ADCP in the Northern Dvina River Flood Management

1. Where is the Northern Dvina River?

The Northern Dvina River is in north-western Russia. The river originates in the Valdai Hills and flows into the White Sea.

The catchment area of this river, which is big geographically, has a highly varying landscape: from the upper reaches of its basin, the river passes through forests, hills, and successive plains and marshy areas. The river is very important for the regions through which it passes and acts as a transportation route for goods and people. It supplies water to various industries and agriculture in the area, apart from domestic use.

It's a cold-temperate region; the precipitation in this place falls throughout the year, much as snow in winter. The breakdown of the snow from these mountains accounts for much volume of water for the river in spring. In addition, rainfall during the summer season feeds the river. Water level fluctuations could be brought about by the combination of snowmelt and rainfall; at the same time, flooding is likely to occur in cases of heavy rainfall or rapid snow melting.

2. What are the causes of flooding in the Northern Dvina River?

Snowmelt: Spring snowmelts are the major causes of flooding. Heavy snowfalls that a place like Valdai Hills and its vast areas receive during winter may suddenly melt away with a sudden rise in temperatures, and the sudden rush of water may be too much for the river to contain.

Heavy Rainfall: During the summer, heavy and continuous rainfall can be another cause of flooding. The catchment area of a river can receive enormous amounts of water in a very short period of time. The ground in the area is incapable of absorbing the water because of its type and permafrost in some areas. A large part of the rainwater runoff ends up in the river.

Topography: Presence of flat and low-lying areas, including plains and marshes along the river, allows water to spread out and accumulate. These may slow down the water flow and give more opportunity for water to flood.

Human Activities: Some human activities have contributed to flood conditions. Deforestation in the upper reaches of the river can reduce the interception potential of the forest to retain rainwater. Agricultural activities may lead to soil erosion. Deposited in the river, the eroded soils decrease its carrying capability and add to the flood risk.

The Acoustic Doppler Current Profiler (ADCP) is an extremely useful tool in understanding and managing the flow of the river in case of flooding of the river.

3. How do ADCPs using the principle of Doppler work?

The basic operating principle for an ADCP current meter is the Doppler principle. It emits an acoustic signal into the water. The circulation of the water causes the signal to collide with moving water particles. While this acoustic signal reflects into the ADCP current profiler, it experiences - because of the so-called Doppler effect-a change in frequency.

In principle, an ADCP measures the differential frequency between the emitted and received signal. From this frequency shift, it can compute the velocity of the water at various depths. These instruments normally have a multiple of transducers capable of emitting and receiving acoustic signals in various directions. This allows them to create a profile of the water velocity across a section of the river.

In return, for example, if it is flowing towards the ADCP flow meter, then the frequency of the reflected signal would be higher than that emitted. In the event of flow away from the ADCP meter, however, the frequency of the reflected signal will be lower. By precisely measuring these changes in frequency and using appropriate mathematical algorithms, the ADCP can calculate with good accuracy the velocity of the water at various points within its measurement range.

4. What are the ADCP applications in floods of the Northern Dvina River?

4.1 Measurement of velocity

In this flood event of the Northern Dvina River, acoustic current meter plays a major role in measuring water flow with much accuracy. Continuously monitoring water velocity at varied depths and locations provides data in real time regarding the speed at which the water is flowing. This helps to form one of the important bases needed for understanding the dynamics of the flood in predicting the direction and intensity of the movement of floodwaters.

4.2 Flow Measurement Application

ADCP profiler can also measure the flow rate of the Northern Dvina River. By utilizing measured water velocities at different points across a section of the river and a known cross-sectional area of the river, it will be able to calculate how much water is passing through the section in every unit time-the flow rate. This information is very important for the estimation of the total volume of water in case of a flood, and later on it provides the relevant base for the decisions concerning flood control and water resource management.

4.3 Application in Sediment Transport Research

Besides measurement of flow and velocity, acoustic doppler flow meter could also be used in research related to sediment transport during the time of floods in the Northern Dvina River. When running, water carries sediments. ADCP is able to detect changes in the backscattered acoustic signal due to the presence of sediments. These variations will be processed to estimate the quantity and mobility of sediments, key information in understanding the long-term evolution of the riverbed and the impact of floods on the sedimentary environment of the river.

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

5.1 Flood Warning

Velocity and Flow Data Monitoring: ADCP-built real-time velocity and flow data are monitored. This would indicate a forthcoming flood peak or flood situation in case the water velocity is higher than the threshold value or if there is a sudden rise in the flow rate. It allows for early warning to the concerned authorities to take necessary precautionary measures regarding the evacuation of people living in low-lying areas or strengthening of flood defenses.

Water Level Prediction and Warning: Measured flow data correlated with historical water level data and appropriate hydrological models can help in the prediction of future water levels using ADCP data. In case the predicted water level is expected to rise above the flood warning level, timely warnings can be issued to the public to get ready for the flood.

5.2 Risk Management

Support for Scheduling Decisions of Water Conservancy Project: The precise flow and velocity data derived through ADCP will help in deciding the operations of the water conservancy project. For example, operating dams and sluices can be controlled by controlling the water release from the dam, depending on the measured water flow, to control the water level in the Northern Dvina River and mitigate the impact of floods.

Flood Disaster Assessment and Emergency Response: It would be beneficial to use the ADCP dataset after a flood event to understand the intensity of the flood-event area of inundation, the velocity of the flood water, the quantity of sediment deposited, and so on. This information is very helpful in formulating emergency response plans and in carrying out post-flood reconstruction and rehabilitation works.

6. What does high-quality measurement of the currents of the Northern Dvina River require?

High-quality measurement of the currents of the Northern Dvina River requires something. First of all, the equipment used should contain reliable materials. In this case, special attention is paid to the casing of the ADCP. Its casing is recommended to be made from a titanium alloy. The advantages of the usage of a titanium alloy are the following. Because it has high strength, enabling the equipment to bear the pressure and impact of water flow in the river. Furthermore, it is highly resistant to corrosion, which is just proper considering the possible different composition of corrosive elements in the water environment of the Northern Dvina River.

Aside from material reliability, the size and weight of the equipment should be small and light. That means it will be easier to install and operate the ADCP at different locations along the river, especially in those places where access is not so easy. Another important factor is a low power consumption because it provides a possibility of long time of work without changing the batteries all the time or connecting it with some source of power. Besides, the cost of the equipment should be relatively low to provide large-scale measurement. This will lower the cost and allow deploying more ADCPs on the river, thus providing more information with higher resolution for flood management.

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

In the light of the aforesaid, any equipment that would be used for current measurement in the Northern Dvina River substantially relates to a number of factors. If the purpose of measurement corresponds to horizontal cross-section measurement, for instance, a Horizontal ADCP - HADCP-should be selected; if the purpose corresponds to vertical cross-section measurement, then the equipment would include Vertical ADCP.

Different water depth has the corresponding frequency to use. For instance, a 600 kHz ADCP is suitable for those water depths within 70 m. If the water depth in the Northern Dvina River is within this range and meets the measurement requirements, then a 600 kHz ADCP can be considered. At deeper waters, such as in excess of 70 m to 110 m, a 300 kHz ADCP will be appropriate and shall return results more suitable for that depth.

Within the market, there exist several known brands of ADCPs. These include Teledyne RDI, Nortek, and Sontek. For those looking for cheaper means, then China Sonar PandaADCP is good enough. This transducer is made of all - titanium alloy material to make sure it can bear any strength and perform its functionality in a good manner in a water environment. Moreover, it offers an incredible cost - performance ratio. For more information related to it, one can log on to: (https://china-sonar.com/).

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