Investigating Vegetation Patterns in an Urban Wetland Using Electrical Resistivity
The demonstration will focus on the use units 1, 2, and 5, leaving out the more mathematically-intensive units 3 and 4. This approach significantly decreases the time it takes to complete the module, is widely accessible to introductory-level students, while still highlighting the application of geophysical methods to an urban environmental question. The demonstration will include the use of a GIS Storymap to explore real world datasets and to test hypotheses on the physical controls on vegetation patterns in Harrier Meadow.
This module, consisting of 5 units, introduces students to the fundamental principles and uses of electrical resistivity, with a focus on an environmental application. Students explore the characteristics and environmental setting of Harrier Meadow, a saltmarsh just outside of New York City. They investigate the relationship between electrical resistivity and physical properties of the soil in the marsh. Students also discover how variations in survey configuration parameters control investigation depth (how far into the ground the signals sense) and spatial resolution (what size objects can be detected). Finally, students learn about and then perform geophysical inversion, which is the process of estimating the geophysical properties of the subsurface from geophysical observations. In the final unit of the module, students evaluate the extent to which the geophysical dataset and direct physical measurements support the hypothesis, introduced in the first unit, accounting for the distribution of Pickleweed in Harrier Meadow.
This module is intended to require approximately 2-3 weeks of class time. Teaching material includes PowerPoints that may be used in lectures or provided for self-guided learning, videos, a GIS storymap, exercises, and handouts that ask students to synthesize what they learn from the exercises. In addition, multiple choice and short answer questions can be given to students as homework, on quizzes, or on exams. Three units of this module are ideal for introductory-level undergraduate courses such as earth science, environmental science, geology, geophysics, physics, engineering, geography, or chemistry. The additional two units are more involved and better suited to introductory to advanced undergraduate classes in geophysics and engineering.
Why It Works
This module involves the use of real data: Authentic datasets are used throughout the module, allowing students to grapple with the challenges of real data sets, where there is an inherent element of ambiguity. It also shows students how geophysics is used in a real-world setting. This module connects students to the world around them by emphasizing how electrical resistivity is used as a proxy for measuring salinity in a wetland just outside of New York City, and how the presence of an indicator species is used as a proxy for ecosystem health. Comparing these data illustrates how cities impact the environments around them. The module is designed with inherent flexibility so that individual units can be used, or the complete module of five units. Unit exercises can be used as homework or in-class/lab assignments. Exercises can be completed individually or in small groups.