Rainfall patterns and drainage density

Nicole Gasparini
Tulane University
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The students use ARC GIS to make maps of the island of Hawaii to identify the locations of river channels. The students are also given a map of precipitation so that they can relate drainage density to rainfall patterns.

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undergraduate geomorphology course

Skills and concepts that students must have mastered

Students must be familiar with the concepts of drainage density, runoff production, and orographic rainfall.
Students must understand how to interpret slope, contour, and hillshade maps and blue lines on maps.
Students must know how to use ARC GIS to make slope, contour, and hillshade maps and to create river shape files with different drainage area thresholds.

How the activity is situated in the course

The activity is the final part in a series of map and GIS exercises.


Content/concepts goals for this activity

Interpreting maps
Runoff production

Higher order thinking skills goals for this activity

Synthesizing multiple data sets

Other skills goals for this activity

Description of the activity/assignment

The students are asked to identify the drainage area at which channels begin on the island of Hawaii. Using ARC GIS, they are asked to create a slope, contour, and hillshade map. They use these maps as a guide to create river shape files with different drainage area thresholds in order to identify the proper threshold or thresholds. They are then given a map of the actual river locations and a precipitation map. The students must hand in their maps along with a write-up that describes how they used the slope, contour and hillshade maps to determine the location of rivers. They must also report on what drainage area threshold(s) they chose and why. They are also asked to explain why the map of the actual river locations looks different from any of river maps that they created. This activity gives students practice at interpreting and synthesizing multiple data sets.
Designed for a geomorphology course
Uses online and/or real-time data

Determining whether students have met the goals

I looked for the following concepts in the student's write-ups:
1. Channels are in the locations where contours point uphill
2. Steep slopes on either side of a flat area illustrates a canyon
3. Canyons are often shaded on one side and illuminated on the other in a hillshade map
4. Precipitation patterns affect drainage density

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