Evaluation of Drastic and Geograpidc Information System as a Tool in Determining the Groundwater Quality Vulnerability of Kuala Langat Aquifer

This thesis describes the results of a ground water pollution potential modeling, which examined the entire Kuala Langat aquifer using GIS. The pollution potential model implemented within GIS is known as DRASTIC, a model, which was developed by the u.S. Environmental Protection Agency in 1985. In compiling a groundwater vulnerability map of Kuala Langat, it was decided to use the widely known DRASTIC methodology that includes Depth to groundwater, Recharge due to rainfall, Aquifer media, Soil media, Topography, Impact of the vadose zone, and Conductivity (hydraulic). Although not designed for a GIS, this model represents a classic spatial analysis approach for which GIS have become known. This thesis outlines the techniques used in compiling the data sets for those factors that influence the susceptibility of groundwater contamination over Kuala Langat and the techniques involved In manipulating and displaying these data in a GIS. The different techniques employed in the gathering and calculations of the different information sets required by the DRASTIC model to describe the groundwater vulnerability are presented in detail. The final output, which is in the form of a color paper map, will be useful in presenting the concept of groundwater vulnerability and groundwater protection to the layman. Results show that DPPI ranges from 80 to 165 giving 90% of the entire area as moderate vulnerable. However the south and east portion of Kuala Langat pose much more pollution potential than other area. Pesticide DPPI ranges from 1 14 to 166 with higher numbers representing higher pollution potential, indicating that moderate pesticide pollution potential occurs through out the entire Kuala Langat aquifer. The Pesticide DRASTIC Pollution Potential Index of Kuala Langat is higher than DRASTIC Pollution Potential Index (DPPI) of Kuala Langat. From these findings, it can be concluded that the potential source of pollution in the area derived from agricultural activities

Risk Assessment Scenario of Machap Dam Overtopping Using New PMP Malaysian Series

A hydrological dam safety analysis was carried out for existing Machap dam (CA= 77 km2) due to change in the extreme rainfall condition in the watershed. It is important to ensure that extreme meteorologically induced flood rises do not exceed its crest level. Step-by-step procedures were carried out in tandem to evaluate the hydrological performance of the gated spillway capacity in light of an extreme storm event of PMP/PMF magnitude. This study adopts a newly developed “inland” type of PMPs compared to the original design PMPs. A catchment routing and reservoir procedures were then used to translate the PMPs to PMFs and estimate the outflows and corresponding flood rises over the crest level for all durations. The results of the PMPs/PMFs were comparable to the “Creager” type of catchment area-PMP relationship of various dams in Malaysia. A conventional reservoir routing procedure by modified puls technique is then carried out for all PMP/PMF durations; i.e., 1 to 120 hours. Three (3) scenarios are performed; namely, (1) when the gates are fully closed, (2) when the gates are partially open in light of impeding PMP/PMF event and (3) when the gates are fully open. The last scenario (case 3) represents the most efficient and effective management of the reservoir gate operation as the original designer intended. The flood rises for all durations are considered lower than the embankment crest level. The results also show expectedly the failures of both cases (1 and 2) for their inadequate capacity to allow safe passage of flood water of PMP/PMF magnitude

Modelling Approaches for Minimally Gauged Sg Similajau, Bintulu

Minimally gauged river basins are common in Sarawak. Many river basins are lacking in hydrological monitoring mechanism mostly due to the vast land mass and complex river network, hence causing isolation of certain locations. This paper is describing the approaches to model Sg Similajau of Bintulu, Sarawak with little information to support sound analysis. A river model is developed to reconstruct missing flows of the river. In order to have reliable results, a short-term monitoring program is strongly suggested to collect data pertaining to river processes in the field. Pre-processing processes are demonstrated to obtain inflow data for upstream boundaries, tide/King Tide data for downstream boundary and a weir at Samalaju Water Intake for middle boundary. Particularly the weir, its presence convinces the verification of the river model. Post-processing on the impacts of the weir in flow patterns, in this case the water head produced by the weir and with such a head to flush out saltwater brought about by tides are demonstrated as ideal tool to test the model

Floodplain and hydraulic infrastructure system modeling for integrated flood management

en recent years, river floods in Sarawak River seemed to occur more frequently and had been causing more and more economic and social damages. One of the greatest deficiencies of the current flood management system for Sg. Sarawak basin is its inadequate optimization of the existing structural measures. This optimization may be achieved by application of some of the models and the framework developed recently for enhancement of participation of various local stakeholders in flood management.) Hydrological simulations had been conducted and carried out using HEC-HMS for Sg. Sarawak catchment. The model was calibrated and validated using years 1976 and 2000 flood events. The rainfall - runoff hydrographs generated from calibration and validation processes showed Nash-Sutcliffe values of 0.78 and 0.71, respectively. Sensitivity analysis was perfonned to examine the impacts of the three parameters, namely, initial loss, constant loss and lag time parameters on the HECHMS hydrological model. The analysis revealed that the initial loss parameter acted as the most sensitive parameter with respect to peak flow and total runoff volume. It was also found that an increase in constant loss could result in a lower peak, while the lag time was the most sensitive parameter with respect to peak time. ~ . However, lag time parameter was found to be the least sensitive among the three parameters tested. The calibrated hydrological model was then used as inflow hydrographs in InfoWorks RS model. Two hydraulic models, namely, Pre-barrage Sg. Sarawak Model and Post-barrage Sg. Sarawak Model were developed, calibrated and validated by modifying Manning's n values corresponding to field observations. 111 Years 1976 and 2000 flood events were used for calibration and validation purposes, and showed to have an accuracy of approximately 90% for both processes. Sensitivity analysis was carried out to investigate the impact of Manning's n on the water levels. Manning's n sensitivity was tested using values ranging from 0.025 to 0.055. The results revealed that the peak water level was not sensitive to Manning's n values. The hydraulic model was intended to integrate the existing flood mitigation structures available in Sg. Sarawak Basin. Two Scenarios: 1) Sarawak River basin-wide modeling and 2) Flood Bypass Channel modeling were carried out using the models developed for this research to investigate the performance of the existing flood mitigation measures in Sg. Sarawak basin. The results revealed that the existing structure, Sg. Sarawak barrage was able to trim down the backwater due to King Tide or the flood flow from the upstream. However, the barrage had insignificant on water level during king tide and flood event. The modeled results were used in Logical Framework Analysis to look into the possible alternatives that may help reduce the damage. The outcomes of this study showed that the existing condition could be significantly improved once the Flood Bypass Channel and Early Flood Warning System are constructed. Flood Bypass Channel modeling was carried out to determine the impact of the proposed alternatives on the existing conditions of Sg. Sarawak Basin. In this scenario, a flood bypass channel and an additional barrage are proposed to divert the excess flood water from Kuching City in the event of severe flood. It was shown that flooding problems in Kuching can be significantly reduced. However, the areas located upstream of Kuala Maong could still be subjected to flooding. Early Flood Warning system could be provided to evacuate the floodplain dwellers before severe floods strike. An analytical logical framework for Early Flood Warning System IS presented in this dissertation. The models and methods developed in this study are flexible and easy for Sg. Sarawak Basin. In this research, both the feasibility of and effectiveness in incorporating the premise of the combined technical information and institutional setup in flood management are addressed