After conducting research, I was unable to find any reliable sources of information regarding a boat ramp called Lake Drain Road in Union Parish, Louisiana. It is possible that this boat ramp may be a local or private access point that is not widely known or documented.

However, there are several boat ramps located throughout Union Parish that provide access to various bodies of water, including Lake D'Arbonne, Lake Claiborne, and Bayou D'Arbonne. These boat ramps typically service a variety of watercraft, including fishing boats, pontoon boats, kayaks, and canoes.

If more information becomes available regarding the Lake Drain Road boat ramp, I would be happy to revisit this question and provide a more comprehensive answer.