Where are the Watersheds in San Francisco?
Purpose
The purpose of this activity is to familiarize students with San Francisco geography and
the delineation of San Francisco’s watersheds
Objective
Students will check their knowledge of san Francisco geography with sketch their own
map of san Francisco. They will practice their knowledge by locating features on one
map and placing them onto a different type of 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
45 minutes
Background Information
Water flows from areas of high elevation to areas of low elevation, continous
areas of high and low lands that drain water to a common creek or stream are called
watersheds or drainage basins. Topographic highs (hills and ridges) define the
boundaries between different watersheds.
Topographic maps are 2-dimensional representations of a 3 dimensional surface.
Contour lines are used to show vertical elevation. Each contour line represents a line of
equal elevation on earth’s surface. Sea level is the zero elevation contour line. Contour
line basics: Contour lines do not cross but may converge at locations that are steeply
sloped. The farther apart the contour lines are spaced, the more gently sloped the
represented surface is (gradient). The elevation difference between two adjacent contour
lines is called the contour interval. Concentric contours represent hills. Contour lines
take a V-shape pointing upstream or uphill where they cross rivers or the lowest point in
a valley.
V-Shaped Contours
Saddle
Ridge
Hill
Valley
Key Terms
Geography
Topography
Elevation
Contour lines
Drainage Basin
Watershed
Ridge
Valley
Materials Needed
white paper
pencil
Both the North and South USGS 7.5' topo maps
Colored pencils
San Francisco Hillshade Map
Answer Key map of watershed boundaries
Activity
1. Create a map in your mind (mental map) of San Francisco, then sketch this map.
Include the entire city and label important places located within the city.
2. Compare your mental map to the USGS topo maps of San Francisco.
3. To familiarize yourself with San Francisco’s geography identify the following
locations on the USGS topo maps and then transfer these places to the San
Francisco hillshade map. It is ok to number the locations and make a legend so
your map doesn’t get too cluttered with labels.
Topographic Lows
San Francisco Bay
Pacific Ocean
Lake Merced
North & South Basin Reservoirs
South Basin (Double Rock)
Visitacion Point
Islais Creek Channel
China Basin
Topographic Highs
Mt. Davidson
Nob Hill
Lafayette Square
Twin Peaks
Corona Heights
Buena Vista Park
San Bruno Mountains
Hunters Point
Strawberry hill
Bernal Heights
4. On the San Francisco Hillshade place a red X on the topographic highs, both the
ones that you labels and any other obvious hills.
5. Using the rule for V-shaped contour lines Identify locations of possible stream
paths, mark locations with dashed blue lines.
6. Draw lines that connect highpoints, following ridgelines in between hills. These
are watershed boundaries. The boundary lines should separate water flowing in
opposite directions and one watershed should contain all tributaries draining to a
common creek that leads to the ocean or bay. (Note: be aware that some
hills/high points might be contained within a watershed (not part of a boundary)
& watersheds can be defined at many levels; In this assignment define the largest
and most obvious basins)
7. Using the answer key, check your boundaries and label watersheds with their
appropriate names. (Note: Watersheds are usually named for the creek that drains
the basin)
Questions
1. What did you include on your mental map? How often do you explore the city?
Where have you been in the city?
2. Write down some important places that you think you should have included on
your mental map that you did not? Is there anything on your map that is not on the
USGS topo maps?
3. How many watersheds did you define? How many watershed were defined on the
answer key