Lab 4: Station Fire Hazard Analysis

Write-up on process and challenges

First of all, we need to look for data for this lab. I downloaded the digital elevation model from the USGS seamless viewer website. I picked the area where the station fire boundaries and the surrounding areas were and downloaded the DEM. I downloaded the station fire perimeters from the Los Angeles County GIS Data Portal. I was a bit confused at first on what data I should use as they have surface fuel and surface fuel rank. I finally used the surface fuel data from the California Department of Forestry and Fire Protection to finish my map.

The first map I created was the Slope Hazard map. First, I changed the projection of the DEM data to the NAD Projection UTM Zone 11. Then I got an accurate slope map. I followed the tutorial and then reclassify the slope value into NFPA hazard points. This is the first reclassification in this lab. The result image was then overlay with the hill shaded image to get a better visual appearance.

Second, we need to create and reclassify the surface fuel model data. When I opened the surface fuel data, there are about 13 classes of vegetation and they were all assigned with the numbers. I had to go back to the FRAP website to check on the definition of each and add on some descriptions beside those numbers. Then I reclassified the 13 vegetation classes into Non-Fuel, Light, Medium, Heavy and Slash, five different classes. And then I assigned these five classes into the NFPA hazard points as demonstrated in the tutorial.

The last map is the product and purpose of this lab. We need to use the raster calculator to “combine” both reclassified slope and surface fuel data into one map. After having both slope and surface fuel layer activated, we need to enter the formula into the raster calculator. This is the most important part of the lab because it will reclassify the data into a slope/surface fuel map. After summing both classified data, slope/fuel hazard can be assessed. The slope/surface map can be a useful tool in reality such as the safest locations to build residences can be determined, past fire extents can be assessed and fire suppression opportunities can also be explored.

I had a big challenge in doing this lab because I changed all the data projections to NAD 1983 UTM Zone 11. When I reclassified the surface fuel to NFPA hazard points, the image became blurry and could not be used for further investigation or analysis.  I had to re-download the data and do it again. One of the things I learned about in this lab is that I would only change the projection to do the slope map because of the projection would affect the calculations of the slope. The other challenges will be reclassification. Since the reclassification result really base on what I want to reclassify or what I want to group, it’s important to know different types of vegetations and their ability to catch fire. This is so important because the hazard map is completely based on a personal reclassification. Overall, I like using the raster calculator to combine the data and create a new map. This could be really useful to produce a map with two types of related data in GIS.