ADCP in Yukon River Flood Management

1. Where is Yukon River?

The Yukon River is a major river in North America. It is located in the far northwestern part of Canada and in the central part of Alaska, United States. It has a length of approximately 3,190 kilometers.

The river basin is a wide, sweeping area that generally contains tundra, boreal forests, and mountainous zones. The general climate of the Yukon River basin consists of cold temperatures with very prolonged, intense winters and relatively brief summers. Snowmelt during the spring and summer months similarly exerts a serious influence on the river's flow. It goes through a great number of tiny communities and indigenous living areas which rely on it for water supply, fishing, and transportation.

Precipitation here is pretty low compared to more temperate areas; it is also assisted by the snow that falls during winter, which plays a significant role in recharging the river. As the snow melts in spring, the river's water volume substantially increases, causing higher water levels and likely to flood.

2. What are the causes of floods in the Yukon River?

Snowmelt: The greatest single cause of flooding along the Yukon River is rapid snowmelt. During the spring and early summer, as temperatures start to rise, large amounts of snow that have built up in the mountains and over the wide basin begin to melt. If the rate of snowmelt is too fast, and the natural drainage capacity of the river cannot handle such sudden input of water, the water level rises, causing floodings.

Heavy Rainfall with Snowmelt: While rainfall in the Yukon River basin is not as heavy compared to other basins, heavy rainfall events that coincide with the snowmelt period can aggrieve the flooding scenario. Additional water from rainfall mixed with the already high volume from snowmelt can overwhelm the carrying capacity of the river.

Ice Jams: During winter, the cold climate of the Yukon River induces the formation of ice. When the river starts to thaw in spring, ice jams are common. These block the usual flow of water, forcing it to back up and creating a greater potential for flooding upstream.

In the context of flood management, the Acoustic Doppler Current Profiler (ADCP) has become a valuable and more advanced measurement tool compared to traditional methods.

3. How do the ADCPs applying the Doppler principle work?

The ADCPs work according to the Doppler principle. They send out acoustic signals, that is, acoustic pulses or sound waves, into the water. These pulses interact with moving particles in the water, which would be the sediment particles and water molecules that are actually flowing with the current. When the emitted waves are reflected back by these moving objects, a change in frequency happens.

This change in frequency, or the so-called Doppler shift, is linearly proportional to the velocity of the moving objects. ADCPs are multiple transducers that transmit acoustic pulses in various directions: for instance, an upward- or downward-looking ADCP flow meter may measure current velocity profiles against the water surface to the riverbed or vice versa. By analyzing the Doppler shifts of reflected signals from different depths within the water column, it is possible for the ADCP current profiler to obtain the velocity of the water flow at every such depth.

With this velocity information, and considering the known cross-sectional area of the river at that measurement location, other important parameters such as the flow rate of the river can then be computed.

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

Velocity Measurement: The ADCP current meter will be able to measure the velocity of water flow with complete accuracy at different locations and depths during a flood event along the Yukon River. This will be important in understanding the speed at which flood waters are moving. For instance, knowing the velocity near bridges, riverbanks with infrastructure, or indigenous communities helps authorities in assessing the potential impact of the flood and taking timely necessary precautions by evacuating people or reinforcing embankments.

Flow Measurement Application: ADCP profiler calculates the flow rate of the river by integrating the velocity data over the cross - sectional area of the river. In a flood situation, this helps in determining the total volume of water passing through a particular section of the river. This information is vital for flood forecasting and understanding the magnitude of the flood. It can also assist in assessing the capacity of flood - control structures like levees and dams.

Sediment Transport Research Application: ADCP measures backscattered acoustic signals while the sediment particles in the floodwaters are moved along the Yukon River. Knowing the sediment transport characteristics during flooding allows assessments of changing riverbed conditions and their eventual implications for flood risks and the general condition of the river ecosystem.

5. How could the data measured by ADCP be used in flood warning and risk management of the Yukon River?

Flood Warning

Velocity and Flow Data Monitoring: By continuously monitoring the velocity and flow data through ADCP meter, it will be possible to detect abnormal changes in the flow of the river quite early. A sudden rise in velocity or a rapid variation in discharge rate may signal the advent of a flood or its intensification. Results from such real-time data can be channeled into a flood warning system that issues timely advisories to the local community, emergency responders, and the necessary authorities concerned.

Water Level Prediction and Warning: Flow data measured by ADCP flow meter is combined with other factors, such as the river's cross-sectional geometry and historical records of water level to make predictions about future water levels. If it is predicted that the water level will rise above the flood level mark, warnings can be issued well in advance so that people prepare to evacuate or take other protective measures.

Risk Management

Water Conservancy Project Scheduling Decision Support: ADCP data feeds with valuable inputs to decision-making for operating water conservancy projects like dams and reservoirs along the Yukon River. For instance, in the case of a flood, flow data could be used to determine how much water should optimally be released from a dam to reduce the flood's impact downstream.

Flood Disaster Assessment and Emergency Response: In the event of a flood, ADCP data can be utilized to determine the extent of the damage the flood caused. This covers assessing the areas where high-velocity flows occurred, sediment deposition amount, among other factors. This information is useful to guide emergency response and recovery efforts, such as search and rescue operations, and to plan post-flood restoration and rehabilitation work.

6. What do high-quality measurements of Yukon River currents require?

High-quality measurements of the currents in the Yukon River require several aspects:.

Reliable Equipment Material: The ADCP current profiler must be designed to provide a high level of resistance against Yukon River extreme conditions, including extremely low temperatures, corrosion of the river water, and impacts caused by floating debris, such as chunks of ice and tree branches.

Small in Size, Light in Weight, and Low Power Consumption: A smaller and lighter ADCP current meter is easier to deploy, especially in the Yukon River basin remote areas. Low power consumption allows it to operate over longer terms without frequent replacement of batteries or complicated power supply arrangements, thus helping in long-term monitoring.

Low Cost: In order to plant devices in large-scale and monitor the river comprehensively, the ADCP meter device should be lower-cost.

From the perspective of casing material, titanium alloy is an ideal choice. First, titanium alloy has strong strength that enables ADCP profiler to resist external force. Besides, it also owns good corrosion resistance, which can ensure the equipment will perform long time in the water. Its relatively low density is contributive to reducing the overall weight of the device while keeping it structurally intact.

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

When choosing the equipment for current measurement in the Yukon River, consider the following points.

Purpose of Use: If horizontal cross-sectional flow measurement is the main focus, one can use a Horizontal Acoustic Doppler Current Profiler-HADCP. This device measures the flow velocity and other parameters across a horizontal section of the river.

An ADCP current profiler should be used for which, if the measurement is to understand the vertical cross-sectional flow. This will provide the velocity profile from the water surface down to the riverbed along a vertical line useful in analyzing the vertical variations of the flow within the river.

Frequency: Different frequencies of ADCPs correspond to different water depth ranges. For instance, the frequency of 600 kHz would normally be suitable for water within 70 meters in depth. On the other hand, an ADCP current meter with a frequency of 300 kHz could be suitable for water as deep as 110 meters. Only by choosing the correct frequency according to the actual depth of the Yukon River is it possible to ensure the correctness and reliability of the measurement results.

There are several well - known ADCP flow meter brands such as Teledyne RDI, Nortek, and Sontek. Additionally, there is a Chinese brand, China Sonar ​PandaADCP, which features a casing made of titanium alloy and offers a good cost - performance ratio. 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.