Why Do We Monitor River Flow in Kuala Terengganu

1. Where is Kuala Terengganu?

Geographical Background

Kuala Terengganu, which is the state capital of Terengganu in Malaysia, is situated on the northeast coast of the Peninsular Malaysia. It is at approximately 5.32°N latitude and 103.13°E longitude, facing the South China Sea. The city is cut by a combination of low-lying hills and coast plains and a small patch of rolling hills within the hinterland region. An average elevation of around 10 meters above sea level, the flat surface is due to centuries of deposition by regional rivers that created a fertile alluvial soil that is fertile enough for agriculture and settlement.

Kuala Terengganu features a tropical monsoon climate of type with distinct wet and dry seasons because of the northeast and southwest monsoons. Heavy rain and gale-force winds are the features of the northeast monsoon from November to March, and it significantly influences the hydrological regime of the area. There is comparatively lesser precipitation in the dry months from April to October, but still there is high humidity. Average annual rainfall is around 2,500 - 3,000 millimeters and temperature generally 24°C to 32°C throughout the year.

Cultural and Economic Significance

Kuala Terengganu boasts a rich Malay culture reflected in its building architecture, celebrations, and traditional arts. The city is also marked with landmark places such as the Crystal Mosque (Masjid Kristal), a futuristic architectural marvel built on stilts over water, and the Terengganu State Museum Complex, the largest museum complex in Southeast Asia comprising an absolute enormity of artifacts that reflect the state's history and culture. Traditional Malay handicraft products like batik, songket weaving, and boat-making also prevail in the city, which is a testament to the indigenous ability.

Finances-wise, Kuala Terengganu is a diversified economy. Fisheries and aquaculture are major, keeping in view the fact that it's a coastal city. The city's port is a big center for seafood exportation, including fish, shrimp, and squid. Moreover, the manufacturing sector, especially from the textile, food processing, and petroleum sectors, plays a major role in the local economy. There has been a growth in tour activities with the scenic beaches of Redang Island and Perhentian Islands, and city cultural tours, which draw tourists globally.

Hydrology and River Overview

Terengganu River is Kuala Terengganu's principal river system. It originates in the Titiwangsa Mountains of the state's west coast and flows east for approximately 225 kilometers before emptying into the South China Sea in Kuala Terengganu. En route, it is supplied by many tributaries that create a complicated network that has been instrumental to the development of the region. Historically, the Terengganu River was a significant transport route, goods movement, and population movement, and performed a vital role in inter-state and international trade.

Today, the river is still significant as a source of water supply, agricultural sustenance, domestic supply, and small-scale industries. It is, however, plagued with a variety of issues. Urbanisation and industrialisation have led to industrial effluent, domestic sewage, and agricultural runoff, reducing the level of water quality. The river is also susceptible to floods, especially during the northeast monsoon, that may cause catastrophic damage to infrastructures and hinder the way of life of residents. The observation of Terengganu River and tributary flow is essential in flood control, water resource management, and the conservation of aquatic ecosystems.

2. How is the River Flow Near Kuala Terengganu?

Influencing Factors

Precipitation and Runoff

Intense northeast monsoon rains in Kuala Terengganu exert a significant impact on the streamflow of the Terengganu River and its tributaries. Intense rainfall generates intense runoff and rapid increase in the level and rate of river water and flow rates. Urbanization in terms of urban extension and pavement and building development also contribute to minimizing rainwater infiltration into the ground and maximizing surface runoff and the flood hazard. Rain patterns changes due to climate change, including more frequent but less duration rains, are among the challenges in managing the river flow within the city.

Terrain and River Morphology

River morphology from the western hilly highlands where it is hillier to the coastal plains of Kuala Terengganu affects its flow conditions. Towards the hilly catchment in the upstream, the river flows in a fast run with a steep gradient cutting through the land. As it reaches the plains, the gradient reduces and the river becomes wide, resulting in sluggish currents. Artificial modifications in the form of embankment development, bridge development, and straightening of river courses for urban and flood control reasons have, however, modified the natural meandering nature of the river. These changes have the ability to disrupt sediment transport, affecting water flow distribution, and even increasing the threat of erosion and flooding in certain locations.

Human-Made Structures

Various man - made features along the Terengganu River affect its flow. Weirs and dams at upstream locations are used for irrigation, water supply, and flood mitigation purposes, regulating the amount of water flowing into Kuala Terengganu. There are riverbank reclamation, bridge, and construction that had encroached on natural floodplains and narrowed river channels in some sections. Construction of urban runoff drainage also commonly discharges directly into the river, adding pollutants and altering the natural flow regime, with long-term effects on the river's ecosystem.

Historical Hydrological Events

Kuala Terengganu suffered many times from huge flood events. During the northeast monsoon in 2014, historically unprecedented rainfall occurred, causing the overflow of the Terengganu River. The flood covered most of the city's low-lying areas, disrupting traffic patterns, destroying the infrastructure, and displacing thousands of residents. Recent flood events have demonstrated the city's vulnerability to hydrological catastrophes, calling for accurate river flow monitoring and effective application of flood-mitigation measures.

3. How is the River Flow in Kuala Terengganu Measured?

Traditional Methods

Surface Drift Float Method

The surface drift float method is an easy method of measuring river flow. A floating object, such as a buoy, is placed on the Terengganu River surface. The measurement of the time taken for the float to cover a known distance will enable the calculation of the surface velocity of the river. However, the technique provides information only of the surface flow and is highly susceptible to wind and other surface disturbances and can provide potentially wrong measurements.

Anchored Boat Method (Staff Gauge / Current Meter)

An anchored boat method involves anchoring a boat at a specific point on the river. A staff gauge takes the height of the water, and a current meter is lowered to various heights in the river to record the speed of the water. Various readings of speed are taken across the cross - section of the river, and by calculating the cross - sectional area, the discharge of the river can be estimated. This method yields more detailed data than the surface drift float method but is time - consuming, labor - intensive, and hazardous, especially in a monsoon river with strong currents.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

The Acoustic Doppler Current Profiler (ADCP) is a newer and more efficient technology for observing river flow in Kuala Terengganu. It is non-intrusive, gauging water velocity at different depths using sound waves. ADCPs can provide a continuous record of river flow from the surface to the bottom in a relatively short interval, providing a better overall view of the flow characteristics of the river. The technology is central to understanding Kuala Terengganu's river dynamic hydrological processes, enabling more efficient water resource management, flood prediction, and environmental protection.

4. How does an ADCP Operate Based on the Doppler Principle?

An ADCP profiler operates based on the Doppler principle. It emits sound waves of a given frequency into the water. As such sound waves engage moving particles of the water, say, sediment, plankton, or molecules of water, the frequency of backscattered sound waves is altered. If the particles are heading towards the ADCP, the frequency of the waves returned is greater; if they are moving away, the frequency decreases. By detecting this frequency change (the Doppler shift) with precision, the ADCP can calculate the water velocity at different depths, providing accurate data on the river flow dynamics of Kuala Terengganu.

5. What is Required for High-Quality Measurement of Kuala Terengganu's River Flow?

Equipment Requirements

To provide accurate ADCP current meter readings in the rivers of Kuala Terengganu, the equipment has to be strong enough and resistant to the indigenous river environment. Due to the presence of pollution, sediment, as well as monsoon - triggered flow variations, ADCPs made of corrosion - resistant materials like stainless steel or titanium would be preferred. Lightweight and portable design is beneficial for rapid transfer and deployment, especially where flooding or remote access has occurred. Proper quality sensors with sufficient resolution are also needed to supply correct measurement of the complex flow pattern, which can be significantly influenced by the monsoon and urbanization.

6. How to Choose the Right Current Measurement Equipment?

Deployment Method

• Ship - Borne (Moving Boat) ADCP: Appropriately to conduct large - scale surveys of the Terengganu River and its tributaries. It can quickly measure the discharge of the river along long reaches and map flow patterns along sections, providing an integrated overview of the river flow dynamics.
• Bottom - Mounted (Fixed) ADCP: Suitable for long - term continuous monitoring at certain points. It can be installed on the riverbed for recording data for extended periods, which helps to comprehend the long - term trends of flow, seasonal variations, and the impact of various parameters on river flow.
• Cable - Way ADCP: In cable - way equipped river reaches, the method offers reliable measurements in a series of points along the river, which could be of value where the flow patterns are complex or in places where boat - based measuring is inconvenient.

Working Frequency

• 600 kHz ADCP: Offers the perfect balance between the range and the resolution, with the ability to go up to 70 meters horizontally. It is suitable for most of the Kuala Terengganu rivers' sections, providing accurate flow velocity measurements at different depths.
• 300 kHz ADCP: Although it has a greater range of up to 110 meters, it would be more effective for deeper and wider sections of the rivers, e.g., close to the estuary or where tidal impact is more in the monsoon.

Brand Recommendations

Reputable and high-quality ADCP brands such as Teledyne RDI, Nortek, and SonTek are renowned globally. Chinese brands also include the ADCP supplier’s "China Sonar Panda ADCP," which is cost-effective. It is made of all-titanium alloy, which gives it high durability as well as corrosion resistance, and is capable of weathering the tough environment of Rajasthan's rivers. It is also very cheap and therefore accessible to use in the majority of the monitoring projects in the state. For further information, you can visit their website at https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and models.