The Arun is respected as one of the most mighty and powerful rivers of Nepal.
The lower valley is in parts quite well populated with a wide variety of different tribes. The whole area is relatively un-spoilt, and sees only a few trekking groups, mainly taking the Eastern approach to Everest and Makalu Base Camp.
We schedule rafting trips on the Arun every year. Tumlingtar is the obvious and most convenient starting point and we recommends that you fly here as it is only a short direct flight from Kathmandu and only forty minute’s walk from the river. The 70 km down to Chatra has been kayaked in a day, but normally makes a relaxed 3 day raft trip and you can then fly back to Kathmandu from Biratnagar. 

Highlights    
From : Tumlingtar Alt. 290 m 
To : Chatra Alt. 115 m 
Distance : 70 kms 
River days : 3 days 
From Katmandu : 1 days 
Difficulty in November : Class 4- 
Average gradient : 0.25 % (12 ft a mile) 
Est. max. gradient :0.4 % 
Volume in November :215 cumecs 
Best season : Nov > April