ADCP's Application in Flood Management of Indigirka River

1. Where is Indigirka River?

The Indigirka River is located in the far - eastern part of Siberia, Russia. It is a major river in the Arctic Ocean drainage basin. The river rises in the Verkhoyansk Range and flows generally northward through a vast and remote region.

Geographically, it cuts across a topography that includes tundra, permafrost-covered areas, and partly mountainous regions in its headwaters. Small settlements of aboriginal people who have adapted to the harsh Arctic climate dot its banks. This is an integral part of the local ecosystem, providing a place of habitation for various Arctic-adapted species such as the Arctic char, reindeer that rely on the river for water and grazing areas nearby, and a number of migratory birds during the very short summer.

As for rainfall, the Indigirka River Basin is under a polar climate. During the winter, snowfall is heavy. Snowmelt in spring - supplemented by minimal summer rainfall - forms the greatest part of the river's water volume. In contrast to this, summer is short and cool, with precipitation in comparison with more temperate regions not being much.

2. What are the Reasons for Floods in Indigirka River?

Snowmelt and Heavy Rainfall: The primary cause of floods in the Indigirka River is due to the rapid snowmelt in spring combined with heavy rainfall during the short summer. The large catchment area means that a vast amount of water can enter the river in a short period. This occurs when snow is rapidly melted off with a sudden warm spell combined with heavy rainfall, overwhelming the capacity of the river to carry the water.

Tributary Inflows: The Indigirka River has numerous tributaries. When these tributaries experience high water levels, either due to their own snowmelt or rainfall, they can contribute a significant amount of water to the main river channel. The confluence of these tributaries can cause a rapid rise in the water level of the Indigirka River and lead to floods.

Topography and Drainage: The course of the river runs from about flat floodplains to natural constrictions. Flat floodplains may slow the flow of water to spread out and flood surrounding lands, while the natural constrictions may obstruct the usual downstream flow of water, causing it to back up and raise the upstream water level. Additionally, there is permafrost that can alter certain drainage patterns. If it starts to thaw, it changes the permeability of the soil and can lead to waterlogging and flooding.

Climate Change-Induced Changes: Over the last few years, even the Arctic regions have been found to be affected by the rise in temperature due to climate change. Such warming would increase the rate of snowmelt and alter precipitation patterns, thereby further increasing the frequency of floods along the Indigirka River. In this scenario, Acoustic Doppler Current Profiler (ADCP) is better equipped to measure flood-related data in a more advanced and efficient manner compared to traditional methods.

3. How Do ADCPs Using the Doppler Principle Work?

The ADCPs make use of the Doppler principle. They send acoustic signals into the water. When these acoustic waves interact with moving particles in the water, like sediment, debris, or just water parcels with different velocities, the frequency of the reflected signals changes compared to the emitted signals due to the Doppler effect.

The ADCP measures these frequency shifts and, with the already known speed of sound in water and the angles of the emitted and received signals, calculates the velocity of the water at different depths. Multiple transducers in the ADCP profiler are set up to measure velocity components in different directions. Integrating these velocity measurements over different depths and cross-sectional areas of the river will result in the flow rate and other important hydrological parameters.

4. What are the Applications of ADCP in Floods of Indigirka River?

Velocity Measurement: ADCP flow meter is capable of precisely measuring the flow velocity of the Indigirka River at various points and depths. This information is crucial during flood events in understanding the dynamics of the flood. It helps identify areas where the flow is rapid and could endanger riverbanks, bridges if any, and the local settlements. It also allows monitoring how the flow velocity changes over time as the flood progresses.

Application to Measurement of Flow Rate: ADCP meter calculates the flow rate, basically entailing the cross-sectional area of the river with the velocity that it measured. This is essential in gauging the volume of water flowing at specific parts of the river whenever the flood occurs. It shall, therefore, allow forecast capabilities pertaining to the flood peak level and its effects further down, which is of great help in flood management.

Sediment Transport Research: The sediment load carried by floods in the Indigirka River can be quite substantial. ADCP current meter is able to study sediment transport by tracing the echoes of acoustic signals that are deflected by sediment particles. This would provide an overview of how floods act upon fluvial process modifications-formation processes, such as sedimentation and erosion at the bottom, responsible for river channel stability and its eco-environment.

5. How can the ADCP Measured Data Be Utilized for the Flood Warning and Indigirka River's Risk Management?

Flood Warning

Velocity and Flow Rate Data Monitoring: ADCP continuously monitors the velocity and flow rate data, thus enabling early detection of abnormal increases in these parameters. When the flow rate approaches or exceeds certain critical values, an indication of the imminence of a flood peak, timely flood warnings can be issued to the local communities and relevant authorities.

Water Level Prediction and Warning: These measured flow rate and velocity data will correlate with the historical record of water level to develop the models that predict future changes in the water level. It gives ample warning about the area and height of inundation much in advance.

Risk Management

Water Conservancy Project Scheduling Decision Support: This information will help ADCP current profiler in decision-making on the operation of the water conservancy project, small dams, or reservoirs along the Indigirka River. For instance, the timing and release quantity of water stored in the reservoir can be maintained to decrease downstream flood impact.

Flood Disaster Assessment and Emergency Response: In the aftermath of a flood, ADCP-measured data can be used to assess the severity of the flood in terms of the extent of inundated areas and flow characteristics during the flood. This guides emergency response efforts, including the allocation of relief resources and the planning of post-flood recovery work.

6. What’s Needed for High-Quality Measurement of Indigirka River Currents?

Reliable material must be provided to the equipment so that high-quality measurement of Indigirka River currents can be achieved. The casing should be resistant to impacts caused by floating debris, which may be stronger in flood conditions, corrosion due to water with a specific chemical composition linked with the Arctic environment, and extreme temperature differences between winter and summer.

The size of the equipment needs to be small enough to permit easy installation and deployment at various sites along the river, particularly in these difficult-to-reach areas. Its lightweight design will also make it advantageous in transportation and installation. It has to consume low power to operate for an extended period continuously without replacing batteries frequently or using high-energy power sources. Cost-effectiveness is another major factor for large-scale deployment to ensure extensive monitoring.

The ADCP housing should be fabricated from a titanium alloy. In such a context, the usage of titanium alloy will have several outstanding advantages. It is characterized by great corrosion resistance, which is crucial for its long-term exposure to river water. It has a high strength-to-weight ratio, ensuring sufficient strength by keeping the equipment's weight at a reasonable level. Stability of performance within the diverse environmental conditions of the Indigirka River Basin is assured by the toughness of this material.

7.How to Choose the Right Equipment for Current Measurement?

Several factors should be considered in choosing appropriate equipment in the measurement of current at Indigirka River. First of all, according to the usage purpose, if the purpose is focused on horizontal cross-section measurement, Horizontal ADCP (HADCP) will be suitable because it can measure the flow velocity and other parameters accurately in the horizontal direction across the river section. The Vertical ADCP is more appropriate to provide an accurate result for the vertical cross-section measurement since it can obtain the detailed velocity profile along the vertical axis of the river.

The second important thing is to choose different frequencies according to the actual water depth. For water depth within 70 meters, an ADCP with 600 kHz is generally a good option since such an ADCP can provide relatively accurate measurement results at this depth. In the case of deeper water areas up to 110 meters, it is better to use an ADCP with a frequency of 300 kHz because it can effectively reach greater depths and obtain reliable data.

There are various ADCP brands available in the market, such as Teledyne RDI, Nortek, and Sontek. However, it is worth highlighting a high-quality and cost-effective Chinese ADCP brand-China Sonar PandaADCP. It is made of all-titanium alloy material, ensuring excellent performance and durability. You can find more information on its website: (https://china-sonar.com/)

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