Recreational / Hobbyist UAS pilot reported they were flying in an approved location. The UAS had a near miss with a low flying rotor wing aircraft which departed from an off airport location.

Narrative

Subject: Near Mid-Air Collision Between Unmanned Aircraft System and Manned HelicopterLocation: Over the Grand Lagoon; Bay County; FloridaInvolved Aircraft: Unmanned Aircraft System (Drone) and HelicopterI was operating an Unmanned Aircraft System (UAS or drone) over the Grand Lagoon area in Bay County; Florida; at an altitude of 400 feet; within the Visual Line of Sight (VLOS); adhering to FAA regulations. At approximately XA:00; I noticed a helicopter lifting off from a vacant lot across the water. Due to the tree line and the fact that the helicopter was located in a vacant lot shielded by several homes; it was not visible until it had risen above the trees. Upon noticing the helicopter; I immediately initiated a descent of the drone to yield the right of way and maintain a safe distance; in accordance with FAA regulations.During my drone's descent; it shared the same altitude with the helicopter at one point. The lateral distance between the drone and the helicopter at its closest point was approximately 1;200 feet; as verified by Automatic Dependent Surveillance-Broadcast (ADS-B) data; before the helicopter altered its flight path. I was actively trying to avoid a potential collision as soon as the helicopter came into view; and I safely descended and landed the drone. Though an actual collision was avoided; I am reporting this incident due to the potential safety risks posed in such situations. It demonstrates the need for enhanced awareness among UAS operators of possible low-altitude manned aircraft operations in residential areas; even in the absence of formal launch or landing pads.I recommend that further steps be taken to improve coordination and communication between UAS operators and operators of low-flying manned aircraft; especially in residential areas where obstacles may hinder the early detection of manned aircraft. Awareness campaigns targeting drone operators about the possible presence of low-altitude manned aircraft operations could also help mitigate such incidents in the future.In addition; technological solutions such as detection and avoidance systems for drones may provide additional safety measures in similar situations. I believe that data from incidents like this one; particularly when corroborated by ADS-B data; can help inform and improve such solutions. Thank you for your attention to this matter. I trust that this information will be useful in enhancing aviation safety.