LiDAR Applications for Sea Level Rise Mapping

JUN 6, 2016    by BENJAMIN IGNAC AND EMILY CAMPBELL

Parts of Key West’s famous Duval Street flooded during rainstorms. Photo: Rob O’Neal/Florida Trend Magazine

Have you ever wondered how we know what coastal sea rise is going to look like at the end of the century? Climate change and sea level rise are strongly connected and pose a threat especially for coastal cities and ecosystems, for example, including in the Florida Keys. The inhabitants of Key West are losing ground quickly and remote sensing can help us visualize what the future holds as the seas rise. Urban planners, policymakers and homeowners can then use that information to make more informed decisions about how to respond and prepare for rising seas.

Study area – City of Key West, FL. Created by Benjamin Ignac and Emily Campbell

A changing climate = a rising sea 

One of the most severe consequences of global warming is the rise in global sea levels. According to IPCCprojections, by 2100 the average global sea level could rise between 2 and 3 feet.  It is estimated that 5 million people in the US live in homes less than 4 feet above high tide. Homes at such low elevations are already at risk and that threat is only going to grow as sea levels rise, partly due to global warming.  Some of the effects of a global sea level rise include extensive coastal inundation, ecological damage, property damage, loss of coastal habitats, loss of economic and cultural resources, as well as more extreme weather events.   During extreme weather events such as hurricanes, coastal habitats are also at immediate risk due to higher storm-tide flooding. Projections and models for immediate and long-term threats such as climate change, sea level rise, and flood inundation assist legislators in making pragmatic decisions. The challenge is providing accurate, useful data to help inform these decisions. LiDAR is a new technique that shows a lot of promise in providing high quality information.

LiDAR (short for Light Detection And Ranging) was developed in the 1970s as a tool to measure distances and create highly accurate land surface maps.  A laser beam attached to a plane scans the surface below it, which allows researchers to then create a 3D model of the scanned area. For our project, we downloaded LiDAR data covering Key West, which amounts to a staggering 67,335,239 individual data points. We chose Key West, an island city at the west end of the Florida Keys, because of its proximity to the ocean and therefore its vulnerability to climate change and extreme weather events (Figure 1). A densely populated area of only 5.9 square miles, Key West is home to around 25,000 people. Its highest elevation is only 18 feet, but most buildings start as low as 3 feet above sea level. In 2005, Hurricane Wilma brought storm tides up to 8 feet above mean sea level, damaging more than half of the buildings on the island. Key West houses important naval military posts, an international airport, as well as cultural and historic sites and over 17,000 homes.

Flood Simulation Maps

The IPCC projects that by 2100 the average sea level will rise 1.97 feet in the best-case scenario and 3.2 feet in the worst-case. This means that Key West would lose between 8% and 20% or 0.5 and 1.2 square miles of its land surface. Hurricane flooding causes even worse damage. In the present day, a storm tide during a category 1 hurricane would flood 2.7 square miles of land, while a category 5 hurricane would flood 4.4 square miles. If we take into account the rising sea level by the end of the century, Key West may be almost entirely flooded during future hurricane events! Based on projections for 2100, Key West could lose 53% or 3.1 square miles of its land surface during a category 1 hurricane and 79% or 4.6 square miles of its land surface during a category 5 hurricane.

Video: The gloomy future of Key West is visualized in this video, which animates the rising sea level up to 25 feet on top of current sea level.

Our project helped visualize and calculate the extent of possible future flooding in Key West, through the use of LiDAR. Working with LiDAR was not only useful, but also exciting, which is how good research should feel, we think. Florida is only one of many coastal settlements that are at risk because of rising sea levels. To many people, the consequences of climate change often seem intangible and far away. It is hard to be alarmed about the consequences of climate change or other environmental disasters if there is not concrete proof or visual evidence. It looks like LiDAR and GIS can, in combination with climate projections, help us visualize threats like sea level rise and perhaps alert people of what might be to come. Hopefully our work and other efforts like it can help people plan accordingly and more effectively for the changes that are coming. 

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Benjamin Ignac is a Geography senior at the University of Oklahoma interested in the interaction between human and physical systems on Earth and the use of GIS and remote sensing in geographic research. ignac@ou.edu

Emily Campbell is an Environmental Sustainability senior at the University of Oklahoma interested in remote sensing applications and the natural environment. Emily.J.Campbell-1@ou.edu

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Sources

Climate Change 2013: The Physical Science Basis. (2014). Cambridge: Cambridge University Press.

Solomon, S. (2007). Climate change 2007: The physical science basis. Cambridge, UK: Published for the Intergovernmental Panel on Climate Change Cambridge University Press.

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