Topographic Maps

Topographic Maps

• A topographic map shows the elevation of an area on Earth

• Topographic maps allow you to see a three-dimensional landscape on a two-dimensional surface

Topographic Maps

• Topographic maps typically have a scale of 1:24,000 (which means that 1 inch measured on the map represents 24,000 inches on the ground)

Contour Lines

• Elevation is indicated by contour lines

• A contour line is a line of equal elevation

• All points on a contour line have the same elevation

• Contour lines never touch or cross

Contour Lines

• What do these concentric circles represent?– A peak (hill,

mountain, etc.)

Consider an Island . . .

Consider an Island . . .

• Contour lines are like imaginary shorelines

Contour Lines

Slope• You can tell how steep the terrain is by

how close the contour lines are to one another– If contour lines are close = steep slope– If contour lines are far apart = gentle slope

What is the elevation at points X?

• X(a) – 540 m

• X(b) – 580 m

• X(c) – 600+ m

Match the Contour Lines to the Topographic Profile

Water Flow

• Which direction does water always flow?

DOWNHILL!• Water always flows perpendicular to

contour lines (i.e. downhill)

Which direction will water flow?

Topographic Map Rules

• Lines that are close together indicate steep slopes– The area circled in red is

very steep, because it has many lines crowded close together

• Lines that are far apart indicate gentle slopes– The area circled in blue is

not steep, because it has lines that are spread far apart

Topographic Map Rules

• Since contour lines must remain at the same elevation, they bend when they cross riverbeds

• A riverbed drops downward, so the contour line must bend upstream to stay at the same elevation

• When contour lines cross a stream, they form a “V” that always points uphill

Watersheds

• A watershed is the area of land where all of the water that drains off of it goes into the same place

Delineating a Watershed

1. Mark the area of interest

2. Mark the high points adjacent to the area of interest

3. Starting at the area of interest, draw a line connecting all of the high points on one side of the waterbody

– Watershed lines must ALWAYS cross contour lines perpendicularly

Delineating a Watershed

Delineating a Watershed

Practice Problem #1 Answer

Practice Problem #2 Answer