Natural Disasters

Prof. Stephen A. Nelson

Homework IV: Mass Movement Exercises

1. The web site at http://landslides.usgs.gov/learning/nationalmap/index.php shows the National Landslide Hazards Map, published by the U.S. Geological Survey.   This is a map of the lower 48 states showing areas where there have been a high incidence of landslides, and areas that have a high susceptibility to landslides.  Notice that you can click on various dots on the map and map legend to get an enlargement of various areas or the legend of the map.  On the large map, the areas colored in red are areas where there is a high incidence of landslides (covering greater than 15% of the area).  There are three major zones where high incidence of landslides occur. (1) near the west coast in the states of California, Oregon, and Washington, (2) in the Rocky Mountain states of Colorado, Utah, and Wyoming, and (3) in the Appalachian mountain states of Ohio, Pennsylvania, Virginia, West Virginia, Kentucky, Tennessee, and Georgia.  Surrounding these areas are areas of high to moderate susceptibility to landslides.

1. For each of these three areas that have high incidence or susceptibility to landslides, what geologic features are present that contribute to the high incidence or susceptibility to landslides?  In answering this question, think about the major factors involved in landslides (the role of gravity, especially slope angle, the role of water, the role of different geological materials like soil and rock, and the presence of processes that trigger landslides (see lecture notes on Slope Stability if you need reminders about these factors).  BE VERY SPECIFIC FOR EACH OF THE 3 AREAS. (6 points)
    
2. Find as near as possible the area where you live (when not attending Tulane).  What zone do you live in (answer by first stating exactly where you live, then by indicating the color zone on the map and the meaning of the color zone from the map legend)?  If it is a zone with a moderate to high incidence of landslides or a zone with a moderate to high susceptibility to landslides, what features in the area do you think are responsible for the incidence or susceptibility rating?  If it is zone with a low incidence or low susceptibility of landslides, what features or lack of features are responsible for the incidence or susceptibility rating? (2 points)

2. Since you decided not to take the job in Tacoma because of the mudflow threat, you are back in your house near San Francisco and comfortably settled into your job as an executive with Denyallclaims Insurance Company.  One of your friends is a developer who is planning a resort hotel project in southern California and wants to get a good deal on insurance coverage from Denyallclaims.  His project is on the bluff located just to the northeast of a town called La Conchita, on the coast in Ventura County, California.  to see an image of the proposed property, click HERE. 
   
   Before agreeing to insure this project, you vaguely recall having heard something about La Conchita in the news within the last few years.  Because you know that your company will probably take away your job (and house) if they have to pay large claims, you decide to fly down to La Conchita to check it out.  But, since your company does not like to pay travel expenses either, you decide that a better approach would be to use the internet (particularly a U.S. Geological Survey site, but you should also look at several other sites) to check out this property. By doing so, you quickly learn that there have been two events in the last 20 years that have affected the community.
   
   
   
   1. Discuss any disastrous events that have occurred in La Conchita within the last 20 years, including a description of events, any damage that has occurred, and any serious injuries or deaths that have resulted from these events. (2 points)
      
      
   2. Were any mitagation measures taken between the two events to prevent further disasters?  If so, what measures were taken and how effective were they? (2 points)
      
      
   3. You should be able to find plenty of photos, maps, and diagrams of the area that includes the area northeast of La Conchita.  From those photos, what is your evaluation of the risk involved in building a resort hotel on the bluff just to the northeast of La Conchita?  Be sure to consider not only the possible damage to the hotel, but possible risk to other properties as well.  (2 points)
      
      
   4. Have any lawsuits been filed and decided concerning the most recent event that occurred at La Conchita?   If so, who sued, who was sued, and who won?  (2 points)
      
      

3. Whether or not you currently live in an area prone to landslides, you may in the future.  It would be a good idea to know something about some of the features to look for that might indicate a landslide may occur in the near future, especially if there is any sloping ground around the area.  Find an internet site (hint, the U.S. Geological Survey has a good one) that tells you what features to look for.
   
   
   1. Give at least 14 such features that might be noticed before landslides occur. (2 points)
      
      
   2. List 3 things you should do if you suspect immediate landslide danger. (1 point) 
      
      

4. At the last minute, Denyallclaims decides that they will pay your airfare to Ventura County California so that you can have a better look at the property.  You call your friend and tell her that you will be going to down there.   She says "that's groovy" (showing her age) and offers to let you stay in a rental property that she owns in the city of Ventura.  The address of the property is 372 E. Lewis St., Ventura CA.  Before agreeing to stay there instead of the Motel 6, you decide to check out this property.  So, you go to Google Maps - http://maps.google.com/ (or Google Earth, if you have it installed on your computer), and type in the address.  This brings up a map of the area around this address and you can click on the Satellite button to see a satellite image of the area.  Note that you can zoom in an out by using the scroll wheel on your mouse and you can pan the image (move up and down or side to side) by holding down the left mouse button to drag the image around. 
   
   (You might want to compare this satellite image with an image of the area around La Conchita.  To do this, go to Googlemaps (or Google Earth) again and enter the address - 6905 Surfside Dr, Ventura CA 93001 [this is the location of a store in La Conchita], again, in satellite view you can zoom and scroll around this image, just like you did when looking at the area around the Vince Drive property)
   
   Do you see anything on the satellite image around the Vince Drive property that would aid you in making your decision to stay at this rental property (hint: look at the hillside to the east of the property), especially, if you factor in your knowledge from looking at weather reports that it has been raining in Ventura County pretty much constantly for the last 2 weeks?  Explain your answer. (2 points)
    

5. Go to the following web site: http://sciencecases.lib.buffalo.edu/cs/files/landslide.pdf, which is about litigation concerning the 1956 Portuguese Bend landslide in Los Angeles County, California.  The document is divided into 3 parts.  At the end of each part is a series of questions (10 questions in all).  Proceed through each part, then read the questions very carefully and answer each one.  (Note that most of the information you need to answer these questions is contained on the web site, but you may also want to refer to your lecture notes.  Remember this is a science class, so you should try to use the terminology and concepts that you have learned in this course to answer the questions). (10 points total)
   

6. For each of the following drawings, determine (i) What potential mass-wasting hazards exist, (ii) why these hazards exist, and (iii) what might be done to mitigate the hazard or remove the danger. Be sure to consider all information available, such as direction of fractures, type of rock or soil, slope angle, and any other features shown on the drawings. (This question will be graded on how well you use the terminology and concepts that we will have discussed in lecture). (2 points each)

4. 
   
   For this one (d) also state which site (X, Y, or Z), if any, would be the best site on which to build your house. (1 point).

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