ADCP Application in Flood Management of Mamoré River

1. Where is Mamoré River?

The Mamoré River is one of the most important South American rivers. The river lies in northern Bolivia and extends into the Amazon rainforest regions of Brazil. It is notably one of the major tributaries of the Madeira River.

The basin covers a large area comprising tropical rainforests with a variety of ecosystems. This area normally has a tropical climate with high levels of humidity and significant rainfall throughout the year. However, slight seasonal variations occur; generally, the regular rainfall maintains the river well-supplied. The Mamoré River traverses areas that are home to indigenous communities, and it forms a vital part of their way of life in providing water for drinking, fishing, and transportation.

It is also important for cities and settlements along its course, such as Guayaramerín in Bolivia and some smaller Brazilian towns, for economic activities involving trade and tourism. Its contribution towards agriculture within the surrounding area is also indispensable: water from the river helps irrigate farmland during the dry period and usually enriches the floodplains with sediment to retain their fertility.

2. Why does Mamoré River flood?

Heavy Rainfall: Heavy and incessant rains in the tropical region have been the major and well-pronounced cause of flooding of the Mamoré River. The large catchment area of its basin gathers enormous amounts of water in the wet season. The various tributaries further add to the influx of water, and if the volume of water that is coming in exceeds the carrying capacity of the main river channel, then flooding results.

Relief and Drainage: Relief in the river basin, as well as areas outside it, prevents proper water drainage. There exists a portion of land along or around the river that is flat or low-lying where water can be retained. Equally, thick vegetation cover and types of soil of the rainforest influence the infiltration rate. In some cases, the soil quickly becomes saturated and excess water runs off into the river, increasing the flood risk.

Deforestation and changes in land use, such as those occurring for agricultural purposes, logging, and so on in the Mamoré River basin, may greatly affect flood patterns. Trees are important in intercepting rainfall and enabling water to infiltrate into the soil slowly. Once land loses its forests, the ability of the land to absorb water decreases. This results in a larger amount of runoff at the surface and, subsequently, an increase in the overtopping of the river banks.

In flood management, the Acoustic Doppler Current Profiler (ADCP) also finds its application important because of the improved accuracy and efficiency in measuring the flow of the river, compared to the traditional methods.

3. How do Doppler Principle-based ADCPs work?

ADCPs work off the principle of Doppler. They send acoustic signals-usually ultrasonic-into the water. These sound waves will act among the moving particles in the water: sediment grains, organic matter, and water molecules themselves, which are flowing with the current. When those emitted acoustic waves are reflected back by such moving objects, a change in frequency occurs.

This frequency shift, commonly referred to as the Doppler shift, is linearly proportional to the velocity of the moving objects. ADCPs are fitted with several transducers, each transmitting acoustic pulses in different directions. For instance, a downward-looking ADCP current profiler will be able to measure the velocity profile of a water column from the water surface right down to the riverbed. By analyzing the Doppler frequency shifts of the reflected signals from different depths within the water column, the ADCP flow meter calculates the velocity of the water flow at each depth.

Once the velocity at different depths is determined, and with knowledge of the river's cross-sectional area-which can be measured or estimated-it becomes possible to calculate other important flow-related parameters such as the flow rate of the river.

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

Velocity Measurement: In the event of flooding of the Mamoré River, the ADCP profiler can very accurately measure the actual velocity of flow of water from several locations in depth. Information provided by the knowledge of speed and direction of the flood waters is essential. For instance, the information will help in forecasting the time when the flood water reaches a place, such as a riverside community or an agricultural area. Continuous velocity monitoring allows the authorities to take appropriate, timely precautionary measures regarding evacuation of people and strengthening flood-protection structures.

Flow Measurement Application: ADCP current meter works out the flow rate of the river by integration of the velocity data over the cross-sectional area of the river. In a flood situation, this measurement is vital for assessing the magnitude of the flood. This would allow a better understanding of whether the flood waters will exceed the flood-control structure capacities like levees or dams and can help in planning the water-management strategies to mitigate the impact of the flood.

Sediment Transport Research Application: The ADCP profiler, operating with the flooded sediment-carrying waters of the Mamoré River, can investigate backscattered acoustic signals for research into sediment movement. Knowledge of sediment transport during the flood is very relevant to understanding the morphodynamic variation in the riverbed. The deposition and erosion of sediments change the depth and width of the channel and may render it unstable, affecting flood risks in the future and altering the health of the river ecosystem.

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

Flood Warning

Monitoring of the Velocity and Flow Data: Continuously monitoring the velocity and flow data is possible through ADCP flow meter, enabling early notice of abnormal changes in the river flow. These signals show a sudden increase in velocity or an abrupt change in flow rate, which can represent an impending flood or a worsening flood scenario. Such data can be incorporated into flood-warning systems for the timely dissemination of warnings to residents, emergency response agencies, and other authorities concerned. Water Level Prediction and Warning: Measured flow data with ADCP current meter combined with other factors such as the cross-sectional geometry of the river and historical records of water levels allows the prediction of future water levels. If the predicted water level is expected to exceed the flood stage, then warnings can be issued in advance to enable people to vacate or take protective measures.

Risk Management

Water Conservancy Project Scheduling Decision Support: Data from ADCP offers useful input for decision - making on the operation of water - conservancy projects like dams, reservoirs, and diversion channels along Mamoré River. In the case of a flood, for instance, the flow data can be useful in deciding on the release rate from the dam so as to reduce the impact of a flood downstream.

Flood Disaster Assessment and Emergency Response: The data from an ADCP flow meter also comes in handy in the assessment of damage after a flood has occurred. This comprises of determination of the areas where the flooding caused high-velocity flows, the amount of sediment deposition, among other factors. This information is useful for guiding emergency response and recovery efforts, such as search and rescue operations and post - flood rehabilitation of infrastructure and ecosystems. 

6. What’s needed for high - quality measurement of Mamoré River currents? 

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

Durable Equipment Materials: The ADCP current profiler should be manufactured from materials capable of withstanding the most hostile aquatic conditions. The equipment must be resistant to corrosion by river water, impacts caused by floating debris, and abrasion by sediment particles.

Compact and Portable Design: Smaller in size, lighter in weight, and low power consumption are preferred. A compact and lightweight ADCP flow meter is easier to install and deploy, especially at remote areas of the Mamoré River basin. Low power consumption may allow longer-term operation without the need to frequently replace batteries or to implement complex power-supply arrangements, which are advantageous for continuous and long-term monitoring.

Cost - Effectiveness: A cost-effective ADCP profiler is preferred to facilitate large - scale deployment for comprehensive monitoring of the river.

For casing material, it is an excellent choice. In this context, the titanium alloy has high strength so that the ADCP meter can bear the action of outer water. Its corrosion resistance is excellent, ensuring long-term performance in water. As its density is relatively low, its structural integrities keep the weight of the equipment lower.

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

When choosing equipment for current measurement in the Mamoré River, consider the following:

Measurement Purpose: If the focus is on horizontal cross-sectional flow measurement, a Horizontal Acoustic Doppler Current Profiler (HADCP) is a suitable choice. It measures the flow velocity and other parameters across a horizontal section of the river. If the measurement is for a vertical cross - section, a vertical ADCP is more appropriate as it can measure the velocity profile from the water surface to the riverbed along a vertical line.

Frequency Selection: The ADCPs of different frequencies are all appropriate for different water-depth ranges. For instance, a 600 kHz frequency ADCP flow meter is normally suitable for water depth up to 70 meters, while the 300 kHz ADCP is more suitable for waters with depth up to 110 meters. A properly selected frequency by the actual water depth of the Mamoré River will ensure accurate and reliable measurement results.

There are well-known ADCP profiler 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.