Lab 7: Mapping the Station Fire in ArcGIS

Wildfires, though a natural part of the ecosystem, can cause a variety of problems in graded urban areas. Landslides, debris flow, and flooding are just a few negative events that can result from wildfires that have burned over sloping terrain. Land, mud, or debris flow have a higher potential depending on the gradient of the slope, make-up of the soil, and water saturation. With increased slope gradient and water saturation, soil make-up is less of a factor in slides due to the overwhelming gravitational forces. Though these factors are commonly understood, wildfires effects on slides can be counter intuitive.

The problem with wildfires is when ,as mentioned by US Forest Service, the "intense heat... can cause the soil to 'seal' itself and water will not easily penetrate it." This act of sealing the soil causes the rain runoff to flow directly into creeks and watersheds without the normal absorption from soil and plant life. This additional water acts as a massive storm for the soil and plant life below the burn zones. This additional water can over saturate the soil below and cause land, mud, or debris flows.

This diagram from the Council of Geoscience shows some of the contrast between soil types, saturation levels, and speed of soil movement. The added water flow from the lack of absorption within burn areas can cause the levels of saturation to quickly increase for soils below the burn zones, regardless of the strength of the storm. Though according to the USGS's report on Post-Fire Debris Flow Hazards, the stronger and shorter duration storms have the potential to do the most harm. In order to better monitor the saturation levels in the soil along these target locations of the Angeles National Forest, the USGS has embedded water saturation sensors in the soil. These sensors upload information about the change in saturation in order to be aware of rapidly changing situations.

I have attempted to address these target locations with my GIS maps. The first map indicates the complete burn area of the Station Fire as of September 2nd, 2009. I have complimented this data with a DEM, Digital Elevation Model, of the area as well as county names and boundaries to better orient the data. The second map illustrates the significant relationship between rainfall intensity and elevation. As stated, the importance between these two factors is clear and the overlay analysis can emphasize the target areas. The rainfall data is a compilation of 24 hour periods over a series of 50 yrs. This information becomes an averaged value of rainfall over the 50 year period, indicating a trend of heavier rainfall intensity at higher altitude. This trend is evidence for orographic lifting caused by the increase of moist air in reference to the mountains increase in altitude. An indicator on the map of this trend would be the areas of higher elevation receiving the highest rainfall intensity.

My third map, Slope Map, stands to serve as an indicator of extreme slope that could result in added gravitation force on the saturated soil. As mentioned, the gravitational forces caused by steep slopes can also contribute greatly to slides. In conjunction, these two maps can offer a very insightful view into potential land, mud, or debris flow locations.


Los Angeles County. "GIS Data." Los Angeles County Enterprise GIS. WordPress. 22 November 2009. <http://gis.lacounty.gov/eGIS/?page_id=117>.

U.S. Forest Service. "Post Fire Watershed Rehabilitation Activities." Inci Web - Incident Information System. 26 September 2009. U.S. Forest Service. 22 November 2009. < http://www.inciweb.org/incident/article/9512/ >.

Council for Geoscience. "Landslides and Slope Instability." Council for Geoscience. 14 March 2009. The Collective Advisory (TCA). 22 November 2009. <http://www.geoscience.org.za/index.php?option=com_content&task=view&id=996&Itemid=434&limit=1&limitstart=4>.

USGS. "Emergency Assessment of Postfire Debris-Flow Hazards for the 2009 Station Fire, San Gabriel Mountains, Southern California." 2009. 11 November 2009. <http://www.thecvcouncil.com/sitebuildercontent/sitebuilderfiles/USGS_report.pdf>.

USGS. "2009 Station Fire, Dunsmore Canyon, Glendale California." USGS - Science for changing the world. 13 October 2009. U.S. Department of the Interior. 11 November 2009. <http://landslides.usgs.gov/monitoring/dunsmore/>.

Lab 6: DEMs in ArcGIS

Shaded relief model (color-ramped DEM) layered
over the hillshade model of the Locaiton


Slope Map of Location


Aspect Map of Location


3D Image of Location


My selection area can be found in the Wasatch Mountains within north-eastern Utah. The dramatic changes in elevation drew me to this location. My goal was to locate an area that had peaks near areas of significantly lower altitude flats. This is well demonstrated in the 3D model of the area selected. The relevant metadata has been provided below.


NED_97153813

Datum: D_North_American_1983

Extent

* Top = 40.6441666662
* Left = -111.774999999
* Right = -111.251944444
* Bottom = 40.4241666662

Spatial Reference = GCS_North_American_1983

Lab 5: Projections in ArcGIS

Conformal Map Projections


Equal Area Map Projections


Equidistant Map Projections


The process of accurately transforming the spherical shape to flat surface, while preserving shape, size, distance, and area, has baffled cartographers and mathematicians a like for centuries. Since it is not possible to perfectly transform all points on a sphere to a flat surface while preserving all aspects of the image, various methods have been developed to accurately preserve characteristics of the sphere. These methods are called Map projections. These projections, named projections because early forms were created by projecting light from the inside of a sphere, are tools to create accurate flat maps based on the spherical earth. Since carrying a globe, or globes for that matter, around with you is not an option, projections have been the key in creating accurate flat maps. Projections are only able to preserve a number of spatial characteristics while no one projection can preserve them all at once. Three main classifications of map projections are the Conformal, Equidistant, and Equal Area projections. Each of these projections has its own advantages and disadvantages which are clearly displayed through the maps above.

These three projection categories, Conformal, Equidistant, and Equal Area, each have their own unique advantages. Conformal maps allow for shape to be preserved while making longitudinal and latitudinal gridlines to intersect at right angles. These examples of conformal maps can be seen in the Mercator and Gall Stereographic maps above. Equal Area maps preserve area as suggested by their name. The whole of the Equal Area map has the same equivalent area as the Earth as a whole. This element of Equal Area projections is well illustrated by the Mollweide projection map shown above. Equidistant maps show true distances along certain designated lines or from the center of the projection outward (or visa versa) but not between points that are not near the center. The Equidistant Conic projection above shows how true distance from Africa to Australia could not be easily measured using this map. These map projection categories have their key uses but also could be the wrong choice for certain location data depending on the elements of interest.

Though one category may work very well in one instance, it is certainly not guaranteed to work well next time. Conformal maps, though very good at preserving angles between gridlines, distort sizes of areas significantly. This is well demonstrated by the size of Antarctica in the Mercator projection above. Equal Area maps also have disadvantages in contrast with their ability to preserve area well. Equal Area maps can never offer the preservation of gridline angles while still sustaining accurate area. As shown above when comparing the Mercator projection to the Equal Area projections, you can see how the gridlines look nothing alike. Equidistant projections have trouble, as mentioned before, with measuring distances of locations outside of the center, or along the lines, designated. Another disadvantage to these types of maps is that they can never offer true distances while still preserving equal areas. This is illustrated well by the distortion in area within the Plate Carree projection above. These types of disadvantages come with all projections and are a necessary evil to properly presenting map data.

Map projections are a very important concept to be understood when working with or even reading any maps. This knowledge allows the map observer and creator to better understand how to decipher and construct accurate features. This understanding of both advantages and disadvantages to projections allows for a better realization of which projection is the best and most accurate choice for a two dimensional map.

Lab 4: Introducing ArcMap

ArcGIS is a very powerful tool for understanding geographical information. The introductory tutorial illustrated the great potential and difficulties that the revolutionary software holds. I enjoyed my overall experience with the program despite the moments of uncertainty. In the process of completing the tutorial I enjoyed many opportunities to put the knowledge learned from class lectures into action and better understand the complexities of the software. I found ArcGIS to have great potential within its capabilities to manipulate data while still having some pitfalls for new users.

The benefits of the ArcGIS software are wide ranging. The software’s overall attention to detail when dealing with attribute tables, beautification of the visual aspects, and organization of the data groups is very impressive. The user interface of the program is well designed to quickly negotiate general processes. This quality construction of the software allows the user to make quick and effective use of the many tools available within the program’s inner workings. Organization of data tables through joining data groups was very helpful, in addition to the potential to construct formulas for calculation within charts and graphs. Though these great benefits allow the user to control large quantities of tools, the difficulties for new users abound.

The tremendous benefits that ArcGIS offers to its users can pose severe complications for those new to the program. The advantages of having access to all levels of detail can also hold a steep learning curve. Complications can quickly arise when the user of the software is not extremely focused. One wrong click or box unchecked can set the new user back precious time. Yet, I believe these moments of confusion are only temporary for the new user who does not fully understand the methods of the program. With time and experience the benefits will out-weight the difficulties and simply leave an invaluable tool for the geographer.

Though difficulties loom around the use of the powerful ArcGIS program, I look forward to better understand its features and tools. I hope future labs will help me to better understand the techniques of using ArcGIS so as to lessen the difficulties of the new user. Though the tutorial was very helpful, I look forward to more independent research and development of maps.