ADCP's Application in Flood Management of Niagara River

1. Where is Niagara River?

The Niagara River is a considerable stream that connects two of the Great Lakes, Lake Erie and Lake Ontario, in North America. It constitutes part of the border between the United States and Canada.

The river is relatively short, stretching about 58 kilometers in length. It originates at the eastern end of Lake Erie and flows north to empty into Lake Ontario. Along its course, it passes through regions of varied landscapes and land use. The Niagara River hosts one of the world's most famous natural wonders, Niagara Falls. The area around the falls is a magnet for tourists from all over the world, forming a vital part of the local economy.

The climate in the Niagara River basin is influenced by the larger North American climate patterns. It experiences four distinct seasons. Winters can be cold with significant snowfall, and summers are generally warm and humid. Precipitation throughout the year, including rain and snowmelt, contributes to the river's water volume. The water flow from Lake Erie is also a major factor in maintaining the river's flow characteristics.

2. Why do floods occur in Niagara River?

Heavy Rainfall and Snowmelt: Among the major reasons for the flooding of Niagara River is the heavy rainfall and snowmelt. In spring, most of the snow accumulated during the winter season around the catchments begins to melt. If there is also sudden heavy rainfall during this period, it can raise the volume of water inflow into the river in no time. The tributaries of the Niagara River add to these waters, which may swell out of the river's natural carrying capacity and flood areas along the banks.

Ice Jams: During the cold season, most of the river freezes. When the temperatures rise and the ice breaks in the spring, it causes an ice jam. These pieces can block the usual flow of water from the river, causing the water to back up and flood the areas upstream. Water against the ice exerts a strong force that may further cause damage to infrastructure on the banks.

Upstream Water Management and Dam Releases: Sometimes, the operation of dams and water management systems upstream can affect the flow of the Niagara River. If there are sudden or unexpected releases of large volumes of water from upstream reservoirs or dams, it can cause a significant increase in the river's water level and potentially lead to flooding downstream.

Within the perspective of flood management, Acoustic Doppler Current Profiler (ADCP) has been recognized as a more modern and effective measurement device than traditional methods.

3. How do ADCPs using the Doppler principle work?

ADCPs work on the Doppler principle. They transmit acoustic signals-certainly sound waves-into the water. These signals are scattered by moving particles in the water, mainly sediment particles and water molecules flowing with the current. If those emitted waves are reflected back to the instrument by such moving objects, a frequency shift ensues.

This change in frequency, the so-called Doppler shift, is linearly related to the velocity of the moving objects. ADCPs are fitted with several transducers that transmit acoustic pulses in different directions. For instance, a downward looking ADCP measures the velocity profile of the water column from the water surface to the riverbed. The ADCP current profiler, through the analysis of Doppler shifts from the reflected signals coming from the different depths within the water column, calculates the velocity of water flow at each depth.

With known velocity at different depths, one could calculate other important parameters in the flow rate of rivers if the cross-sectional area (which can be measured or estimated) is known.

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

Velocity Measurement: During flood events on the Niagara River, ADCP current meter can accurately measure the velocity of water flow at different locations and depths. This information is crucial for understanding how fast the floodwaters are moving. It may serve to predict the time of floodwaters' arrival at some susceptible spots, like a riverside community, park, or infrastructures such as bridges and power plants. Through continuous monitoring of the velocity, authorities can comfortably take mitigative measures by evacuating people or constructing emergency flood protection measures.

Application in Flow Measurement: The flow rate of the river can be deduced by integrating the velocities from the ADCP flow meter over the cross-sectional area of the river. It could come in handy during floods because then one would know just what proportion of water is passing by and also the volume of that amount of water. All that knowledge is crucial for forecast work to be done on this nature of occurrence. It can also assist in assessing the capacity of flood-control structures like levees and small dams along the river.

Sediment Transport Research Application: As the floodwaters of the Niagara River carry sediment, ADCP profiler can analyze the backscattered acoustic signals to study the movement of these sediment particles. Understanding sediment transport during floods is important for assessing changes in the riverbed. Sediment deposition and erosion can affect the river's depth, width, and stability, which in turn impacts future flood risks and the overall health of the river ecosystem.

5. How does the ADCP-measured data be utilized in the flood warning and risk management of Niagara River?

Flood Warning

Velocity and Flow Data Monitoring: With ADCP meter, the continuous monitoring of velocity and flow data facilitates the early detection of abnormal changes in the flow of the river. A sudden increase in velocity or an abrupt rise in the rate of flow can indicate that a flood is imminent or that a flood is worsening. This information can be integrated into flood-warning systems for timely warning to the local community, the emergency services, and the relevant authorities.

Water Level Prediction and Warning: Measured flow data from ADCP flow meter coupled with other parameters like cross-sectional geometry of the river and historical records of water level could be used to predict the future level of water. The advance warning will enable people to evacuate or take necessary protection measures if the predicted water level is above the flood level mark.

Risk Management

Water Conservancy Project Scheduling Decision Support: ADCP data forms the main inputs into decision-making on water conservancy projects operating at small dams and water diversion channels on the Niagara River. For instance, the flow data would be helpful during a flood to determine how much water to release from the dam to reduce the effects of the flood further downstream.

Assessment of Flood Disaster and Emergency Response: When a flood event is over, ADCP data provide information on the damage from the flood.

This will involve assessment of regions affected by high-velocity flow, sediment deposition amount, and more. This information is useful to guide emergency response and recovery efforts, including search and rescue operations and post-flood rehabilitation of infrastructure and ecosystems.

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

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

Reliable Equipment Materials: The ADCP current meter should be manufactured from materials that will resist the harsh conditions of the Niagara River environment: resistant to corrosion by river water, impacts from floating debris such as branches and logs, and ice during colder months, and abrasion by sediment particles.

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

Low Cost: A lower-cost ADCP profiler is preferred to allow for large-scale deployment that will enable comprehensive monitoring of the river.

For the casing material, titanium alloy can be a good alternative. Because of its high strength, this could mean that the ADCP meter could easily resist external forces. This also has excellent corrosion resistance, thereby allowing long-term performance in water. Being of relatively low density is very important to reduce the weight in general while maintaining structural integrity.

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

When selecting equipment for current measurement in the Niagara River, consider the following:

Intended Use: In case the focus is on horizontal cross-sectional flow measurement, HADCP shall be a suitable option. This measures the flow velocity and other parameters across a horizontal section of the river. If the measurement is to be done for a vertical cross-section, then a vertical ADCP will be more appropriate, since it can measure the velocity profile 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 current meter 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 Niagara River will ensure accurate and reliable measurement results.

There are well-known ADCP 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.