GIS 4048 Module 2: Natural Hazards - Lahars

Figure 1: Lahar hazard assessment surrounding Mt. Hood, Oregon.

Having been away from GIS coursework for a few months, the first assignment of Applications in GIS was a welcome return to learning new GIS tools and skills. Specifically, this module focuses on the manipulation of raster data with a focus on tools used for hydrology as well as tools to perform mathematical functions on raster data. The purpose of using these tools was to produce a map depicting potential hazardous areas that would arise from lahars triggered by an eruption of Oregon's Mt. Hood.

Lahars are mixtures of material, generally mud and rock combined with water and volcanic material, that flow down the slopes of a volcano into surrounding valleys. The above map uses digital elevation model (DEM) data to predict the areas most likely to be affected by lahars originating at Mt. Hood. We proceeded through multiple steps to arrive at the final data product. First, two DEMs were mosaicked into one, then the Fill tool was used to "smooth" the raster data to diminish the potential for errors in the data affecting the subsequent analysis. The output of the Fill tool was the input for the Flow Direction tool, the result of which was a colorful raster wherein cells were categorized based on the direction water would flow over the surface. This output, in turn, was used with the Flow Accumulation tool. The output raster shows streams and rivers based on the previous calculations. The Int, Con, and Stream to Feature tools were then used, resulting in a line vector shapefile. The final step of the assignment was to create a buffer of 0.5 miles around this shapefile to catch the schools, cities and overall population (as represented by census block groups) that would most likely be at risk from lahars from Mt. Hood.

Although I do not know how often I will utilize the hydrology tools in my career, I am glad to have been introduced to them should the need arise.