Kathmandu is a fun place to hang out, kinda big city overwhelming but fun. There are some good day hikes to get you out of the city on days off (check out any of the National Parks around there) and also be sure to see Swyambu (Monkey temple), the oldest Buddist estupa in the world. While you are in town check out the local boaters pub. I am blanking on the name but will post it if I remember.
As far as boating goes some rivers should be at a pretty good flow right now (low ish water). The Trisuli is one of the closest big water rivers (class III-IV) with good day stretches and two-day streches. The Bhota-Kosi is another close river to Kathmandu (class III-IV/V) that is a more technical low volume river. The Seti is a nice option too if you want a more relaxed float. There are other options too such as the Karnali and Sun Kosi, great multi-day classics, but require a little more committment due to shuttle (24+ hours) and length of trip. If you want to swing it though they are both incredible class III-IV 4-7 day trips.
My advice would be to go to a company there in Kathmandu and see if you can hop on one of their trips they have going out on a river you are interested in. Unless you have your own boat, gear, time to figure out logistics, and people to boat with this is usually the easiest option (and fairly cheap too if you kayak). Go and see Kumar at Hotel 7 corner and tell him Jon sent you. He should be able to set you up with one of his trips or one of his cousin's (Bishnu's) trips. They would be good people to get on the water with.
If you are interested in finding out more about Nepals whitewater (there is a ton of class III-IV beautiful mulit-days possible with the right crew) the book Whitewater Nepal is a great option to check out. Go to the Pilgrims book store and check it out. It is out of print but I believe they should have it. There is a cafe in the back that you can buy a coffee at and sit down and read the book.
Have fun over there, Nepal is a great place. The real beauty of the country is out of Kathmandu so try and get out of the city as much as possible. Feel free to email me if you have any specific questions (firstname.lastname@example.org) and have a great time.
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