Fire Risk Map

In the previous chapter, we prepared the different layers needed, which we will need to create our final risk map. To do this, we will perform a Weighted Overlay Analysis. 

A Weighted Overlay Analysis lets us calculate the potential risk zones in our study area by giving all the factors scores. We are going to score every layer we made separately and then combine them using a formula to calculate our final risk map. You can give scores in multiple ways, but we are going to use a scoring from 0 to 10. You can think of it as 10 being 100% (high risk) and 0 being 0% (no risk). Depending on how important we think that certain factors are, like land cover types and the distance of a road, we can score them accordingly. For example, a shrubland has a higher fire risk than a mangrove forest. In the scoring you can give the tree cover an 8 and the mangrove forest a 1. In the table below, you can see what the scores mean:

Note: For added nuance, sub-criteria can be given an in-between score: 1, 3, 5, 7, 9.

So, before we calculate our final risk map, we need to score our data using the Reclassify tool. Here we can choose the values from the maps and give them scores based on what we think has a higher and lower fire risk. When doing the scoring, it’s important to do research about your study area. What can you find there? What factors are a potential fire risk? Knowing this, you can give them the most accurate scores possible. However, there is always a bit of guesswork involved. There is no universal rule for a score that something can get. You have to think about it carefully and explain why you chose the scores for the analysis. If you think a mangrove forest should get an 8 instead of a 1, explain why you think that is needed.

You should have 5 different layers:

• NDMI
• Slope
• Land Cover
• Roads
• Buildings