Activity 26 Boomtown’s Topography

Challenge: What can topographical maps tell you about the stability of a building site? Key Vocabulary: Stability Stability of the land is a major factor in deciding whether an area is suitable for building. If an area has had unchanging topography for an extended time, it is considered more stable. This makes the area a more desirable building site than an area that has changed. GO TO PAGE 11

Create this table in your journal Boomtown Through Time   100 Years Ago 20 Years Ago Today Marsh Hillside Cliff

procedure Read the introduction on page 11. Complete steps #1-5 on page 12. IMPORTANT: Make sure you RECORD your observations from step #3 on your “Boomtown Through Time” table. When you are finished, answer Analysis #1-4 in our notebooks!

Boomtown through time:

Analysis Questions (page 12) Work in your groups to answer questions #1, #2 and #3. (Answers should be written in complete sentences in your journal.) Work independently to answer question #4. WHY are there possible problems? Refer to the paragraph you wrote in your journal at the beginning of this activity.

Answers to analysis questions 1. The contour interval is 25 meters. (This is approximately 75 feet.) 2. A.The major changes through 100-25 year period are: movement of the cliff (receded west) branching of the river more land in the delta significant road and house construction increased curvature of the river

2B. The changes from 20 years ago to today are: significant change in the hill, which has become steeper on the southeastern side Some movement of the cliff, which continued to recede to the west at a steady pace More branching of the river and Some addition of land in the delta

Answers continued A. The Seaside Cliff seems to be the most stable: Cliff has moved less It changed at a more steady rate The Delta marsh is the least stable because it shows the most change in its contour lines The evidence for this is the contour lines that show how the heights have or have not changed over time.

Answers continued The maps DO indicate that there may be problems because of changes to the building sites and to the Rolling River. If the landforms continue to change there could be expensive repairs and potential safety concerns at the building sites in the future.