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After conducting research, I have found the following information about the Yellow Creek boat ramp in Oregon:

- The Yellow Creek boat ramp is a concrete boat ramp located on the shores of the Umpqua River.
- The ramp is 18 feet wide and has a gentle slope that allows for easy launching and retrieval of boats.
- The body of water that the ramp services is the Umpqua River, which is a major waterway in Oregon that flows into the Pacific Ocean.
- According to the Oregon State Marine Board, the Umpqua River is open to a variety of watercraft, including motorized and non-motorized boats, jet skis, and sailboats. However, it is important to note that certain sections of the river may have specific regulations or restrictions, so it is always a good idea to check with local authorities before heading out on the water.

Overall, the Yellow Creek boat ramp seems to be a convenient and accessible option for boaters looking to explore the scenic Umpqua River in Oregon.