Part 107 UAS pilot reported an NMAC with a helicopter while operating with clearance near a towered airport.

Narrative

This is the information about the flight as submitted on the airspace authorization and forwarded to Airport Director/Tower Manager:A radius of 1 NM about the following coordinates at or below 400 ft. AGL: Latitude XX; Longitude YY. The Aviation Division has been tasked by the State's commission to collect video and photographs of the selected site. The Airport Director; Person A; has agreed to operations at or below 400 ft. AGL in the proximity of the above location. The requested five day window is Day 0 - Day 4. This window is to allow for optimal weather. The authorization system rejected submittal for multiple days. The following error appeared in the form: 'Date of Operation must be a single day for a LAANC enabled airport.' Operations will be conducted in the presence of the Airport Director and in coordination with the ATC Director. In order to maintain an appropriate level of safety; the remote pilot in command (RPIC) holds both a remote pilot certificate and a private pilot certificate. Two or more visual observers (VO) will be utilized to increase situational awareness and safety of operation. The operation will be conducted during visual meteorological conditions (VMC). The RPIC will give way to all manned aircraft. The operation will occur one day within the five day window and will last approximately three hours beginning at approximately XA:00 CDT.The incident occurred in Area C; a 0.2 NM circle centered on Latitude ZZ ; Longitude AA as depicted on FAA Authorization XXXX-XXX-XXXX ZZZ Airport. As required by the authorization I notified tower by phone call that I would be taking off in ten minutes at Area C and that the flight would last 10-15 minutes. I activated the custom DJI Flysafe zone and was operating for about 10 minutes when tower cleared a helicopter to take off from taxiway A with the instructions to remain east of the field. My VO informed me to land the drone when the helicopter pointed directly east. I deconflicted by descending and maneuvering southwards towards the home point and when the drone had descended to about 300 ft. AGL the helicopter banked sharply left to deconflict. I landed the drone after the encounter. The helicopter informed the tower afterwards that a drone was operating to the east of the field. It is of my opinion that the tower should have advised the helicopter that a UAS was operating prior to giving instructions to transit the authorized area in which I was operating. When we moved to Area A north of the field; the tower began advising pilots as he should have done prior to our incident in Area C. Also; I should have landed the drone more quickly rather than wait to make visual contact with the helicopter. I had immediately questioned the tower's reasoning behind clearing the helicopter without advising of our operation; however I expected that the helicopter to maintain a south heading east of the field and then transition to an east flight path as opposed to his immediate transition to an east flight path; and therefore did not land immediately.