Case study //

Happisburgh Intertidal, Beach & Cliff Erosion Monitoring

Category: Survey & Mapping

Client: Vattenfall – Norfolk Offshore Wind Zone (NOWZ)

Date: January 2021 to November 2021

Summary: Quarterly drone surveys of 1.5km of the North Norfolk coastline between Happisburgh beach car park and Cart Gap. The surveys used photogrammetry techniques to provide reliable height data for use by the project design team to assess beach levels and coastal erosion rates at the export cable landfall site for the Norfolk Offshore Wind Zone projects: Vanguard West, Vanguard East and Boreas.

The eroding coastline between Happisburgh and Cart Gap experiences constantly changing beach levels and cliff profiles. Vattenfall required high quality surveyed level data of the intertidal zone, beach and cliffs to help assess the rate of erosion over a 12 month period to assist in cable landfall design decisions.

Data needed to be captured over a wide area and as close as possible to low spring tide, meaning that traditional survey techniques were not suitable in the short window of time available either side of low tide. HexCam proposed the use of RTK-equipped drones and accurately surveyed temporary Ground Control Points (GCPs) to quickly and unobtrusively capture accurate level data.

Our DJI Phantom 4 RTK and, subsequently, our DJI M300 RTK drone were used to capture imagery at a resolution required to produce an accurate 3D point cloud using photogrammetry processing techniques.

As the project progressed we moved to the new M300 drone allowing us to use 2 Remote Pilots and our ‘hand over take over’ method of operation. This, together with DJI’s ‘P1’ high resolution sensor, allowed us to fly higher and faster. The M300’s extended battery endurance, and the ability to ‘hot-swap’ batteries, dramatically reduced the time the drone needed to be on the ground and eliminated the need to relocate Take-Off and Landing Sites (TOLS) during the survey. By using our new survey equipment in the most efficient way possible, we were able to reduce our data capture time from an initial 2 hours and 30 minutes to just 30 minutes for the final survey.

By constantly innovating, investing in new equipment and developing new flight techniques and permissions, we managed to drastically reduce data capture time. With fewer take-offs and landings, risks to the public were reduced and disturbance was minimised.

The HexCam team have shown the utmost in professionalism, capability and responsiveness; providing the services in a safe and controlled manner with detailed risk assessments and method statements, complimented by proactive communication regarding the works both in the pre-mobilisation and on site phases

Andy Hardcastle

EPC Director (Transmission) Vattenfall Norfolk Offshore Wind Zone, Vattenfall