ADCP Application in the Flood Management of Brazos River

1. Where is Brazos River?

Brazos River is in Texas, United States, and it is one of the longest rivers that run across the state. The river has its headwaters in the Llano Estacado region, from which it flows southeast before it empties into the Gulf of Mexico.

Course-wide geographically, it traverses all types of landscapes that vary from plains to rolling hills to coastal areas. It flows beside Waco and Bryan-College Station urban complexes. The river gives essentially needed water to such places for domestic use, industries, and agriculture, maintaining a healthy ecosystem composed of different fish and animal species in these waters.

The rainfall in the Brazos River Basin ranges from a semi-arid to humid climate. It might be arid for the upper portion while highly humid in the lower reaches at the coast. In the normal course, it rains all over the year without specific months that would experience increased rainfall in either spring or fall. However, heavy rainfall events during the summer months, typically associated with thunderstorms and tropical weather systems, can cause the river's water level to rise significantly.

2. Why do Floods Happen along Brazos River?

Heavy Rainfall and Tropical Systems: Heavy thunderstorms and the passage of tropical weather systems, such as hurricanes or tropical storms, can dump a great amount of rainfall into the Brazos River Basin. This can raise the water level of the river very rapidly. The large catchment area ensures that water from an extensive region converges into the river, overwhelming its normal carrying capacity and leading to flooding.

Snowmelt (Rarely): Rarely, in the case of mild winters, snowmelt from the upper regions contributes to the water volume of the river. When this coincides with heavy rain or when the river is already at a high level, it further deteriorates the flood situation.

Topography and Drainage: The course of the river has a general topography consisting of areas with relatively flat floodplains and some constrictions. The flat areas impede the speed of flow, thus allowing the water to spill over and flood the adjoining land. Constriction to the normal flow of water may cause it to back up and raise the water level upstream. Poor drainage in some areas due to urban development or natural factors contributes to water accumulation and flooding.

Land Use Changes: Human activities relating to the expansion of urban areas, agriculture, the building of dams, and raising levees have altered the flow pattern of this river. It is quite obvious that with paved surfaces in cities, surface runoff increases, as does soil impermeability due to agricultural practices. While dams and levees are basically water-control mechanisms, poor management or breach of the structure may result in disastrous floods. ADCP current meter offers a more advanced and efficient way to measure and manage flood-related parameters than traditional methods.

3. How do ADCPs Using the Doppler Principle Work?

ADCPs work according to the principle of the Doppler effect. They send acoustic signals into the water. The frequency of the reflected signals from these acoustic waves is different from that of the emitted signals when these signals encounter moving particles of sediment, debris, or simply water parcels with different velocities due to the Doppler effect.

The ADCP current profiler measures these frequency shifts and, using the known speed of sound in water and the angles of the emitted and received signals, calculates the velocity of the water at different depths. Multiple transducers in the ADCP are arranged to measure velocity components in different directions. By integrating these velocity measurements over different depths and cross-sectional areas of the river, the flow rate and other important hydrological parameters can be determined.

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

Velocity Measurement: ADCP flow meter can accurately measure the velocity of the water flow in the Brazos River at different locations and depths. During flood events, this information is crucial for understanding the dynamics of the flood. It helps identify areas where the flow is rapid and could endanger riverbanks, bridges, and other infrastructure. It also allows for the monitoring of how the flow velocity changes over time as the flood progresses.

Flow Rate Measurement Application: Combining the velocity measured with the cross-sectional area of the river, ADCP meter can calculate the flow rate. This is crucial in order to predict the volume of water that will pass through different sections of the river during a flood. This allows for the anticipation of the flood peak and its consequences downstream, which is crucial for flood management strategies.

Sediment Transport Research: Brazos River floods can carry a lot of sediment. ADCP can analyze the movement of sediment by detecting the echoes of acoustic signals affected by sediment particles. This can provide valuable insights into the way floods affect the riverbed's evolution, sediment deposition, and erosion processes regarding the stability of the channel and the surrounding ecosystem.

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

Flood Warning

Velocity and Flow Rate Data Monitoring: ADCP profiler can continuously monitor the data regarding the velocity and flow rate for an abnormal rise. When these approach or surpass their critical values, that may be considered an early warning of an impending flood peak. This enables timely warnings to be issued to the communities and emergency management agencies along the river.

Water Level Prediction and Warning: By correlating the measured flow rate and velocity data with historical water level records, models can be developed to predict future water level changes. This helps in providing advance warnings about the areas that may be inundated and the height of the floodwaters.

Risk Management

Water Conservancy Project Scheduling Decision Support: The ADCP meter data can be useful in decision-making for the operation of water conservancy projects, such as dams and reservoirs along the Brazos River. For instance, it will help in deciding on the right time and amount of water to be released from the reservoirs to reduce the impact of a flood downstream.

Flood Disaster Assessment and Emergency Response: Starting from the occurrence of a flood, ADCP-measured data could be used in assessing the severity of the flood in terms of the extent of the inundated area and flow characteristics during the flood. It guides emergency response in terms of the allocation of relief resources and planning post-flood recovery work.

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

The equipment for high-quality measurement of the Brazos River currents should be made from reliable materials. The casing must be able to bear harsh conditions in the river: impacts from floating debris, corrosion from water, and varying temperature conditions.

Equipment should be of a size that is easy to install and deploy at different locations in the river. The lightweight design further enables easy transportation and installation of the equipment. The consumption of power should be low enough to enable the instrument to operate for a continuous period without frequent changes of batteries or other high-energy power sources. It has to be cost-effective to allow large-scale deployment for comprehensive monitoring.

The casing of ADCP flow meter is preferably made of titanium alloy. Titanium alloy has several outstanding advantages: excellent corrosion resistance, which is very important and can bear the long-term exposure to the river water; it also has a high strength-to-weight ratio, which provides enough strength while keeping the weight of the equipment at a reasonable level. This material's durability ensures stable performance under the diverse environmental conditions of the Brazos River Basin.

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

Purpose of Measurement: According to whether the horizontal cross-section is to be measured, for a river, an HADCP would be a perfect alternative to accurately measure the velocity of flow and other variables in the horizontal direction through the river section. Measurement on a vertical cross-section definitely calls for a Vertical ADCP current profiler for finer details regarding the velocity profile along the vertical axis of the river.

Based on Water Depth: The different frequencies of the ADCP are useful to be applied in waters at different depths. For water with less than 70 meters deep, an ADCP should be used with a 600 kHz frequency; deeper waters, up to a depth of 110 meters, would be better dealt with using an ADCP having a frequency of 300 kHz, as this shall allow deeper penetration to ultimately give reliable data.

There are well-known ADCP current meter brands like Teledyne RDI, Nortek, and Sontek. Additionally, a cost - effective Chinese brand, China Sonar PandaADCP, is worth considering. It is made of all-titanium alloy material, ensuring excellent performance and durability. You can find more information on its website: (https://china-sonar.com/)

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