Fluoride toxicity in Jharkhand State of India- People eating Chakwad plants are less affected.
By
Dr. Nitish Priyadarshi
Tragedy has struck many a family in the Bakhari and Chukru, village of Jharkhand's Daltanganj district, where excess fluoride in water has left several with severe physical deformities and even paralyzed some.
Bakhari village, situated about 20 km from the district headquarters, has a population of nearly 700, comprising mostly tribals and members of socially underprivileged groups. Two-thirds of the villagers have reportedly developed physical deformities as all the sources of drinking water in Bakhari have excess fluoride content.
Residents of the remote village of Chukru, are experiencing various physical disabilities due to the presence of excessive fluoride in the ground water of the area. Every second person - children as well as adults - is suffering from deformed limbs, cataract, or premature ageing. Fluorosis hit the village in 1980 when the Government constructed borewells here to solve the drinking water problem of the village. A boon soon became a curse.
Bakhari residents draw water from 30 wells and six hand pumps in the village, all of which have excess fluoride. Without alternative sources of water, they are forced to continue using water from the contaminated wells and pumps.
According to sources in the Singhbhum and Seraikela-Kharsawan, district of Jharkhand fluoride and iron have been detected above the permissible limit in underground water in some areas.
According to the recent report people especially tribal consuming Chakwad (ring worm plant) plant are less affected of fluoride toxicity. Chakwad plants are consumed by the local tribal people in believe that it keeps them healthy. Without knowing that it is also helping them to minimize fluoride contamination they regularly eat Chakwad plant with other daily foods. According to the report those people who are not eating this plant are more affected with fluorosis. In Madhya Pradesh, the promotion of Chakwad (Cassia tora), which is rich in calcium, has helped mitigate the disease.
Main cause behind this effect is the presence of high calcium in this plant. Calcium , binds fluorine --assisting in safe excretion of fluorine, and also helping replenish body calcium stores depleted by fluorine.
It is similar to Stellaria spp. (common chickweed) which is generally used as a tea. This plant, a common garden weed which is edible in apparently unlimited quantities without toxic effect. It can be used as a vegetable and in green drinks. It is rich in Vitamin. C and in minerals, especially calcium, magnesium, and potassium.
Other Calcium-rich herbs include nettle, sage, chickweed, red clover, comfrey leaf, and raspberry leaf. A tasty infusion of any one or a combination of these herbs every day should be taken.
According to the different research reports, to minimize fluoride in the body one should eat plenty of foods that are high in calcium and vitamin D. Good sources of easily assimilable calcium include broccoli, chestnuts, clams, dandelion greens, most dark green leafy vegetable (see above), flounder, hazelnuts, kelp, molasses, oats, oysters, salmon, sardines (with the bones), sea vegetables, sesame seeds, shrimp, soybeans, tahini (sesame butter), tofu, and wheat germ. Include garlic and onions in the diet.
The Chakwad plants are very common in Jharkhand. People are not aware of the quality of these plants of minimising fluoride from the body.
Chakwad plant is found in warm moist climatic conditions and is generally found in tropical region where sun rays fall directly, it is also seen in areas where rains are in excess. It is found everywhere in India especially middle and south India.
It is an annual small plant that attains a maximum height of 1 to 5 feet. Seed contains rhein, aloe-emodin and chrysophanol. It also contains nearly 7% resins. There is also certain minerals like calcium, iron and phosphorus.
It also acts in skin ailment. It also acts as nerve tonic, liver stimulant and heart tonic. It acts on cholesterol thus maintaining the normal level of cholesterol. It also act as curing the infection occurring in the body and is given in worm infestation.
Jharkhand Government should promote such types plants in Fluoride affected areas.
It will cover all types environmental and geological research work and studies both ancient and present. It will also cover impact of environment and geology on the human civilization. All types of news from all over the world related to environment and geology will also be discussed here.
Friday, September 26, 2008
Wednesday, September 24, 2008
Photos of radiation affected children in Jadugodda in Jharkhand, India.
These are the photos of the children affected by the Radiation in Jadugodda area of Singhbhum district in Jharkhand State of India. Jadugodda is famous for Uranium mining. All these photographs are taken by my friend Mr. P. Madhavan from Delhi.
Thursday, September 18, 2008
Kosi floods in Bihar, India may trigger major earthquakes in future.
The Kosi floods in Bihar, India may trigger major earthquakes in future.
By
By
Dr. Nitish Priyadarshi
The recent Kosi floods and deposition of sediments in the North Bihar Plain may trigger earthquakes in coming future. Deposition of sediments alter the loading of the earth’s crust and tectonic stresses in its interior. Such stresses could reactivate preexisting faults.
As North Bihar is already under seismic zone such types disastrous flooding and sedimentation may trigger earthquakes in future.
New research indicates sediment buildup in seismic zone may play a major role in determining the severity of earthquakes.
Northern Bihar plain falls in the seismic zone of India and is liable to severe earthquakes as on 15th January, 1934 and 20th August, 1988. An earthquake is generally caused by dislocation in the earth’s crust along pre-existing cracks or faults. The cause of earthquakes is probably the existence of such faults or cracks in the bottom of the depression hidden under alluvium. Moreover, there are well marked reversed faults at the junction of the outer and the inner Himalayas, and when dislocation occurs along these faults, earthquakes result.
An additional factor favoring dislocation along such surface or subterranean faults is the strain which exists between the Himalayas and the Bihar plains. This strain is due to the following facts. The section of the Himalaya north of the Bihar is the highest mountain region of the world. The higher a region, the more it is subjected to erosion. So, vast amount of sediments are being eroded from the Himalayas and carried down to the Bihar plains as in the case of Kosi river which contributes heavy sediment in Bihar plains. The silt yield of the Kosi is about 10 cubic yard /acre/yr, one of the highest in the world. As the mountains are eroded they are deloaded and have a tendency to rise. On the other hand, the plains get loaded by the sediments and have a tendency to subside. These opposed tendencies of movements between the Himalayas and the Bihar plains cause strain in the hinge-zone, i.e. in the southern part of the mountains. Here fault already exists. Dislocation may occur along these faults as a result of the strain and devastating earthquakes may result.
The most damaging and significant of the seismic events was the Bihar –Nepal 1934 earthquake. The Bihar-Nepal event, with an estimated magnitude of 8.1, occurred on 15th January 1934 and was followed by several aftershocks of much lower magnitudes. These continued through 19th January 1934 and with much lower frequency till the 13th April 1934. the main shock was felt over a very large area of 4.92 million sq.km and was recorded by almost all seismic stations in the world. The death toll associated with the event was 7253. this is possibly due to the fact that the shocks occurred during the day and also took some 2.5 minutes to reach their maximum intensity. Severe dislocations were caused by damages to railway, telegraph and other communication lines. Sand and water emissions were noticed from many fissures and from individual vents, a feature common in alluvial tracts.
During the early hours of Sunday, the 21st August,1988 an earthquake rocked severely the entire North Bihar and adjacent areas. The shock was felt almost all over North and Eastern India, from Rajasthan in the west to North Eastern states in the east and from Himalayan foothills in the north to Chhotanagpur plateau in Jharkhand State in the south. Dharbhanga and Madhubani were the worst affected districts, but damages of gradually diminishing intensity extended upto Ranchi and Palamau in Jharkhand State.
The earthquake immediately devastated a large area of Madhubani, Munger, Saharsa and several other districts of North Bihar, killing about 300 people.
Seeing the severity of the earlier earthquakes, the disaster management department of the Bihar State should be kept on high alert so that lives and property may be saved in the event of any major future earthquakes. It cannot be said with accuracy that when the future earthquake may show its presence but seeing the amounts of sediments being brought by the Kosi river, major earthquakes in coming days cannot be ruled out.
The recent Kosi floods and deposition of sediments in the North Bihar Plain may trigger earthquakes in coming future. Deposition of sediments alter the loading of the earth’s crust and tectonic stresses in its interior. Such stresses could reactivate preexisting faults.
As North Bihar is already under seismic zone such types disastrous flooding and sedimentation may trigger earthquakes in future.
New research indicates sediment buildup in seismic zone may play a major role in determining the severity of earthquakes.
Northern Bihar plain falls in the seismic zone of India and is liable to severe earthquakes as on 15th January, 1934 and 20th August, 1988. An earthquake is generally caused by dislocation in the earth’s crust along pre-existing cracks or faults. The cause of earthquakes is probably the existence of such faults or cracks in the bottom of the depression hidden under alluvium. Moreover, there are well marked reversed faults at the junction of the outer and the inner Himalayas, and when dislocation occurs along these faults, earthquakes result.
An additional factor favoring dislocation along such surface or subterranean faults is the strain which exists between the Himalayas and the Bihar plains. This strain is due to the following facts. The section of the Himalaya north of the Bihar is the highest mountain region of the world. The higher a region, the more it is subjected to erosion. So, vast amount of sediments are being eroded from the Himalayas and carried down to the Bihar plains as in the case of Kosi river which contributes heavy sediment in Bihar plains. The silt yield of the Kosi is about 10 cubic yard /acre/yr, one of the highest in the world. As the mountains are eroded they are deloaded and have a tendency to rise. On the other hand, the plains get loaded by the sediments and have a tendency to subside. These opposed tendencies of movements between the Himalayas and the Bihar plains cause strain in the hinge-zone, i.e. in the southern part of the mountains. Here fault already exists. Dislocation may occur along these faults as a result of the strain and devastating earthquakes may result.
The most damaging and significant of the seismic events was the Bihar –Nepal 1934 earthquake. The Bihar-Nepal event, with an estimated magnitude of 8.1, occurred on 15th January 1934 and was followed by several aftershocks of much lower magnitudes. These continued through 19th January 1934 and with much lower frequency till the 13th April 1934. the main shock was felt over a very large area of 4.92 million sq.km and was recorded by almost all seismic stations in the world. The death toll associated with the event was 7253. this is possibly due to the fact that the shocks occurred during the day and also took some 2.5 minutes to reach their maximum intensity. Severe dislocations were caused by damages to railway, telegraph and other communication lines. Sand and water emissions were noticed from many fissures and from individual vents, a feature common in alluvial tracts.
During the early hours of Sunday, the 21st August,1988 an earthquake rocked severely the entire North Bihar and adjacent areas. The shock was felt almost all over North and Eastern India, from Rajasthan in the west to North Eastern states in the east and from Himalayan foothills in the north to Chhotanagpur plateau in Jharkhand State in the south. Dharbhanga and Madhubani were the worst affected districts, but damages of gradually diminishing intensity extended upto Ranchi and Palamau in Jharkhand State.
The earthquake immediately devastated a large area of Madhubani, Munger, Saharsa and several other districts of North Bihar, killing about 300 people.
Seeing the severity of the earlier earthquakes, the disaster management department of the Bihar State should be kept on high alert so that lives and property may be saved in the event of any major future earthquakes. It cannot be said with accuracy that when the future earthquake may show its presence but seeing the amounts of sediments being brought by the Kosi river, major earthquakes in coming days cannot be ruled out.
Thursday, September 11, 2008
Kosi floods in Bihar, India- Different methods to minimize flood must be adopted.
Kosi floods in Bihar, India- Different methods to minimize flood must be adopted.
By
Dr. Nitish Priyadarshi
Seeing devastating floods by the kosi river now it is ripe time to search for the methods which can help to minimize such floods. Earlier I have suggested for the construction for new big dams in the Bihar state on kosi river. There are other methods too which can be implemented in the affected areas. Most important is removing the sediments from the river beds because every year Kosi contributes heavy sediment in Bihar plains. Owing to extensive soil erosion and landslides in its upper catchment by factors both natural and human, the silt yield of the Kosi is about 10 cubic yard /acre/yr, one of the highest in the world. It was observed earlier that at many locations water level in the channel within the embankments is significantly higher than the general ground level in the surrounding areas. Deposition of sediments either within the channels or on the channel margin restricts the passage of water and thus reduces the carrying capacity of the channel.
Making inter-linking canals parallel or vertical to the flow of the river can also be adopted, so that surplus water during the rainy season can be diverted to other areas devoid of water. Small check dams should be built in frequent intervals in the canals to maintain water level. Building canals is not the recent method. The oldest known canals were built in Mesopotamia circa 4000 BC, in what is now modern day Iraq and Syria. The Indus Valley Civilization in Pakistan and North India (from circa 2600 BC) had a sophisticated canal irrigation system. Agriculture was practised on a large scale, and an extensive network of canals was used for the purpose of irrigation. Sophisticated irrigation and storage systems were developed, including the reservoirs built at Girnar in 3000 BC.
Construction of storage dams along the river course will considerably reduce the severity of floods and the resultant damages.
Interlinking of kosi river with other rivers is expected to greatly reduce the regional imbalance in the availability of water. Surplus water which spreads in bigger areas during floods would be fruitfully utilized.
Flow diversion is one of the efficient ways of coping with flood situation. The primitive way of achieving this is to break levees in the area where the flood damage will be relatively small. Such area should be a depression surrounded by secondary dikes, and free of habitation. Further, there should be good drainage facilities to get the water back into the river after the flood recedes. Diversion channel is an effective way of diverting part of the flow.
Water management is perhaps the most serious problem facing the nation. The critical problem is the uneven distribution of the run-offs and precipitation rates during the monsoon season. In the kosi and Ganga regions not only is the area liable to floods high, but the frequency at which the floods occur is also high. In general human life in the Kosi and Ganga plains is significantly affected by the flood hazards more often than in the Peninsular India, where the areal extent of the flood-prone lands is limited and the recurrence interval of big floods is greater.
Large floods on most of the North Bihar rivers are a direct result of intense cyclonic storms and depressions. Also due to effect of global warming, glaciers in the Himalayas are melting which are contributing water to the rivers. Water from the melting glaciers and rain water together is creating menace over the area.
Some of the largest and most calamitous floods in the Indian subcontinent have been produced from failure or breaching of natural or man-made dams as it happened in Kosi dam built in Nepal. Seeing this situation I earlier suggested for new big dam on the Kosi river in Bihar. Building big dams will definitely create problems like displacement, more area coming under water etc. But seeing the miseries, deaths and displacements due to devastating floods on large scale every year by the people of North Bihar ,one time displacement can be accepted.
By
Dr. Nitish Priyadarshi
Seeing devastating floods by the kosi river now it is ripe time to search for the methods which can help to minimize such floods. Earlier I have suggested for the construction for new big dams in the Bihar state on kosi river. There are other methods too which can be implemented in the affected areas. Most important is removing the sediments from the river beds because every year Kosi contributes heavy sediment in Bihar plains. Owing to extensive soil erosion and landslides in its upper catchment by factors both natural and human, the silt yield of the Kosi is about 10 cubic yard /acre/yr, one of the highest in the world. It was observed earlier that at many locations water level in the channel within the embankments is significantly higher than the general ground level in the surrounding areas. Deposition of sediments either within the channels or on the channel margin restricts the passage of water and thus reduces the carrying capacity of the channel.
Making inter-linking canals parallel or vertical to the flow of the river can also be adopted, so that surplus water during the rainy season can be diverted to other areas devoid of water. Small check dams should be built in frequent intervals in the canals to maintain water level. Building canals is not the recent method. The oldest known canals were built in Mesopotamia circa 4000 BC, in what is now modern day Iraq and Syria. The Indus Valley Civilization in Pakistan and North India (from circa 2600 BC) had a sophisticated canal irrigation system. Agriculture was practised on a large scale, and an extensive network of canals was used for the purpose of irrigation. Sophisticated irrigation and storage systems were developed, including the reservoirs built at Girnar in 3000 BC.
Construction of storage dams along the river course will considerably reduce the severity of floods and the resultant damages.
Interlinking of kosi river with other rivers is expected to greatly reduce the regional imbalance in the availability of water. Surplus water which spreads in bigger areas during floods would be fruitfully utilized.
Flow diversion is one of the efficient ways of coping with flood situation. The primitive way of achieving this is to break levees in the area where the flood damage will be relatively small. Such area should be a depression surrounded by secondary dikes, and free of habitation. Further, there should be good drainage facilities to get the water back into the river after the flood recedes. Diversion channel is an effective way of diverting part of the flow.
Water management is perhaps the most serious problem facing the nation. The critical problem is the uneven distribution of the run-offs and precipitation rates during the monsoon season. In the kosi and Ganga regions not only is the area liable to floods high, but the frequency at which the floods occur is also high. In general human life in the Kosi and Ganga plains is significantly affected by the flood hazards more often than in the Peninsular India, where the areal extent of the flood-prone lands is limited and the recurrence interval of big floods is greater.
Large floods on most of the North Bihar rivers are a direct result of intense cyclonic storms and depressions. Also due to effect of global warming, glaciers in the Himalayas are melting which are contributing water to the rivers. Water from the melting glaciers and rain water together is creating menace over the area.
Some of the largest and most calamitous floods in the Indian subcontinent have been produced from failure or breaching of natural or man-made dams as it happened in Kosi dam built in Nepal. Seeing this situation I earlier suggested for new big dam on the Kosi river in Bihar. Building big dams will definitely create problems like displacement, more area coming under water etc. But seeing the miseries, deaths and displacements due to devastating floods on large scale every year by the people of North Bihar ,one time displacement can be accepted.
Saturday, September 6, 2008
Kosi floods in Bihar, India- New Big Dam is the only solution.
Kosi floods in Bihar, India- New Big Dam is the only solution.
By
Dr. Nitish Priyadarshi
The swollen Kosi River breaking its embankments and changing course has ravaged many villages on its way to join the river Ganges affecting over a million people in Bihar.
Kosi River flows from Nepal to India and is known as the ''Sorrow of Bihar'' for the havoc it wreaks in many districts of the eastern state each year. The Kosi River, called Koshi in Nepal, is a transboundary river between Nepal and India, and is one of the largest tributaries of the Ganga. The river, along with its tributaries, drains a total area of 69,300 sq. km up to its confluence with the Ganga in India.
The river basin is surrounded by the ridges separating it from the Brahmaputra in the north, the Gandaki in the west, the Mahananda in the east, and by the Ganga in the south. The river is joined by major tributaries, approximately 48 km north of the Indo-Nepal border, breaking into more than twelve distinct channels with shifting courses due to flooding.
India is second in the world after Bangladesh in deaths due to flooding, accounting for one fifth of global flooding deaths.
Every year during the monsoon season, the Bihar region appears in the headlines because of large scale flooding. In general, this is also the time to go through the annual ritual of accusing the peasants of Nepal and the nearby mountain regions for sending down floods in even-higher volumes.
The Kosi river fan located in the northern part of India (in northeast Bihar and eastern Mithila) is one of the largest alluvial cones built by any river in the world. This 180 km long and 150 km wide alluvial cone shows evidence of lateral channel shifting exceeding 120 km during the past 250 years through more than 12 distinct channels. The river, which used to flow near Purnea in the 18th century, now flows west of Saharsa in Bihar.
It is said that due to large scale of deforestation in the Himalayas the rivers bring high influx of water and sediments and create havoc in the Bihar fields just like Kosi river did today. Kosi area is devoid of vegetation. The nature and extent of vegetation have strong control on runoff characteristics of the river catchments. The vegetation generates greater infiltration, and consequently a lesser amount of runoff. in North Bihar except Champaran where forest is significant (10.92%) most districts including Saharsa, Purnea, Supol etc the forest cover is very thin.
Even the areas affected today have very thin forest cover. It is now essential to create more forest cover which I am sure will minimize the flood calamity.
The other important solution to prevent this flood is to build big dams in Bihar bordering Nepal. Seeing the area coming under seismic zones proper precaution must be taken in building the Dams.
The Dam built on the Kosi river in Nepal has now become old and ill maintained. So it has now become essential to build more bigger dam in Bihar compared to Nepal to prevent such calamity.
All the tributaries of Kosi river encircle Mt Everest from all sides and are fed by the world's highest glaciers. These melting of the glaciers contribute high volume of water to the Kosi river with rain water during monsoon. High sediment load with water flow multiply the menace. Every year Kosi contributes heavy sediment in Bihar plains. Owing to extensive soil erosion and landslides in its upper catchment by factors both natural and human, the silt yield of the Kosi is about 10 cubic yard /acre/yr, one of the highest in the world.
Several workers have reported neotectonic movements in north Bihar. On the basis of experimental result it was showed that subsidence in an area causes flooding in the downstream reaches of a braided stream. In case of meandering channel, subsidence results in flooding in downstream reaches at the axis of deformation because of cut offs. The major parts of north Bihar plains are actively subsiding. Further, the neotectonic activities in the Himalayan region have resulted in unstable slopes, loose and fragmented rocks and higher river gradients. All these effects contribute to high sediment load of these rivers and, as a result, the beds of these rivers are rising rapidly. The bed of Kosi in Bihar is now at a higher level than the flood plain. It seems therefore that rapid subsidence combined with very high sedimentation rates have resulted in reduction in carrying capacity of channels in downstream reaches which experience frequent and severe flooding.
Big dams are constructed for the storage of more water so that the stored water is available in non-monsoon months. If the stored water is not used in non-monsoon months, then during the high monsoon with intense bouts of rain water level in these reservoirs will definitely increase the possibility of destructive floods in the river basins. Kosi dam may have faced the same phenomenon as this year Kosi river catchment area in Himalayas received heavy rainfall building pressure on the Dam in Nepal. Most of the big dams in India and Nepal are old and due to lack of proper maintenance they favour such types of devastating floods. As in the case of Kosi river engineers have cautioned about the damage being created due to high influx of water in the dam.
Further, the mountain fed rivers have mixed contributions from snowmelt runoff and monsoonal rainfall. Even during lean periods (summer), runoff contribution due to snowmelt is quite significant. The cumulative effect of monsoon rainfall and snow melt runoff results in sudden increase in the river discharge mounting pressure on the ill maintained dams. The shallow alluvial channels between the narrow banks and embankments cannot effectively carry this sudden jump in discharge consequently resulting in breaches and spilling of banks.
Further, river Kosi and other rivers of Bihar are characterized by high sediment load, mainly wash load which causes rapid aggradation of the river bed. It was observed earlier that at many locations water level in the channel within the embankments is significantly higher than the general ground level in the surrounding areas. Deposition of sediments either within the channels or on the channel margin restricts the passage of water and thus reduces the carrying capacity of the channel. This again results in over spilling of water on the adjacent plains- Kosi being the best example.
By
Dr. Nitish Priyadarshi
The swollen Kosi River breaking its embankments and changing course has ravaged many villages on its way to join the river Ganges affecting over a million people in Bihar.
Kosi River flows from Nepal to India and is known as the ''Sorrow of Bihar'' for the havoc it wreaks in many districts of the eastern state each year. The Kosi River, called Koshi in Nepal, is a transboundary river between Nepal and India, and is one of the largest tributaries of the Ganga. The river, along with its tributaries, drains a total area of 69,300 sq. km up to its confluence with the Ganga in India.
The river basin is surrounded by the ridges separating it from the Brahmaputra in the north, the Gandaki in the west, the Mahananda in the east, and by the Ganga in the south. The river is joined by major tributaries, approximately 48 km north of the Indo-Nepal border, breaking into more than twelve distinct channels with shifting courses due to flooding.
India is second in the world after Bangladesh in deaths due to flooding, accounting for one fifth of global flooding deaths.
Every year during the monsoon season, the Bihar region appears in the headlines because of large scale flooding. In general, this is also the time to go through the annual ritual of accusing the peasants of Nepal and the nearby mountain regions for sending down floods in even-higher volumes.
The Kosi river fan located in the northern part of India (in northeast Bihar and eastern Mithila) is one of the largest alluvial cones built by any river in the world. This 180 km long and 150 km wide alluvial cone shows evidence of lateral channel shifting exceeding 120 km during the past 250 years through more than 12 distinct channels. The river, which used to flow near Purnea in the 18th century, now flows west of Saharsa in Bihar.
It is said that due to large scale of deforestation in the Himalayas the rivers bring high influx of water and sediments and create havoc in the Bihar fields just like Kosi river did today. Kosi area is devoid of vegetation. The nature and extent of vegetation have strong control on runoff characteristics of the river catchments. The vegetation generates greater infiltration, and consequently a lesser amount of runoff. in North Bihar except Champaran where forest is significant (10.92%) most districts including Saharsa, Purnea, Supol etc the forest cover is very thin.
Even the areas affected today have very thin forest cover. It is now essential to create more forest cover which I am sure will minimize the flood calamity.
The other important solution to prevent this flood is to build big dams in Bihar bordering Nepal. Seeing the area coming under seismic zones proper precaution must be taken in building the Dams.
The Dam built on the Kosi river in Nepal has now become old and ill maintained. So it has now become essential to build more bigger dam in Bihar compared to Nepal to prevent such calamity.
All the tributaries of Kosi river encircle Mt Everest from all sides and are fed by the world's highest glaciers. These melting of the glaciers contribute high volume of water to the Kosi river with rain water during monsoon. High sediment load with water flow multiply the menace. Every year Kosi contributes heavy sediment in Bihar plains. Owing to extensive soil erosion and landslides in its upper catchment by factors both natural and human, the silt yield of the Kosi is about 10 cubic yard /acre/yr, one of the highest in the world.
Several workers have reported neotectonic movements in north Bihar. On the basis of experimental result it was showed that subsidence in an area causes flooding in the downstream reaches of a braided stream. In case of meandering channel, subsidence results in flooding in downstream reaches at the axis of deformation because of cut offs. The major parts of north Bihar plains are actively subsiding. Further, the neotectonic activities in the Himalayan region have resulted in unstable slopes, loose and fragmented rocks and higher river gradients. All these effects contribute to high sediment load of these rivers and, as a result, the beds of these rivers are rising rapidly. The bed of Kosi in Bihar is now at a higher level than the flood plain. It seems therefore that rapid subsidence combined with very high sedimentation rates have resulted in reduction in carrying capacity of channels in downstream reaches which experience frequent and severe flooding.
Big dams are constructed for the storage of more water so that the stored water is available in non-monsoon months. If the stored water is not used in non-monsoon months, then during the high monsoon with intense bouts of rain water level in these reservoirs will definitely increase the possibility of destructive floods in the river basins. Kosi dam may have faced the same phenomenon as this year Kosi river catchment area in Himalayas received heavy rainfall building pressure on the Dam in Nepal. Most of the big dams in India and Nepal are old and due to lack of proper maintenance they favour such types of devastating floods. As in the case of Kosi river engineers have cautioned about the damage being created due to high influx of water in the dam.
Further, the mountain fed rivers have mixed contributions from snowmelt runoff and monsoonal rainfall. Even during lean periods (summer), runoff contribution due to snowmelt is quite significant. The cumulative effect of monsoon rainfall and snow melt runoff results in sudden increase in the river discharge mounting pressure on the ill maintained dams. The shallow alluvial channels between the narrow banks and embankments cannot effectively carry this sudden jump in discharge consequently resulting in breaches and spilling of banks.
Further, river Kosi and other rivers of Bihar are characterized by high sediment load, mainly wash load which causes rapid aggradation of the river bed. It was observed earlier that at many locations water level in the channel within the embankments is significantly higher than the general ground level in the surrounding areas. Deposition of sediments either within the channels or on the channel margin restricts the passage of water and thus reduces the carrying capacity of the channel. This again results in over spilling of water on the adjacent plains- Kosi being the best example.
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