Bihar at a glance

Bihar is situated in the central portion of indo-Gangetic plain. The portion lying on the northern side of left bank of ganga is known as north Bihar and that lying on the southern side as south Bihar. As per “Second Bihar State Irrigation Commission 1994” report, the rivers of Bihar have been divided into 14 basins namely, 1. Ghaghra 2. Gandak 3. Burhi Gandak 4. Bagmati-Adhwara 5. Kamla-Balan 6. Kosi 7. Mahananda 8. Main Ganga stem which includes the drainage area of Kao river, Dharmawati river, Ganga, Mahi river, and Baya river, 9. Karmnasa 10. Sone 11. Punpun 12. Kiul-Harohar 13. Badua which includes the drainage area of Belharha river also 14. Chandan which includes the drainage area of Bilasi river and chir river also.

The Ganga flowing from east to west in this state is the main drainage channel with seven major rivers/basins namely Ghaghra, Gandak, Burhi-Gandak, Kamla Balan, Bagmati, Kosi and Mahananda on its north and six namely Karmnasa, Sone, Punpun, Kiul-Harohar, Badua and Chandan on its south. All the rivers excluding Burhi-Gandak joining Ganga on its left bank in Bihar originate from Himalayas, flow through a considerable length in Nepal and large part of their catchment falls in the glacial regions of the great Himalayas. These rivers are snow fed and hence perennial. About 80% to 90% of the annual rainfall occurs in monsoon months on account of south-west monsoon. As a result, entire northern region of this state is affected by flooding almost every year due to excessive rainfall in their catchment. The average annual rainfall in Bihar is 1205 mm with significant variations in its areal distribution.

Geographical Area :	94163 Sq. Km
Population (2011 census) :	103,804,637
Number of Districts :	38
Number of flood prone districts :	28
No. of River Basins:	14
Average annual Rainfall:	1205 mm
Flood Prone Area:	68800 Sq. Km
Total length of Embankment Constructed:	3759.94 Km
Area protected by flood:	36,460.46 Sq Km

Source: Second Bihar State Irrigation Comission Report,1994

Ghaghra

The basin has a total catchment area of 1,27,950 Sq Km, of which the area lying in Bihar is 2995 Sq Km, the rest 70,303 Sq Km being in Nepal ahd 54,652 Sq Km in UP. The annual rainfall in the whole catchment varies from 1500 mm in Trans-Himalayaan region to 1200 mm in rest of the Ghaghra basin upto its confluence with the Ganga near Chapra. Sixteen districts of UP and three districts namely Gopalganj, Siwan and Chapra of Bihar are covered by the catchment of this basin in India. Nearly the entire plains of the catchment lies below the south of the lndo-Nepal border line in India. This forms part of the alluvial Gangetic plains.

In Bihar State, the tributaries such as the Little Gandak, the Jharahi and the Daha joining the Ghaghra on its left bank flow through silted cross sections. There are also some low-lying lands called `Chaurs' which remain submerged for considerable period due to drainage congestion. The Ghaghra brings large quantity of silt during the floods and deposits the same in its bed due to Very flat bed slope and this results in its tendency to meander and consequent inundation of vast areas. Flooding is generally caused due to spilling through gaps in left embankment in Siwan and Chapra district which causes problems in considerable areas.

Salient Features

Total Length of Main River in Bihar:	83 Km
Average annual Rainfall:	1200 mm
Total length of Embankment:	132.9 Km
Area protected by flood:	790 Sq Km
Flood Prone Area:	2530 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Gandak

The total catchment area of the basin upto its outfall into the Ganga is 40,553 Sq Km of which- 4,188 Sq Km lie in Bihar, 895 Sq Km lies in UP and the rest 35,470 Sq Km lies in Nepal. The basin is roughly trapezoidal in shape upto Valmiki Nagar. It gets most of its rainfall during the south west monsoon that is from June to October. The annual rainfall in the whole of the catchment varies from 2030 mm in the northern portion of the catchment in hills to 1100 mm in the southern portion in plains. The river has very steep slope in the mountains but after it debouches into the plains, the slope gradually becomes flatter. Like other rivers of North Bihar, it also brings enormous quantity of sediment load along with its flow during the monsoon period. The silt load carried gets deposited on its bed as the river flows through plains. This results in aggradation in bed and tendency to spill its banks and in course of time to shift its course.

The river Gandak flows more or less on ridge line and therefore, any breach in the banks causes great devastations. The problem of flooding gets` further aggravated when the Ganga is also in floods simultaneously and the outfall of the river Gandak is choked resulting in back flow of the Ganga into the Gandak. The river has been embanked on its both banks and the problem is one of proper maintenance of these embankments. Any breach in the embankment, therefore, results in catastrophe in the area.

Salient Features

Total Length of Main River in Bihar:	260 Km
Average annual Rainfall:	1125 mm
Total length of Embankment:	511.66 Km
Area protected by flood:	6240 Sq Km
Flood Prone Area:	3350 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Burhi Gandak

The catchment area of the Burhi Gandak is 12,021 Sq Km out of which 2420 Sq Km of the hilly catchment lies in Nepal and the rest 9601 Sq Km lies in Bihar. The catchment is fan shaped upto the confluence of the Dhanauti and thereafter its shape is elongated, narrow and rectangular. The Burhi Gandak river basin is bounded by the Someshwar range of hills in north, the Bagmati basin in the east, the Gandak river basin in the west and the main Ganga stem in the south. The river bed slope in hilly and terai region in Nepal is very steep and is of the order of about 2 in per Km to 5 in per Km and is flat in the plains of Bihar. The river system of the Burhi Gandak originating from the Someshwar range of hills has played a major role in building up the land formation of this basin. The sediment brought by the system formed inland deltas where the steep slope of terai converged into the flat slope of the plains. This resulted in the meandering and braiding tendencies in the river leading to shifting of courses. Such changes in the river course and avulsions and cut-offs of the meander loops formed local depressions known as Mauns. The Burhi Gandak river basin has numerous gullies and ridges and also saucer type natural depressions locally known as chaurs. The southern portion of the basin, however, is fairly level and without much undulation.

The average annual rainfall in the basin is 1283 mm and it varies from 1041 mm in the lower catchment to 1569 mm in the upper catchment. During monsoon period due to heavy rainfall in the catchment of the Sikrahana river, as it is known in the upper reaches, spilling over the banks cause inundation in the area. Flood in the main stream also occurs due to floods in the tributaries. The flood situation in the area further aggravates due to inadequate waterway provided in some of the bridges culverts in the roads and railways falling in this basin. The areas generally affected by floods in West Champaran are the areas around Plamnagar, Narkatiaganj, Mainatand and Chanpatia etc and Sugauli, Semra, Moti,hari,and Lalbegiaghat etc in the East Champaran. Motihari town is frequently affected due to the spill of the Sikrahana river. Flooding in the basin also occurs due to spilling of the tributaries and streams.

Salient Features

Total Length of Main River in Bihar:	320 Km
Average annual Rainfall:	1283 mm
Total length of Embankment:	779.26 Km
Area protected by flood:	6730 Sq Km
Flood Prone Area:	8210 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Bagmati-Adhwara

The total catchment area of the basin is 14,384 Sq Km including the catchment of the Adhwara group of rivers. Out of this 6500 Sq Km lies in Bihar and the rest 7884 Sq Km lies in Nepal. Most of the catchment in Nepal, covering about 55 per cent lies in the Shiwalik foot hills, while areas lying in Indian portion in Bihar State are mostly in alluvial plains. This basin is located on the south of the Himalayan range in Nepal and north of the river Ganga in India and lies between the Burhi Gandak basin on the West and the Kamla-Balan basin on the east. The average annual rainfall in the catchment area in India varies between 1392 mm to 1184 mm.

The Bagmati river system carries a lot of sediment load contributed by its own catchment as well as its tributaries which has put the river regime in disarray and created problems like drainage congestion, meandering of the river course, rising of the river bed resulting in rising of the flood level and reduction in channel capacity etc. On the other side, the Khiroi and the Darbhanga-Bagmati rivers, which are the two principal rivers of the Adhwara group in this basin, do not carry heavy load of sediment and, therefore, they do not exhibit any serious meandering tendency and the river cross-sections do not indicate any noticeable signs of bed erosion or silt deposition on a large scale. During floods the rivers of the basin spill over its banks and inundate large part of lands in the district of Sitamarhi, East Champaran, Muzaffarpur, Darbhanga, Samastipur and Khagaria. The flood is mainly due to heavy rain in the hilly catchment in Nepal which often synchronises with heavy rains in the plains lower down in India.

Salient Features

Total Length of Main River in Bihar:	394 Km
Average annual Rainfall:	1255 mm
Total length of Embankment:	478.14 Km
Area protected by flood:	1800 Sq Km
Flood Prone Area:	4440 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Kamla-Balan

The river Kamla-Balan drains a total catchment area of 7232 Sq Km, out of which 4488 Sq Km lies in Bihar and the rest 2744 Sq Km in Nepal. The catchment in India lies in Madhubani 63 per cent, Darbhanga 31 per cent, Samastipur 3 per cent, Khagaria 1 per cent, and Saharsa 2 per cent districts of Bihar. This basin is bounded by the Adhwara group of rivers (a part of the Bagmati basin) on the west, the Kosi basin on the east, the Kareh river (lower reach of the Bagmati basin) on the south and Mahabharat range of hills in Nepal on the north.
The bed gradient of the Kamla upto Chisapani in Nepal is quite steep of the order of 2.44 in/Km. There after, from Chisapani to lndo-Nepal border near Jainagar it is 1.07 m/Km and then it goes on flattening. The Kamla-Balan carries heavy sediment load. Due to flattening of the slope in the lower reach and `heavy sediment load which the river carries below Jaynagar, it has been changing its course frequently.
The average annual rainfall in India portion of the Kamla-Balan basin is in the range of 1459 mm at Khutauna and 1000 mm at Kusheshwarasthan rain gauge stations. The river Kamla and its tributaries used to cause flooding mainly in the districts of Madhubani and Darbhanga. The construction of embankments on its both banks from Jainagar to Jhanjharpur in 1958, Jhanjharpur to Darjia in 1962 and its subsequent extension upto Kothram (taken up in 1980) has checked flooding to a great extent in the middle reach of the river as the flood waters now remain confined within the embankments. However, above Jainagar in Nepalese territory the spill from the river during monsoon period enters the protected area. This can be solved by extending the embankments on both banks in Nepalese territory and tie them with high ground. The Darbhanga- Bagmati river, which drains the Adhwara group of rivers, a pills into the old Kamla at Faghauli during floods resulting in overtopping of the old Kamla banks and flooding of the area below Darbhanga-Sakri. road. As described earlier, the Kamla-Balan river is jacketted by embankments from Jainagar (lndo-Nepal border) to Kothram. The flood discharge carried by the river within the embankments is released at Kothram with high velocity and spills in the area below Kothram. Such Spilling spreads as far as 6 to 8 Km on both banks of the river Kamla-Balan and inundates large areas of Ghanshyampur, Biroul, Kusheshwarasthan and Singhia blocks.

Salient Features

Total Length of Main River in Bihar:	120 Km
Average annual Rainfall:	1260 mm
Total length of Embankment:	203.9 Km
Area protected by flood:	5620 Sq Km
Flood Prone Area:	3700 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Kosi

The Kosi drains a total catchment area of 74030 Sq Km out of which only 11410 Sq Km lies in India and the rest 62620 Sq Km lies in Tibet and Nepal. It is a snowfed river and hence perennial.
The catchment area up to Bhimnagar in Saharsa district of Bihar is hilly and the rest in India forms part of the Gangetic plains. The catchment area falling within Indian territory is distributed under several districts of Bihar namely

• Madhubani
• Darbhanga
• Saharsa
• Supaul
• Madhepura
• Araria
• Purnea
• Katihar
• Bhagalpur
• Khagaria

The basin is bounded by the ridge of the Himalayas in the north separating it from the Brahmputra river system, the Mahananda in the east, the Kamla-Balan in west and the Main Ganga stem in south. The vast plain, on which the Kosi delta has fo-rmed, has a general slope from north to south and west to east, being steeper in the north and flatter in the south. In the north, the slope is 56-76 cm per Km but it is 6 cm/Km beyond Bhaluahi in India. Thus the entire lower catchment is nearly a level country which is split into numerous `Dhars' in the old beds of the Kosi river. There are undulations and innumerable depressions called `Chaurs', where water remains accumulated for most part of the year. The main monsoon season of the basin extends from June to October during which period about 80 per cent of the annual precipitation occurs. The mean annual rainfall in, the catchment varies from 1589 mm in the upper portion of the river system to 1323 mm in the lower part. The Kosi brings enormous amount of silt from the Himalayas. This varies from year to year and month to month depending on the flow of the river and is highest during the months of July to September. The silt load is deposited in the bed as the river travels in the plains and causes the river to spill its banks and shift its course. Such excessive deposition of silt has resulted in reduction of the channel capacity gradually and lots of shoals and islands have been formed in the bed of the river. The average annual silt load carried by the river is about 95 MCM as observed at Barahkshetra site. Due to excessive quantity of silt load being brought down by it during monsoon period, the river Kosi is known to have shifted its course about 112 Km to the west in the last 250 years. The trend of transitory movement is still continuing in the shape of attacks on-the embankments on its both banks. Unlike many rivers in India the river Kosi does-not have any defined flood plain. It is rather extensive and changing along with the shift in the course of the river towards west. The severity of the flood problem has been mitigated to a great extent with the construction of flood embankments on its both banks. The eastern embankment 144 Km in length (inclusive of eastern afflux bund) starts from Chakarghati in Nepal to Koparia in India and the western embankment having 123.2 Km length (including Western afflux bund) starts from Bharda in Nepal and extends upto Nirmali in India and tied to the Railway embankment of Sakri-Nirmali section of NE F3ailway. Lower down it extends from Ghoghardiha to Ghoghepur opposite Mahesi. The flood problem gets aggravated when the Ganga is also in flood simultaneously and the outfall of the river Kosi is choked resulting in back flow of the Ganga waters into the Kosi.

• Supaul
• Saharsa
• Madhepura
• Araria
• Purnia
• Katihar

• Madhubani
• Darbhanga
• Khagaria

Salient Features

Total Length of Main River in Bihar:	260 Km
Average annual Rainfall:	1456 mm
Total length of Embankment:	637.41 Km
Area protected by flood:	9720 Sq Km
Flood Prone Area:	10150 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Mahananda

The river Mahananda drains a total catchment area of 23700 Sq Km, out of which 6150 Sq Km lies in Bihar and rest 17550 in Bangladesh, Nepal and West Bengal. Three-fourth of the upper part of the catchment area is more or less triangular in shape and remaining one-fourth in the lower part is triangular converging at its confluence with the Ganga. It is bounded by the Himalayas in the north, the ridges separating it from the Tista river system in the east, the Ganga in th`e south and the Kosi in trfe west-. The rainfall in the upper catchment of the basin is very high of the order of 5590 mm per annum. The average annual rainfall in the Mahananda river system in India in about 1563 mm. About 80 per cent of this-rainfall occurs during the monsoon months (June to Sept). The bed slope of the river in the upper portion from its origin to Siliguri in West Bengal is about 80 in per Km and from Siliguri to Sonapurhat is 1.57 in per Km. From Sonapurhat the bed slope goes on flattening. The slope near its outfall with Ganga is about 0.14 in per Km.

The Mahananda spills in almost its entire reach in Bihar. The basin experiences floods almost every year. With the construction of flood embankments in Bihar and West Bengal along both banks of the Phulhar branch and the right bank of the Barsoi branch, the areas on the countryside of the embankment have been protected from flood spill. But the areas falling on the left bank of the Barsoi branch in Bihar and West Bengal are still facing extensive flooding. The river Mahananda brings enormous amount of silt from the Himalayas. Due to excessive deposition of silt the capacity of the river channel has been gradually reduced resulting in meandering tendency of the river in the alluvial plains and over bank spilling during floods.

Salient Features

Total Length of Main River in Bihar:	376 Km
Average annual Rainfall:	1563 mm
Total length of Embankment:	225.33 Km
Area protected by flood:	1010 Sq Km
Flood Prone Area:	5150 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Main Ganga Stem

The main Ganga stem drains a total catchment area of 1,36,970 Sq Km out of which only 15205 Sq Km lies in Bihar. It is a snow fed river and hence perennial.The upper part of the sub-basin upto Haridwar and some areas in Varanasi, Munger and Santhal Pargana districts are hilly and the rest of the area lies in plains. The river Ganga travels from west to east almost in full length in Bihar.

The main Ganga stem basin in Bihar includes the drainage area of

• the Kao river
• the Dharmawati river
• the Ganga river
• the Mahi river
• the Baya river
• the Balan river

These small tributaries directly join the main Ganga river and they do not have any significant flood problem of their own. Only a portion of the areas of the districts of East Champaran, Muzaffarpur, Vaishali, Gopalganj ,Siwan, Saran, Samastipur, Begusarai, Khagaria, Buxar, Bhojpur, Patna, Munger, Bhagalpur and Katihar fall into the drainage area of the main Ganga stem basin in Bihar. The main Ganga stem basin in Bihar is bounded by the Ghaghra, the Gandak, the Burhi Gandak, the Kosi and the Mahananda basins on the north and the Karmnasa, the Sone, the Punpun, the Kiul Harohar and Badua Belharna basins on the south. The entire 2525 Km course of river Ganga from source to outfall can be divided into five major sections. The river slopes in different stretches such as source to Rishikesh, Rishikesh to Allahabad, Allahabad to Farakka, Farakka to Nabadwip and Nabadwip to Outfall are 1 in 67,1 in 3,196,1 in 15,795, 1 in 23,000 and 1 in 24,000 respectively .The river Ganga flows in a meandering pattern in plains. The meandering is maximum between Allahabad and Varanasi and minimum between Sara and the Bay of Bengal. Almost all the rivers of the Gangetic plain, which originate from the Himalayas, join the river Ganga, and bring enormous sediment with them. The sediment brought by them formed inland deltas which resulted in the meandering and braiding tendencies in the river leading to shifting of courses. There are many big inland deltas in the main Ganga Stem basin, Known as diara in Bihar.

The Ganga causes damage by spilling over its bank at Several places. The major problem of flooding along the Ganga occurs below its confluence with the Yamuna at AIIahabad beyond which considerable damage is caused by spilling of flood water over its banks during higher stages. It also erodes its banks near Mirzapur, Varanasi, Ballia, Patna, Begusarai, Barahia Khutaha , Munger, Khagaria, Mansi, Narayanpur and Karhagola etc where important anti erosion Schemes have been executed in past to hold the river. It has been observed in Bihar that, when the river Ganga is flowing at higher stages, the discharges from the tributaries get locked and cause widespread flooding in the river systems and near their confluence points. The condition worsens when the floods in the Ganga and its tributaries synchronises. Therefore, the water level of the Ganga at any particular time during monsoon controls the intensity and duration of the flood in the catchment of its tributaries also. Flooding is quite wide spread in khadir is the meander belt of the river .The villages situated on the Diara land are the victims of the floods almost every year. The low lying areas are also affected due to drainage congestion for longer period even during normal floods. For instance, the area covered under Mokama Group of Tals starting from Fatuha to Lakhisarai as well as Dakra and Bariarpur Sultanganj Tal area poses serious drainage problem due to flood of the Ganga river. This type of problem due to similar topography also exists on the left bank between Chapra and Bajitpur and between Narayanpur and Kursela. The problem of bank erosion on the Ganga is primarily due to changing pattern of its meandering tendency.

Salient Features

Total Length of Main River in Bihar:	445 Km
Average annual Rainfall:	1152 mm
Total length of Embankment:	596.92 Km
Area protected by flood:	2440 Sq Km
Flood Prone Area:	12920 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Karmnasa

The Karamnasa River basin is situated between latitudes 24 32 N and 25 31 N and longitudes 83 0 E and 84 5 E. The Karamnasa rises near Sarodag on the northern face of the Kaimur range about 29 km west of Rohtasgarh in Mirzapur district of UP at an elevation of 350m and forms a boundary between Bihar and UP from the point River Gurwat joins Karamnasa. Then it flows through Varanasi district in UP and finally falls in Ganga near Chausa. Its important tributaries are the Durgawati, the Gurwat and Chandraprabha.The Total geographical area of the basin is 5127 sq km. The total length of the river is 192 km of which 92 km lies in UP, 24 km in Bihar and balance 76 km forms the common-boundary between Bihar and UP. Its other tributaries are Lorse, Kumda, Geria, Dharmawati etc.

Salient Features

Total Length of Main River in Bihar:	24 76 km (forms Common boundary between Bihar and UP)
Average annual Rainfall:	929 mm
Total length of Embankment:	NIL
Area protected by flood:	NIL
Flood Prone Area:	NIL

Source: Second Bihar State Irrigation Comission Report,1994

Sone

The Sone basin extends over an area of 70228 Sq Km and covers large areas in the states of Madhya Pradesh, UP and Bihar,15820 Sq Km of its catchment area lies in Bihar and Jharkhand and 1483 SQ.Km in Bihar as per GIS. The basin is roughly rectangular in shape, has a maximum length of 460 Km in the east-west direction and a maximum width of 220 Km in the north-south direction. The normal annual rainfall in the basin varies from 1472 mm in the upper catchment to about 954 mm in the plains where the Sone joins the Ganga. Except in the lower most reaches where the river enters into the Gangetic plain in the F}ohtas district, the river flows in hilly and well forested areas of Madhya Pradesh & UP. The problems of floods in the basin arises only in the lower reaches of the river after it emerges out of the hilly reaches into the plains and it is caused by spilling over its banks causing inundation of adjoining areas. The river generally spills in Bihar below Daudnagar on the right bank and below Nansagar on the left bank in Bhojpur district. Further down below the Koilwar bridge, the spilling is more acute, which also affects the low lying areas in Bhojpur and Patna districts. The main reason of over bank spill are the heavy rainfall in the upper catchment and inadequate capacity of the river within its banks.

The flood affected reach of the river has been protected by some important embankment schemes such as Buxar-Koelwar embankment(Part), Sone left embankment from Koilwar to Harpur lock and Sone Right embankment schemes. The problem becomes severe, whenever flood of the river Sone synchronises with that of the Ganga causing drainage congestion and due to which the duration of flooding in the catchment considerably increases. In 1975, the flood due to spill of the river Sone in its lower reach resulted in flooding of the entire Danapur and most part of the Patna town causing extensive damage to private and public properties. Practically there appears no silt problem in the Sone basin because annual silt load does not follow a regular pattern. This basin covers Rohtas, Bhojpur, Aurangabad and Patna districts.

Salient Features

Total Length of Main River in Bihar:	202 Km
Average annual Rainfall:	954 mm
Total length of Embankment:	59.54 Km
Area protected by flood:	210 Sq Km
Flood Prone Area:	3700 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Punpun

The Punpun basin drains a total catchment area of 9026 Sq Km lies in Bihar and Jharkhand and 7536 Sq.Km in Bihar. The catchment covers the districts of Patna, Jahanabad, Gaya, Aurangabad. The catchment is elongated. About 85 per cent of the total rainfall occurs during the monsoon months from June to September. Average annual rainfall varies from 954 mm near its confluence with the Ganga to 1817 mm in uppermost reaches. Due to low bank and inadequate channel capacity, all the channels in the lower reaches spill heavily over their banks even during norinal floods. Spilling is more acute on both banks of the Punpun north of Jahanabad-Kinjer road. The spill of the Punpun after flowing north-eastwards meets the spills of its' two. tributaries the Morhar and the Dardha. The Morhar spills north of Taregana-Bharatpur road, whereas, the Dardha spills north of Taregana-Dumari road. The spilling of flood water on left bank of the Punpun has, however, been checked to a great extent after construction of its left bank embankment under Patna Town Protection Scheme.

Some portion of the flood water on the right bank of the Punpun flows to the Dhowa river system and aggravate the flood situation in Mokama Tal area. The flood situation worsens during the period when the Ganga is in high stage simultaneously and the Ganga back water flow enters into the Punpun and the Dardha and the Dhowa river system resulting inundation of a large area besides adversely affecting the Mokama Tal area.

Salient Features

Total Length of Rivers in Bihar:	235 Km
Average annual Rainfall:	954 mm
Total length of Embankment:	37.62 Km
Area protected by flood:	200 Sq Km
Flood Prone Area:	6130 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Kiul-Harohar

The Kiul-Harohar river system drains an area of 17225 Sq Km in Bihar and Jharkhand and 12806 Sq.Km in Bihar as per GIS. The upper catchment of the river system lies in Chotanagpur plateau area which is characterised by low hills and slopes with depressions and valleys. This basin consists of a number of small rivers which during the course of flow bifurcate and rejoin meeting each other a number of times maKmg it difficult to ascertain their exact length.

The average annual rainfall in this basin is 1104 mm. The lower catchment receives lesser rainfall than upper catchment and generally all the rain gauge stations receive 90 per cent of their annual rainfall during monsoon months from June to October.

The flood problems of Kiul-Harohar basin are not of very serious nature like those of the river basins of North Bihar. However, flash floods have been occurring during period of heavy rains in the catchment. The Kiul and the Harohar rivers flow almost on the ridges in their lower reaches. The bankful capacity of these rivers as well as that of its tributaries like the Sakari, the Falgu, the Mohane and the Paimar are inadequate due to which they are unable to contain the flood discharge and consequently spilling takes place over their banks causing floods in the basin. At places such spills causing flood in the basin are prevented by Zamindari embankments, which are generally of inadequate section and poorly maintained, therefore, incapable of withstanding even medium flood conditions. The rivers of Kiul-Harohar basin are mostly in regime condition and are non-perennial in nature.

The flood problem of the basin as identified so far are indicated below :

1. The Kiul spills over its bank in the lower reaches near Lakhisarai, flooding the nearby areas.
2. The Sakari river which flows into the Harohar river is a shallow river and it carries a lot of silt. Also it creates flood problem, occasionally, due to occurrence of flash floods in the river. Some local Zamindari embankments are existing on this river below Sakari weir-in which there are number of gaps and the flood water spills through these gaps.
3. The river Falgu also creates flood problem sometime due to occurrence of flash floods on account of heavy rain in its upper catchment.
4. The river panchane also causes flooding sometime due to inadequate capacity of its several bifurcated channels.

Salient Features

Total Length of Main River in Bihar:	41 Km
Average annual Rainfall:	1104 mm
Total length of Embankment:	14 Km
Area protected by flood:	60 Sq Km
Flood Prone Area:	6340 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994

Badua

The basin is situated between latitudes 240 35 N and 250 25 N and Longitude 860 22 E and 860 55 E. The river Badua originates from hills of chakai black in Munger district and falls into the Ganga near Nathnagar (West of Bhagalpur) through Chanal Nadi.

The Belharana river runs almost parallel to the Badua river on its left and falls independentally into the Ganga about 26 Km above the outfall of Badua. The drainage area of these two rivers have been grouped together for studies and planning as the water of one basin. The total catchment area of the basin is 2215 Sq Km and the length of main river Badua in Bihar is 130 Km.

Salient Features

Total Length of Main River in Bihar:	130 Km
Average annual Rainfall:	114 mm
Total length of Embankment:	Nil
Area protected by flood:	Nil
Flood Prone Area:	1050

Source: Second Bihar State Irrigation Comission Report,1994

Chandan

The basin is situated between latitudes 240 30 N and 220 51 N and Longitudes 840 36 E and 870 27 E. The basin is drained independently by the river Chandan and the chir. The river Bilasi runs almost parallel to the Chandan river on its left and falls into Chandan which ultimately outfalls into the Ganga. The watershed of these three rivers have been grouped together as one basin.The river originated from the hills of Deoghar in Jharkhand state at an elevation of 274 M and after travelling 110Km length bifurcates into number of small channels with deltaic river characteristic before meeting the river Ganga through Jamunia Nala. The important tributaries of Chandan are Orhni, Kuldar and Chatri. Its total catchment area is 4093 Sq Km and Catchment in Bihar is 2371 Sq.Km as per GIS.length of main river Chandan in Bihar is 118 Km.

Total Length of Main River in Bihar:	118 Km
Average annual Rainfall:	118 mm
Total length of Embankment:	83.18 Km
Area protected by flood:	1640 Sq Km
Flood Prone Area:	1130 Sq. Km

Source: Second Bihar State Irrigation Comission Report,1994