Based on the latest information available, the boat ramp named Boulder Flat is located in the state of Oregon at a latitude of 43.30403519 and a longitude of -122.52629852. This boat ramp provides access to the Umpqua River, which is a popular destination for boaters and fishermen.

The Boulder Flat boat ramp is a concrete ramp with a width of approximately 20 feet, making it suitable for launching a wide variety of watercraft. It also has a gravel parking area adjacent to the ramp that can accommodate up to 20 vehicles and boat trailers.

According to the Oregon Department of Fish and Wildlife, the Umpqua River supports a wide variety of fish species, including salmon, steelhead, sturgeon, and numerous varieties of trout. As such, the Boulder Flat boat ramp is a popular destination for anglers looking to access the river's abundant fishing opportunities.

In terms of watercraft, the Boulder Flat boat ramp is suitable for launching a wide variety of boats, including kayaks, canoes, fishing boats, and larger vessels. However, it is important to note that certain regulations regarding boating and fishing may apply, and it is always best to consult with local authorities or reference the latest regulations to ensure compliance.