Why Do We Monitor River Flow in Miri

1. Where is Miri?

Geographical Background

One of the state cities of Sarawak in Malaysia, Borneo Island, Miri is situated at approximately 4.31°N latitude and 113.92°E longitude. It is situated on the northern shore of Borneo, overlooking the South China Sea and amidst a chain of coastal plains and rainforest hills. The city stands at an average elevation of about 20 meters above sea level, and its coastal lowland plains were formed by alluvial deposits of local rivers, while the nearby mountains, belonging to the Crocker Range, rise to the southeast.

The weather of Miri is a tropical rainforest climate (Köppen climate classification: Af), with moderate humidity and relatively uniform temperatures throughout the year, generally between 24°C to 32°C. Heavy rainfall, with a mean of 3,000 - 3,500 millimeters yearly rainfall. The city is affected by the northeast and southwest monsoons. Both the November to March northeast monsoon and May to September southwest monsoon cause heavy rain and gales that significantly influence the area's hydrological system.

Cultural and Economic Importance

Miri is a multicultural city, home to indigenous Dayak tribes, Malays, Chinese, and other ethnic minorities. The multicultural nature of the city is evident in the architecture, celebrations, and cuisine. The Niah National Park, which is near Miri, is famous for containing archaeological evidence, including ancient cave paintings and burial sites, that offer insights into the early history of man in the area. The park also has unique limestone karst scenery and a rich wildlife and thus attracts nature enthusiasts as well as historians.

Mirir is Sarawak's industrial and commercial hub economically. Miri is linked historically to the oil and gas industry when the first Malaysian commercial oil well was drilled successfully here in 1910. Exploration, oil and gas production, and support services are still significant economic drivers until this day. Aside from this, the city also boasts a developing tourism sector, with the Miri City Fan being a popular recreational park and the nearby beaches and marine parks offering water sports amenities and wildlife watching. The agricultural and timber industries also help to sustain the economy, with palm oil and rubber being two of the major agricultural products.

Hydrology and River Overview

One of the larger river systems surrounding and through Miri is the Baram River. It originates in the central mountains of Sarawak and winds its way for some 320 kilometers before emptying into the coastal plains surrounding Miri and into the South China Sea. There are a number of tributaries along the way which flow into the Baram River and form a network of rivers. In the past, the rivers were used as modes of transport, and transportation of people and goods was facilitated by the rivers, especially when trade and logging of timber were the dominant activities. The rivers also acted as sources of water supply for domestic, agricultural, and industrial use.

The Miri rivers, however, face a myriad of problems. Pollution has resulted from industrialization, especially oil and gas and logging, as well as urbanization. Industrial effluents, chemical run-off, and domestication sewage have polluted the water as well. The rivers are prone to floodings during monsoon seasons, which would result in the loss of infrastructure, economic loss, and displacement of residents. The Baram River and tributary flow measurement would be needed for flood control, water resource management, and aquatic ecosystem preservation.

2. What is the River Flow Like Near Miri?

Factors Influencing

Rainfall and Runoff

One of the key parameters that influence the flow of the Baram River and its tributaries is the high rainfall intensities received by Miri during its monsoons. The component of high rainfalls intensities causes a sudden rise in runoff, thus resulting in a sudden rise in river water level and flow rate. Urbanization, through expanding impervious surfaces and industrial estates, reduces rainwater infiltration into the land surface, hence maximizes surface runoff and increases flood hazard. Rainfall pattern variation induced by climate change, i.e., more frequent but shorter-duration flooding, contributes to complication in river flow management in the city.

Terrain and River Morphology

The Baram River flow is governed by its orientation from the interior mountains to the coastal lowland of Miri. At the undulating upstream zones, the river flows with steep gradient and speed, cutting through the landscape. Closer to Miri and emptying into the relatively flatter coastal plains, the gradient lessens, and the river widens, creating slower streams. Artificial changes like embankment construction, bridge spans, and straightening of the river course for flood management and urbanization have, nonetheless, diverted the river's natural meandering course. These actions can potentially interrupt sediment transport, modify the water discharge pattern, and even increase the threat of erosion and flooding in certain areas.

Man - Made Features

There are various man - made features found in the Baram River that affect its flow. Upstream weirs and dams are utilized for water supply, flood control, and hydroelectric power generation, managing the amount of water permitted to flow into Miri. Bridges, oil and gas pipelines, and terminal facilities along riverbanks have encroached on the natural floodplains and narrowed the river channels at locations. Additionally, the construction of drainage schemes to manage urban and industrial runoff can discharge directly into the river, taking pollutants with it and altering the natural flow regime, with long-term consequences for the river ecosystem.

Historical Hydrological Events

Miri has experienced several major floodings. In 2018, heavy monsoon rains produced serious flooding in the city when the Baram River overflowed its banks. The floods covered extensive low-lying areas, brought transport disruption, damage to infrastructure, and displacement of thousands of individuals. These flooding events of the recent past have rendered evident the exposure of the city to hydrological hazard, the necessity for precise measurement of river discharge, and efficient flood-control strategies.

3. How is River Flow in Miri Measured?

Traditional Methods

Surface Drift Float Method

The surface drift float method is one of the simplest methods to measure river flow. A floating object, i.e., a buoy, is maintained on the river surface. Surface velocity of the river can be calculated by observing the time taken by the float to travel a known distance. This method, nevertheless, provides information about the surface current alone and is very susceptible to wind and other surface disturbances, causing erroneous readings.

Anchored Boat Method

In the anchored boat method, a boat is anchored at a particular point in the river. A staff gauge is used to estimate the water level, and a current meter is suspended in the river at various depths to estimate water velocity. Velocity is calculated at several points along the cross-section of the river and by determining the cross-sectional area, the discharge of the river can be approximated. This method is more precise than the surface drift float technique but is labor-intensive, time-consuming, and dangerous, especially in a river with strong currents.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

The Acoustic Doppler Current Profiler (ADCP) is a newer, more advanced river flow measurement technology in Miri. It is likewise non-invasive and makes use of sound waves to approximate the velocity of the water at different depths. ADCPs have the ability of providing ongoing profiles of the river flow from the surface down to the bed over a relatively short duration, giving a better idea of the nature of the river flow. The technology is crucial in understanding Miri rivers' complex hydrological processes, which can enable better water resource management, flood prediction, and protection of the environment.

4. How Does the ADCP Work on the Doppler Principle?

An ADCP works on the principle of the Doppler effect. It sends sound waves of a specific frequency into water. When these sound waves strike moving water particles, such as sediment, plankton, or water molecules, the frequency of the sound waves that are backscattered is changed. If particles are moving towards the ADCP, the frequency of the backscattered waves is greater; when particles are moving away, the frequency is lower. By accurately measuring this frequency change (the Doppler shift), the ADCP can estimate the water velocity at various depths, giving insight into the flow dynamics of the river.

5. What Is Required for High-Quality Measurement of River Flow in Miri?

Equipment Requirements

To obtain accurate ADCP current profiler measurements in Miri rivers, the equipment must be of high quality and appropriate for the prevailing river conditions. Because of the pollution, sediment, and the impact of monsoon - induced flow variation, ADCPs made from corrosion - resistant material like stainless steel or titanium are preferred. Small and light weight is suitable to provide easy transportation and installation, especially in the industrial and rural areas closer to the rivers. Good-quality, high-resolution sensors are also required to adequately capture the complex flow patterns, which can be affected by the specific geographical and industrial characteristics of the city.

6. How to Select Suitable Current Measuring Equipment?

Deployment Method

• Ship - Borne (Moving Boat) ADCP: Ideal for the conduct of large - scale surveys of Baram River and its tributaries. It possesses the capability to quickly measure the river discharge along long reaches and map the patterns of flow in different sections with a broad - based analysis of the dynamics of the river flow.
• Bottom - Mounted (Fixed) ADCP: Suitable for continuous long-term monitoring of a fixed point. It can be mounted on the river bed to measure continuously for long periods to understand the long-term flow patterns, seasonal trends, and the impact of various factors on the river flow.
• Cable - Way ADCP: Where cable - way facilities exist on river reaches, this method can obtain precise measurements at multiple points on the river, which is advantageous where there are complex flow patterns or boat - based measurement becomes unfeasible.

Working Frequency

• 600 kHz ADCP: Nice balance between resolution and range, with up to 70 meters horizontal range. It can be used in most of the rivers of Miri and is able to give good velocity measurements at varying depths.
• 300 kHz ADCP: With a longer range of up to 110 meters, it is better suited for deeper and wider parts of the rivers, i.e., where there is a lot of seasonal variation in flow.

Brand Recommendations

Proven and tried international ADCP brands such as Teledyne RDI, Nortek, and SonTek are highly reputable for their quality and reliable products utilized in various hydrological researches and monitoring operations. A good alternative at a low cost is the ADCP supplier Chinese company’s "China Sonar Panda ADCP". Made of all - titanium alloy, it possesses superior strength and dependability and is especially well - adapted to withstand the harsh river conditions along Srinagar. It is a "budget ADCP" with high - class performance at budget prices, hence an excellent choice for monitoring the river flow along Srinagar without digging deep into the pockets in terms of equipment costs. To know more, visit https://china-sonar.com/.

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