As of mid-2021, four hydroelectric dams are operational on the main channel of the Teesta River in the mountainous and tectonically active Sikkim-Darjeeling-Kalimpong region of India. Riparian ecological and fluvial morphological changes after damming have not been documented. This paper describes an early study of a section of the middle Teesta River, at two of the dam-created reservoirs, just before the river enters the plains. High-resolution, multi-beam, geo-located sonar was used to map the bathymetry of the reservoirs. This resulted in the creation of 30cm-resolution bathymetric maps of the two reservoirs showing valley bottom morphology within them. The bathymetric maps were compared with pre-dam digital elevation models of the valley to create topographic change-maps. The change-maps indicate significant differences in valley morphology due to erosion and deposition processes. Land cover changes due to inundation were quantified from analysis of satellite imagery time series data of the reservoir riparian zones. Land cover change analysis showed a loss of ~ 74,000 trees in ~ 225 ha of flooded riparian corridors due to long-term inundation. The study shows that the dams have caused 7.4% of the river length to become quasi-lentic, and drastically altered sediment dynamics and hydrologic flow. Sediment deposition calculations indicate the reservoirs losing almost three-quarters of their surface areas to sediment deposition features within 15 years. This study will serve as an important baseline for future studies, and influence design and policy regarding riparian and fluvial ecosystem management, monitoring, and evaluation in the Teesta and similar mountainous river basins in the Eastern Himalaya.

截至 2021 年年中，在印度多山且构造活跃的锡金-大吉岭-噶伦堡地区的提斯塔河主航道上，有四座水电站大坝正在运行。尚未记录筑坝后河岸生态和河流形态变化。本文描述了对提斯塔河中段的早期研究，该河段位于两个大坝建造的水库，就在河流进入平原之前。高分辨率、多波束、地理定位声纳被用来绘制水库的水深图。这导致创建了两个水库的 30 厘米分辨率的测深图，显示了其中的谷底形态。将测深图与河谷的大坝前数字高程模型进行比较，以创建地形变化图。变化图表明由于侵蚀和沉积过程导致山谷形态的显着差异。通过对水库河岸带的卫星图像时间序列数据的分析，量化了因淹没而导致的土地覆盖变化。土地覆盖变化分析表明，由于长期淹没，在约 225 公顷被淹的河岸走廊中损失了约 74,000 棵树木。研究表明，大坝已导致 7.4% 的河流长度变为准静止状态，并极大地改变了沉积物动力学和水文流量。沉积物沉积计算表明，在 15 年内，由于沉积物沉积特征，水库失去了近四分之三的表面积。这项研究将作为未来研究的重要基线，并影响有关河岸和河流生态系统管理、监测、