LiDAR – The First Line in Flood Defence?
Homes washed away, crops destroyed and the risk of airborne diseases; floods are one of the most common and devastating of natural disasters, costing an estimated £13.7bn in damage each year. According to the United Nations Office for Disaster Risk Reduction, an estimated 96.9 million people will be affected by flooding in 2016.
Most disasters cannot be predicted, yet new technology available is starting to help some of the most vulnerable countries to monitor environmental conditions which are often responsible for mass destruction and loss of life.
LiDAR (Light Detection And Ranging) systems were originally used to measure clouds and became more well-known following the use of a laser altimeter to map the surface of the moon during the Apollo 15 mission in 1971. Advances in LiDAR technology now allow rescue and research teams to map an at-risk or post-incident area within hours, without putting additional lives at risk. Detailed data can be gathered in 3D using mobile mapping devices which now allow for remote capture, allowing for fast deployment and giving operators the ability to map areas which have been rendered inaccessible. From planning routes for emergency vehicles after Hurricane Katrina to scanning the tsunami hit ports of Japan, LiDAR systems are now invaluable to us in times of trouble.
The recent floods in Louisiana devastated large parts of the state with around 7.1 trillion gallons of water falling during the storm. With 13 dead and over 110,000 home damaged, it is hard to imagine that things could have been worse. Louisiana’s LiDAR project began in 2000 in response to the high level of repeated flood-loss insurance claims across the state, as well as frequent oil spills caused by flooding. Given Louisiana’s low relief and remote wetland environment, LiDAR has been the ideal solution to monitor the state’s floodplains as it has allowed for access in to remote areas, including areas with dense vegetation which are impassable on foot.
When Hurricane Katrina hit New Orleans in August 2005, it exposed huge flaws in the construction of the city’s food defences. With nearly 2000 deaths and over a million people displaced, Louisiana’s flood protection systems and levees came under great scrutiny, with LiDAR maps from both before and after the disaster assisting in the creation of the Hurricane and Storm Damage Risk Reduction System (HSDRRS); a 133-mile perimeter system, incorporating flood walls, improved levees, pump stations and gated structures .
In the aftermath of the surge, emergency services used pre and post-event LiDAR images to route emergency vehicles around the city. This not only helped identify areas where people may be trapped but also enabled responders to reach locations such as hospitals, much faster.
Terrestrial and airborne laser scanning has continued to be invaluable to the state, enabling regular monitoring of the most at-risk areas, proving that the new flood defence measures are effective and helping to prevent another disaster on the scale of Katrina. In 2012 mobile mapping devices were used to conduct a field survey of the structural stability of the new levees, giving in-depth 3D images of selected sections. This practice continues.
Global Collaboration: Project NOAH
With a long history of flooding in the UK, the Environment Agency have been using lasers to map the British landscape for 18 years, assisting with the monitoring of flood plains and coastlines and helping to enhance flood modelling methods.
Following a series of devastating typhoons, the Philippian Government requested the Environment Agency’s help with Project NOAH, the National Operational Assessment of Hazards. According to the UN’s World Risk Report, the Philippines is the third most vulnerable to country to natural disasters. The EA helped to set up the DREAM-LiDAR project which would map 18 Major River Basins, covering approximately a third of the country, to enable the production of flood risk maps. 4 years on, with most of the basins mapped, government agencies have been able to relocate at risk communities as well better visualize emergency response and relief efforts needed when the floods inevitably come.
The images below show pre-LiDAR flood mapping methods compared with the detail now available within the NOAH flood hazard system.
After Hurricane Desmond hit Cumbria, the UK Government announced a £50m relief fund to help with temporary accommodation and clean-up operations. With estimated annual flood damage costs said to be around £1.1bn per year, even the £700m committed to the cause after the increase in Insurance Premium Tax leaves a significant hole in the accounts.
Getting funding for new technology is always a difficult task, especially in the public sector where budgets are tight and the benefits are not able to be accurately quantified prior to the spend. When we consider the amount of funds deployed after a severe flood surely it makes sense to fund preventative research?
Between 2006 and 2009, the state of Florida, assisted by the Florida Division of Emergency Management, instigated a LiDAR project to monitor areas affected by hurricane surge following the House Bill 7121 - Disaster Preparedness Response and Recovery which stated "The Legislature finds that hurricane evacuation planning is a critical task that must be completed in the most effective and efficient manner possible. Appropriated funds may be used to update current regional evacuation plans and shall incorporate current transportation networks, behavioural studies, and vulnerability studies. In addition, funds may be used to perform computer modelling analysis on the effects of storm-surge events." Paving the way for public funds to be used for LiDAR projects in the US.
Flood Plain Monitoring via LiDAR offers the opportunity to understand changes in coastal areas and waterways on a large scale, with the ability to spot fluctuations in danger areas quickly, enabling early warning procedures to be activated. In the cases of both Louisiana and the Philippines, monitoring also enables the fast mobilisation of emergency teams to flood-hit areas, saving lives and limiting damage.
Whatever we learn from these amazing advances in technology, it should be shared with developing countries and communities with limited infrastructure and skills, who are often most vulnerable to these catastrophic disasters.
Want Free LiDAR Data from the UK?
In December 2015, under an agreement with the Government, the UK’s Environment Agency made data, covering around 72% of the UK, open for all to use for free. This data covers over 95% of the UK’s coastline and 90% of its floodplains.