A new generation of specialised drones is enabling flood defences along the Thames Estuary to be monitored in much greater detail and at lower cost, it has been revealed.
Speaking at New Civil Engineer’s Flood Management Forum, Thames Estuary Management 2100 (TEAM2100) programme manager Darren Milsom said that this year’s trials of submersible and confined space drones has shown that a revolution in data collection was now on-going.
“We’ve used conventional aerial drones before, to carry out lidar surveys, and continue to do so, especially on the outer estuary,” Milsom said. “They’re much more sustainable than lidar from an aircraft, and more accurate as well.
“They do have their limitations, so the introduction of submersible and confined space drones is a major step forward.”
An integrated delivery team made up of the Environment Agency, Milsom’s employer Jacobs, Balfour Beatty and others, is delivering the TEAM2100 programme. It covers the first 10 years of management of the 4,000+ assets that make up the estuary’s tidal flood defences, including the Thames Barrier and 350km of walls and embankments.
Milsom said that the team was working with drone operator Geocurve to refine the details of the confined space drones. “The nature of our work demands that such drones be fully waterproof, which the prototype wasn’t.
“Development work continues. The submersible drones work well in controlled locations, but they still need further investigation to confirm their usefulness in the estuary.”
He pointed out that the accuracy of data captured by drones was still below that of traditional topological surveying techniques. “However, the drones can flag up inconsistencies, such as low points along an embankment.
“We can then check these out with a conventional topological survey. What the drones offer, however, is the collection of lots of data quickly and at relatively low cost.”
Upstream of Tilbury Fort, a well-preserved 17th Century artillery bastion on the north bank of the Thames, another new tool is being deployed to monitor the hard flood defences and the foreshore. The portable Leica Pegasus lidar equipment can be deployed from a boat on the river or carried as a backpack.
“This means we are much less affected by the tides on the river,” Milsom pointed out. “We can run surveys at low tide, collect all the data, and use it in the office when convenient.
TEAM2100 service manager for the Environment Agency Ed Uden added: “It doesn’t completely remove the need to go out on site, but it allows us to target critical areas. Some assets are very difficult to access, some are even dangerous, and the Pegasus is very useful in such cases. It eliminates significant health and safety risks when compared to visual inspections on foot.”
One of TEAM2100’s main areas of concern is changes in the Thames foreshore. Pegasus makes monitoring the foreshore much more efficient, Milsom stated. It can flag up areas where there is significant lowering, posing the risk of undermining to adjacent hard defences. “This means we are able to intervene earlier,” he added.
Machine learning could in the future analyse the masses of data collected by Pegasus and the drones, Milsom said. “We believe that the data from quarterly Pegasus surveys could flag up hard defence movements of as little as 20mm over three months, anywhere across the estuary.
“This targeting of vulnerable structures before they deteriorate badly is one of the great benefits of the new technology.”
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