The use Of 137Cs and 210Pbex to investigate sediment sources and overbank sedimentation rates in the Teesta River basin, Sikkim Himalaya, India

This paper presents results from an investigation of suspended sediment sources and overbank sedimentation rates within the Teesta River basin, India. Sediment source fingerprinting techniques were used to provide information on the primary sources of the suspended sediment exported from the mountain part of the basin. Erosion of areas disturbed by mass movement provided the major source of the suspended sediment load of the river and channel and gully erosion were also important sources. The Pb-210(ex), Ra-226 and Cs-137 depth distributions in sediment cores collected from flood plains within the Teesta River basin have been used to derive estimates of overbank sedimentation rates. The estimated sedimentation rates at these flood plain sites vary from 0.21 cm year(-1) for the upper flood plain level at the site near Boogadong to 3.56 cm year(-1) at the site near the confluence of the Teesta River with the Great Rangit River.