Fluvial Environment of Jiadhal River Basin, Dhemaji District, Assam

摘要

The Jiadhal river is a flashy river, which is tributary of Brahmaputra. 3848 mm is the maximum annual rainfall and 874.91 m3s-l is the maximum flow found in the basin during the study period. 98.93m is the water level corresponding to the maximum flow occurred in the year 1990. Whereas, 4.7 m3s-l is the annual minimum flow and 95.88m is the corresponding water level recorded in the year 1991. It is observed that the maximum annual discharges have shown a decreasing trend whereas similar trend is not observed in the case of minimum annual discharge of the river. Correlation study shows higher variation in case of maximum discharge whereas low variation is found in case of minimum discharge. The flood frequency analysis made using ask AE factor methods reveals that the Log-Pearson Type III, for which D-index value is found lowest and hence is the most appropriate method for estimating the design flood of any return period. Because of the flashy nature of flow the river, it has devastating impacts like flood, erosion and sedimentation. Total damage (in Rs) due to flood ranges from 0.033 crores in 1997 to as high as 14.123 crores in 2002. Maximum area was affected in 1998, whereas in 1994 and 1995 the affected area was minimum. Therefore, it influenced socio-economy of humans and ecology of the basin. In the present paper the fluvial environment of the river basin has been presented.