The policy of encouraging agriculture and development for mass tourism has led to environmental problems in Cameron Highlands, Malaysia. Rampant development and land clearing have significantly altered the land cover of Cameron Highlands for the past 30 years. Sensitive highlands areas are prone to landslides and soil erosion which then contributed to the main water pollution issues in the network of river system, sedimentation and siltation. The continuous trend of river water quality deterioration in Cameron Highlands has raised the issues for discussion in this review article. The purpose of this review is to briefly summarize the land use change, agriculture practices, agro-tourism, and agriculture policy and management toward water quality of the river system network in Cameron Highlands specifically in the downtown where most of the development and agriculture activities are concentrated. A rigorous review has been done on the existing literature to determine the relationship between land use change and agriculture practices toward river water quality in Cameron Highlands from 2001 to 2017. The total number of reviewed papers was 68. The outcomes established from previous researchers have highlighted factors such as soil erosion, landslides, agriculture activities, urbanization, and unplanned development associated with land use change have significantly influenced the river water quality in the highland areas. Continuous land use changes without proper development plan and law enforcement may critically threaten the sustainability of river network in the highlands area.
Geographical information system (GIS) techniques and Remote Sensing (RS) data are fundamental in the study of land use (LU) and land cover (LC) changes and classification. The aim of this study is to map and classify the LU and LC change of Lake Kenyir Basin within 40 years’ period (1976 to 2016). Multi-temporal Landsat images used are MSS 1976, 1989, ETM+ 2001 and OLI 8 2016. Supervised Classification on Maximum Likelihood Algorithm method was used in ArcGIS 10.3. The result shows three classes of LU and LC via vegetation, water body and built up area. Vegetation, which is the dominant LC found to be 100%, 88.83%, 86.15%, 81.91% in 1976, 1989, 2001 and 2016 respectively. While water body accounts for 0%, 11.17%, 12.36% and 13.62% in the years 1976, 1989, 2001 and 2016 respectively and built-up area 1.49% and 4.47 in 2001 and 2016 respectively. The predominant LC changes in the study are the water body and vegetation, the earlier increasing rapidly at the expense of the later. Therefore, proper monitoring, policies that integrate conservation of the environment are strongly recommended.
High-intensity land-use activities occur near lakes including in their watershed and increase of population density in areas neighbouring the lakes have caused overexploitation of lake water resources and discharge of large volumes of pollutants into lakes water. As a consequence led to escalating deterioration of lake water quality. Water quality conditions of lakes are significantly influence by their watershed behaviours. The lentic nature of lakes allows problems to build up and symptoms to go unnoticed for a lengthy period and commonly only appearing at a delayed and dangerous stage given that similarly a slow and often equally long period is needed to treat before positive results begin to show again. Hence, it is quite complex to comprehend types and strengths of pressures that impact water quality status, when do the changes will occur and what the status of water quality would be, not only on the presence situation but over the long term. Lake water quality and catchment relationship is an intricate issue and required the lake managers and planners to be attentive and prepared to engage in sustained actions over a long-term time frame relating to the development of lakes because progression of degradation inside a lake mostly takes place on a wider and deeper scale than is readily apparent. The comprehensive understanding on anthropogenic upheaval and hydrological linkages within lake watershed influences the dynamics of the lake water quality and is vital to the resulting livelihood including the cultural, biodiversity, and economic activities that are supported by lakes. This paper highlights the issues and challenges in managing lake water quality, variables that significantly influence lake catchment-water quality relationship, discussing the water quality parameters that must be regularly monitored, and proposing a management support tool as the expected research output to ensure lake water quality is not compromise while meeting the country's socioeconomic demand.
Many slope failures take place during or after rainfall events. Landslides are one of the tragedies associated with slope failures and often lead to fatal accidents. A study on the effects of extreme rainfall on slope stability considering the historical rainfall data, slope characteristics and properties, and flow boundary conditions was undertaken. This study investigated the behaviour of the Sg Langat slope under the influence of extreme rainfall gathered from historical data. Sg Langat was selected as the research area because of its high riverbank failures. The focus of this study are as follows: 1) to determine the effect of slope angles on slope stability, 2) to assess the development of pore-water pressure based on the changing groundwater levels, and 3) to analyse the influence of extreme rainfall events on the slope behaviour via numerical modelling. This study enhances the understanding of certain slope conditions and contributes to the analysis of slope stability through numerical modelling, making it relatively convenient to observe the soil conditions for determining the slope stability of the research area in regards to the effect of extreme rainfall. The results were obtained with respect to the changes in the pore-water pressure and the factor of safety. It was observed that the pressure changes were different for every channel, demonstrating that the generation of negative pore-water pressure was not directly affected by the type of analysis and the rainfall infiltration alone. Moreover, the slopes on all channels presented were considered unstable because of the considerable changes in the negative pore-water pressure at a relatively shallow depth, causing soil strength reduction. The factor of safety recorded for Channel 1 was the lowest at 0.18, whereas Channel 3 had the highest factor of safety of 1.11 but was still considered unsafe as it fell below the standard safety margin of 1.3. Apart from the different rainfall intensities applied, the geometry of the slopes also affected the slope stability.
The impact of flood mitigation project in the Kemaman River Basin was assessed in this study. Salinity intrusion was simulated in the study area by 1D numerical model. A 1-D hydrodynamic model coupled with a salinity model was used to analyze the salinity intrusion within Chukai River after the implementation of the flood mitigation project. The model was calibrated and validated using the data measured in Chukai River at 3 points from January 2007 until August 2013. Water quality simulation of salinity has been carried out once an excellent hydrodynamic model was established. The simulated river flow was reasonably matched to the measured data with R2 value 0.88, 0.92 and 0.82, respectively. Results suggest that after the realignment of Chukai River, the seawater intrudes further to the upstream river, causing the increasing salinity in the river about 10 - 15 ppt. However, with the floodway development, the channel would allow more water from Kemaman River being discharged into Chukai River. Increased in the volume of water in Chukai River has led to seawater dilution. Further, it invades the unique stretch of Chukai River and takes the salinity back to the initial state. Findings from the implementation of the flood mitigation project in the Kemaman river basin has benefitted the local society, watershed, and the surrounding biota ecosystems. Importantly, a greater prevention with the risk of repetitive flood damage to the buildings and structures in Kemaman area which has significantly achievable. HIGHLIGHTS Salinity model is used for flood mitigation project High salinity in Chukai river resulted from seawater intrusion Hydrodynamic model is to assess the water quality simulation
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