- The Kuntipuzha is a major river that flows 15 km southwest from Silent Valley.
- It takes its origin in the lush green forests of Silent Valley. In 1928 the location at Sairandhri on the Kunthipuzha River was identified as an ideal site for electricity generation.
- In 1970 Kerala State Electricity Board(KSEB) proposed a hydroelectric dam across the Kunthipuzha River that runs through Silent Valley, that will submerge 8.3 sq km of untouched moist evergreen forest. In February 1973, the Planning Commission approves the project at a cost of about Rs 25 crores.
- Because of concern about the endangered lion-tailed macaque, the issue was brought to public attention. Romulus Whitaker.
- In 1977 the Kerala Forest Research Institute carried out an ecological impact study of the Silent Valley area and proposed that the area be declared a biosphere reserve.
- In 1978 Indira Gandhi, Prime Minister of India, approved the project, with the condition that the state government enact legislation ensuring the necessary safeguards.
- Kerala Sasthra Sahithya Parishad (KSSP) effectively aroused public opinion on the requirement to save Silent Valley.
- The poet activist Sugathakumari played an important role in the Silent Valley protest.
- Dr. Salim Ali, eminent ornithologist of the Bombay Natural History Society, visited the valley and appealed for cancellation of the hydroelectric project.
- Dr. M.S. Swaminathan, the renowned agricultural scientist, and then secretary to the Department of Agriculture, called at the Silent Valley region and his suggestion was 389.52 km2 including the Silent Valley (89.52 km2 ) should be made into a national rainforest biosphere reserve.
- In January 1980 the High Court of Kerala lifted the ban on clear cutting, but then the Prime Minister of India requested the Government of Kerala to stop further works in the project area until all aspects were fully discussed.
- In 1982, a multidisciplinary committee with Prof. M. G. K. Menon as chairman and Madhav Gadgil, Dilip K. Biswas and others as members, was created to decide if the hydroelectric project was feasible without any significant ecological damage.
- On 31 October 1984 Indira Gandhi was assassinated and on 15 November the Silent Valley forests were declared as a national park, though the boundaries of the Silent Valley Park were limited and no buffer zone was created, despite recommendations by expert committees and scientists
- Ten months later, on 7 September 1985 the Silent Valley National Park was formally inaugurated and a memorial at Sairandhri to Indira Gandhi was unveiled by Rajiv Gandhi, the new Prime Minister of India.
- On 1 September 1986 Silent Valley National Park was designated as the core area of the Nilgiri Biosphere Reserve.
- Since then, a long-term conservation effort has been undertaken to preserve the Silent Valley ecosystem