Why aren't Tokyo's rivers used more for recreation?

Question

I never see anyone kayaking, etc. in the Edo or Tone rivers. Is there a reason for this? Wouldn't it be possible to go all the way from Gumma to Tokyo Bay by kayak?

Answer 1

http://www.jrec.or.jp/waterfront/
People in Tokyo are kayaking.

this guy go down the edo river to the tokyo bay by kayak.
http://cascadeloop.org/main/2005/10/09/212048.html

Answer 2

Why not in Tokyo? I think there are 2 reasons.

One is that all the rivers, lakes, and beaches in Japan are under tight control of the Ministry of Land, Infrastructure and Transport, or local prefectural government. Living on the boat is impossible in Japan (like the scene on the Thames river in London).
Two, historical reason. Rivers in Tokyo were historically used for commercial purpose mainly. And most part of down town, such as Shinagawa, Tokyo station, Chuoh-ku, Sumida-ku, were sea in Edo era, the rivers were rather "bays" then. And local merchants often changed the river flow with feudal lords for their right and interest.
http://www.mid-tokyo.com/18/aboutthis.html

Many regatta and yacht races are held on the rivers or bays in Tokyo and Saitama area. However, probably most personal recreation is required to get a permit from local river management office (and maybe it's impossible in Tokyo).
If you went to on the outskirts of Tokyo, such as Chichibu, Gunma, Tochigi, you can enjoy kayak, canoe and rafting (but probably some places ask you to pay some money to keep the environment). All are under control.
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oh I forgot to tell you something, going all the way from Gumma to Tokyo Bay is impossible. Because there are lots of dam between Gunnma and Tokyo. You will recall the water surface of Aarakawa river and Edogawa river are tranquil.

Answer 3

I'm afraid they are little bit dirty and therefore recreation there might have opposite effect. There are nice spots in some of the nearby prefectures, and people use them.