Thursday, May 28, 2015

Natural Hazards: Lahars and Module 2

It has started again. I can feel my pulse trying to jump out of my body. I have not had so much excitement in a while. Module 2 for GIS Applications was an exercise in learning about Natural Disasters, such as Meteor strikes, Hurricanes, Floods, and, my map of the day: Lahars. The lab consisted of using several new tools including:

-  Hydrology toolset.
-  Mosaic to New Raster (Data Management)
-  Fill tool
-  Flow Direction
-  Flow Accumulation
-  Conditional Evaluation of Rasters
-  Raster to Feature
-  Using Raster Math >  Math > Int
- And using  Spatial Analyst Toolbox > Hydrology > Stream to Feature

The objective was to determine where Lahars or streams would flow in the event that Mt Hood erupted. "Lahars, or volcanic debris flows, are water-saturated mixtures of soil and rock fragments that can travel very long distances (over 60 miles) and as fast as 50 miles per hour in steep channels close to a volcano." (Oregon Geology Fact Sheet)

I also had to take two DEMs and combine them to make one mosaic to then compute the flow by changing the cells to integers from floating points. I used the Spatial Analyst Toolbox and executed the Math > Int tool. This converted the floating point raster to an integer raster-- this was way cool!
After this step I could use other tools such as the Con Tool to control the output value for each cell. Ultimately, I wanted to arrive where I could determine the flow or streams the Lahars would follow and what schools, cities and the amount of population that would be at risk. The below map shows that, in the event that Mt Hood erupts, a number of schools and cities would be in danger. Also a large population, 58, 260 people, would also be in the path or near enough the Lahars to be at risk.

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