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After conducting research, I was not able to find definitive information about a boat ramp specifically named "Riverside Boat Ramp" at the given latitude and longitude coordinates. However, there are several boat ramps located in the state of Virginia that could potentially fit this description.

Assuming that the Riverside Boat Ramp in question is located in Virginia, here is some general information about boat ramps in the state:

- Virginia has a wide variety of boat ramps located throughout the state, including ramps on rivers, lakes, and the Chesapeake Bay.
- Most boat ramps in Virginia are operated and maintained by local governments or state agencies such as the Virginia Department of Game and Inland Fisheries.
- Boat ramps in Virginia vary in size and design, but most are concrete or paved and have one or more launching lanes.
- The width of boat ramps in Virginia can vary, but most are at least 10-12 feet wide.
- The body of water that a boat ramp services can vary depending on its location. Some ramps may provide access to a specific river or lake, while others may be located on a larger body of water such as the Chesapeake Bay or Atlantic Ocean.
- The types of watercraft that are permitted on a particular body of water can vary based on local regulations and restrictions. In general, most boat ramps in Virginia are open to a variety of watercraft, including powerboats, sailboats, canoes, and kayaks.

In summary, without more specific information about the Riverside Boat Ramp in question, it is difficult to provide detailed information about its size, location, and permitted watercraft. However, the above information provides a general overview of boat ramps in Virginia and the types of watercraft that are typically permitted on state waters.