A beel thicky infested with water hyacinth

sediments are of recent origin and largely consist of silt which can he easily emded.
The Indo-Gangetic alluvial tracts, especially in the northeast, are also geologically
unstable and experience ehquakes of varying intensities from time to time. 'Two
devastating earthquakes occumed in the northeast during 1897 and 1950.
Origin of floodplain wetlands
The lithololgy, yeological structure. tectonic status. seasonal variation In rlvcr
discharge and flow characteristics, largely deterniinc thc formation of the Iluodpla~n
wetlands. The heels of the country owe their orig~n eithcr to the ofic~~ changing course
of rivers in the potamonic stretches or lo tectonic adjustment.
In the northern pan of Bihar and Wcst Bengal its also In Assam. tlic rl\crs
cmcrglng from the central and easten) Htmalayas suddcrtly debouch into tlic plains .~ntl
ultimately flou down as the river Ganga, Brahmaputra and Barak. Tliesc rl\ crs c;~r.l-\
heavy loads of silt and dctritus from the Himalayas and ovcrflo~ dur~ng the sotrtt~ucsl
monsoon season submerging huge tracts of lands every ycar. Ihesc rl\crs changc 111~1r
course vcry oncn creatlng numerous floodpla~n lakes ;ind bralded channels. nia~til! 111
the forni ol'ox-ho\*. lakes. In delta~c Wcst Bengal. due to low gradielit and h~gli rl\crltlc
d~scharge dur~ng Ihc monsoon season. rccha~incl~sat~on of rivers occurs at tlic sl~glltcsi
ob~t~ctlon to flow. resulting in creation of heels of varicd typcs. In thc n~rthc~~sl
(Assam. f~iotli~lls of Arunaclial Pradesh arid Meghalaya), frequent cartltquahcs cuuplcd
w~th heavy ramfall and cuttlng actlon of rlver meanders havc rcsultcd 111 thc Ibnlii~t~O~l
of typical ox-bow lakes, lake-like becis or true tccto~tlc deprcsslons. 'Shc Ilnrs 01
Van~pur owe thetr orlgin mainly to the cutting actlon of the stream nlcandcrs.
Classification of floodplain wetlands/beels
S~nce the floodpla~n wetlands ~n~lude low lying udter bodlcs ul d~versc orlglrt
SIL~, shape. depth, ~nundat~on pattern, ecologtcal charilc~enst~cs, err many dttcmpts
havc been made to classify them according to these cr~terld Somc of thew
class~ficat~ons are glren below