Lab 7: Hawai'i


Students extract streams and watersheds from a DEM for the island of Hawai'i. They then look to seeif there is a correlation between precipitation and the way a stream network develops on a mountain. Students also investigate if this is related to vegetation, soil type, and slope.

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This exercise is used in an introductory GIS course for geology and environmental studies students.

Skills and concepts that students must have mastered

Familiarity with ArcMap and ArcCatalog; geoprocessing; familiarity with Python scripting; projecting a dataset; familiarity with DEMs; familiarity with Editor.

How the activity is situated in the course

This is the fifth in a series of stand-alone GIS exercises that introduce students to using Python Scripting for ArcGIS.


Content/concepts goals for this activity

Experience with using DEMs for hydrologic analyses, extracting statistics from rasters ; using strings in Python, working with feature classes in Python.

Higher order thinking skills goals for this activity

Thinking about the connections between drainage and topography and the controls on both; writing computer scripts.

Other skills goals for this activity

Description and Teaching Materials

In this lab students use GIS to look at how stream networks develop on a mountain using some of ArcGIS's tools for Hydrologic analysis of DEMs. Students learn new ways of extracting information from rasters, and writing python scripts to process and analyze data.

Lab 7a: In this homework exercise, students download and prepare elevation, precipitation, and hydrology data for the island of Hawai'i.

Lab 7b: In this lab exercise, students derive a stream network from a DEM and compare it to mapped rivers on the island.

Lab 7c: In this lab exercise, students write a script from prewritten helper functions to extract watersheds for the island calculate zonal statistics for each watershed.

Lab 7d: In this lab exercise, students calculate drainage density for the watersheds and compare to statistics extracted in Lab 7c.
Lab 7a: Data Prep (Acrobat (PDF) 101kB Jun12 17)
Lab 7b: Rainfall Patterns and Drainage Density (Acrobat (PDF) 151kB Jun12 17)
Lab 7c: Rainfall Patterns and Drainage Density (Acrobat (PDF) 291kB Jun12 17)
Lab 7d: Rainfall Patterns and Drainage Density (Acrobat (PDF) 106kB Jun12 17)

Teaching Notes and Tips

Although we belief the Python exercise to be clear, students should be given an opportunity to do the Python component, Lab 7c in an environment where a teacher or T.A. will be available to over one on one help to assist students with any conceptual issues they are having, particularly regarding variable assignment.


Students are assessed based on a map showing the relationship between drainage density and one or more of the parameters investigated as well as a workflow and letter summarizing what they did and learned in the lab.

References and Resources

The following paper provides good context for the work done in this lab: Montgomery, D. R., & Dietrich, W. E. (1989). Source areas, drainage density, and channel initiation. Water Resources Research, 25(8), 1907-1918.