ADCP's application in flood management of Culgoa River

1. Where is Culgoa River?

The Culgoa River originates in Australia. It forms a major part of the river system there. It flows through different regions and affects the local topography as well as the ecology to a great extent.

It flows through some rural areas and small towns of New South Wales. In terms of rainfall, the region where the Culgoa River is located experiences variable rainfall patterns throughout the year. Generally, the wet season usually brings more significant rainfall, often influenced by the broader climate systems such as the monsoon trough and frontal systems that can bring moisture from the ocean. However, during the dry season, the rain is not frequent, which can also affect the river's water volume and nature of flow.

2. What are the reasons for floods in Culgoa river?

There are many factors that eventually lead to flooding in the Culgoa River. One such factor is intense rainfall. When heavy rainfall falls upon its catchment area, specifically if the rainfall intensity is greater than the infiltration and storage capacity of the land, a high volume of runoff makes its way into the river, where the water level will rise very quickly.

It also depends on the topography of the river basin. If there are areas of relatively mild slopes with poor drainage, accumulation is more and the flow into the main river channel is faster in times of heavy rainfall. Similarly, factors of land-use change, such as extensive deforestation or poor agricultural methods that reduce soil infiltration rates, enhance runoff and thereby the chances of flooding.

The Acoustic Doppler Current Profiler (ADCP) has become a more advanced and convenient measurement method while dealing with the monitoring of floods and understanding the flow characteristics of the Culgoa River. In fact, it will be able to provide detailed real-time information on flow conditions of the river, which is again essential for flood management.

3. How do ADCPs using the Doppler principle work?

Doppler Principle : On the basis of the Doppler principle, ADCPs work. They send acoustic signals-usually sound waves-into the water. When these acoustic waves encounter moving particles in the water, like sediment grains or small organisms that are being carried along with the flow, the frequency of the reflected waves shifts. The change in frequency due to the motion of the targets relative to the acoustic source is called the Doppler shift. This constitutes the Doppler shift that is measured by ADCPs from multiple directions and at different depths within the water column to calculate the velocity of the water flow at those points. By continuous sampling and data processing over a period of time and across different locations in the river, it builds up a comprehensive profile of the flow velocity distribution both horizontally and vertically in the river.

4. What are the applications of ADCP in floods of Culgoa river?

Velocity measurement: In flood events occurring at the Culgoa River, acoustic doppler flow meter can get accurate velocity of the water flow at different locations and depths. Such knowledge regarding the speed with which floodwaters are running is very essential to help predict the area where such a flood would spread to and how bad the impact will be further downstream. For example, if the flow velocity near a bridge or any weak area is found to increase rapidly, appropriate precautionary measures can be taken in advance.

Flow measurement application: The ADCP can integrate the measured velocity data over the cross-sectional area of the river to calculate the total flow rate. Knowing the flow rate is essential for estimating the volume of water passing through a particular section of the river during a flood, which in turn assists in flood forecasting and managing water resources.

Sediment transport research application: Since the sediment will be carried along by the floodwaters in the Culgoa River, acoustic doppler velocity meter will also help in the study of the sediment movement. Researchers will be able to understand how sediment is redistributed by floods within the riverbed and on the banks when they study the relation between the flow velocity and the sediment concentration inferred from the backscattered acoustic signals, which helps in maintaining the morphological stability of the river and aids in understanding the long-term changes in the river channel.

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

Flood warning:

Velocity and flow data monitoring: Continuous monitoring of flow velocity and flow rate data by ADCP flow meter installed at key locations along the Culgoa River allows for early detection of changes in the river flow regime. For example, if the flow velocity significantly increases or the flow rate exceeds a certain threshold, that can indicate an upcoming flood or intensification. This real-time data may then be used for timely flood warnings to communities along the river.

Water Level Prediction and Warning: Flow velocity and flow rate data integrated with other information regarding the river's cross-sectional geometry and historical flood data provide better predictions of future water levels. If the predicted water level is expected to reach or exceed the critical value, necessary warnings may be issued to help people take proper preventive measures such as relocation into safer areas.

Risk management:

Water conservancy project scheduling decision support: The data from ADCP current profiler ​helps in making informed decisions about the operation of water conservancy projects like dams and weirs along the Culgoa River. For example, based on the measured flow data during a flood, the release of water from a dam can be adjusted to balance flood control and water storage needs, minimizing the overall flood risk downstream.

Flood Disaster Assessment and Emergency Response: The data measured by the ADCP current meter following a flooding event can determine the amount of damage caused by the flood, such as which areas were subjected to high-velocity flows and how much sediment was deposited. These data guide emergency response, which includes search and rescue operations and prioritizing infrastructure repairs and restoration.

6. What is required to achieve high-quality measurement of Culgoa River currents?

To measure the currents of the Culgoa River with high quality, several aspects of the equipment are important: firstly, material reliability, such that the device will be resistant to aggressive aquatic conditions-like water corrosion and possible impacts caused by sediment and floating debris. Small size, low weight, and low power consumption provide additional advantages.

For its installation and maintenance, a smaller and lighter ADCP is more feasible, especially in remote or unreachable parts along the river. Low power consumption provides an operation of equipment for a longer period without constant changes of batteries or problems in the power supply. Besides, low cost is preferred to allow the large-scale deployment of measurement devices down different sections of the Culgoa River for full-scale monitoring. In this respect, the casing of ADCP is preferably made from titanium alloy.

Titanium alloy has a number of exceptional advantages. For one thing, it has superb corrosion resistance; that is, it will not be easily damaged if immersed in river water for a long time. It has a high strength-to-weight ratio that enables the ADCP to be strong yet relatively lightweight in design. Besides, it will keep up its structural integrity against different temperature and pressure conditions commonly encountered in a river environment.

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

Selection of the right ADCP equipment for current measurement of the Culgoa River requires consideration of a number of factors.

Accordingly, depending on the purpose of use, horizontal cross-sectional measurement is adequately served by the HADCP since it is designed for the precise measurement of flow velocity and flow rate across a horizontal plane in the river, while the Vertical ADCP would be more appropriate for vertical cross-sectional measurement with its main objective of profiling the flow conditions in the vertical direction.

Second, different frequencies of the ADCP correspond to different operational water depth ranges. For example, an ADCP with a typical frequency of 600 kHz is generally applicable in water within 70 meters of depth. On the other hand, an ADCP with a typical frequency of 300 kHz is suitable for a higher water depth up to 110 meters. With the different parts of the Culgoa River having different depths, determination of the appropriate frequency will be essential in any measuring process for accurate results.

There are some famous brands selling the ADCP in the market, like Teledyne RDI, Nortek, and Sontek. But for a more budgetary option, China Sonar PandaADCP is highly recommended. It is all made of titanium alloy material, which ensures not only durability but an incredibly good cost-performance ratio. More about the product is on: [https://china-sonar.com/.

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