ADCP for Saint Clair River Flood Management Application

1. Location of Saint Clair River

Saint Clair River is an important water body in North America, connecting Lake Huron with Lake Saint Clair between the United States of America at Michigan and Canada at Ontario.

It stretches approximately 64 kilometers. Along its course, it passes through areas with a mix of natural landscapes and human-developed regions. The cities and towns in the vicinity, such as Port Huron in Michigan and Sarnia in Ontario, depend on the river for various purposes, including shipping, fishing, and as a water source. The Saint Clair River is a significant transportation route for goods and commodities, facilitating trade between the Great Lakes and other regions.

The climate of the Saint Clair River basin is typical of the mid-latitudes with four distinct seasons: cold winters with snowfall and warm, humid summers. The river's water volume varies according to precipitation that includes rainfall and snowmelt. The flow from Lake Huron and input from tributaries provide important inputs for maintaining the levels of water in the river and the characteristics of its flow.

2. Why are there floods in Saint Clair River?

Heavy Rainfall and Snowmelt: One of the contributing factors to the occurrence of floods in Saint Clair River is heavy rainfall combined with the melting of snow. The snow that falls over a winter season melts at the onset of spring; during this time, if the snowmelt coincides with strong rainfall, the water contributed to the river system increases overwhelmingly. Additional water is brought in by the tributaries feeding into the Saint Clair River, and when the volume of water surpasses the natural carrying capacity of the river, flooding can occur along its banks, especially in low-lying areas.

Lake-Effect Storms: The Saint Clair River, lying close to the Great Lakes, is very prone to lake-effect storms. This can lay down a remarkable amount of precipitation in a very short period of time. The water from these storms, along with the usual river flow and water from tributaries, causes a sudden rise in the river's water level, leading to flooding.

Ice Jams: During winter, this river may freeze. At the onset of spring, while the ice starts to break up, ice jams are likely to occur. If the ice jams block the usual flow of the river, water will be backed upstream, causing flood upstream of the obstruction. The forces exerted by the water that has been backed up damage infrastructure such as docks, levees, and bridges.

In the context of flood management, the Acoustic Doppler Current Profiler (ADCP) offers a more sophisticated and efficient means of measuring the flow of the river compared to traditional methods.

3. How do ADCPs using the Doppler principle work?

They operate based on the principle of the Doppler effect. Basically, an ADCP current profiler generates acoustic signals in water - sound waves, which would engage moving particles of the sediment and the water molecule tag-along particles, and upon reflection back by the respective moving objects, it leads to a frequency change for the emitted waves.

This frequency shift, commonly known as the Doppler shift, directly depends on the velocity of the moving objects. These ADCPs are multiple-transducer instruments that send out acoustic pulses in different directions. A typical example is a downward -looking ADCP able to measure the velocity profile within the water column from the water surface down to the riverbed. By analyzing the Doppler shifts of the reflected signals from different depths within the water column, the ADCP current meter can calculate the speed of the water flow for every depth.

Once this speed at various depths is found, and with knowledge about the river's cross-section area, which can easily be measured or estimated, other important parameters such as river flow rate can be calculated easily.

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

Velocity Measurement: During flood events on the Saint Clair River, ADCP flow meter can measure the velocity of water flow with great accuracy in various locations and depths. This is essential for realizing the speed at which floodwaters are moving. This might enable prediction of when the flood waters would reach the most sensitive areas like communities along riversides, industrial sites, and other infrastructures such as bridges and water treatment plants. With continuous monitoring of velocity, authorities can take steps in advance to evacuate the people or strengthen flood protection structures.

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 very important for flood forecasting and to understand the magnitude of the flood. Also can help assess the capacity for all types of flood-control structure constructions like levees or dams.

Sediment Transport Research Application: ADCP flow meter can evaluate the backscattered acoustic signals while sediment particles are transported by the floodwaters of the Saint Clair River. Understanding sediment transport during floods is important for assessing changes in the riverbed. Sediment deposition and erosion can change the depth, width, and stability of the river, impacting future flood risks and the overall health of the river ecosystem.

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

Flood Warning

Velocity and Flow Data Monitoring: By continuous monitoring of the velocity and flow data with ADCP meter, early detection of abnormal changes in the flow is possible. A sudden rise in velocity or a significant alteration in flow rate may signal an imminent flood or an aggravating flood condition. It can be incorporated into the flood warning system to ensure timely warnings to the local community, emergency operators, and other relevant authorities.

Water Level Prediction and Warning: Measured flow data from ADCP current meter, when combined with other parameters like the cross-sectional geometry of the river and historical records of water level, enable the prediction of future water levels. In case the predicted water level is seen to rise above the flood level mark, warnings can be issued in advance to enable people to evacuate or take protective measures.

Risk Management

Water Conservancy Project Scheduling Decision Support: The data input with ADCP flow meter is essential as they provide valuable input regarding a decision on the operation of every water-conservancy project such as dams, reservoirs, and diversion channels along the Saint Clair River. For instance, under flood conditions, this could contribute to determining the proper dam releases to minimize the extent of any flooding downstream.

Flood Disaster Assessment and Emergency Response: In cases of a flood, the aftermath of the damage caused by the flood can be assessed using ADCP data.

This includes assessing high-velocity flow areas, sediment deposition amount, among other factors. This information is useful in emergency response and recovery efforts such as search and rescue operations and post-flood rehabilitation of infrastructure and ecosystems.

6. What's needed for high-quality measurement of Saint Clair River currents?

A number of things must be considered for high-quality measurement of the Saint Clair River currents.

Reliable Equipment Materials: The ADCP profiler should be of a material able to sustain the harsh environmental conditions it will be found in. It should withstand corrosion caused by the water, impact and floating debris of branches and logs, bottom ice during colder months, and erosion due to moving sediment particles.

Small in Size, Light in Weight, and Low Power Consumption: A smaller and lighter ADCP meter is easier to install and deploy, especially in areas that are difficult to access along the river. Low power consumption enables longer-term operation without the need for frequent battery replacement or complex power-supply arrangements, which is beneficial for continuous and long-term monitoring.

Low Cost: A lower-cost ADCP flow meter is preferred to facilitate large-scale deployment for comprehensive monitoring of the river.

On the casing material, the titanium alloy is an excellent choice. The titanium alloy is of high strength that can make the ADCP current meter resistant to outer forces. Besides, it has excellent corrosion resistance that ensures long-term performance of the equipment in the water. Its relatively low density helps reduce the overall weight of the device while maintaining its structural integrity.

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

When selecting equipment for current measurement in the Saint Clair River, the following shall be considered:

Purpose of Use: If the focus is horizontal cross-sectional flow measurement, a Horizontal Acoustic Doppler Current Profiler (HADCP) is quite adequate. It measures the flow velocity and other parameters across a horizontal section of the river. If the measurement is for a vertical cross-section, a vertical ADCP is more appropriate as it can measure the velocity profile from the water surface to the riverbed along a vertical line.

Frequency Selection: Different frequencies of ADCPs are suitable for different water - depth ranges. For example, an ADCP with a frequency of 600 kHz is typically suitable for water depths within 70 meters. While an ADCP flow meter with a frequency of 300 kHz is more appropriate for water depths up to 110 meters. Selecting the right frequency according to the actual water depth of the Saint Clair River ensures accurate and reliable measurement results.

There are well-known ADCP profiler 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.