Large central Bihar Plain - divided by the Ganges into two unequal part. Highlands and mountains of Shivalik Range in north-west with forest, low mountains and valleys in the mid-south, subtropical tropical laurel jungle in South-West Kaimur Range of Southern Plateau Region, intermittent hilly and mountainous regions in central South with few valleys.
Bihar is located in the eastern region[4] of India, between latitudes 24°20'10"N and 27°31'15"N and longitudes 83°19'50"E and 88°17'40"E. It is an entirely land–locked state, in a subtropical region of the temperate zone. Bihar lies between the humid West Bengal in the east and the sub humid Uttar Pradesh in the west, which provides it with a transitional position in respect of climate, economy and culture. It is bounded by Nepal in the north and by Jharkhand in the south. Bihar plain is divided into two unequal halves (North Bihar and South Bihar) by the river Ganges[5] which flows through the middle from west to east. Bihar's land has average elevation above sea level of 173 feet.
Bihar is in Indo-Gangetic plain so naturally fertile soil is one asset of the state.[citation needed] Thus Indo-Gangetic plain's soil is the backbone of agricultural and industrial development. The Indo-Gangetic plain in Bihar consists of a thick alluvial mantle of drift origin overlying in most part, the siwalik and older tertiary rocks. The soil is mainly little young loam rejuvenated every year by constant deposition of silt, clay and sand brought by streams but mainly by floods in Bihar[14]
Bihar is mainly a vast stretch of very fertile flat land. It is drained by the Ganges River, including northern tributaries of other river. The Bihar plain is divided into two unequal halves by the river Ganges which flows through the middle from west to east. Other Ganges tributaries are the Son, Budhi Gandak, Chandan, Orhani and Phalgu. The Himalayas begin at foothills a short distance inside Nepal but influence Bihar's landforms, climate, hydrology and culture. Central parts of Bihar have some small hills, for example the Rajgir hills. The Himalayan Mountains are to the north of Bihar, in Nepal. To the south is the Chota Nagpur plateau, which was part of Bihar until 2000 but now is part of a separate state called Jharkhand.
Bihar has notified forest area of 6,764.14 km2, which is 7.1 per cent of its geographical area.[17] The sub Himalayan foothill of Someshwar and Dun ranges in Champaran district another belt of moist deciduous forests. These also consists of shrub, grass and reeds. Here the rainfall is above 1,600 mm and thus promotes luxuriant Sal forests in the favoured areas. The hot and dry summer gives the deciduous forests. The most important trees are Shorea Robusta (Sal), Shisham, Cedrela Toona, Khair, and Semal. This type of forests also occurs in Saharsa district and Purnia district.[18]
Total human deaths is 5874 and animal deaths is 19044 in Bihar due to floods between 1979–2006[22][23]
Bihar is India's most flood-prone state, with 76% of the population in the north Bihar living under the recurring threat of flood devastation.[24] According to some historical data, 16.5% of the total flood affected area in India is located in Bihar while 22.1% of the flood affected population in India lives in Bihar.[25] About 68,800 square kilometres (26,600 sq mi) out of total geographical area of 94,160 square kilometres (36,360 sq mi) comprising 73.06% is flood affected. Floods in Bihar are a recurring disaster which on an annual basis destroys thousands of human lives apart from livestock and assets worth millions.[24]
Bihar has cool winters, the lowest temperatures being around 0–10 degrees Celsius (33 to 50 degrees Fahrenheit). Winter months are December and January. It is hot in the summer with average highs around 35–45 Celsius ( 95–105 Fahrenheit). April to mid June are the hot months. The monsoon months of June, July, August, and September see good rainfall. October & November and February & March have cool, pleasant climate.
