Trail per say, not really. I've always parked walked across the street, down the concrete inbankment across the creek over the island. Boom there you are. Not as bad as it sounds, watch for snakes. Good Luck!
If you park at the restrooms / camping area, walk towards the dam on the road; you will cross over the concrete drainage section that feeds down to the creek. From this section walk about another 125 to 150 feet or so(there are big rocks about 5 to 10 feet apart, count out 10 to 15 rocks), you will see a little clearing and a path on the left side..... it will take you down to the island at the beginning of the creek. Probably clear as mud, but hopefully this helps you out.