ADCP's Application in Flood Management of the Green River (Western U.S.)

1. Where is the Green River?

The Green River is a major river in the western United States. It is the chief tributary of the Colorado River. The headwaters of the river are in the Wind River Range of Wyoming. It then flows through Utah and Colorado.

This river passes through or near several cities and towns such as Green River, Utah. The Green River Basin experiences a semi - arid to arid climate. In the upper reaches, snowfall during winter is an important water source. The snowmelt in spring and early summer feeds the river. In the lower areas, rainfall is relatively scarce and erratic. The annual average precipitation varies with elevation and location within the basin. The higher-elevation areas receive most of their precipitation as snow, whereas the lower-lying areas receive less rainfall and depend on the runoff from the upper parts of the basin.

2. Why do floods occur in the Green River?

Flooding in the Green River can be due to a few causes. The leading cause of this is intense snowmelt. In years when there has been an enormous snowpack over the upper reaches of this basin, a sudden increase in temperatures can result in a rapid release of massive volumes of water into this river. If the natural capacity to carry the water downstream is reached and surpassed, flooding occurs.

Other than that, intense rainfall events can also trigger floods, although such events are rare under arid climatic conditions. A large amount of rainfall in a very short period of time, especially in the upper and middle sections of the basin, raises the water mark in the river very fast.

Other factors include the condition of the riverbed and channels, since over a long period, sediment deposition can decrease the conveyance capacity of the river. Other human activities involve the construction of dams and diversions, which interfere with the natural flow regime. In many instances, poor water management from dams or unexpected releases can lead to flooding downstream.

These flood-causing factors therefore mean that, in providing their measurements, the ADCP current meter system does this more efficiently and accurately than older systems. Better flood management practices can then be implemented.

3. How do ADCPs using the principle of the Doppler work?

The working of ADCPs is based on the Doppler effect. They emit acoustic pulses into the water. These pulses interact with moving particles in the water, such as suspended sediment and small organisms. As the acoustic waves bounce back after hitting these moving objects, a change in frequency occurs.

The amount of this frequency shift is directly related to the velocity of the moving particles and, consequently, the velocity of the water. For example, if an ADCP current profiler is placed in the Green River, say on a floating platform, it sends out sound waves that penetrate the water column. Since the flowing water and its contents reflect back the waves, ADCP analyzes the received signals to calculate the speed and direction of water flow at different depths.

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

Flow velocity measurement: ADCP flow meter can accurately determine the speed of water flow in the Green River. This information is vital during the time of flood as it indicates the speed at which the floodwater is moving. It helps in predicting the spread of the flood and identifying areas where high - velocity flows may cause erosion or other damage.

Flow rate measurement: By integrating the measured velocities with the cross-sectional area of the river (also measurable using ADCP), the flow rate of the river can be computed. In the context of a flood, knowing the flow rate is essential in understanding the volume of water passing through a particular section of the river and predicting its impact downstream.

Sediment transport research: ADCP meter can trace the movement of sediment particles along with the water flow. In cases of flooding, this gives very important information on the amount of sediment the river is carrying. Understanding sediment transport is crucial for predictions of changes in the riverbed, where sediment may deposit or erode, which can affect the stability of the river and its infrastructure.

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

Flood warning

Monitoring of Flow Velocity and Flow Rate Data: With continuous flow velocities and flow rate monitoring, the ADCP profiler helps to identify in advance abnormal changes that can trigger a flood. In case these velocities and flow rates go above their normal levels, alerts can be triggered to ensure timely warnings down to the communities along the riverbanks.

Water Level Prediction and Warning: Future prediction of water levels by finding a relation between flow rates, velocities, and water level through historical data and the actual ADCP measurement, information important for providing appropriate warning to the residents, allowing them to take precautions by either evacuating or securing themselves against flood hazards.

Risk Management:Water Conservancy Project Scheduling Decision-Support, ADCP profiler data are useful in making decisions on the operation of dams, reservoirs, and other water conservancy projects along the Green River. For instance, if a flood is forecasted, water release from the reservoirs can be adjusted based on ADCP-measured data to reduce flooding downstream and maintain the safety of the structures.

Flood disaster assessment and emergency response: In the aftermath of a flood event, ADCP meter data can be used to assess the extent of damage in terms of erosion, changes in the riverbed, and impacts on infrastructure. This guides emergency response and future flood mitigation strategies.

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

The equipment should be made of reliable materials for high-quality measurement of the currents in the Green River. A compact size and lightweight are advantageous, as it allows for easy deployment in various locations along the river, including on boats or at bridges. Low power consumption is necessary for long-term monitoring, especially in areas where power supply is limited. It also needs to be cost-effective to enable extensive deployment for comprehensive monitoring.

The casing of ADCP flow meter is preferably made of titanium alloy. Titanium alloy has excellent corrosion resistance, which is essential in dealing with water from the Green River that may contain various minerals and salts. Besides, it has a good strength-to-weight ratio, making the equipment durable and relatively easy to handle and install.

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

Selection of equipment for current measurement in the Green River, Horizontal cross-section measurements can be performed with an HADCP. It measures the flow velocities across a horizontal plane and gives a clear understanding of the overall flow pattern in a particular reach of the river. In the case of vertical cross-section measurements, it is better to use a Vertical ADCP current profiler as this profiles the velocities from the water surface to the riverbed along a vertical line.

As far as frequencies are concerned, an ADCP with 600 kHz has quite an appropriate scope of water depth up to ~ 70m. In much deeper sections, an ADCP with 300 kHz can go up to approximately 110 m of water depth.

There are well - known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option, the China Sonar PandaADCP is recommended. It is made of all - titanium alloy materials and offers a good cost - performance ratio. You can find more information at (https://china-sonar.com/).

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