topographic maps and topographic profiles nick d’anna hhs 2007 adapted from r. demarco

TOPOGRAPHIC MAPS AND

TOPOGRAPHIC PROFILES

Nick D’Anna HHS 2007

Adapted from R. DeMarco

CLOSER CONTOUR LINES = STEEPER GRADIENT

TOPOGRAPHIC MAPS WOULD BE VERY CLUTTERED IF ALL CONTOUR LINES WERE LABELED, SO ONLY HEAVIER LINES SHOW LABELS

What is the pattern of the contour lines around a simple hill?

Concentric circles getting smaller - hill

Identify the features marked at A and B

Hachure contour lines (lines with tick marks) show depressions – the first hachure is equal to the last contour line passed

20 2010

WHAT DOES THIS PROFILE SHOW?

VOLCANO

NOTICE HACHURE DEPRESSION LINES IN CENTER SHOWING VOLCANIC VENT

TOPOGRAPHIC PROFILES

• TOPOGRAPHIC MAPS SHOW THE ELEVATION OR VERTICAL DISTANCE ABOVE SEA LEVEL OF THE SURFACE OF THE EARTH

• TOPOGRAPHIC PROFILE IS A SIDE VIEW OF AN AREA.

So, if we were to look at a profile view of line AB on our

topographic map, what might we expect to see? Predictions?

Time to FIND OUT!

Step 2

Make the X-axis exactly as long as line AB.

Next, decide what the HIGHEST and LOWEST elevation values are that line AB crosses on your topographic map and create a scale. You may wish to increase your scale by the contour interval on the map to make things easier. In this case, we are going up by 10’s, because our contour interval on the map is 10 meters.

Hold your scrap paper page up to the profile.

Transfer the tick marks directly onto the profile.

This is what This is what you might you might expect the expect the “profile” or “profile” or cross section cross section view of line view of line AB to look AB to look like! like! Notice how Notice how the line dips the line dips below 250m below 250m where it where it crosses Long crosses Long CreekCreek

Does it make sense? SURE! There is a creek flowing through this region. Think about where it would flow on your profile. We also recognize the V shaped contour lines that indicate the direction of water flow.

The contour lines point up the page (orange), but Long Creek flows down the page.

Contour lines point upstream. Stream flows from high elevation to low

elevation. So a stream flows in the oppostite direction the contours point.

CONTOUR LINES BEND WHEN CROSS STREAMS

UPSIDE DOWN V’S POINT UPSTREAM STREAMS FLOW DOWN

Or… if you are lucky enough to be able to do your profile on the same

page as the topographic map…

You can use the:

“Drop down a dotted line” method!

Same idea, but no need for tick marks and scrap paper!