and the minimum drought period (MDP) of drought events for 45 days is used as a threshold level of drought events. The 39 year discharge data for Mengalong stations is used to determine the Q percentile value. From the analysis, the cumulative period of the drought events is recorded around 390 days covers 3.6% of the entire record. There were four drought events throughout the record that is in 1992, 1998, 2015 and 2016. The lowest duration was 59 days recorded in 1992, while the longest was 135 days recorded in 1998. This long period is associated with the presence of extreme weather phenomena such as El-Niño.

The Liwagu River is one of the most reliable river systems in Ranau which had experienced a mudflows event due to massive landslide of Mount Kinabalu. The aim of this study is to determine the water quality and compare the level of heavy metals in water and sediment of the Liwagu River and a non-impacted mudflows of Mansahaban River. Water and sediment were collected from four sampling stations on each river. Water samples were filtered with 0.45 μm membrane filter and acidified to pH<2 and conducted by means of ICP-OES while AAS was used for sediment analysis prior to aqua regia digestion method for the determination of five heavy metals (Cd, Cr, Cu, Pb and Zn). The Paired T-test shows that there were significant different between impacted and non-impacted river especially for turbidity, conductivity, temperature, Cuw, Crw, Znw, Cds, Crs and Cus, (P<0.05). Liwagu River shows the Cu concentration in sediment and water were exceeded the Guideline for the Protection and Management of Aquatic Sediment quality in Ontario and Interim National Water Quality Standards (INWQS): >110 mg/kg and >0.02 mg/L, respectively. The correlations coefficient shows that there were significant relationship between heavy metals in water and sediment from Liwagu and Mansahaban River (0.413<r<0.888, p<0.05). For conclusion, the quality of water from both river are fairly the same but not for the sediment. However, further in depth investigation is needed to identify a wider perspective towards the behavior of heavy metals prior to mudflows event in Ranau, North Borneo of Malaysia.

Sea level rise around the world caused by global warming since decade and effects on coastal especially country below mean sea level and country island. The prediction of sea level rise by 2100 is over 3m. Sea level rise increases caused by melting ice and thermal expansion. The impact of sea level rise concentrated along the coastal area. This paper studied the impact of sea level rise to physical parameters along the East Coast of Peninsular Malaysia. Seven physical variables such as geomorphology, shoreline change rate, coastal slope, lithology, maximum wave height, mean tidal range and sea level change were chosen to find an physical vulnerability index. The index also was mapped using ArcGIS software to picture the vulnerability. The worst area for physical vulnerability index is along the Pahang coastline especially Kuantan district. The prevention and adaptation from government and non-government agencies should be taken to reduce the effects of sea level rise.

Flood causes substantial economic loss and hindrance to development activities in many developing countries of the world. Bangladesh, a developing country in South-east Asia is ranked as the world’s ninth-most disaster-prone country by the World Risk Report, 2018 because of its high exposure to multiple hazards and less coping and adaptive capacities. The country is recurrently hit by flood hazard almost every year. Being a densely populated country with the fragile economic condition, Bangladesh urgently needs to focus on future flood-risk reduction with more effective measures in order to sustain the development milestone achieved till now. Flood hazard mapping, an initial phase of risk understanding (i.e., perception and knowledge), is often considered to be an indispensable component of flood-risk reduction strategies. In line with the contention, the present study aimed towards flood hazard mapping in Bangladesh where flood prone northeastern part of the country is taken as a case area. Multi-cri teria evaluation technique (MCE) for hazard mapping has been employed where elevation, slope, distance from river, land use and landcover (LULC), precipitation, flow length, and population density were taken as the causative factors. Each factor, as well as their subclasses, were assigned with pertinent weight values based on expert knowledge by analytical hierarchy process (AHP)and subsequently integrated into geographic information system (GIS) platform. According to the final flood-susceptibility map, ~4241 km2 (~ 20% of the total area) area is categorized as the highest flood potential zone which encompasses mostly the southern part of the study area, including Gazipur, Narsingdi, and Brahmanbaria districts. In contrast, low flood potential zone covers ~9362 Km2 (~43% of the total area) area covering the northwestern and southwestern parts (e.g., Mymensing and Tangail districts) of the study region. Besides, a considerable portion of the study region, mostly in the western part (e.g., Sunamganj and Kishoreganj districts) is categorized as moderate flood potential zone encompassing ~7823 km2 (~ 35% of the study area) area. Population density, distance to river and topographic characteristics are found as the most influencing factors for the mapping of flood-risk zones in the current study. This type of assessment in a regional scale may serve as a guide to the relevant stakeholders to formulate flood hazard atlas and minimize the adverse impact of the future flood in Bangladesh.

Heavy metals are known as an important group of pollutants in soil. Major sources of heavy metals are modern industries such as mining. In this study, spatial distribution and environmental behavior of heavy metals in the Jajarm bauxite mine have been investigated. The study area is one of the most important deposits in Iran, which includes about 22 million tons of reserve. Contamination factor (CF), the average concentration (AV), the enrichment factor (EF) and geoaccumulation index (GI) were factors used to assess the risk of pollution from heavy metals in the study area. Robust principal component analysis of compositional data (RPCA) was also applied as a multivariate method to find the relationship among metals. According to the compositional bi-plots, the RPC1 and RPC2 account for 57.55% and 33.79% of the total variation, respectively. The RPC1 showed positive loadings for Pb and Ni. Also, the RPC2 showed positive loadings for Cu and Zn. In general, the results indicated that mining activities in the bauxite mine have not created serious environmental hazards in the study area except for lead and nickel. Finding potential relations between mining work and elevated heavy metals concentrations in the Jajarm bauxite mine area necessitates developing and implementing holistic monitoring activities.

Micro-watershed planning and management play an important role in addressing the issues and challenges of water scarcity of a region. The assessment of hydrological framework using morphometric calculation and GIS technology is a recognized tool for carrying out planning activities for the watershed. The uncertainties associated with the earlier work of watershed prioritization can be easily addressed with new emerging geospatial-statistical correlation techniques. A sum weightages methodology is applied on the upper watershed of river Subarnarekha in the state of Jharkhand, India, for identification of critical subwatershed, a priority level ranking and zonation mapping of each individual subwatershed is developed using the morphometric calculation coupled with GIS tools. This approach helps in identification and bifurcation of subwatershed with three level of priority, i.e, Low, Medium, High. The result reveals that 5.8 % of subwatershed lies in high priority zone that signifies the area as critical and susceptible zones of soil erosion, which requires immediate attention from planners and policymakers. The high-level priority region should be considered for soil, water, and land conservation work. This approach of prioritization techniques can further be extended to another critical watershed of India for better decision support system and planning.

Despite existing literature suggesting that Dhaka City, Bangladesh is undergoing subsidence, few researches have been carried out to actually measure the subsidence rate. Previously conducted studies either do not provide sufficiently accurate subsidence results, or the study period is not long enough. In this research, we have tried to address that gap by performing time series subsidence analysis of Dhaka City utilizing Interferometric Synthetic Aperture Radar (InSAR) technique for a study period of 20 years. Synthetic Aperture Radar (SAR) C-band images from ERS, ENVISAT and Sentinel-1A were used to obtain the results. We had to use C-band SAR data from multiple sensors considering data availability issue of the period of investigation (i.e. 1992 to 1999(using ERS); 2003 to 2010(using ENVISAT); 2014 to 2017(using Sentinel 1A)). Most parts of the city is found to be subsiding. Mirpur and Uttara have subsided by over 221mm and 232mm respectively over the 20 years. Ramna and Cantonment subsided ar ound 205mm compared to their level in 1992, whereas both Gulshan and Tejgaon have subsided by about 200mm. Demra and Lalbagh show similar subsidence to the Ramna area, whereas Dhanmondi and Mohammadpur show subsidence rates similar to Tejgaon. We have also assessed the parameter sensitivity to perform this time series subsidence analysis. The parameter selection of coregistration, filtering and unwrapping was found to greatly influence the results. The result is being calibrated with the available GPS observation.

Pattani Basin hosts the greatest number of hydrocarbons producing fields in the Gulf of Thailand. Early to Middle Miocene fluvial channel and overbank sands are the main reservoirs in this basin. Due to their nature of very limited vertical and horizontal distribution it is not always easy to predict the geometry and distribution of these sands based on the conventional seismic interpretation. This study aims to study seismic geomorphology at different stratigraphic intervals to predict sand distribution by applying advanced imaging techniques such as RMS amplitude analysis, spectral decomposition, semblance and dip steered similarity. For this purpose, the study interval is divided into three periods. In period 1, RMS and semblance successfully identified sand bodies and mud filled channels associated with channel belts. On the other hand, deeper stratigraphic levels (period 2 & 3) can be imaged more effectively by using spectral decomposition and dip steered similarity volumes. Horizon slices from these attribute volumes show the distribution of sands and mud filled channels at different stratigraphic level. The width of channel belts varies from 200 m to 3 km. These channel belts are N-S and NW-SE oriented. The findings from seismic geomorphology analysis in these three (3) periods were then validated by well log analysis and correlation. Broad channel belts in horizon slices in period 3 correspond to stacked channel sands in well log. Whereas narrow channel belts correspond to thin sand units in well log in period 2. Widespread occurrence of coals has also been noticed in this interval. Very well-developed meander belts in horizon slices are transpired as fining upward succession in well logs in period 1. Mud filled channels identified in the horizon slices might act as a barrier and compartmentalize the reservoir. The proposed workflow of predicting sand distribution in this study might help to reduce exploration risk as well as in planning infill development wells.