Can drones help risk engineers to better assess and model potential flood risks on construction sites? AGCS' risk consulting experts put the question to a simulated test in Angola.
Depending on topography, the flood risk of construction sites can change during excavation work. Large losses from recent years confirm that more frequent extreme weather events also help increase the exposure of large construction projects to flash flood, river flood or storm surge. In response to this loss experience, John Warton, Regional Manager Allianz Risk Consulting (ARC), at AGCS UK, proposed the idea to use drones to monitor the flood exposure of large construction sites. Together with Thomas Gellermann, Senior Risk Engineer, ARC Innovation Group, at AGCS, he looked into the feasibility and benefits of such drone-based topographic surveys.
Background
By coupling 3D topographical data with hydro-geological modeling software and rainfall simulation data it should be possible to assess water flow across a construction site or operational facility to determine how effective site drainage and flood defense plans are (including temporary drainage during construction and permanent facilities).
For a first test case, AGCS collaborated with Industrieanlagen-Betriebs-gesellschaft mbH (IABG), an engineering company with expertise in 3D modeling, analysis and flood simulation, to use existing drone data of an ARC site survey of a large hydropower construction project in Angola. The data was captured by FairFleet, a professional drone services provider.
Methodology
In this case, flow velocity was determined by gradient, water volume, shape of the river’s channel and friction caused by bed, rocks, and plants. Cofferdams, enclosures built within, or in pairs, across a river to allow the enclosed area to be pumped out, and/or diversion tunnels would be built to accommodate excess water flow safely. Beside the proof of concept, the simulation showed that the diversion tunnel and cofferdam would withstand the highest flood levels of a 50-year high water event. Thereby, the simulation confirmed the design criteria of the temporary structures of the construction phase.
In the case of modeling flash flood risks of construction sites, historical rainfall data is combined with information on terrain, geology and changes in land cover during the construction phase, to determine the likelihood of extreme flash flood events. Potential landslide risks, mostly caused by hydrological events, can be identified and monitored.
Results
The results showed that flood defense plans during the construction phase (such as site drainage) could be evaluated and, if needed, the customer could be supported to develop improvements. The impact of earthworks on actual flood risk can easily be rechecked by using current data from repeated drone flights. Such analysis could be requested by the customer as an additional risk control service.
“We were very pleased with the results of our simulation exercise on a
site that was not necessarily a flood-prone site,” says Gellermann. “The feasibility study now means that we are ready to take what we’ve learned into a real-world flood mitigation scenario soon.”
Drone data can help engineers model a project site in order to make a 3D simulation to measure potential flood risks. Source: ARC.
More information
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This article is part of the our Global Risk Dialogue. Appearing twice a year, Global Risk Dialogue is the Allianz Global Corporate & Specialty magazine with news and expert insights from the world of corporate risk.
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