Engage: What does an area prone to landslides look like?
Step 1: Go to the ArcGIS Online map, Using Remote Sensing to Avoid Disasters, and explore the map. When the map opens, there are tan lines that show elevation. Topographic maps are the types of maps that include this type of information.
Step 2: Click the link in the upper-right corner, Modify Map.
Step 3: Click the button, Bookmarks, and select Hills and Mountains.
- What do the topographic lines look like around hills or mountains?
Step 4: Select the bookmark, Steep Hills, and Flat Areas.
- What is the difference between steep hills and flat areas?
Explore: How many people can a landside impact?
Step 5: With the Details underlined, click the button, Show Contents of Map (Content).
Step 6: Check the boxes to the left of the two-layer names: Oso Image Before Landslide, Area of Interest.
Step 7: Select the bookmark, River. Zoom and pan around the area, counting the houses.
- How many houses were in the area of interest?
Step 8: Turn on the layer, Oso Image After Landslide.
Step 9: Click the button, Measure. Set the Tooltip to measure linear distance in miles. At the top of the map, click the Measure button. Hover and click the Distant button. Click continuously along what you want to measure. Then double-click to finish the measurement.
Step 10: Measure from the top of the slide to the southern edge of the rubble field.
- How far did the hill move?
Step 11: Click the Measure button and reset it to measure Area in Acres.
Step 12: Measure the total area that the landslide covered.
- How far did the landslide cover?
Explain: Could they have seen it coming?
Other factors contribute to the landslide. The area had received twice the average rain in the prior two weeks.
Step 13: Turn off the layer, Oso Image After Landslide and turn on the layer, Hillshade Post Slide.
- How does this change the look of the picture?
- There are at least three other areas where landslides had occurred and debris is visible below the hillside. (T/F)
Elaborate: What part might the river have played in the slide?
Faster moving water erodes better than slow-moving water?
- On a curve, where is the water moving the fastest?
- What does the river look like directly under the hill that failed?
Step 14: Click the button, Basemap. Select Topographic.
Step 15: Zoom in to the hillside that failed until you can read the topo lines.
- How tall was this hill from the base topo line in the river?
Evaluate: Where is a safer place to live while still staying near the river?
Step 16: Now that you can see that this area had slid in the past, look for a place along the river that you think would be safer.
- Can you find a place where the hills are less steep, and the river is not present to erode the hill? List the distance and direction from the original Oso site in your answer.