Soil of the area:
The soil of this district is alluvial in nature and has a light texture and defined as sandy loam to loamy sand which highly permeable porosity. The Geological point of view soils are mainly the products of weathering of fluvial clastics.
Pedagogically the deposits can be grouped into five unit based on soil formation, colour of topsoil and composition of soil, quaternary terrace deposits.
The first one has no soil cover which is the present day flood plain, the second unit consists of enormous well developed coarse to fine sand size grading southward away form the foot hills, to silt and clay. The third and fourth unit ranges form boulder to sand size fraction, which is developed highly porous and permeable soil.
The last unit mainly made up of boulder of various sizes, with little or no matrix.
Land use:
The dramatic transformation of land use pattern of Jalpaiguri district has taken place during the second half of the last century. Huge migration vis-à-vis influx of population compelled the people to settle in the former water bodies, marshy lands, hilly forest, decayed water bodies and interior area of the district. So the land use pattern has also been changing from natural land to man made or artificial structure.
The land use pattern of the area is forest (25%), teagarden (15%), cultivated and non-cultivated land (43%), and others (17%) (Water bodies, residential, hill etc.). The tea garden and hill area covered in the northern part of the district. Forest covers area scatter in whole district.
Land use pattern changed dramatically from last decade that is the one of the major cause of environmental hazard of this district.
Hydrological characteristic:
Hydrological condition at a particular point is guided by topography, geology, and rainfall (Annual rainfall 3736 mm) of the region. Under uniformly excellent water aquifer condition groundwater simulates topography. Most of the aquifer is semi-confined and unconfined in this belt. (Prevalence of sand to boulder size material) Groundwater contour map depicts the region spanning form east to west where as to the North to South depth to water level increase gradually. The groundwater table coincides with the surface water, so many rivers originates from the groundwater in this region. In monsoon period ground water level upper than surface water, which causes more danger for contamination.
Hydrological characteristics also have changed from last decade. Ground water level and water quality of the region varies from pre to post monsoon period due to recharge of rainfall.
Environmental hazards:
The Jalpaiguri district is a part of sub-Himalayan West Bengal which is generally known as ‘Terai’ or ‘Duars’. The study area which situated in the foothills region of Himalayas, facing different type hazards which is natural and also man made like floods, landslides etc. Main four causes which affects vulnerably are-
- Due to River Shifting
- Due to Deforestation
- Soil Erosion
- Ground and surface water Quality
River Shifting:
The region is the interfluves of numerous rivers and rivulets. Because of foothills situation, rivers are coming from hills suddenly reaches the plain. Due to this sudden flattening of slope rivers are not capable to carry the debris which flow through from hills and deposit the detritus in different region as per their specific gravity, like boulders, pebbles, singles, bozri, course sand, fine sand, silt and finer silt particles, that formation is called alluvial fan. For this reason height of the riverbed increase, river siltation increase, which cause shifting and changing of river course. With the help of LISS-III satellite image March, 2001 have observed, shifting of river Teesta and Jaldhaka from West to East 2.9km.and 2.1km respectively. River Torsha including Sil and Char Torsha shifts frequently. The only exception is shifting of Diana River from East to West.
So, changing of river course and shifting of river is not new features for this region. But with increasing habitation and changing landuse pattern, it become vulnerable headache for now-a-days. Adding insult to injury, deforestation heavily occurred due to natural and man made hazards like illegal cutting of trees, unscientific dolomite mining in Bhutan and surrounded hills etc. Now we are trying to discuss how river shifting becomes very serious problem for this region with suitable example.
- Shifting of Teesta :-
Teesta was originally a river of Ganga basin as per history. In 1787, due to heavy flood and devastating earthquake Teesta shifted its course to Bhramaputra basin (Source: Hunter’s Statistical Account of Bengal)
In recent times, after the flood of 1950’s it is observed that a huge quantity of water of river Teesta is flowing through Buri Teesta and falling into theYamuna in Bangladesh. This course tends to develop further with the course of time. To prevent this Jalpaiguri town protective embankment had to extend up to Jharsing Swar near Haldibari in Coochbehar district.
During the flood of 1968, river opens a new course through Upalchand Forest near Kathalbari in Mal block. It devastated huge quantity of forest area and took its course again to its main course. A big chunk of Upalchand Forest was washed out in this case.
- Shifting of Torsha:-
River Torsha bifurcates itself near about a 1.5 km .down of the road bridge near Suhasini Tea Garden Hasimara , into two branches namely-I)Sil Torsha- the eastern branch ii) Char Torsha , the western one. During 1950’s due to sudden flood the Sil Torsha course developed severely and washed out the road bridge on NH-31 over Sil Torsha and widened its width in double.
During 1954 , on the other hand the Torsha river developed the Char Torsha course and wash out the bridge over Char Torsha on NH-31 and widen the course about 1 km. Width.
- Shifting of Jaldhaka:-
Since the flood of 1954, river Jaldhaka was shifting towards East near Tandu Tea Garden in Nagrakata block. The river devastated 10 km (approx) of forest and almost 50% of the Tandu Tea Garden. To prevent the tendency of avulsion of Jaldhaka to river Bamni, an embankment had to be constructed.
In the late 90’s another shifting took place. Jaldhaka, by breaching the left bank embankment avulsed into river Doikhowa and ruined a huge area of Northwestern part of Dhupguri block.
- Shifting of River Diana:-
During 1956, river Diana avulsed through a rivulet Jhumur and Rangati just south of Kalabari Tea Garden, devastating about a100 sq. km (approx) area. Due to this original course of river Jhumur was abandoned and it is now a tributary of river Rangati. By constructing embankment at Kalabari, the course of Diana was thrown back to its own. But this river has a tendency to avulse to river Rangati.