This was a very difficult lab due to the freedom that we were allowed. For this reason I have chosen to further explore, using GIS, the article, Where Land Slides, Trying to Learn Why, that was part of last week's reading. The article dealt with landslides and how the threat of landslides is increased after a fire has passed a region.
According to www.dictionary .com, a landslide is defined as, "The rapid downward sliding of a mass of earth and rock. Landslides usually move over a confined area. Many kinds of events can trigger a landslide, such as the oversteepening of slopes by erosion associated with rivers, glaciers, or ocean waves; heavy snowmelt which saturates soil and rock; or earthquakes that lead to the failure of weak slopes." Knowing that the slope of a region increases the possibility of landslides makes it easier to decide the manner in which to display the information on ArcGIS. We can download the topographic data from the USGS web site. Once this information is acquired, a slope map of the region that was affected can be made. As is displayed below:
This map shows the areas that have steep slopes along with a one-Mile buffer around all the burnt areas.
The article also stated that weather was a big factor in the development of landslides. "Rainfall is the key parameter for all this, so we’re always measuring rain" (Fountaine, 2). The slope's information coupled with the location of the burnt areas will help researchers share the data with other agencies, such as the "National Weather Service, which uses it and information from a network of other rain gauges to decide whether to issue local alerts about potential mudslides" (Fountaine, 2) In the thematic map that I provided, Los Angeles tracts that are at risk of landslides are highlighted in blue. Doing this makes it easier for researchers to choose appropriate locations for their equipment in order to maximize resources. This is essential when conducting first-hand research. As the article states, "We understand the process through which these landslides occur incredibly poorly" (Fountaine, 1), and acquiring useful and accurate data is essential in order to learn about landslides.
Understanding landslides and the factors that trigger them is important in order to be able to predict or anticipate the location of future landslides in order to save lives. Although the soil content of the region in question is important, all landslides have a common factor, water. The more saturated soil becomes, the more it acts as a liquid. At the point of full capacity, landslides take effect. This was the case of the La Conchita landslide in Ventura County, 1995. "The extraordinary rainfall of January 1995 probably was the principal contributing factor to the elevated ground–water levels and, hence the landslide movement." This is why it is important for agencies to be able to share information.
Using the map that I generated, local police departments can use this map in order to help them save lives. It can be seen clearly on the map, tracts that are within one mile of the burn area. One mile was used as the buffer since the La Conchita landslide traveled approximately 1,150 ft. Additionally, it can be seen that the Southern region of the burn area, has more steep hills than the North. By acknowledging this observation, emergency officials can distribute their personnel most efficiently.
References:
http://pubs.usgs.gov/of/2005/1067/508of05-1067.html
Fountaine, Henry. "Where Land Slides, Trying to Learn Why ". The New York Times. 05/25/2010 <http://www.nytimes.com/2009/10/20/science/20mud.html?_r=3>.
"landslide." The American Heritage® Science Dictionary. Houghton Mifflin Company. 25 May. 2010. <Dictionary.com http://dictionary.reference.com/browse/landslide>.
Jibson, Randall. "Landslide Hazards at La Conchita, California". USGS. 5/25/2010 <http://pubs.usgs.gov/of/2005/1067/508of05-1067.html>.
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