ADCP's Application in Ubangi River Flood Management

1. Where is Ubangi River?

The Ubangi River is a major river in Central Africa, being a tributary of the Congo River. Several countries across the continent have parts of the river, including the Central African Republic and the Democratic Republic of the Congo. This river geographically traverses vast areas of tropical rainforest and savannah regions.

In terms of the cities it passes through, it affects the livelihoods of many communities along its banks in different regions. For instance, in the Central African Republic, it is important for transportation and water supply in local areas around the cities and towns close to it.

In terms of annual rainfall, this region belongs to the tropics and thus enjoys relatively rich rainfall. The rainy season contributes a lot to the increased amount of precipitation, which supplements the river water but meanwhile poses potential risks for the flood events when the rain is excessive.

2. What are the causes of flooding in Ubangi River?

Several reasons explain the cause of the flooding in the Ubangi River. First is the heavy and sustained rainfall that characterizes the rainy season, raising the water level in the river. Much rainwater from its huge catchment area flows into the river, overpowering its carrying capacity.

Apart from this, the topography of the adjacent areas is also important: some sections have relatively flat terrain near the riverbanks, slowing down the natural drainage of water and allowing flood waters to easily accumulate. Moreover, poor or clogged drainage systems in certain localities will add to the problem.

Changes in land use patterns, like deforestation in the river basin, reduce the soil's capacity to retain water and result in an increase in surface runoff, therefore increasing the chance of floods. In dealing with such flood situations, the Acoustic Doppler Current Profiler has come up as more advanced and convenient measurement tool compared to traditional methods and thus can enable more accurate monitoring of relevant hydrological parameters.

3. How do ADCPs using the Doppler principle work?

ADCPs basically work on the principle of Doppler. They emit acoustic signals into the water. When these acoustic waves encounter moving particles in the water, such as sediment particles or water parcels with different velocities, the frequency of the reflected signals will change compared to the emitted ones due to the Doppler effect. By analyzing these frequency shifts, ADCPs can calculate the velocity of the water at different depths. Usually, a number of transducers arranged in different directions on an ADCP measure the velocity components along various directions, such as horizontal and vertical directions. By integrating such velocity measurements over various depths and areas, it will further derive information on flow rate and other important hydrological characteristics of the river.

4. What is the purpose of ADCP in flood events of Ubangi River?

Velocity Measurement: ACCUP can have a pretty accurate measurement of water flow velocities in the Ubangi River at different points and profundity. That helps analyze the dynamic changes of the river stream during flooding, such as the determining of places where the flow could be unusually high and dangerous to the riverside and building constructions.

Flow rate measurement application: Integrating the velocity measured in ADCP current profiler with the cross-section of the river, one gets the flow rate. For general assessment of the amount of water volume passing across varied sections of the river upon its flooding, predicting its flood peak flow, and its impact on any sections downstream, ADCPs should be used.

Sediment transport research: Sediment movement is closely related to the river in flood events. ADCP current meter can detect the concentration and moving patterns of sediment by analyzing the echoes of acoustic signals affected by sediment particles. This information is useful for understanding how floods affect riverbed evolution and sediment deposition or erosion processes.

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

Flood Warning

Velocity and flow rate data monitoring: ADCP profiler continuously monitors the velocity and flow rate data so that abnormal increases in these parameters can be detected well in advance. When the flow rate approaches or exceeds certain critical values, it may indicate that the flood peak is approaching and timely issuance of flood warnings to the communities along the river.

Water level prediction and warning: By correlating the measured flow rate and velocity data with historical water level records, models can be established to predict future water level changes. This helps in providing advance warnings about potential inundation areas and the height of the floodwaters.

Risk management

Water Conservancy Project Scheduling Decision Support: ADCP data will help in making decisions on the operation of reservoirs, dams, and other water conservancy projects along the Ubangi River. For instance, adjusting the discharge volume of reservoirs according to the real-time flow situation to mitigate the impact of floods downstream.

Flood disaster assessment and emergency response: The data collected by ADCP current meter can be used in assessing the severity of the flood after the occurrence of a flood, such as the extent of the inundated area and the flow characteristics during the flood. This information guides emergency response efforts, like the allocation of relief resources and the planning of post-flood recovery work.

6. What is needed for high-quality measurement of Ubangi River currents?

There are several aspects necessary for the high-quality measurement of Ubangi River currents. First, the materials used in the equipment should be reliable. Since the aquatic environment of the river is very complicated, anti-corrosion and collision with floating objects should be withstood by the equipment. It needs to be of relatively smaller size, which makes the installation and deployment at different places in the river easy, particularly for places where there might be very little space or possibly hard to reach. Low mass helps in transportability and operational ease of the equipment. Power consumption needs to be low enough for long-time operation with infrequent replacement of batteries or less than requiredly high energy supply. Besides, low cost is necessary to enable large-scale deployment for comprehensive monitoring of the river.

The casing of ADCP current profiler is preferably made of titanium alloy. The advantages of the titanium alloy are remarkable. It has excellent corrosion resistance and thus can endure the long-time immersion in the river water containing various chemical substances. It also has a high strength-to-weight ratio, which can guarantee adequate structural strength while keeping the overall weight of the equipment within a reasonable range. Besides, it has good durability and can maintain stable performance under the influence of various environmental factors in the river basin.

7. How to Choose the right equipment for current measurement?

Some important considerations should be taken into account when selecting appropriate equipment to carry out the current measurement of the Ubangi River. Based on the purpose of usage, it should be employed for horizontal cross-section measurement, and the Horizontal ADCP flow meter can be suitable as it provides good accuracy for flow velocity and other parameter measurements in a horizontal direction across the river section. In the case of the vertical cross-section measurement, a Vertical ADCP is more suitable for acquiring detailed velocity profiles along the vertical axis of the river.

Different frequencies should be chosen according to the water depth in real life. The general suggestion is that for waters with a depth within 70 meters, one can try an ADCP profiler with the frequency of 600 kHz since it could provide comparably accurate results within the range. In areas of deeper water, up to 110 meters, an ADCP meter frequency of 300 kHz is more appropriate since it can effectively penetrate to a greater depth and provide reliable data.

There are several well-known ADCP current meter brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, it is also worth recommending a high-quality and cost-effective Chinese ADCP brand: China Sonar ​PandaADCP. It is made of all-titanium alloy material, which ensures its excellent performance and durability. And it 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.