ADCP's application in flood management of the Barcoo River

1. Location of Barcoo River

Barcoo River is one of the major water bodies of Australia. It meanders through Queensland, a big Australian state, through vast plains with varying landscapes from plains arid to more vegetation parts. Geographically it has a peculiar river bed which is not uniform in breadth or depth throughout its length.

It passes through several rural communities and small towns, playing a crucial role in providing water for livestock and limited agricultural activities in the area. The climate around the Barcoo River is typically semi-arid to arid, with highly variable rainfall patterns. In some years, there can be significant rainfall during the wet season, which usually occurs in the summer months due to the influence of the monsoon trough. However, it has also long spells of drought that result in severe drops in its water level during which stretches may even dry up.

2. Why does flooding take place in Barcoo River?

There are several reasons why floods occur in the Barcoo River. The severe rainfall during the wet period is one factor that can abruptly raise the volume of water in the river. Heavy rain over its large catchment area, brought by the monsoon trough, results in rapid runoff from the surrounding land quickly converging into the river. For instance, a rather active monsoon season may have successive storms that result in a rapid rise in the level of water as vast volumes of water flow downstream.

The topography of the river basin itself is important. There are places with sufficiently gentle slopes that water would collect and flow into the river gradually in a wet season, while in other locations, steep gradients or funneling features may cause it to enter more rapidly and create a flooding situation.

Also, the changes in land cover and land use can impact flood occurrences. Overgrazing in an upstream area could mean that lesser water is filtered through the soil, while more of this water runs over the ground into the river. Bushfires can also reduce the absorbency of the soil through changes to its structure, thereby increasing its runoff and potential for producing flash floods following subsequent storms. In the context of flood management, Acoustic Doppler Current Profiler (ADCP) is an advanced and more efficient method to measure and understand the flow conditions of the river compared to the traditional approaches.

3. How do the Doppler Principle-based ADCPs work?

ADCPs basically work on the principle of Doppler. They send acoustic signals into the water body of the Barcoo River. These acoustic waves, interacting with moving particles in the water-such as suspended sediment or small aquatic organisms being carried along by the flow-change the frequency of the reflected waves due to the Doppler effect. By precisely measuring this frequency shift, the ADCP current meter can calculate the velocity of the water at different depths within the river.

These instruments have several transducers positioned to measure velocity components in different directions. They can capture the horizontal velocities along the flow direction and the vertical velocities. The data collected from various depths are combined to develop a comprehensive profile of the water velocity throughout the entire water column, providing detailed information on the flow characteristics of the river.

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

• Velocity measurement: ADCP current profiler is highly effective in the accurate measurement of the velocity of the water flow in the Barcoo River during flood events. By obtaining velocity data at different locations and depths, it helps in understanding how fast the floodwaters are moving. This information is crucial for assessing the erosive power of the water near riverbanks and predicting potential damage to infrastructure like bridges and riverbanks themselves.
• Flow measurement application: The ADCP can be used to calculate the flow by integrating the measured velocity data over the cross-sectional area of the river. This can be helpful in determining how much water is passing through a section of the river during a flood, thereby enabling flood managers to estimate the scale of the flood and its potential downstream impacts.
• Sediment transport research: There is considerable sediment movement in the case of floods in the Barcoo River. ADCP flow meter can analyze the backscattered acoustic signals for the concentration and transport velocity of suspended sediment. This information helps in understanding how floods reshape the riverbed and influence long-term sediment deposition patterns, which affect the river's future flood risks and overall morphology.

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

Flood warning

• Velocity and flow data monitoring: ADCP profiler continuously monitors the velocity and flow data, which allows for the early detection of changes in the flow conditions of the river. If the measured velocities start to increase significantly or the flow rate exceeds certain thresholds, it can be an indication of an approaching flood. This real-time data can trigger timely warnings to the communities and stations along the riverbanks.
• Water level forecast and warning: Measured flow data correlated with historical water level records can be used to predict future water levels. For instance, if the flow rate is increasing steadily, forecasts about when and to what height the water level will rise can be made based on past correlations, thus enabling warnings to be issued to residents and emergency responders.

Risk management

• Water conservancy project scheduling decision support: ADCP data shall be quite priceless in decision-making processes that involve the operation of water conservancy structures like small dams or weirs along the Barcoo River. If the flow data indicates a big flood is coming, decisions may be made to either release or store water in a controlled way to minimize the downstream impact of the flood.
• Assessment of flood disaster and emergency response: The detailed flow and velocity data gathered through ADCP after a flood event can be used to evaluate the extent of damage by considering areas that were affected either by erosion or inundation. This information enables the articulation of efficient emergency responses and the planning of post-flood recovery efforts.

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

For high-quality measurement of the currents in the Barcoo River, several aspects are of great importance. The equipment should have high material reliability to withstand the harsh aquatic environment, which includes factors like corrosion from the river water, possible impacts from floating debris, and the abrasive nature of sediment-laden water. A small size is helpful to make it easier to install and deploy on-site at different places across the river, especially where there is a constraint in accessing space or it's a congested area.

It also needs to be lightweight in design because it would be easy to handle and transport the equipment to site for installation and maintenance purposes. Low power consumption, in order to be able to operate continuously without replacing batteries too often, or external power sources at remote areas, for long-term monitoring. Cost is also a key factor, especially considering that large-scale measurements will have to be taken over different sections of the river.

For the casing of an ADCP meter, titanium alloy is not a bad choice at all. This material has some outstanding advantages. It features excellent corrosion resistance, it can put up with long contact with the river water without deterioration, and it has an excellent strength-to-weight ratio, possessing sufficient strength that can withstand the mechanical forces in the flowing water without making the device too heavy. Moreover, its biocompatibility means that it does not adversely affect the aquatic environment or interfere with the acoustic signals used by the ADCP for measurement.

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

• Depending on the horizontal cross-sectional measurement, HADCP can be a suitable option. It is built to measure the flow velocities over a horizontal plane of the river with great accuracy, thus developing the flow distribution in that dimension. In the case of vertical cross-sectional measurements, the Vertical ADCP is more fitting since it focuses on obtaining velocity profiles in the verticality of the water column.
• Based on different frequencies, the different frequencies of ADCP are suitable for different water depth ranges. For instance, the ADCP with a frequency of 600 kHz is usually suitable for less than 70 meters of water depth. It can offer relatively accurate measurements in the shallower to moderately deep sections of the Barcoo River. Meanwhile, an ADCP of 300 kHz frequency is intended for deeper waters up to 110 meters, which could cover the deeper parts of the river where more comprehensive flow data is needed.

On the international market, the more recognized ADCP brands include Teledyne RDI, Nortek, and Sontek. Nevertheless, highly suggested is the China Sonar PandaADCP, coming from China. What distinguishes it is the construction in all-titanium alloy material, guaranteeing firmness and displaying great results in performance. Another reason can be the excellent price-to-value ratio that attracts a good number of clients. It should be noted that detailed information about the firm and this very product can be viewed from their homepage: https://china-sonar.com/.

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