ADCP's Application in Flood Management of Detroit River

1. Where is Detroit River?

Detroit River is an important waterway in North America. It connects Lake St. Clair to Lake Erie and forms part of the border between the United States (Michigan) and Canada (Ontario).

The river is about 51 kilometers long. It flows through an area of rich history and vibrant urban and industrial landscapes. It passes through the city of Detroit, Michigan, with which it has been long associated and from where much of its economic and transportation functions were made possible.

The Detroit River has formed an important artery for shipping and trade, facilitating the movement of goods between the Great Lakes and other regions.

The climate in the Detroit River basin is typical of the mid-latitudes, with four distinct seasons. Winters can be cold with snowfall, and summers are usually warm and humid. Precipitation, including rain and snowmelt, contributes to the river's water volume. The flow from Lake St. Clair and other tributaries also plays an important role in maintaining the river's water levels and flow patterns.

2. What causes flooding in Detroit River?

Heavy Rainfall and Snowmelt: A major cause of floods in the Detroit River is the combination of heavy rainfall and snowmelt. During spring, snow that accumulated during winter melts, while intense rain contributes a large volume of water to the river system. The many tributaries into the Detroit River can quickly flash this excess water into the main channel. If this is more than the carrying capacity of the river, then flooding may result along its banks, particularly low-lying areas. Lake-effect storms can occur due to the proximity to the Great Lakes. Precipitation may be great in quantity during these events in a very short period of time. This, added to the normal river flow and other sources of water, results in the rapid rise of the river and flood adjacent areas.

Ice Jams: During winter, the Detroit River can freeze. When the ice starts to break up in spring, there is the possibility of ice jams. These would impede the normal flow of the river, allowing water to back up and flood areas upstream. The force of the backed-up water can also be strong enough to damage infrastructure such as docks and levees.

Within the framework of flood management, the Acoustic Doppler Current Profiler (ADCP) offers a more sophisticated and effective way to measure the flow of a river than that of traditional methods.

3. How do Doppler Principle-based ADCPs work?

ADCPs work on the principle of Doppler. They transmit acoustic signals, or simply sound waves, into the water. These signals interact with moving particles in the water, such as sediment particles and water molecules that are flowing with the current. When the emitted waves are reflected back by these moving objects, a change in frequency occurs.

This frequency shift, or Doppler shift, is proportional to the velocity of the moving objects. ADCPs are usually fitted with several transducers that transmit acoustic pulses in different directions. For instance, a downward-looking ADCP current profiler will measure the velocity profile of the water column from the water surface to the riverbed. From these Doppler shifts, the ADCP flow meter is able to calculate reflected signals from different depths in the water column for the calculation of the velocity of water flow at every depth.

With the known velocity variation with depth and information on the cross-sectional area of the river (usually measured or estimated), other useful parameters, such as the river flow rate, can be estimated.

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

Velocity Measurement: The ADCP current meter will be able to measure the actual velocity of the water flow at various locations and depths accurately during the flood events taking place along the Detroit River. This information is further helpful in knowing how fast the floodwaters are moving. For instance, it can be used to predict when the floodwaters will reach vulnerable areas such as riverside communities, industrial sites, or infrastructure like bridges and water treatment plants. By continuously monitoring the velocity, authorities can take preventive measures such as evacuating people or strengthening flood-protection structures.

Flow Measurement Application: The velocity data in the ADCP profiler are integrated across the cross-sectional area of the river to calculate its flow rate. In this manner, it will determine the quantity of water passing through that section during a flood event. This is very helpful during flood forecasting, as the magnitude of the flood could be gauged through such information. This can also be helpful in evaluating the capability of flood-control structures such as levees and dams.

Application in Sediment Transport Research: While sediment is transported by the floodwaters of the Detroit River, ADCP current meter can study the movement of these sediment particles through the backscattered acoustic signals. Understanding sediment transport during a flood has vital linkages with assessing changes to the bed. Deposition and erosion affect the depth, width, and stability of the river and consequently alter future flood risks and general health of the river ecosystem.

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

Flood Warning

Velocity and Flow Data Monitoring: By continuous monitoring of velocity and flow data using ADCP meter, one could observe an abnormal change in flow at the river very much in advance. Such an instantaneous increase in velocity or such a change in flow rate could very well indicate the onset of flooding or an increase in the flooding situation. This information can be incorporated into flood-warning systems to provide timely warning to local residents, emergency services, and relevant authorities.

Water Level Prediction and Warning: By integrating the flow data measured by ADCPs with other factors like cross-sectional geometry of the river and historical records of water levels, one can make forecasts on the water level for future time. If the water level predicted is likely to rise above the flood level mark, one can give warnings in advance so that people move out or take all protective measures.

Risk Management

Water Conservancy Project Scheduling Decision Support: It gives valuable inputs for decisions related to the operation of water-conservancy projects like dams, reservoirs, and diversion channels along the Detroit River. During a flood, for instance, the flow data can provide indications as to the appropriate release rates from a dam for mitigating the impact of the flood downstream.

Flood Disaster Assessment and Emergency Response: In cases of flood events, ADCP current profiler can be used in post-flood assessments of damage caused by the flood. This includes assessing the area of high-velocity flow, sediment deposition, and other factors. This information is useful for guiding 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 Detroit River currents?

For high-quality measurement of the Detroit River currents, several aspects need to be considered.

Reliable Equipment Materials: The ADCP current meter should be manufactured from materials that are resistant to the extreme Detroit River conditions. The equipment should also be able to resist corrosion by water, impacts that may arise from floating debris like branches and logs and ice during the colder months of the year, and even abrasion by sediment particles.

Small Size, Light Weight, and Low Power Consumption: The smaller and lighter an ADCP current profiler would be, the easier it would become to mount and deploy the equipment even in poorly accessible areas of the river. Low power consumption allows for longer-term operating without any frequent battery replacements and complex arrangements of power supplies for its operation to be carried on continuously in a long run.

Low Cost: In favor of wide deployment towards adequate monitoring of the river is the preference for a low-cost ADCP current meter.

Regarding the casing material, titanium alloy is an excellent option. The Titanium alloy material has great strength to resist external forces on an ADCP flow meter. It has great resistance to corrosion, ensuring the equipment's efficiency in the water for a long time. It is of relatively low density that helps reduce the overall weight of the device while keeping its structural integrity.

7. How does one choose the right equipment for current measurement?

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

Purpose of Use: In case the concentration is on horizontal cross-sectional flow measurement, HADCP is applicable. This can measure flow velocity and other parameters in a horizontal section of the river. If the measurement is for a vertical cross-section, a vertical ADCP should be more suitable since it has the capability to measure the profile of flow velocity from the water surface to the bed along a vertical line.

Frequency Selection: Different frequencies of ADCPs are suitable for different water-depth ranges. For example, an ADCP profiler with a frequency of 600 kHz is generally suitable for water depths within 70 meters, while the one with 300 kHz is more appropriate for water depths up to 110 meters. The right frequency should be selected according to the actual water depth of the Detroit River to ensure the accuracy and reliability of the measurement results.

There are 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.