Week 9: Mapping the Station Fire in ArcGIS

Reference Map

Erosion Map

The largest wildfire in the Angeles National Forest, and 10^th largest in California since 1933, happened on August 26^th, 2009. The wildfire occurred at the Los Angeles River Ranger District/ Angeles National Forest and was later found to be caused by arson. This arson contributed to severely burning more than 160,000 acres of forest and burned over 250 square miles of the San Gabriel Mountains. Though many places/aspects can be affect by this large of a wildfire, I was especially interested in the extent of erosion. ArcMap was essential to be able to map which areas result in more erosion after a wildfire, so that they can be controlled.

 For this week’s lab, I wanted to incorporate post-fire erosion around the Angeles National Forest area, where there was a tremendous wildfire in 2009. My map shows the fire extent of the 2009 wildfire and the rankings of erosion according to the methods gathered from CALFIRE.  The color scheme on my map shows tons/acres/year soil loss and ranks it that way from high to low. The high values (in umber) show the highest levels of erosion which appear to be located throughout most of the fire extent but mostly in the southwest region of the extent boundary. I wanted to base my map on erosion because I think it is a significant issue with hillside wildfires.

 I chose this data because it incorporated aspects of the area that I did not have to. Gathered from the post-fire erosion methods pdf from CALFIRE, it incorporated levels of vegetation and levels of fuel in an area, so places with low vegetation cover and high fuel would be more prone to erosion. Therefore areas with high levels of vegetation and low fuel, as shown in South LA County, will obviously have lower erosion rates.  I think it’s important because wildfires burn vegetation and destroy the litter layer (organic material) of the soil. Plant roots at this level are essential to stabilize the soil in hillslope areas, such as the Angeles National Forest. It also takes rainfall intensity into account, because as soil gets exposed to rain, the silt ends up in streams and rivers, which can affect main ecosystems and fish. What this map does not cover, however are other factors that affect soil erosion such as percent cover, contributing area, slope, soil texture, aspect, and precipitation that could be developed to predict sediment yields.

 In my second map, I only showed the rivers of LA County, not including the streams but all of these water sources can be extremely affected by erosion, which can threaten ‘life, property and water quality and water ecosystems.” The high runoff and erosion rates in headwater areas deliver large amounts of sediment to downstream channels. I think it’s crucial to map this because not only does erosion after fires cause many problems for vegetation and soils in the areas but it can also affect diverse ecosystems from small fish in estuaries to large animals that rely on them for drinking water.

I think my few maps show where more erosion control is needed in the future to protect against erosion from wildfires causing silt deposits in the rivers that are located in high threat locations. I think this information could be helpful for people in this field to prevent large devastation from erosion. Types of soil and vegetation would be much more effective to use for this project, if it were available for comparison before and after the 2009 wildfire.

Works Cited

“All Station Fire Perimeters (as of September 2, 07:02) – Complete set.” 

           http://egis3.lacounty.gov/eGIS/.

Mark Greninger, 2 Sep. 2009. Web. 28 Nov. 2012.

“LA County Boundary.” http://egis3.lacounty.gov/dataportal/2011/01/20/l-a-county- b

            oundary/drp_county_boundary/, 20 Jan 2011. Web. 29 Nov. 2012. 

“Los Angeles County Highways.” http://gis.ats.ucla.edu//Mapshare. ESRI, 1 April 

          2008. Web. 2 Dec. 2012.

“Los Angeles County Rivers.” http://gis.ats.ucla.edu//Mapshare. ESRI, 1 April

           2008. Web. 29 Nov. 2012.

MacDonald, Lee, and Peter R. RobiChaud. "Post-fire Erosion and the Effectiveness

           of Emergency Rehabilitation Treatments over Time." Stream Notes. 1-6. 

          Web. 13 Dec. 2012.

Moench, R, and J Fusaro. "Soil Erosion Control After Wildfire." . Colorado State

          University Extension, n.d. Web. 4 Dec 2012. 

“Post-Fire Erosion.” http://frap.fire.ca.gov/assessment2010/data.html. California 

           Department of Forestry and Fire Protection, 2010. Web. 29 Nov. 2012.

Pietraszek, Joseph H.  Controls On Post-Fire Erosion at the Hillscope Scale,

          Colorado Front Range. Diss. Colorado State University, 2005. Print.

"Station Fire." Inciweb. Angeles National Forest, 10 2009. Web. 4 Dec 2012.