ADCP Application in the Jubba River Flood Management

1. Where is the Jubba River?

The Jubba River is situated in the Horn of Africa. The river runs through the East African state of Somalia and is the backbone of its waterbody. The topography of this part of the land that it courses through is made up of arid plains and parts that are semi-arid.

The river passes through a number of small towns and villages along its course. The climate of the Jubba River basin is influenced by the monsoon. Precipitation falls under a clearly defined wet and dry season. The wet season normally falls between April and June and October and November. The rainwater is the main source of the volume of water in the river, and it is important in the agricultural activities and livelihood of the local communities who rely on it for irrigation and other water-related needs.

2. What are the causes of flooding in the Jubba River?

Flooding in the Jubba River occurs primarily as a result of heavy and sustained rainfall during the wet season. Too much rain in a short time can overwhelm the capacity of the river.

The flat topography of its flood plain is also relatively another contributor to flooding within the course of the river. Thus, it is easy to spread all over the low-lying areas. Coupled with poor land management practices or forest cutting in the upper catchment of a river basin, this enhances runoff at the surface. Water intake by the river is even further reduced due to soil erosion and resultant sedimentation. Given these complex, very many flood-causing factors, the ADCP method comes in handy as a way to measure and manage water flow in the river much more precisely and with less cumbersome human labor during flooding.

3. How are Doppler Principle ADCPs works?

ADCPs work on the Doppler effect. They transmit acoustic signals into the water. These signals have some interference with the moving particles of water. When acoustic waves reflect back after being struck by the moving particles, their frequency changes due to the Doppler effect.

The ADCP current meter has multiple transducers that can emit and receive acoustic signals in different directions. By precisely measuring the frequency shift of the reflected signals, the velocity of the water flow at different depths and across different sections of the river cross-section can be determined. It can measure, for example, the flow velocity from the bottom to the surface of the water and across different widths of the river.

4. Application of ADCP in the Jubba River Floods

Flow Velocity Measurement: The flow velocity of the Jubba River during flooding can be correctly measured by using an ADCP meter. It is essential for knowing the rate at which water is moving along every portion of the river. It helps us to monitor the flow velocity so that it shows a high velocity in any place; that will mean there might be a flood surge, or a shift may take place in the behavior of the flood. The change in flow velocity may be monitored closely near the riverbanks or in the main channel.

This latter, in particular, being relevant for flow-rate determination simply from flow-velocity measurement combined with cross-sectional area, the desired volume per unit time will follow: such information in floods such as those in Jubba River is extremely vital to make good estimates of volume transit at any section at all instants of time to develop flood forecasting. It was essential to estimate the actual extent of the flood, according to its magnitude.

Sediment-transport Research: During floods, a lot of sediment is transported along the Jubba River. ADCP flow meter can detect the movement of sediment particles through the analysis of backscattered acoustic signals. This allows researchers to study the sediment - transport patterns during floods, which is important for understanding the long - term evolution of the riverbed and the impact on the river's hydrological characteristics.

5. How can the data measured by ADCP be utilized in flood warning and risk management of the Jubba River?

Flood Warning Aspect

• Flow-velocity and Flow-rate Data Monitoring: The ADCP current profiler provides continuous monitoring of flow velocity and flow rate. In this way, abnormal changes in flow velocity or sudden increases in the flow rate can easily be detected to potentially allow the issuance of an early flood warning. Such information can then be passed on to local communities and other relevant authorities in areas surrounding the river.
• Water-level Prediction and Warning: The flow data obtained from ADCP profiler can be used in conjunction with other hydrological models to predict changes in water level. Studying the relation between flow rate and water level allows for more accurate flood warnings, especially in the flood-prone areas of the Jubba River.

Risk Management Aspect

• Water-Conservancy Project Dispatching Decision Support: The precise flow data from ADCP contributes a great deal to the operation of water-conservancy projects such as small dams or flood-control structures along the Jubba River. Decisions regarding the release or storage of water can be made more effectively in mitigating flood risks downstream.
• Flood-disaster Assessment and Emergency Response: The ADCP-measured data after the occurrence of a flood would be used in assessing the event with regard to the extent of flooding and impact. The result is an appropriate emergency-response strategy that would include rescue operations and damage-assessment surveys.

6. What's needed for high-quality measurement of Jubba River currents?

For the measurement of the Jubba River current in high quality, the equipment has to be made of reliable materials. It should be able to resist the harsh aquatic environment, including the corrosive effects of the water and the impacts from floating debris and sediment. A small size and light weight are advantageous because these make the installation and deployment of the equipment easier in different locations along the river.

Besides, it needs to have low power consumption for continuous operation, particularly at a place with very poor power supply. Another thing is cost-effectiveness; a large-scale deployment might be involved in the river-current monitoring. The casing of ADCP meter is preferably made of titanium alloy. For example, good corrosion resistance is realized by the use of titanium alloy, which is very important for withstanding the corrosive effects of Jubba River water over time. Besides, it offers a rather good strength-to-weight ratio; thus, the equipment would be stronger yet easy to manage.

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

In the selection of equipment to measure current in the Jubba River, consider the purpose. A Horizontal ADCP would therefore be a suitable option for horizontal cross-section measurement since it measures flow velocity across the width of the river in great detail. A Vertical ADCP is fitted for vertical cross-section measurements that require the measurement of the flow-velocity distribution from the bed of the river up to the water surface.

For the frequency of ADCP, in relatively shallower parts of the Jubba River, for example, a water depth of less than 70m, a 600kHz ADCP is appropriate. In deeper areas, approximately 110m, a 300kHz ADCP is more suitable. Several brands are available, including the well-known Teledyne RDI, Nortek, and Sontek. There is also a recommended Chinese ADCP brand - China Sonar PandaADCP. It is made of all - titanium alloy material and offers excellent performance and cost-effectiveness. 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.