How to respond to a hurricane: Using GIS to get a grasp on Hurricane Katrina

Hurricane Katrina was a big deal.  It brought a lot of attention to natural disasters, throughout the news.  My dad’s first book strictly on climate change was published a year later in 2006, in which he discusses the relationship between climate change and natural disasters.  He has been writing articles on this topic ever since.  I was in elementary school at the time, and this storm is part of what sparked my interest in environmentalism.  I remember for my birthday, which was in late September shortly after the hurricane, I asked friends that attended my party to bring money to donate for relief efforts for the storm instead of presents.  It has been around 14 years since the event and people still talk about Hurricane Katrina.

Hurricane Katrina sparked a concern for Americans, because we realized the damage these types of storms can cause to populations if they are not prepared.  And yet, we have since 2005 had numerous other hurricanes in different parts of America seriously disrupt and damage individual people and families, as well as city infrastructure.  The truth is, not every city was built to sustain such weather.  We saw this in New York, where hurricanes do not usually reach such high latitude during Hurricane Sandy.  And the fact is, as our global average temperature is warming, we are experiencing hurricanes that are more intense.  Therefore, regions that are known to experience hurricanes, may still not be prepared for hurricanes at this level of intensity. When this is the case, we need to know how to respond to these events.  A large part of this is knowing what is occurring spatially during these events, such as what areas would be the most flooded, and what areas to prioritize in terms of allocating response resources.  This is where GIS comes in.

For this lab I investigated the issue of hurricane response with, as might have been guessed, Hurricane Katrina.  A GIS professional would be creating this information for the use of government officials and aid responders.  The first important information that would need to be understood is what the layout of the land where Katrina hit looks like.  This includes elevation, water bodies, counties, cities and any islands.  Figure 1 displays this information, showing that their are three counties in the area most effected by the storm, along the gulf coast in Mississippi.  You also see there are significantly more cities near the coast which is more likely to be flooded in a storm, and six islands.  Fig. 2 is a true color composite map of the area, and shows what land would actually look like from an aerial view using satellite imagery.  The discoloration near shore shows more urbanized areas, which checks out with the city locations in Fig. 1.  Going back to Fig. 1, There is higher elevation farther inland, with veins of lower elevation pulsing through the land, indicating the land is hilly, not flat.  You also see there is significant marsh/swamp land along the coast that veins inland.

Fig. 1: Map of Gulf Coast Counties, Elevation and Water.

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Fig. 2: True Color Composite Map

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There are numerous wavelengths humans cannot see such as heat, which is why I then created a false color composite satellite imagery map shown in Fig. 3.  This way we can see the amount of infrared radiation from different parts of the region.  For this map I made infrared displayed as red, which means the land is emitting the most infrared.

Figure 3: False Color Composite Map with Infrared shown as Red

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Now government officials and responders would understand the general layout of the land.  The next piece of important information is the path of the hurricane, as well as the wind speed and air pressure over time.  Figure 4 shows a map of Hurricane Katrina’s path, as well as graphs of its wind speed and pressure over time.  The map shows that Katrina once near land first was traveling west, and once on land was traveling north east.  The graphs show pressure and wind speed as inversely related.  As one increases, the other decreases.  Pressure increases near/on land and wind speed starts to decrease.

Fig. 4:  Hurricane Katrina Path, Wind Speed and Pressure over Time

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The next question, and the first big question in assessing damage is where and what was flooded.  Figure 5 shows both what land was flooded and what land types were flooded.  All of the waters were completely flooded during this storm, and as expected, the areas closest to the coast were flooded most.  This means that the majority of the cities in these three counties, and the more urban areas were flooded.  Figure 5 also shows that Wetlands were the most flooded land type, which can be expected considering they are aquatic ecosystems.  Using color composite satellite imagery I created the map in fig. 6.  For this map I let ArcGIS calculate an estimate of the different land types.  You can see this estimate generally checks out, with the main exception that significantly ore agricultural/barren area is shown.  The main finding from both maps though is that there is a significant amount of Wetland, which is the most important aspect of these maps to agree on.

Fig. 5:  Map of Land Types and Flooded Land

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Figure 6: Land Type Estimate using Color Composite Satellite Imagery

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Figure 7 then shows what percent of each land type was flooded in both a graph and a map.  This map and graph project the same information as the map in figure 5, which is that wetlands were significantly more flooded than any other land type at about 55%.  Developed land comes in second, also as predicted by the previous maps.  Agricultural areas and barren land are the least flooded, which makes sense considering these land types would be in the more rural areas farther inland.

Figure 7: Percent Flooded Land

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The final crucial piece of information in terms of prioritizing aid and resource allocation in response to Hurricane Katrina, is what infrastructure would be damaged.  Figure 8 shows a map of infrastructure in the Mississippi coastal area, including roads, churches and hospitals, as well as displaying what areas were flooded in light blue.  Churches can be used as a useful indicator of where the highest populations are, and fig. 8 shows multiple flooded areas with a high density of churches, where instead of individual church symbols an area becomes a blob of purple.  Large highways such as 90, 10 also would be flooded from the storm.  This is important in terms of what roads need to be closed, as well as limitations in transporting resources to the affected areas.  All of the hospitals are located in flooded areas, and this would be the first place to prioritize resources.  To start, hurricane damage could cause an influx of  people who need medical care, but hospitals also have some of the most vulnerable populations, who may require electricity for life support, or be unable to move themselves for evacuation.  These are people who need immediate care and attention.

Figure 8: Map of Infrastructure

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