Then and Now, A Watershed in San Francisco

 

Purpose

The purpose of this activity is to show students how the landscape of the city has been changed by human activities and demonstrate how human activities can affect watersheds and their local environment.  The goal is to connect students with their natural environment by helping them to see how the natural processes have functioned in the past and how humans have altered those processes.

 

Objective

Focusing on the shoreline and the disappearance of creeks, students will compare historic maps with current maps and look at historic photographs.  Students will then explore their understanding of the changing landscape of San Francisco by identifying the current shoreline and stream systems of San Francisco and then drawing the historic stream system and shoreline on a modern map.  

 

CA State Science Standards (9-12):

State Investigation and Experimentation Standards:

1.h. "Read and interpret topographic and geologic maps."

1.m. "Investigate a science-based societal issue,"e.g..."Land and water use decisions in California."

Time Needed

20 minutes

Background Information

In the urban setting, it is often difficult to recognize natural features because they have been altered, paved over, and filled in. San Francisco water sheds (for example the Yosemite and Islais Creek watersheds) once had numerous stream channels that moved water from the ridges down to the bay.  However, most of these channels have now been replaced by concrete drain pipes that move both sewage and storm water to treatment plants and into the bay.  

Key Terms


Natural

Altered

Urban

Impact

Drainage divide

Channels

Topographic map


Materials Needed

Air photo of both Yosemite Creek and Islais Creek watersheds

USGS 7.5' topo quads of SF (north and south)

Colored pencils

1890 San Francisco Historic Creeks Map

Historic Map of Yosemite Creek

Historic Map of Islais Creek

Photographs of Islais Creek

 

Activity

  1. Explore each of the topo maps and air photos, find prominent features on the topo maps and match them to the air photos.

  1. Now compare the modern maps with the historic ones. See if you can find the prominent features that you identified on the modern maps and photos
 


  1. Look at the two photos and describe the difference between historic Islais Creek and modern Islais Creek
  1. Use the Historic Map of the entire city to draw with a colored pencil the historic shoreline onto the modern map.
 


Questions:

  1. What prominent features could you identify in both the air photos and on the topo maps?
  2. Where you able to identify the same features on the historic maps?
  3. What are the main differences that are obvious between the two photos?
  4. Where are the channels that used to carry the water to the bay? How does water get to the bay today if these natural channels have been destroyed/urbanized?
  5. How has the landscape in San Francisco changed during the past 150 years? Discuss the human impact on the watershed. Discuss the implications of habitat loss, etc.