When most people hear the phrase "L.A. River" they also expect to here the words "dead body". It has a horrible reputation for being a cement pit better suited for teen drag races (Go Grease Lightning) than for a white water kayak destination. That's because you haven't been to the Glendale Narrows recently.
This stretch of the LA River is natural-bottomed and a great place to see wildlife, go fishing and go kayaking. You can bring your own kayak or rent one from one of the tour guides along the banks. The recreation areas of the L.A. River open this Memorial Day and are open from sunrise to sunset seven days a week. If you are lucky you may see a deer, egret, beaver or an unlucky kayaker flipped upside down in her kayak (me).
The L.A. river is expanding the number of recreation zones and adding constant improvements to make the river more of a destination for people and wildlife. You can visit this website for more information on L.A. River rec locations. Check it out at least once each summer to see how the river transforms from concrete into natural beauty.
There is a great group of LA River enthusiasts who organize fun events, schedule kayak trips, and improve the river. You can find out more by visiting their website here - Friends of the LA River.
I challenge you this summer to go see the natural places in your own city. Checkout these kayak tours where you can rent a kayak or take a guided kayak tour.