ADCP in Flood Prevention Management of the Ghaghara River

I. Where is the Ghaghara River?

Natural and Geographic Features 

The Ghaghara River forms one of the major rivers within the Indian subcontinent. It is a trans-boundary river that rises in the Tibetan Plateau and flows through Nepal into the Indian territory. The course of the river is very long and meandering while traveling through mountainous terrains, valleys, and extensive plains. A tributary to the Ganges River, it has a wide channel and carries a heavy volume of water regulated by snowmelt from the Himalayas and rainfall in the plains.

Cities and Settlements Along the River 

It has many cities, towns, and villages. People living along the river depend on it for water supply, catching fish, agriculture (irrigation), and transport. This river is a lifeline for the locals as well as a significant economic source.

Situation with Rainfall and Snowmelt 

The upper parts of the Ghaghara are fed by the melting snow of the Himalayan mountains and therefore form a major contributory factor to the volume of water in the river, especially in the spring and summer months. Middle and lower reaches develop under the monsoon-influenced climate with heavy rainfall from June to September. A combination of heavy snowmelt and much monsoon rain causes a high potential for flooding due to large fluctuations in the water level of the river.

II.Cause of Floods in Ghaghara River

Causes of Floods

1. Heavy Monsoon Rainfall: The basic cause of flood incidence is the heavy rainfall during the monsoon for several successive days. The incredible quantity of water falling on the catchment area of a river fills it and its tributaries in no time. On the plains, the ground may get saturated, and extra water runs off into the river and causes overflow.
2. Snowmelt: In the catchment area, rapid snowmelt during the months of higher temperatures brings a sudden deluge of water. If this is concurrent with heavy rainfall in the lower reaches, or if the snowmelt is more than usual due to abnormal changes in temperature, the swollen river bursts its banks and causes floods.
3. Tributary Overflow: Ghaghara has a number of tributaries feeding into it, their catchments drawing water from several sub-basins. These tributaries, upon receiving significant rises due to local rainfall or snowmelt, contribute their surplus to the Ghaghara, increasing the total volume of flow and flooding potential.
4. Geographic Features: The course of the river and the extended floodplains in the plains region have been very susceptible to flooding. During periods of high water, the natural levees along the river break and the water spills into low-lying areas beside the river.

Frequency and Magnitude of Floods 

Flooding in the Ghaghara River is a common feature during the monsoon season. The frequency depends upon the variability of the monsoon and snowmelt patterns. The scale of flood events ranges from minor, affecting only the immediate riverbanks and low-lying agricultural fields, to major floods that can inundate large areas of the floodplains and disrupt the lives and livelihoods of the communities along the river. 

Impacts of Floods

1. Infrastructure Destruction: Floods can destroy roads, bridges, railways, and even water and irrigation supplies, thus disrupting transportation and access to clean water and farm products.
2. Effects on Agriculture: The floodplains are extensively used for agriculture since the soil in the plains is very fertile. These floods submerge the crops, wash away the rich topsoil, and destroy agricultural infrastructure, thus greatly impacting agricultural production.
3. Displacement of People: During heavy flood situations, people inhabiting the low-lying areas have to be relocated. This causes temporary displacement, and there is a need to provide shelters along with relief supplies.
4. Economic Losses: The infrastructural loss combined with agricultural loss and disruption of other economic activities like fishing and trade brings huge economic losses for the region.

The Acoustic Doppler Current Profiler(ADCP) assure a more advanced and efficient way of measurement and understanding the flow in the Ghaghara River, a necessity in flood prevention and management.

III. How do ADCPs using the principle of Doppler work?

ADCP current meter operate based on the Doppler principle. They emit acoustic pulses, or simply sound waves, into the water. These sound waves are reflected back after interaction with the moving water particles to the ADCP doppler. Because of the Doppler effect, there is a change in frequency of the reflected sound waves. The change in frequency is related to the velocity of the water particles.

From this point of view, ADCP current profiler can be installed in boats, floating platforms, or fixed structures near the riverbanks when deployed in the Ghaghara River. The instrument emits a sequence of sound pulses of certain frequency. The received and reflected signals are then analyzed by the ADCP's internal electronics. Calculation of the frequency shift of the reflected signals from different depths allows determination of the velocity of the water column at different depths. It can then be processed for real-time display that provides useful information about the water flow in the Ghaghara River.

IV. Applications of ADCP in the flood of Ghaghara River

Velocity Measurement 

Thus, ADCP flow meter is important in measuring the water flow velocity of the Ghaghara River. It provides clear insight into its flow dynamics by accurately determining the velocity at different depths and locations along the river. This becomes vital in predicting how the floodwaters will move downstream and also the erosive power of such water. For example, high-velocity water during the flood can cause more severe erosion of riverbanks and floodplain areas. 

Application of Flow Measurement

Measuring the flow rate in the Ghaghara River with ADCP meter for the purpose of flood control is an imperative task. By correctly measuring the volume of water passing a given cross-section of the river, the flood management authorities can thus estimate the quantum of water that may cause flooding. This data operates any flood-control structure such as weirs or small dams and to manage the level of water. 

Application in Sediment Transport Research 

The Ghaghara River carries very high sediment loads within the flood seasons. ADCP profiler can be used in measurements of sediment concentrations and sediment transport rate. Sediment transport plays an important role in keeping the river and its environments healthy. The data obtained can be used to assess where sediment is deposited, which is relevant for land-building processes and for the understanding of the long-term evolution of the river and its flanking areas.

V. How does the data measured by ADCP contribute to flood warning and risk management in general for the Ghaghara River?

Flood Warning

1.Monitoring of Velocity and Flow Data 

• ADCP continuously monitors velocity and flow rate in the Ghaghara River. Setting of threshold values for these would result in warning signals to authorities once the flow of water shows signs of abnormal increase. For example, if the velocity or flow rate exceeds a certain limit, it might point to an impending flood. It enables timely evacuation of people inhabiting the area that are prone to floods and activates measures for flood protection. 

2. Water Level Prediction and Warning

• By combining ADCP data with other hydrological data, such as rainfall measurements and snowmelt estimates, better predictions of water level can be obtained. Comparing these projected levels against historic flood-stage levels allows warnings to be issued in a timely manner to communities along the river. 

Risk Management

1.Decision Support for Water Conservancy Project Scheduling 

• The acoustic doppler flow meter data helps the operating and scheduling procedure of water conservancy projects along the Ghaghara River. For example, flow rate and velocity information will be useful in finding the exact release of water from any flood-control structures to have a proper balance between flood control and water supply needs. This also helps design and maintain flood-protection infrastructure, such as levees and flood-walls.

2.Flood Disaster Assessment and Emergency Response

• After a flood disaster, acoustic doppler velocity meter can be used to perform assessments of conditions and situations during and after the disaster. Analyzing post-flood velocity and water depth patterns will give emergency response personnel an idea of the degree to which any given area is or has been affected. Such knowledge helps plan and deliver rescue operations and the distribution of relief supplies and in long-term recovery and reconstruction efforts. 

VI.What is needed to do precise, accurate measurement of the Ghaghara River currents?

Reliability Material Equipment

The equipment used to measure the current of the Ghaghara River is designed using materials that are reliable for the same. The casing of ADCP is preferably made of titanium alloy. The alloy has excellent strength that can resist the pressure of the Ghaghara River and physical forces. It will also significantly resist water corrosion and sediments in the river, keeping the equipment durable over a long period. 

Small Size

A small-sized ADCP is useful for the deployment process in the Ghaghara River. It can be installed more easily on various platforms such as small boats, buoys, or at riverbank monitoring stations without importantly impeding the river flow. This allows for more flexible placement to obtain comprehensive current measurements. 

Light Weight 

Light-weight ADCPs are easier to transport and install, especially in remote areas along the Ghaghara River. They could be easily carried by field technicians at various sites and rapidly deployed for measurement. This is particularly important during emergency flood-monitoring situations. 

Low Power Consumption 

To allow the Ghaghara River to be monitored for a long period of time, ADCPs must consume power at low rates. Because this is a river of considerable length, equipment that would collect data without the need for frequent battery replacements or disruptions in power supplies would be desirable. 

Low cost 

The ADCP equipment for large-scale measurements along the Ghaghara River should be comparatively inexpensive, allowing the possibility of installing multiple units at different locations along the river to capture useful information on current patterns and flood hazards.

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

Determine by Usage

1. Horizontal Cross - Section Measurement  

• The horizontal cross-sectional measurement of the Ghaghara River would, however, be ideal with HADCP. HADCP can provide the velocity and flow rate across the width, which is the comprehensive representation of the flow characteristic across a particular cross-section. It would, therefore, be vital in determining how water spreads across the river in regards to flood-plain management. 

2. Vertical Cross - Section Measurement

• In the case of vertical cross-section measurement, a vertical ADCP will be more appropriate; it measures the velocity and flow rate at different depths to analyze the vertical structure of the river flow. This becomes important in understanding the stratification of water and sediment movement. 

Choose Different Frequencies

Normally, the choice of frequency depends on the depth of the Ghaghara River. A 600-kHz ADCP will suffice for all depths up to 70 meters, while for more depth, as much as 110 meters, 300 kHz is considered better. 

Finally, there are several well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, for cost - effective and high - quality ADCPs, the Chinese brand ChinaSonar PandaADCP is highly recommended. It features an all - titanium alloy material construction and offers excellent value for money. You can visit(https://china-sonar.com/) for more information.

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