ADCP in The Kapuas River Flood Management

1. Where is The Kapuas River?

The Kapuas River is the longest river in the Indonesian part of Borneo.

Geographical Location and Course It is located in the Province of West Kalimantan, Indonesia. The Kapuas River originates from the Muller Mountains, with an east-west course for a stretch of about 1,143 kilometers before falling into the South China Sea. It has an immense and intricate drainage basin that covers a large portion of tropical rainforest.

Cities and Settlements Along the River There are numerous small villages and towns with the Kapuas River as their borders. They depend on the river for transportation, catching fish, and a water supply. Boats and canoes remain one of the most important sources of movement and exchange in trade between communities. The river also plays a vital role in the social and cultural life of the people who live there.

Rainfall and Water Conditions

The Kapuas River basin is generally within a tropical rainforest climate. There is a high amount of rainfall throughout the year without any marked differentiation between a wet and dry season. Most areas receive more than 3000 - 4000 millimeters every year. Due to the heavy and incessant fall of rain, there is always a good volume of water in this river. This also makes the river very susceptible to sudden increases in its water levels during episodes of extreme rainfall or changes in the pattern of rainfall.

2. What are the causes of the flood in The Kapuas River?

Heavy and Continuous Rainfall Heavy and continuous rainfall in a short period is the most dominant factor in flooding the Kapuas River. This sets the stage for massive volumes of rain falling in a very short time to saturate the ground rapidly and raise the water level in the river and its tributaries. Even though rich in organic matter, the rainforest soil has limited water retention capability during a very heavy downpour of rain. Thus, the water level in the river rises rapidly and may overflow its banks inundating the adjacent low - lying areas.

Poor Drainage in the Rainforest The Bornean rainforest, which the Kapuas River flows through, is a really complex and wild area. Most of the area has no artificial drainage system in place. Natural drainage across the rainforest depends on the topography and permeability of the soil, and the rainforest may not have enough power to handle the excessive quantity of water brought by heavy rain. This may easily lead to the mass pooling of water and spread the floodwaters over a large area.

River Morphology and Sedimentation On the other hand, morphology and sedimentation processes may sometimes be responsible for more floods within the Kapuas River. Narrow reaches in the river channel may exist, coupled with meanders. At high-flows, the water will be pushed to go through those constricted reaches and thus raise the upstream level. Centuries of deposition of sediment in the bed of this river reduce the cross-sectional area of the river and carrying capacity; hence, the emergence of flooding.

Considering these issues, ADCP current meter is an advanced and more convenient measurement method for better flood management.

3. How does an ADCP work using the Doppler principle?

The working of Acoustic Doppler Current Profiler(ADCP) is based on the principle of the Doppler effect. A device sends acoustic pulses into water at a known frequency. The frequencies usually range from 300 kHz to 600 kHz, depending on the type of measurement one intends to perform and the nature of the river itself.

Transmitting and Receiving Signals The acoustic pulses are transmitted in a fan-shaped pattern. As these pulses pass through the water, they confront the water particles that happen to be moving and any suspended sediment as well. When the pulses encounter these moving objects, a portion of the energy is scattered back towards the ADCP current profiler.

Detecting the Doppler Shift Due to the Doppler effect, the frequency of the reflected signals is different from that of the transmitted signals. If the water particles or sediment are moving towards the ADCP doppler, then the frequency of the reflected signal is higher than the original. On the other hand, if they are moving away, the frequency is lower. The sensors of the ADCP are designed in such a way to accurately detect these changes in frequency.

Calculating Velocity and Other Parameters Internal algorithms within the ADCP flow meter use the detected Doppler shifts to estimate the velocity of water currents at different depths into the water column. It can also compute the flow rate of water passing a given point by integrating the data of the velocities over the cross-sectional area of the river. This, it can give information on the movement and the concentration of suspended sediment in the water.

4. What are the applications of ADCP in floods of The Kapuas River?

Velocity Measurement

The most key applications of ADCP meter during the flooding of the Kapuas River are for velocity measurement. They can provide current water speed at different depths in real time. This helps in observing the dynamic behavior of the floodwaters, indicating whether the current is stronger near the surface or at the bottom. The velocity data can also show how the current changes with time and space-a very critical variable in the prediction of the spread of the flood and its impacts.

Application of Flow Measurement

The ADCP profiler can measure the flow rate of the Kapuas River during the flood very accurately. From the measured velocities, with the cross-sectional area at the place of measurement, they provide an estimate of volume of water that can be flowing downstream. This is very important in flood forecasting for ascertaining the magnitude of the flood to know how much water reaches different areas along its riverbanks and how much damage can be done.

Application of Sediment Translocation

Research in flood events, sediment usually moves along with the current of the flood in Kapuas River. The sediment translocation can be studied by ADCPs through the detection of Doppler frequency shifts induced by the suspended sediment particles. This enables the analysis of sediment transport during flood stages of sediment movement and, more importantly, how the floods reshape the riverbed and the banks with the sediment distribution. It will give a glimpse of what the river morphological changes can be in the future and what sedimentation can do to infrastructures such as bridges and dams.

5. How can data measured by the ADCP be used for flood warning and risk management of the Kapuas River?

Flood Warning

Velocity and Flow Data Monitoring: In real-time, the velocity and flow rate data are essential elements of acoustic doppler flow meter in flood warning systems. Continuously monitoring these parameters will enable the authorities to spot sudden surges either in the speed or volume of water flowing in the river. For example, if the flow rate exceeds a threshold value correlated with historical flooding events, then an early warning can be issued. This allows for the timely evacuations of people from flood-prone areas by making all necessary preparations about emergency response measures.

Prediction and Warning of Water Level: ADCP data can also be used for predicting water levels. The trend in velocity and flow rate has some relationship with the water level, so one should be able to predict how the water level would be in the near future by analyzing the trends in the measured data. This allows for the issuance of water level warnings to the communities down stream in good time, to take precautionary measures such as transfer of valuable goods to higher levels or strengthening the flood defenses.

Risk Management

Water Conservancy Engineering Scheduling Decision Support: ADCPs data are useful in making decisions with regards to scheduling water conservancy engineering. For example, when flow rate and velocity data predict an approaching large flood, one can adjust the water dam release to mitigate its impact downstream. They can hold up more water when possible to reduce the peak flood flow or can even release water in a controlled manner instead of releasing it all at once to prevent sudden surges that could damage infrastructure downstream.

Flood Disaster Evaluation and Emergency Response: After a flood disaster, acoustic doppler velocity meter data can be used to assess the damages and destruction caused by the flood. From the study of the velocity and flow pattern during the flood, the location and areas that were most hit by the flood can be obtained. More importantly, this information is highly needed in coordinating the emergency response efforts, deploying rescue teams to the most heavily affected areas, and delivering relief supplies to the needy people.

6. What is needed to obtain high-quality measurement of the currents in The Kapuas River?

Reliability of Material

Reliability of materials is a critical issue to be considered, especially when measuring currents in the Kapuas River as accurately and constantly as possible. Among others, the casing of the ADCP has to be resistant to severe environmental impacts of the river, such as water and sediment contact, with possible impacts.

Small Size, Light Weight, and Low Power Consumption

Since the large-scale measurements have to be done in Kapuas River, the ADCP should be of small size, light weight, and power consumption. A very small-sized and lightweight device is manageable on boats, buoys, and other platforms for measurement installation. The low power consumption allows them to operate for a longer period without necessarily changing batteries or even access to a continuous power source, especially in areas where reliable supply of power may not be available.

Low Cost for Large-Scale Measurement This allows the use of ADCPs to monitor the current in the Kapuas River to be widespread in real applications because the equipment cost must be reasonable. High costs constrain the number of devices deployable, which in turn constrains how comprehensive data may be collected.

Advantages of Using Titanium Alloy for Casing

In this aspect, for casing ADCPs operating in the Kapuas River environment, titanium alloy is a pretty good material. It has excellent corrosion resistance, which is very important because the river water may contain various corrosive substances. It is also strong and durable, with the capability to stand against physical stresses and impacts that will be brought to the device during deployment and operation.

Also, because of its relatively low density, the overall weight of the device remains low, thus meeting the requirement of being light enough to be easily deployable.

7. How to select appropriate equipment for current measurement?

According to Measurement Orientation If the measurement is about horizontal cross - sectional currents, then the HADCP must be selected. In particular, HADCPs work under the principle of correctly measuring the flow in a horizontal plane across the river.

The Vertical ADCP would be the appropriate option for measuring vertical cross-sectional currents. It also enables the Vertical ADCPs to give full information on the velocity profile from the surface to the bottom of the water column. 

According to Frequency Selection In this respect, frequency depends on depth and particular measurement needs. A 600 kHz might be quite suitable in waters up to 70 meters, for example. The frequency provides good resolution and accuracy at depth in relatively shallower waters.

In case of deeper waters-like those that may be found in parts of the Kapuas River, where the depth in some areas even exceeds 70 meters, an ADCP with a frequency of 300 kHz is relatively better since it can go deeper down into the water column to still give reliable measurement of the currents.

Among the known brands of ADCPs in the market are Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option with high quality, the China Sonar PandaADCP is a great choice. It is made of all - titanium alloy material, which ensures its durability and performance in various river environments. It also offers an incredible cost - performance ratio.

You can learn more about it on its official website: https://china-sonar.com/.

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