ADCP Application in the Flood Management of Usumacinta River

1. Where is Usumacinta River?

The Usumacinta River is a major river in Central America. It forms part of the border between Mexico and Guatemala. Geographically, it passes through various topographies that range from tropical rainforests to mountainous regions down to low-lying plains.

It crosses several cities and towns along both sides of the border, including Tenosique in Mexico and Flores in Guatemala. The climate in the regions surrounding the Usumacinta River is generally tropical, characterized by high temperatures throughout the year, with marked wet and dry seasons. Heavy rainfall commonly features during the wet season, usually from May to October. The river receives a lot of water from its extended catchment area, composed of runoff from the chain of surrounding mountains and rainforest areas. This abundant amount of rainfall and runoff contributes a lot to the flow and building up the water level inside the river, which contributes greatly to the local ecosystem, agriculture, and traffic.

2. What are the Reasons of Floods in Usumacinta River?

There are several causes for flooding in the Usumacinta River. The first, more obvious, cause of such flooding is the heavy amount of rainfall during the wet season. With its large catchment area, when heavy rain falls over a wide area, enormous volumes of water run into the river. For example, a succession of tropical storms or an unusually heavy wet season can lead to an unusually quick rise in water volume in the river.

Also the nature of the terrain at the river basin comes in handy. The mountainous areas upstream make water stream quickly down the slopes into the river, hence the resultant quantity and speed of the flow within the river. Additionally, its tributaries provide extra water and, of course, if they run a high inflow together, it would mean disastrous overflowing into the main river.

Humans also contributed to the cause of the flood situation. The result is that, because of the reduced catchment ability in upstream rainforest areas due to deforestation, runoff, now less filtered and soaked up, courses more directly into the river. Infrastructure such as roads and settlement building in floodplains may interfere with the natural course of water and enhance flood vulnerability. In this context, ADCP or Acoustic Doppler Current Profiler offers a more advanced and convenient way to measure and understand the flow conditions of the river compared to the traditional methods, thus making flood management easier.

3. How do ADCPs Using the Doppler Principle Work?

ADCPs rely on the principle of the Doppler effect. They emit acoustic signals into the water column of the Usumacinta River. When these acoustic waves encounter moving particles in the water, such as suspended sediment or small aquatic organisms that are being carried along by the water flow, the frequency of the reflected waves changes due to the Doppler effect.

From this frequency shift, the ADCP current meter calculates the velocity of the water at various depths within the river by precisely measuring it. These devices are normally fitted with several transducers that are positioned in such a way that they can measure the velocity components in different directions.

They can measure simultaneously the horizontal velocities along the flow direction as well as the vertical velocities. These measurements are taken at various depths, and the data obtained from these measurements are combined to give a comprehensive profile of the water velocity throughout the entire water column, providing detailed information about the flow characteristics of the river.

4. What are the Applications of ADCP in Floods of Usumacinta River?

• Velocity Measurement: The ADCP current profiler is a highly effective instrument in measuring the accurate velocity of the current water flow in the Usumacinta River during flood events. With the velocity at each location and depth determined, it gives an understanding of how fast the floodwaters are moving. It's crucial information when evaluating the erosive power of the water near riverbanks and predicting probable damage to infrastructure such as bridges and levees.
• Flow Measurement Application: By integrating the measured velocity data over the cross-sectional area of the river, ADCP can compute the flow rate. It is crucial because it helps determine the volume of water passing through a section of the river during the flood, allowing flood managers to estimate the scale of the flood and its likely downstream impacts in terms of the inundation of low-lying areas.
• Sediment Transport Research: The Usumacinta River carries a huge amount of sediment during floods. ADCP can analyze the backscattered acoustic signals for determining the concentration and transport velocity of suspended sediment. These data are useful in learning how floods reshape the riverbed and influence long-term sediment deposition patterns, thus controlling the morphology of the river and future flood risks.

5. How can the Data Measured by ADCP be Utilized for Flood Warning and Risk Management of Usumacinta River?

Flood Warning

• Velocity and Flow Data Monitoring: ADCP flow meter continuously monitors the velocity and flow data, which helps in quick detection of changes in flow conditions of the river. When the measured velocities start showing a significant increase or the flow rate exceeds certain thresholds, it could indicate an imminent flood. Real-time data can trigger timely warnings to communities along the riverbanks.
• Water Level Prediction and Warning: By correlating the flow data measured with historical water level records, it will be possible to predict the future levels of water. For instance, if the flow rate is increasing, from past correlations, one can make forecasts about at what time and to what height the water level may rise, and thus, warnings to residents and emergency responders can be issued accordingly.

Risk Management

• Scheduling Decision Support for a Water Conservancy Project: Based on the ADCP's data, decisions about the dams, reservoirs, and another conservancy project on both sides of the Usumacinta River can be made. For instance, if the flow data portrays a big flood is coming, decisions can be made to let out or store water within the reservoirs to lower the impact of the flood in the downstream area.
• Flood Disaster Assessment and Emergency Response: Detailed flow and velocity data recorded by ADCP profiler after the occurrence of any flood event may be used in assessing the actual extent of damages, for example, which areas have eroded or become inundated. Such information will contribute to planning an effective response strategy during emergencies and considering post-flood recovery actions.

6. What's Needed for High-Quality Measurement of Usumacinta River Currents?

In making high-quality measurements of currents in the Usumacinta River, there are a number of issues of high importance. This is equipment that requires very high material reliability to ensure its long survival in quite harsh aquatic conditions, considering the corrosive action by the river water, impact due to floating debris, and abrasive sediment-laden water. A small size is preferred, enabling it to be installed easily and deployed in various places along the river, even when space or access may be somewhat restricted.

The design should also be lightweight to ease handling and transportation of the equipment during installation and maintenance. It should consume low power to allow for continuous operation without changing batteries frequently, since access to external power sources might be difficult in remote areas for long-term monitoring. Cost is another important factor, considering that large-scale measurements are made across different sections of the river.

Talking of the ADCP casing, titanium alloy is a pretty excellent choice. Titanium alloy itself has a number of outstanding advantages: excellent corrosion resistance against the long-term action of the river water and high strength with rather light weight in order to provide sufficient strength to bear the mechanical forces in flowing water. Furthermore, it is biocompatible and therefore does not have adverse effects on the aquatic environment or interfere with the acoustic signals used by the ADCP meter for measurement.

7. How to Choose the Right Equipment for Current Measurement?

• Based on Usage Purposes: For horizontal cross-sectional measurements, the Horizontal ADCP (HADCP) is a suitable option. It is designed to accurately measure the flow velocities across a horizontal plane of the river, providing essential information about the flow distribution in that dimension. When it comes to vertical cross-sectional measurements, the Vertical ADCP is more appropriate as it focuses on obtaining the velocity profiles in the vertical direction of the water column.
• Based on Different Frequencies: Different frequencies of ADCP are suitable for different water depth ranges. For example, an ADCP with a frequency of 600 kHz is usually suitable for water depths within 70 meters. It can give quite accurate measurements in relatively shallow to moderately deep sections of the Usumacinta River. Meanwhile, the 300 kHz ADCP will go better for deeper waters, up to 110 meters, which could cover the deeper parts of the river where more comprehensive flow data is needed.

There are several well-known ADCP brands in the market, like Teledyne RDI, Nortek, and Sontek. However, a highly recommended Chinese ADCP brand is China Sonar PandaADCP. It stands out for its all-titanium alloy material construction, which combines durability and excellent performance. Moreover, it provides an incredible cost-performance ratio, making it a very appealing choice for users. You can find out more about it on its official website: (https://china-sonar.com/).

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