Teesta - Ministry of Power

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Preliminary Feasibility Report
Teesta (I) HE Project (4 x 80 MW)
4.3 TOPOGRAPHIC AND GEOTECHNICAL ASPECTS OF COMPONENT
STRUCTURES
The river Teesta from its confluence with Kalep Chhu and up to its confluence with
Zemu Chhu flows N-S in a steeper gradient and is joined by Jongten Chhu,
Gyamthang Chhu, Chento Chhu and Burum Chhu in the left bank while Goma Chhu
meets the river in the right bank. The river and most of its tributaries are snow fed.
The river valley in this stretch is generally narrow with occasional ballooning at
places, especially in the vicinity of Yathang and Shacham area. The area has a rugged
terrain with elevations rising from 2500 m to about 6000 m. Also the area is under a
moderate to thick cover of vegetation. In the river valley, at places moraine deposits
have been observed.
The major left bank tributary Zemu Chhu flows NW-SE and meets Teesta near Zemu.
Between Jekthang and Zemu, this nala is bound by steep N-S trending ridges. Zemu
Chhu in the vicinity of Dozam is joined by Dozam Chhu and Alakhade Chhu on the
left and right banks respectively. Towards Zemu, thick vegetal cover has been
observed along this nala. Few settlements are observed on the banks of river Teesta.
The area is approachable by a fair weather road, however, Zemu Chhu is approachable
by foot track, which was reported destroyed during the current visit.
4.3.1 Diversion Structure
The proposed dam shall be located about 600 m downstream of the confluence of
Chento Chhu and Teesta River. In this stretch, the river Teesta takes an easterly
convex bend and flows in a relatively wider valley. The area during the visit was
covered by snow (Photo 1A & 1B). Towards the right bank the river is covered by
debris material, which was noticed along the road and in the uphill. The overburden
appears to be of the order of ± 30 m below the road, which comprises of boulders and
pebbles in a silty/clayey matrix. Further uphill, rock exposures are exposed as steep
rocky escarpments. The river course at present is flowing within a 20-25 m wide