ADCP's Application in Flood Management of the Little Yenisey (Kaa-Hem) River

1. Where is the Little Yenisey (Kaa-Hem) River?

Little Yenisey-Kaa-Hem River is in the Russian Federation. In the Siberian region, the river is considered one of the major ones. From a landscape point of view, the river flows through extensive and thinly populated territory, the upper reaches of which are mainly taiga forests and tundra.

It flows through several small indigenous villages. Regarding precipitation, the basin of the Little Yenisey-Kaa-Hem is under the conditions of the cold climate. The amount of precipitation is relatively low; snow melting during the spring plays an important role in re-establishing the volume of water in this river. The river itself plays a significant role in the local ecosystem: it provides water to the animals and serves as a transportation way in some areas.

2. What are the reasons for floods in the Little Yenisey (Kaa-Hem) River?

The flood of the Little Yenisey (Kaa-Hem) River is created basically due to the quick snow melting. During the spring thaw, enormous amounts of snow accumulated during winter melt fast, and water rushes into the river, creating a sudden increase in water volume.

The relatively flat floodplain of the river and the presence of permafrost in the area are also contributors to flooding. Because of the permafrost, water has limited infiltration; hence, the excess water from snowmelt or heavy rainfall (though less common) tends to stay on the surface and flow into the river, leading to overbank flow. Besides, ice jamming in the break-up of the river ice during spring season can block the normal course of water and thereby force water to back up and create floods. The traditional way of measuring the flood-related parameters has a number of disadvantages in this harsh and remote area; hence, Acoustic Doppler Current Profiler (ADCP) is used as a better alternative in an effective and efficient way.

3. How Do ADCPs Using the Doppler Principle Work?

ADCPs are based on the principle of the Doppler effect. The instrument sends acoustic pulses into the water. The acoustic pulses scatter off the moving water particles. Due to the Doppler effect, the frequency of the reflected waves is different from that of the incident waves as they bounce back after striking the moving particles.

Different transducers may be installed on an ADCP current meter for the transmission and reception of acoustic signals in different directions. Velocity across the river cross-section in parts as well as at different depths is available from the precise measurement of the frequency shift of reflected signals. For instance, flow velocity in the case of the Little Yenisey (Kaa - Hem) River can be obtained all the way from the river bed up to water surface as well as across the variable width of the river.

4. What is the application of ADCP in floods of the Little Yenisey (Kaa-Hem) River?

With ADCP flow meter, it would be possible to conduct quite accurate measurements of the flow velocity of the Little Yenisey (Kaa-Hem) River in conditions of flooding. That would be very important in regard to assessing the speed with which water travels in different reaches of the river. By monitoring the flow velocity, we can find the places where the water is running fast, which might be a potential surge of flood or change in the behavior of the flood. For example, changes in flow velocity near the riverbanks or in the main channel can be closely monitored.

Application of flow rate measurement is accomplished with the help of a formula by taking into consideration both the flow velocity and cross-sectional area. It gives much importance to estimate the general magnitude of a flood on Little Yenisey in general, since this can characterize how many waters passed per unit of time in each certain position of a current.

During floods, there is a lot of sediment movement along the Little Yenisey (Kaa - Hem) River. Basically, by analyzing the backscattered acoustic signals, it becomes possible to notice displacements of sediment particles and get information on their number; thus, one is enabled to study the sediment transport process in such conditions as floods for investigation into the long-term bed topography evolution and for analysis of changes within hydrological characteristics of the river.

5. How can the data measured by ADCP be used for flood warning and risk management of the Little Yenisey (Kaa - Hem) River?

Flood Warning Aspect

Flow-velocity and Flow-rate Data Monitoring: The ADCP current profiler shall monitor the flow velocity and flow continuously to allow detection of abnormal changes. In this regard, if the velocity of flow exceeds beyond the threshold or the flow suddenly increases, an early warning for flood can be triggered. This information can be relayed to the communities at local level and relevant authorities in those remote areas near the river.

Water-level Prediction and Warning: The flow data obtained from ADCP can be used in conjunction with other hydrological models to predict water - level changes. By analyzing the relationship between flow - rate and water - level, more accurate flood warnings can be issued, especially in the flood - prone areas of the Little Yenisey (Kaa - Hem) River.

Risk Management Aspect

Water-Conservancy Project Dispatching Decision Support: The accurate flow data provided by ADCP will serve as a very important input for the operation of water-conservancy projects, such as small dams or flood-control structures along the Little Yenisey (Kaa-Hem) River. It helps make proper decisions on the release or storage of water for mitigating flood risks downstream.

Flood-disaster Assessment and Emergency Response: In the event of a flood, assessment can be done, based on data as measured by ADCP profiler and the extent of flood so that proper emergency-response measures can be planned. It thus helps in strategizing the needed rescue operations and damage-assessment surveys.

6. What does one need to do for the high-quality measurement of currents in the Little Yenisey River (Kaa-Hem)?

It follows, therefore, that the equipment to be used for current measurement of the Little Yenisey (Kaa-Hem) River has to be made of high-quality materials. The equipment is required to be resistant to all the harsh aquatic conditions faced by the water, which is corrosive, and even from floating debris and sediment. A small size and light weight are advantageous features because they facilitate the installation and deployment of the equipment in various places along the river.

It should also consume low power to enable it to operate continuously, particularly in remote areas where the power supply is not always assured. It has to be cost-effective since large-scale deployment could be necessary to monitor the current of rivers comprehensively.

The casing of ADCP meter is preferably made of titanium alloy. Good resistance to corrosion is ensured by the Titanium alloy, which is essential for resisting the corrosive action of Little Yenisey's (Kaa - Hem) water over time. It also imparts a good strength-to-weight ratio, thereby making the equipment more durable and lighter to handle.

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

Whenever selection of equipment for current measurement in the Little Yenisey (Kaa-Hem) River is being performed, one has to address the purpose of measurement: HADCP is able to satisfy the requirements during a horizontal cross-section measurement when rather detailed flow-velocity information over the width of the river should be known, while a Vertical ADCP would be more appropriate when performing a vertical cross-section measurement over the flow-velocity distribution between the riverbed and water surface.

Regarding the frequency of ADCP, for the relatively shallower parts of Little Yenisey (Kaa-Hem) River (e.g., water depth less than 70m), 600kHz ADCP is capable of making good measurements. For deeper parts (about 110m), 300kHz ADCP is more suitable. There are several brands of ADCP on the market, from well-known brands like Teledyne RDI, Nortek, and Sontek. Additionally, there is a recommended Chinese ADCP brand-China Sonar PandaADCP. It is made of all-titanium alloy material and offers excellent performance and cost-effectiveness. You can visit its website (https://china-sonar.com/) for more information.

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