Using Drones for River Restoration – Revive the Allan

Drones give a different perspective on a landscape at a relatively cheap price compared to more costly aerial surveys using planes and satellites. Nowadays, drones cost anywhere from a few hundred pounds to a few thousand depending on the make and model you buy. Ultimately though their capabilities are limited but still provide benefit to projects which work across a small section of a catchment.

The main limiting factors are battery length, distance and height the drone can fly. Legally we can only fly 400ft off the ground and a maximum 500m away from the operator unless visibility is reduced. The drone must remain in sight and control at all times. These limiting factors are vital safety features as the sky is a busy place. The camera attached to the drone can also be a limiting factor as the higher you go the less detail you may get within a photo depending on the camera capabilities.

With the above in mind, this means surveying a full catchment by drone is infeasible but surveying a stretch of river is more realistic hence why we are using the drone as part of the Revive the Allan project.

We have been working to map out a stretch of the upper Allan Water which is covered under the Revive the Allan project using the drone to help inform decision making but also monitor before and after changes as the project progresses. Combining the drone with specialist apps and software, an area can be mapped out and uploaded to the drone where it then calculates the most efficient route to fly to start mapping out the project area. As it fly’s the route, the drone takes photos at set intervals so that enough images can be collected and stitched together to allow a visual map of the area.

Using specialist software back at the office, we can stitch the images together to create one large image but also create Digital Elevation Models used to understand the terrain of the area mapped. This model also tends to show up features hidden by vegetation such as old river channels or embankments.

These hidden features are useful to identify as they may show where the river originally flowed before straightening or highlight other features which are useful to know about when deciding how to improve rivers for wildlife.

So far we are halfway through mapping the area we plan to carry out improvement works. Weather is a big factor in how quickly we can progress as if it is too windy or wet, the drone cannot be flown.

We are excited to use this new technology to help develop and deliver this project and it is something we plan to continue using going forward for other projects.