[Cementjungle]

They’ve been doing this for a few years actually:

http://www.cnn.com/2011/US/08/20/california.la.river/index.html?_s=PM:US

http://www.time.com/time/nation/article/0,8599,2092587,00.html

http://lariverexpeditions.com/

[sheana]

Looks more like run off.