There are previous threads that discussed this. Search "Davis Levee Clean up" or something. If you are concerned I would read them. I would advise anyone who asks not to do it. There are a number of reasons why that you can read about in the previous thread I mentioned.
My own personal top three reasons for not doing so are as follows:
1.) The land beyond the canal is a wetland wildlife refuge.
2.) The water in the canal is part of an environmentally protected watershed.
3.) Last summer I watched a Sheriff's helicopter show up when people were shooting there, and proceed to chase them east and then northbound on the freeway towards Natomas. Never heard about the outcome.
It just does not seem to be worth the risk of all the hassle and/or charges they could justifiably or not throw at you.
On a side note, that area may be getting increased attention in the press during the next election. The watershed rights are in dispute yet again as someone tries to sell the water to So-Cal. It might make the local ballot as an initiative.
I don't know how political I am, I don't get into all that crap....I just love freedom...