Why Measure River Flow in Kuching?

1. Where is Kuching?

Geographical Background

Kuching, the capital of Malaysia's Sarawak, is located on the northwestern coast of Borneo Island. It lies at approximately 1.55°N latitude and 110.35°E longitude. Located on the Sarawak River estuary, the city boasts a good coastal location that, in the long term, has facilitated trade as well as cultural exchange. The geology of Kuching consists of flat coastal plains and interior rolling hills. Coastal areas have mangrove swamps, which are essential ecological complexes and natural forms of defense against erosion.

The climate in the city is tropical rainforest climate (Köppen climate classification: Af), with constantly high temperatures between 24°C and 32°C throughout the year. Humidity is constantly high with plenty of rains, amounting to some 3,000 millimeters a year. Kuching does not have any apparent dry season but may potentially have fluctuations in rainfall weight for the months, relying in turn on the monsoon pattern that dominates the area. This and its unique geographical position determine the hydrological character of the river systems in the area.

Cultural and Economic Significance

Kuching is a cultural and racial melting pot of individuals like the Dayak, Malay, Chinese, and the original inhabitants. This is expressed in its architecture, its food, and its festivals. Its former waterfront district, the Kuching Waterfront, is a combination of colonial-era buildings, Malay homes, and modern buildings. Attractions like the Astana, which used to be a palace and now stands open to official functions, and the Sarawak State Museum, with a history of the prosperity and arts of Sarawak, attract tourists from abroad.

Kuching is Sarawak's economic center economically. Its economy is diversified into agriculture (palm oil, rubber), manufacturing, and tourism sectors, which are the most important contributors. The port of the city is the focal point of trade activities, and commodities are exported as well as imported. The city's vibrant culture of transportation, local foods like laksa Sarawak and kolo mee, also help in the growth of the tourism sector, drawing tourists.

River Overview and Hydrology

Sarawak River is the largest of the river systems found in Kuching. The river winds its way from Sarawak's interior mountains, approximately 320 kilometers, before flowing its waters into the South China Sea in Kuching. The Sarawak River in its course has an array of tributaries flowing into it, making it a network of interconnected watercourses.

The Sarawak River has been significant to the development of Kuching. It was traditionally the main transport artery, with the movement of interior and coast traffic, enabling the transportation of people and goods. The river taxis and ferries are used today as popular modes of transport for the locals for short-distance travel across the river. The river also provides water for urban, agricultural, and industrial use but is treated since it can be contaminated through urban runoff and industry.

Aside from that, the Sarawak River and associated estuarine and mangrove ecosystems have a vast array of flora and fauna. Mangrove forests lining the riverbank provide nurseries to various species of fish and crustaceans economically important to domestic fisheries. But as with all urban rivers, the Sarawak River is also plagued with issues such as pollution, loss of habitat, and impacts of climate-related sea-level rise, so it is essential to keep track of its flow and well-being.

2. What is the River Flow Near Kuching?

Factors Affecting It

Rainfall and Runoff

Due to the tropical rainforest weather with heavy and frequent rainfall in Kuching, the Sarawak River has high runoff throughout the year. More intense rain events cause extreme river flow increases and water level rises. Urbanization, with increased areas that are impervious like roads and buildings, decreases rainwater infiltration into the earth, thus raising surface runoff and potential for increasing flood risk during intense rainstorms.

Terrain and River Morphology

The river course from the mountainous interior to the Kuching coastal plains affects the properties of the river's flow. Inside the mountainous region upstream, the river flows with a steep gradient and at high velocity, in opposition to the topography. Closer to Kuching and into the flat coastal region, the gradient reduces towards zero, and the river widens, creating slow currents. The estuarine region near the city is tide-affected, thereby causing the fluctuation in water levels and flow directions, especially at high and low tide.

Human - Made Structures

Various artificial structures have been built along the Sarawak River throughout history. The weirs and dams upstream are used to produce hydroelectricity, regulate flood, and impound water, varying river flow downstream. Riverfront developments and bridges in Kuching also alter natural river morphology in some sections that may affect water flow patterns as well as sediment transport.

Historical Hydrological Events

Kuching has witnessed several previous flood events. Kuching was hit by severe flooding caused by torrential monsoon rains in 2013, which caused the Sarawak River to burst its banks. The flood submerged several low-lying areas, disrupted transport, destroyed infrastructure, and resettled thousands of people. Observing previous historic floods helps in understanding the behavior of the river during catastrophic flood disasters and provide assistance in developing appropriate flood-mitigation strategies.

3. How is the River Flow in Kuching Monitored?

Traditional Techniques

Surface Drift Float Method

This basic method involves putting a floating body, a buoy, on the river surface. The river surface velocity is known from the time it takes for the float to travel a known distance. This method only provides data for the surface flow and is wind etc., dependent, and the results are therefore questionable.

Anchored Boat Method (Staff Gauge / Current Meter)

An anchored boat is used to install a staff gauge for water level measurement and a current meter to measure water velocities at different depths. A number of measurements of velocities are taken across the section of the river, and by multiplying the cross - sectional area with the velocities, an estimate of the river discharge can be made. The method is better than the surface drift float technique but time and labor consuming.

Introduction to ADCP: Acoustic Doppler Current Profiler (ADCP)

Acoustic Doppler Current Profiler (ADCP) is a more modern technology for the measurement of river flows in Kuching. It is able to measure water velocity at different depths non - invasively by using sound waves. ADCPs can make continuous profiles of river flow from the surface to the river bed and, hence, give an overall picture of the flow characteristics of the river within a relatively shorter time, which is required for efficient water resource planning and flood forecasting.

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

An ADCP current meter emits sound waves of a specific frequency into the water. When the sound waves hit moving particles in the water, such as sediment or plankton, the frequency of the reflected sound waves changes. If the particles are moving towards the ADCP, the frequency of the reflected waves is higher, and if the particles are moving away from the ADCP, the frequency is lower. By precisely measuring this frequency change (the Doppler shift), the ADCP can calculate the water velocity at different depths, providing accurate information about the river flow.

5. Requirements for High-Quality Measurement of River Flow in Kuching

Equipment Requirements

For reliable ADCP measurement to be carried out in the Sarawak River, there should be equipment that is dependable and suitable for use in the local river conditions. Given the likelihood of sediment, contamination, and tides interfering with the readings, ADCPs made of corrosion-resistant materials like stainless steel or titanium are best. A light and small frame is also best suited for easy transportation and deployment, especially to hard-to-reach areas. Good-quality sensors that are able to register with high enough resolution to detect the finesse of the river flow are also needed.

6. Choosing the Right Current Measuring Equipment?

Deployment Technique

• Ship - Borne (Moving Boat) ADCP: Most suitable for the task of conducting massive - scale surveys of the Sarawak River, it is able to quickly determine the discharge of the river along long stretches and map flow regimes in different parts, thus providing a complete picture regarding the river flow dynamics.
• Bottom - Mounted (Fixed) ADCP: Suitable for long-term continuous monitoring at fixed locations. It can be fixed on the river floor to measure data continuously over extended periods of time, helping to comprehend trends in river flow over extensive periods, seasonal changes, and how influencing factors affect the river flow.
• Cable - Way ADCP: Where there are cable - way sections of rivers, it can be employed to survey at several locations in the river with great precision, which is advantageous where there are complicated flow areas or boat - based surveys are difficult.

Working Frequency

• 600 kHz ADCP: Offers a good trade-off between range and resolution, with up to 70 meters of horizontal range. It is suitable for most segments of the Sarawak River in Kuching and makes precise flow velocity measurements at multiple depths.
• 300 kHz ADCP: Due to its wider coverage of up to 110 meters, it is ideal for deeper and wider sections of the river, such as in and around the estuary area, where greater coverage is needed.

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.