Wardah Tahir

Radar Hydrology: New Z/R Relationships for Quantitative Precipitation Estimation in Klang River Basin, Malaysia

The use of Quantitative Precipitation Estimation (QPE) in radar-rainfall measurement for hydrological purposes is significantly important. For more than 50 years, radars have been deployed to monitor and estimate the precipitation routine in several countries. However in Malaysia, radar application in QPE is still new and needs to be explored. This paper focuses on the Z/R derivation work of radar- rainfall estimation. The work developed new Z/R relationships for the Klang River in the Selangor area for three different classes of rain events, namely low ( 10mm/hr, 30mm/hr). Looking at the high potential of Doppler radar in QPE, the newly formulated Z/R equations will be useful in improving the measurement of rainfall for any hydrological application, especially for flood forecasting.

Event-based rainfall-runoff modelling of the Kelantan River Basin

Flood is one of the most common natural disasters in Malaysia. According to hydrologists there are many causes that contribute to flood events. The two most dominant factors are the meteorology factor (i.e climate change) and change in land use. These two factors contributed to floods in recent decade especially in the monsoonal catchment such as Malaysia. This paper intends to quantify the influence of rainfall during extreme rainfall events on the hydrological model in the Kelantan River catchment. Therefore, two dynamic inputs were used in the study: rainfall and river discharge. The extreme flood events in 2008 and 2004 were compared based on rainfall data for both years. The events were modeled via a semi-distributed HEC-HMS hydrological model. Land use change was not incorporated in the study because the study only tries to quantify rainfall changes during these two events to simulate the discharge and runoff value. Therefore, the land use data representing the year 2004 were used as inputs in the 2008 runoff model. The study managed to demonstrate that rainfall change has a significant impact to determine the peak discharge and runoff depth for the study area.

Improved estimation of radar rainfall bias over Klang River Basin using a Kalman Filtering approach

Bad weather, consisting of thunderstorms, normally causes the presence of strong winds and heavy rain that may develop into a storm over a certain area. Radar has been the most potential and powerful instrument used to detect and monitor the development of thunderstorms over a large area; however, it also has certain weaknesses. Weather radar can be affected by different sources of errors, which have to be well considered and quantified for a proper interpretation of the collected data. We design a method that combines the Kalman Filter with a multivariate analysis technique. The implementation of this technique is for the purpose of developing a formulation that may help to reduce error. These studies involved parameters such as temperature, humidity, point of gauge rainfall, and weather radar reflectivity. The approach of using the Kalman Filter combined with multivariate analysis is still a new way to improve radar rainfall estimates by prediction (time update) and correction (measurement update). This particular research was developed purposefully to reduce radar rainfall bias due to the uncertain sources of error seen in the weather radar, and many studies have been developed, but still did not achieve suitable values between radar readings with rain gauge returns.

Radar hydrology: New Z/R relationships for Klang River Basin, Malaysia based on rainfall classification

The use of radar in Quantitative Precipitation Estimation (QPE) for radar-rainfall measurement is significantly beneficial. Radar has advantages in terms of high spatial and temporal condition in rainfall measurement and also forecasting. In Malaysia, radar application in QPE is still new and needs to be explored. This paper focuses on the Z/R derivation works of radar-rainfall estimation based on rainfall classification. The works developed new Z/R relationships for Klang River Basin in Selangor area for three different general classes of rain events, namely low (<10mm/hr), moderate (>10mm/hr, <30mm/hr) and heavy (>30mm/hr) and also on more specific rain types during monsoon seasons. Looking at the high potential of Doppler radar in QPE, the newly formulated Z/R equations will be useful in improving the measurement of rainfall for any hydrological application, especially for flood forecasting.

Physical Model of Estuarine Salinity Intrusion into Rivers: A Review

This paper reviews the physical models that had been used in order to conduct the experiment of estuarine salinity intrusion into rivers. Several studies used the physical models to get a better understanding of the estuary salinity mixing process and salt-wedge estuary characteristics along the flume. Besides, the laboratory investigations using the physical model also useful for verification purposes as discussed by previous researchers.

Potential of stagnant water due to dam flooding

During rainy monsoon or flood seasons, it often creates pools of stagnant water and dam water levels are lowered in order to avoid dam flooding. Stagnant water or prolonged flood water is known as public health threat or major environmental hazard. Meanwhile, dam flooding is a rapid and uncontrolled release of reservoir volume leads to severe flood in which there will be a significant impact at the downstream, specifically towards the people and environment of the affected region. Apart from causing severe flood, dam flooding also can accumulate stagnant water within a second or worsen the stagnant water if it already exists due to heavy rainfall. This paper is to explain briefly the potential and ongoing research of stagnant water due to dam flooding.

Study of water quality at mangrove island: Case study of Carey Island

This paper reviews on the water quality for Carey Island which is one of the mangrove islands in Malaysia. The mangrove area has vital functions of its mangrove tress. In order to control and protect the level of contamination at this area, a study on water quality has been carried out. Three rivers that selected as a point of study are Air Hitam, Judah and Keluang River. The parameters tested for the water quality are Temperature, pH, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Turbidity, Total Suspended Solid (TSS), Total Organic Carbon (TOC) and Ammoniacal Nitrogen (NH3-N). The parameters were tested by in-situ and laboratory testing. Finally, it is found that the Air Hitam, Judah and Keluang rivers are experiencing contamination and pollution problems. Water Quality Index calculation shows that all the rivers fall under Class III River category. Air Hitam River has the worst quality followed by Keluang River and Judah River

Simulation of Estuary Transverse Flow Salinity Intrusion During Flood Event: Case Study of Selangor River Estuary

The objective of this paper was to describe the effect of estuarine flooding leading to estuary transverse flow salinity intrusion specifically in the Selangor River estuary. The simulation of Selangor River estuary has been carried out using a multi-dimensional hydrodynamic and transport model. The Selangor River estuary model has been calibrated and validated using data on November 2005 for water-level calibration and from May to June 2014 for salinity validation. The results of the simulation show that the salinity level decreases when the water-level increases due to high fresh water discharge from the river upstream for different return periods of 10, 50, and 100 years.

Use of Numerical Weather Prediction Model and Visible Weather Satellite Images for Flood Forecasting at Kelantan River Basin

This chapter presents the application of Numerical Weather Prediction (NWP) and weather satellite images for flood forecasting in Kelantan River Basin. Flood is known to be damaging due to its ability to cause losses to life and property. Many studies have indicated the adverse effects of flood to mankind. Therefore, it is crucial to develop an accurate flood forecasting system to provide sufficient time for a proper mitigation plan. This early flood warning can also provide decision makers early information on the flood event. The preliminary results have indicated the ability of NWP and weather satellite images to produce a weather forecast. It is believed that there is a bright future direction to adapt NWP for flood forecasting as a tool to produce forecasts. It is also believed that NWP will be used in an effective way to forecast any changes to the flood even though there are still many uncertainties, where it involves the complexity of the NWP model itself to serve as a precise forecasting method.

Salinity Velocity Pattern in Estuary Using PIV

Estuaries are bodies of water along the coasts that are formed when freshwater from rivers flows and mixes with saltwater from the ocean. The mixing process in estuary is due to the forces that forced the freshwater from river to interact with saltwater at the ocean. Thus, it will give effect to the mixing properties of the estuary. The objective of this research is to analyze the salinity mixing pattern using Particle Imaging Velocimetry (PIV). A laboratory investigation was conducted in a Perspex channel to observe the mixing process in estuary. The images of the mixing process had been captured using the PIV system. Five parameters had been analyzed: Reynolds Stress, Turbulence Intensity, U for speed, V for velocity, and Vorticity using Matlab. The results show that two layers of water had been established inside the Perspex channel where saltwater had been observed to be at the bottom of the channel due to difference in density between freshwater and saltwater. This showed typical salt-wedge estuary characteristics.