ADCP Application for Flood Management in Grande River

1. Where is Grande River?

The Grande River is a major river with many different locations in the world; in this context, we will refer to the Grande River, which is located in Brazil. It is situated in the southeastern region of the country and spans across various states.

It cuts across an array of topographies-from agricultural regions and urban areas down to nature reserves. Cities like São Paulo do share a particular affinity with their water resources. The climate of the river basin is of the tropical and subtropical varieties, both being strong elements. There is a proper wet and dry season. On average, the wet season falls from October to March in this region and precipitates a reasonable amount of rain. These heavy rains raise the water level of the Grande River significantly because of a lot of water coming into it from its tributaries and the catchment area surrounding it. Contrarily, during the dry season, from April to September, this river experiences a decline in flow and water level.

2. What are the reasons for floods in Grande River?

Intense Rainfall: Heavy, continuous rainfall during the wet season has been identified as the major reason that causes floods in the Grande River. On account of its extensive basin area, it collects a huge amount of water. When the intensity of rainfall is high and continuous over a long time, natural drainage cannot be handled by the river. These are the tributaries that add more water, and when the main river channel is not capable of handling this inflow quickly enough, the level starts to rise until flooding occurs.

Urbanization and Changes in Land Use: The growth of the urban front along the riverbanks has meant further impervious surfaces like roads, buildings, and parking lots. Due to these surfaces, rainwater does not penetrate the ground; on the other hand, this results in more surface runoff that goes directly to the river. This additional volume of water can contribute to higher water levels and floods.

Poor Drainage Infrastructure: In some river areas, the drainage systems are poorly developed or not properly taken care of. They may not work effectively in carrying away excess water during heavy rainfall and hence end up with water accumulation, leading to flood development.

In flood management, the importance of the Acoustic Doppler Current Profiler (ADCP) cannot be overemphasized because it offers an easier and more accurate way of measuring flow characteristics than conventional methods.

3. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of Doppler. They transmit acoustic signals-essentially, sound waves-into the water. These signals scatter off the moving particles in the water, which would include sediment particles, organic matter, and water molecules that happen to be flowing with the current. If these emitted acoustic waves are reflected back by the moving particles, a frequency shift will result.

This change in frequency, known as the Doppler shift, is directly proportional to the velocity of the moving particles. ADCPs are equipped with multiple transducers that send out these acoustic pulses in different directions. For example, a downward-looking ADCP current meter can measure the velocity profile of the water column from the water surface all the way down to the riverbed. By analyzing the Doppler shifts of the reflected signals from various depths within the water column, the ADCP current profiler is able to determine the specific depth velocity of the water flow.

Once the velocity at various depths is determined, and with knowledge of the river's cross-sectional area at the measurement point, it becomes possible to calculate other essential parameters such as the flow rate of the river.

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

Velocity Measurement: During flood events on the Grande River, ADCP current meter can accurately measure the velocity of the water flow at different locations and depths. This information is vital for understanding how fast the floodwaters are moving. For instance, by knowing the velocity near bridges, embankments, or populated areas, authorities can assess the potential impact of the flood and take timely preventive measures like strengthening flood defenses or issuing evacuation warnings if necessary.

Flow Measurement Application: ADCP flow meter integrates the velocity data over the cross-sectional area of the river for the flow rate calculation. In cases of a flood, an accurate measure of the flow volume denotes the magnitude of the flood. It allows for the understanding of whether the floodwaters will exceed the capacity of the flood control structures or inundate the nearby areas, thus guiding flood mitigation strategies.

Sediment Transport Research Application: The Grande River's floodwaters naturally carry a large portion of sediment across the bed. An ADCP profiler would analyze the backscattered acoustic signals to study these moving sediment particles. Understanding sediment transport during floods is important for assessing how the riverbed may change, where sediment is deposited or eroded, and how this impacts future flood risks and the overall health of the river ecosystem.

5. How can the data to be measured by ADCP be used with respect to flood warning and risk management of the Grande River?

Warning about Flood

Monitoring Velocity and Flow Data: The continuous velocity and flow data through ADCP flow meter current profiler can help in the early detection of abnormal changes in the flow in a river. A sudden rise in velocity or a sudden increase in flow rate can indicate the approach or intensification of a flood. This could constitute real-time data that may be inputted into any flood warning system, providing timely warnings to the concerned local communities, emergency operators, and agencies in communities along the Grande River. Water Level Prediction and Warning: The flow data measured by ADCP profiler can be combined with other parameters like the cross-sectional geometry of the river and historical records of water level to make a prediction of future water levels. If the predicted water level is expected to reach or exceed the flood level mark, appropriate warnings can be issued in advance to allow people to prepare, evacuate if needed, or take other protective measures.

Risk Management

Water Conservancy Project Scheduling Decision Support: The data from ADCP meter provides valuable input for decision-making regarding the operation of water conservancy projects in the Grande River basin, like dams, reservoirs, and diversion channels. For example, during a flood, the flow data can help determine the optimal rate at which water is released from a dam to lower the impact of the flood downstream.

Flood Disaster Assessment and Emergency Response: In the aftermath of a flood, one can use data garnered from ADCP profiler to make informed decisions on the extent of damage caused therein. It can determine which areas were affected by high-velocity flows, the amount of sediment deposition, and other vital information crucial for guiding emergency response efforts in search and rescue operations, and planning post-flood restoration and rehabilitation work.

6. What is required to obtain high-quality measurement of the Grande River currents?

In measuring the currents of the Grande River with high quality, a number of factors should be considered.

Durable Materials: The ADCP current profiler equipment should be made from materials that would thrive well in the acidic aquatic environment of the Grande River. It should be able to withhold attack by corrosion from the river water, impacts from floating debris, and potential abrasion from sediment particles in the water.

Small size, light weight, and low power consumption: The ADCP flow meterwith smaller size and lighter weight is easier to install and deploy at various locations in the river, especially in areas that are not well accessible. Low power consumption enables long continuous operation without frequent battery replacement and complex arrangements for power supply, hence suitable for long-term monitoring.

Low Cost: To make the deployment of the ADCP current meter device large-scale and comprehensive within the Grande River, the preferred one is a device that has a low cost. It can be good in the casing material in the form of titanium alloy.

Titanium alloy has many advantages. High strength can enable the ADCP meter to bear outer forces caused by the flowing water and impacts with objects in the river. It has excellent corrosion resistance and hence is very well capable of retaining its performance and integrity even after exposure to river water for a relatively long period. Because of its relatively low density, it helps reduce the overall weight of the device while maintaining its structural stability.

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

When equipment needs to be selected for the measurement of current in the Grande River, the following aspects can be used:

Intended Use: Horizontal cross-sectional flow will be measured with a Horizontal Acoustic Doppler Current Profiler. This measures the flow velocity and other parameters across a horizontal section of the river, developing substantial information concerning the lateral distribution of the flow.

On the other hand, if the measurement is with the perspective of understanding the vertical cross-sectional flow, then a vertical ADCP would be quite relevant. This can accurately measure the velocity profile from the water surface to the bed along a vertical line, useful in analyzing the vertical variations of the flow within the river.

Frequency: Different frequencies of ADCPs are applied to different water depth ranges. Such as, a 600 kHz frequency ADCP is usually suitable for a water depth within 70 meters. An ADCP with a frequency of 300 kHz is more appropriate for a water depth up to 110 meters. By selecting the correct frequency according to the actual water depth of the Grande River, it will ensure the accuracy and reliability of the measurement results.

The common ADCP profiler brands include Teledyne RDI, Nortek, and Sontek. However, there is also a remarkable Chinese ADCP brand: China Sonar PandaADCP. Its body is made from pure titanium alloy, which combines strong durability with good performance. What's more, it offers an incredible cost-performance ratio. You can learn more about it on its official website: (https://china-sonar.com/).

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