Initial Publication Date: December 12, 2013

Drainage Basins Field Lab:

Jeff Marshall, Cal Poly Pomona University, Geological Sciences Dept.


Intended Audience: Undergraduate course in geomorphology.

Location:

San Gabriel Mountains foothills, near Cal Poly Pomona campus (topo map provided in Activity Description/Assignment download below).

Summary:

This field activity and follow-up assignment explores the geomorphology of drainage basins in an active tectonic setting. It introduces basic concepts of drainage basin structure and landscape analysis using morphometric indices.

Context:

This exercise begins with a field trip to the San Gabriel Mountain foothills near our campus. Students are given a set of topographic maps and asked to follow our progress as we hike into a small drainage basin in the Claremont Wilderness Park. Through interactive discussion, we explore regional landscape and the geomorphic form, function, and processes of a drainage basin system. Students are expected to complete their assignment on drainage basin analysis during the following week, working from the maps provided. Students are asked to identify the basic landscape units in the San Gabriel Mountain foothill region, delineate a set of drainage basins, and analyze the geomorphic characteristics of these basins using longitudinal profiles and morphometric indices. From this information, they are expected to draw basic conclusions about the geomorphic processes affecting this landscape system, and its relative state of equilibrium. Designed for a geomorphology course.

Goals:

This exercise helps students in recognizing form and function of drainage basins, analyzing drainage basin morphology and equilibrium, calculating morphometric indices, interpreting landscape response to tectonics as well as recognizing sensitivity of fluvial networks to landscape forcing (tectonics/climate), interpreting geometric significance of quantitative measurements, synthesizing several data sets to formulate hypotheses on landscape evolution (especially with respect to active tectonics). In addition, students must write a report that presents their results and interpretations.

Notes and Tips:

Before performing this exercise, students should have a good idea of how to read and interpret topographic maps and topographic profiles.

Assessment and Evaluation:

The teacher can examine maps, illustrations, and the final report and rate these relative to classmates.

Materials and Handouts: