Dynamic Watersheds: Impact of Fires and Floods
 
Everyone lives in a watershed. Watersheds have boundaries that are defined by water movement. They can experience a certain number of natural events (e.g. heavy rainfall or high rainfall intensity) or human-influenced events (e.g. grazing) that they can absorb with minimal physical, ecological, or hydrological response. Some events, however, can induce catastrophic change in a watershed. Sometimes the response to these events happens very rapidly, and sometimes the response is relatively slow, over a period of hundreds and thousands of years or more. In this module, students will examine how some U.S. watersheds have responded to natural or human-influenced events in the past, how these watersheds are more vulnerable to certain types of insults, and the hazards to people who live in these watersheds.
 

Overview

Unit 1 - Discovering Watersheds: Variability and vulnerability across landscapes

Unit 1 encourages students to explore the environments, hazards, and risks associated with two very different watersheds — the Big Thompson watershed in Colorado, and the Lower Maumee watershed in Ohio. Students are immediately engaged in learning about the dramatic events that unfolded during the night of the 1976 Big Thompson flash flood that killed 145 people. Using MyWorld GIS and Google Earth, they explore the landscape, terrain, and hydrography of the Big Thompson. The combination of events and landscape characteristics that created the recipe for disaster are slowly revealed in the opening investigations. Next, students learn about the Lower Maumee watershed and its own hazards and risks, including flooding and historical, deadly ice gorges. Finally, they use the Internet as a resource to discover and learn about the hazards and risks to people that are associated with the watershed in which they live.

Unit 2 - A Changing Watershed: A case history of Sabino Canyon

In Unit 2, students investigate a case history of the semi-arid Sabino Canyon watershed in southern Arizona. Here they learn about the physical characteristics of the 2003 Aspen Fire in the watershed, and how it destroyed the community of Summerhaven during the initial days of the fire. In the summer of 2006, after 5 consecutive days and nights of heavy rainfall in the front range of the Catalina Mountains, over 250 slope failures (and 18 subsequently large debris flows) wreaked havoc along the canyon walls and in the drainage, destroying much of the Sabino Canyon Recreation Area. Students use Google Earth and MyWorld GIS to explore the "ingredients" required to produce such a destructive debris flow.
 

Learning Goals

In Unit 1, students will:
 
•   Learn the definition of a watershed
•   Examine relationships between large and small watersheds
•   Consider the sources and pathways of water entering and exiting a watershed
•   Explore the varying landscapes in which watersheds are located, and how these differing landscapes might determine a watershed's vulnerability to change
•   Discover the watershed where they live, and the environmental, social, or economic issues it might be facing now or in the future
 
In Unit 2, students will:
 
•   Discover what are considered the "normal" patterns of rainfall and streamflow in a semi-arid watershed in the southwestern U.S.
•   Understand how and why a semi-arid watershed may become vulnerable to change, or disturbance, under "unusual" conditions
•   Examine examples of natural and human-induced events that may cause instability in a watershed
•   Reflect on why or how disruptions to a watershed may affect its value to individuals and communities
 

Target Learning Audience

The Watersheds at Work module is designed for high-school Earth science, environmental science, integrated science, or global science courses. It can also be used in introductory undergraduate watershed-management, geology, or environmental-science courses. It assumes the students have no knowledge or just a basic, introductory knowledge about watersheds prior to use. It introduces them to using GIS data and Google Earth visualizations, and requires application of basic math. Step by step instructions are provided for using the GIS and Google Earth data. Similarly, no prior experience with a GIS is required, as all instructions are provided.
 

Teaching Tips

The Watersheds at Work module is designed for approximately 1 and 1/2 to 2 weeks of in-class lab, or a mix of homework time and 1 week of lab to complete, depending on how and when it is used in a course. It could also be used as a semester project, with the students exploring pieces of the case histories over the course of the semester or as a wrap up to the semester.
 

Using a GIS

The case study contains full instructions for the user, as we assume neither the instructor or student has prior experience with a GIS. We have chosen to develop these for MyWorld GIS because it works on Windows, Macintosh, and Linux systems. Users can also download a full version of the software and use it for 45 days at no cost. Site licenses are very reasonably priced for institutions. MyWorld is a full fledged GIS geared toward educational users rather than professional users.
 

 

This material is based upon work supported by the National Science Foundation under Grant Number 0607952. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.