A massive flood on the Rapti and Narayani rivers in Chitwan National Park in August 2017 swept away wildlife, including rare Asiatic One-horned Rhinoceros, downstream to India. Nine of the rhinos were rescued in the Balmiki Tiger Reserve across the border, and repatriated to Chitwan a few months later. Another rhino was rescued from the Nepal side of the border a week after the flood. The 11th rhino was finally traced, tranquilised and repatriated to Nepal on Monday, three years after the flood took it to India.
 
A team from the National Nature Conservation Trust and Chitwan National Park chief Rajkumar Aryal received the rhino at Triveni on the Indian border and brought the 9-year-old animal to the park headquarter in Kasara. The rhino got a medical test and has now been let back into the wild.

The animals prefer riverine grasslands, and although they can swim, are vulnerable to floods during the monsoon. In 1992, flash floods on the Rapti River had also washed away a dozen rhinos. This year’s floods on the Brahmaputra River in India’s northeastern Assam state drowned at least eight rhinos from the Kaziranga National Park which has nearly 2,500 rhinos. Some 80% of the park area was submerged by the rising waters, according to reports.

Nepal has achieved zero rhino poaching for the past seven years, but there has been a worrying rise in rhino deaths in Nepal in recent years. Park authorities say 20 rhinos have died so far in 2019-20, and 43 died the year previous to that. Many of them were males gored while fighting for mates and territory as Chitwan became overcrowded, while others died of disease or old age.

There has also been an increase in human-animal conflict while rhinos venturing out to raid farms in the buffer zone, and in the process being electrocuted or poisoned. Another threat to rhino conservation in the post-poaching era is the increase in infrastructure that criss-cross nature reserves.
 
The Greater One-horned Rhinoceros numbered at least 1,000 in Chitwan until the 1950s, before the trans-migration of farmers from the mountains, the eradication of malaria and the clearing of forests. After this, the number plummeted to less than 100, and the government set aside the remaining prime rhino and tiger habitats along the Rapti, Narayani and Reu rivers as Royal Chitwan National Park in 1973.  

Over the years, the wildlife population in Nepal surged back, and a total of 645 rhinos were counted in the last census in 2015. Of these, at least 620 are now said to be in Chitwan National Park alone, with the rest scattered in Parsa, Bardia and Shuklaphanta reserves.  

https://www.nepalitimes.com/latest/india-returns-nepali-rhino-swept-away-by-flood/