ADCP's Application in Flood Management of Arkansas River

1. Where is Arkansas River?

The Arkansas River is a major river in the central part of the United States. Originating in the Rocky Mountains of Colorado, it flows eastward and southeastward through Colorado, Kansas, Oklahoma, and Arkansas before pouring into the Mississippi River.

It covers some of the main cities and towns along its course, including Pueblo in Colorado, Wichita in Kansas, Tulsa in Oklahoma, and Little Rock in Arkansas. These urban areas rely on the river for various purposes like water supply, transportation, and recreational activities. The climate varies from the relatively cooler and drier conditions in the upstream parts of the mountainous basin to a generally warmer, more humid climate in the downstream direction. The rainfall is variably distributed throughout the year, with major falls most often occurring in spring and summer. Additionally, snowmelt from the Rocky Mountains in the springtime contributes notably to the river's water amount.

2. What are the Reasons for Floods in Arkansas River?

Snowmelt: As the Arkansas River has its headwaters in the Rocky Mountains, a large volume of snow accumulates there during winter. In spring, when temperatures rise, this snow begins to melt rapidly. The sudden influx of a substantial amount of water from snowmelt can overwhelm the river's carrying capacity downstream. For instance, a rapid warm spell or an above-average snowpack can make the river rise steeply and flood in the plains regions it traverses.

Heavy Rainfall: Intense rainfall events, especially during the spring and summer months, can cause the river to flood. Sometimes, when heavy rainfall falls over most of the area of the catchment of a river, the ground could be saturated and unable to hold more water. The excess water runs off into the river. If the river is already full from snowmelt or for other reasons, this additional rain can cause it to overflow and flood.

Topography and Land Use: Most of the Arkansas River runs through flat plains that reduce the speed at which water travels. Thus, the facility of water to spread more easily and collect in low-lying areas is obtained. Besides, human activities of urbanization, agriculture, construction of levees and dams change natural flow and floodplain conditions of the river. These changes, in some instances, can reduce the capacity of the river to carry as much water as it would have, resulting in increased flooding.

Due to these challenges of flooding, Acoustic Doppler Current Profiler (ADCP) has become more advanced and convenient in monitoring and managing the flow of the river.

3. How Do ADCPs Using the Doppler Principle Work?

The ADCPs work on the principle of the Doppler. They emit acoustic signals into the water of the Arkansas River. When these acoustic waves encounter moving particles in the water-such as sediment grains, small aquatic organisms, or debris that are being carried along by the water flow-the frequency of the reflected waves is different from that of the original emitted waves. This change in frequency, known as the Doppler shift, is directly related to the velocity of the moving particles and, by extension, the velocity of the water flow.

By using multiple acoustic beams sent out at different angles, and receiving the reflected signals, the ADCPs can measure the water flow velocity at various depths and locations within the water column. Using advanced signal-processing algorithms, they can generate a rather detailed velocity profile of the water flow. This information is crucial for understanding the hydrodynamic characteristics of the Arkansas River.

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

Velocity Measurement: ADCP current meter can measure the velocity of water at different points along the Arkansas River during flood events or periods of high water flow with a high degree of accuracy. This information is crucial in determining the erosive power of the floodwaters. For instance, high-velocity flows near riverbanks can indicate areas where erosion is likely to occur, thus enabling the implementation of preventive measures such as bank reinforcement or the installation of erosion-control structures.

Flow Measurement Application: ADCP current profiler is able to calculate flow by integrating the measured velocity data over the cross-sectional area of the river. Flow is useful in managing floods because it can forecast the amount of water passing through a particular section of the river. This information provides input for decision-making about the type and need for flood-control structures such as dams, levees, and floodgates, along with planning water diversions during flooding.

Sediment Transport Research: The Arkansas River carries a lot of sediment. ADCP flow meter can be used in the study of sediment movement during floods. By studying the relation between water flow velocity and sediment concentration, and the pattern of sediment movement, one can understand how sedimentation and erosion processes in the river are influenced by floods. This knowledge is useful for maintaining the health of the riverbed and the overall ecological balance of the river system.

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

Flood Warning

Velocity and Flow Data Monitoring: This primarily comprises the continuous monitoring of the water flow velocity and flow rate using ADCP meter. If this continues to exceed predefined threshold levels, early warning mechanisms could thus be triggered. For example, if the flow rate in a key monitoring point near the inhabited zone has reached to a level where high possibility for flooding is most expected, an alert is given both to the authorities concerned as well as residents in general.

Water Level Prediction and Warning: The velocity data obtained from ADCP profiler can be integrated with other hydrological models to forecast water levels. By understanding the relationship between flow velocity and water level changes, better forecasts of when and to what extent the water will rise can be made. This allows for better preparation of flood-protection measures such as sandbagging, evacuations, or the activation of emergency response plans.

Risk Management

Water Conservancy Project Scheduling Decision Support: The ADCP data is useful in decision-making for the operation of water conservancy projects along the Arkansas River, such as reservoirs, dams, and water-diversion channels. For instance, if the measured flow indicates that a large flood is about to occur, reservoir managers can consider releasing some water in advance through controlled releases to create room for the arriving floodwaters and thus reduce the risk of overtopping and damage to the projects.

Flood Disaster Assessment and Emergency Response: In the aftermath of a flood, ADCP data can be employed to establish the event's impact. This includes an evaluation of erosion occurrence, sediment deposition areas, as well as changes in the morphology of the river channel. Information obtained from ADCP current meter technologies provides a basis for formulating efficient emergency response and post-disaster recovery plans.

6. What Is Required for Quality Measurement of Currents in the Arkansas River?

For quality measurement of currents in the Arkansas River, the equipment should be made from reliable materials. Considering the changing climatic conditions, the sediment carried, and possible debris effects in the river, the casing of the ADCP flow meter should be strong enough to bear such issues.

The equipment to be set up should have a relatively smaller size and lightweight for easy installation and deployment at various locations along the river. A low power consumption is considered in order to guarantee continuous operation, especially in remote areas where the power supply may become limited. Cost-effectiveness is also an important issue, since large-scale deployment of the equipment may have to be carried out for comprehensive river monitoring.

The ADCP profiler casing could be manufactured from a suitable material such as titanium alloy. It has excellent properties of strength and corrosion resistance. The strength of the material allows it to bear the mechanical forces exerted by the flowing water, impacts from debris, and other physical stresses. Its corrosion-resistance property will ensure that the equipment's performance remains stable over time, even in the water-rich environment of the Arkansas River.

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

Based on the Purpose of Use: For horizontal cross-section measurement of the river, horizontal ADCP (HADCP) is preferred. It provides a detailed view of the flow velocity distribution across the width of the river. Vertical ADCP can be more suitable for vertical cross-section measurement as the vertical profile of the velocity can be measured accurately.

Based on Different Frequencies: Different frequencies of ADCPs correspond to different usable ranges of water depth. An example would be that an ADCP with a frequency of 600 kHz shall be appropriate for water depth up to approximately 70m and hence could be helpful for major parts of the Arkansas River, while a 300 kHz ADCP would be suitable for still deeper water-up to about 110 meters-and can be applied where sections of the river are relatively deeper.

There are famous brands of ADCP flow meter, like Teledyne RDI, Nortek, and Sontek. However, for more economical options, one may consider the China Sonar ​PandaADCP. It is made of all-titanium alloy material, with good durability and an excellent cost-performance ratio. You can find more information about it on its official website: (​https://china-sonar.com/).

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