Kamala dam is a 216m high concrete gravity structure planned to be constructed across Kamla river in Arunachal Pradesh, india. it is one of the three large dams envisaged in Subansiri sub-basin of the Brahmaputra river. In addition to power generation, these dams would also provide flood relief in the Brahmaputra valley through integrated operation. The reservoir created by the Kamala dam will have a gross storage of 2.4 billion m3 and will spread over a length of 67 km. A surcharge storage zone of 15m is provided above the full reservoir level (FRL) for storage of 438 million m3 of water, exclusively for flood moderation. A part of the conservation storage for power generation is also utilized for flood moderation and a permanent flood control zone of 652 million m3 is defined to be available during the monsoon months (rainy season). Additionally, 410 million m3 of active storage for power generation that extends upto the minimum operating level is also available thus providing flexibility in reservoir operation. The spillway is configured 100m below the maximum water level (MWL) to provide the required capacity considering the reservoir size, its operation, sediment inflow and deposition. This provides storage of 2 billion m3 above the spillway crest ensuring abundant buffer for sustainable use of the reservoir for flood mitigation. Reservoir routing studies have been carried out for moderation of floods and to define the reservoir operation rule curve. Rules of operation provide restriction on the outflow for floods upto 100year return period. As competing objectives of power generation and flood moderation are to be achieved, an appropriate portion of the cost of the dam is assigned to flood moderation so that the generation cost and tariff are not impacted negatively. This paper discusses the flood management aspects and spillway configuration to ensure acceptable performance under design conditions.
