| ||Exercise 2: Visualising and examining flooded areas in New Orleans caused by Hurricane Katrina|
LIDAR map of New Orleans flooding caused by Hurricane Katrina, 3 September 2005
The purpose of this exercise is to detect, visualise and examine the flooded areas of New Orleans.
New Orleans is located in southeastern Louisiana, straddling the Mississippi River at the point where it flows into the Gulf of Mexico, building the shape of a distinct delta. Lake Pontchartrain, which contains brackish water and occupies around 1800 square kilometres, is located in the north of the city.
Major parts of the city are below sea level, which makes New Orleans flood-prone. Only the 'French Quarter' - the original settlement - is situated on a little hill and escaped the August 2005 disaster. The loss of everglades and swamps, together with the fact that the area is shaped in the form of a bowl, contributed to the vast floods caused by Hurricane Katrina. The wetlands constituted a natural buffer zone, shielding Louisiana’s coast from the consequences of hurricanes.
In the course of its 300-year history, New Orleans was repeatedly devastated by hurricanes. However, the city has never been hit by a hurricane with the force of Katrina. The large dams along the Mississippi River were able to withstand the hurricane, but two smaller ones couldn't, and burst onto the channels. All efforts of closing these leaks were unsuccessful, leading to the brackish water of Lake Pontchartrain flooding the deeper city. Because of the power outage caused by the hurricane, it was impossible to pump water out for a long time.
In the data zipfile on the right you are provided with a satellite image showing the city flooded by Hurricane Katrina. The image was acquired on 30 August 2005 by the French Space Agency’s Earth Observation Satellite SPOT.
SPOT image note: As the image only contains the channels listed in the table below, LEOWorks 3 automatically creates an RGB view assigning channel 1 the colour red (R), channel 2 the colour green (G) and channel 3 the colour blue (B). What is created is a false colour combination (FCC) showing areas with high NIR reflectivity in red. You can examine the single channels by clicking on “Image/Split to.../ [Red Green Blue]” in order to retrieve the channels listed below.
|Spectral Band||Wavelength Range (nm)||RGB channels|
|Band 1||780 – 890 (NIR)||Red channel|
|Band 2||610 – 680 (Red)||Green channel|
|Band 3||500 – 590 (Green)||Blue channel|
Open the SPOT image using LEOWorks. The automatically generated RGB view is composed as written above.