William E. Dietrich

2009 Robert E. Horton Medal Winner

Department of Earth and Planetary Science, University of California, Berkeley

William E. Dietrich was awarded the 2009 Robert E. Horton Medal at the AGU Fall Meeting Honors Ceremony, held on 16 December 2009 in San Francisco, Calif. The medal is for “outstanding contributions to hydrology.”


It is truly a pleasure to introduce William Dietrich of the University of California at Berkeley as the 2009 Horton medalist for his outstanding contributions to the geophysical aspects of hydrology. That citation pales by comparison with Bill’s accomplishments, for no one comes close to the impact Bill has had in modernizing the field of geomorphology. He maintains the same unflagging energy and creativity in research, teaching, and professional service that have earned him international fame as the most productive, diverse, and influential geomorphologist in the world today.

This influence begins with his superb combination of skill in field observation and his ability to apply mechanistic principles to the analysis of empirical results to construct theories of landscape evolution. His career began with studies of river channel mechanics and of mass wasting in the coastal mountains of Oregon and California. He and his graduate students have extended his discoveries in both of those topics through field studies, laboratory experiments, and analysis of digital topography. They introduced innovations in each field, including high-resolution field measurements of flow and sediment transport, cosmogenic isotope measurement of regolith formation and transport, chemical tracers of floodplain sedimentation patterns, and lidar-resolution measurements of topography. Bill’s group expanded its field, laboratory, and numerical simulation studies to understand regolith formation, runoff processes, sediment transport, channel mechanics, floodplain sedimentation, and bedrock incision by streams and debris flows, typically being the first investigators to demonstrate the utility of a technique for extending landscape theory. Their studies continue to expand into hyperarid landscapes, including Mars.

The novelty and range of Dietrich’s studies begin with his innate curiosity about landscapes and their relevance for humans and other biota. He constantly shares his knowledge openly, and he is relentlessly inquisitive about other disciplines. His friendly demeanor and generosity, especially with young scientists, make him a hero in the discipline, and induce similar behavior among his large and productive group of former graduate students.

Bill is an exemplar of the AGU commitment to “unselfish cooperation in research.” He worked tirelessly within the Erosion and Sedimentation Committee of the Hydrology section to promote geophysical approaches in geomorphology, and to organize special sessions with other sections, leading to seminal interdisciplinary initiatives. These efforts continue and have expanded into other community-building efforts such as the National Center for Earth-surface Dynamics, the National Center for Airborne Laser Mapping, and National Research Council and National Science Foundation committees. His most influential community-building activity must surely lie in organizing the Gilbert Club, an annual gathering of geomorphologists that he established in 1983. At that event, Bill is at his tireless best—reporting scientific results, asking penetrating questions, including specialists from other fields, promoting the role of young researchers, making sure the program runs and that someone has ordered lunch and dinner—essentially driving the field forward with his physical and intellectual energy.

Bill is a model for all we aspire to be as members of this Union, and as worthy a recipient of the Robert Horton Medal as I can imagine.

—THOMAS DUNNE, University of California, Santa Barbara


Robert E. Horton is a hero to all geomorphologists. He lit the candle that guided us to quantitative inquiry. He observed, quantified, analyzed, performed field experiments, and proposed theories linking hydrology, erosion processes, and form. His 1945 Geological Society of America paper is beyond a “classic”—if a “classic” is defined as a paper often cited but never read. Horton’s paper still now, in 2009, deserves reading and rereading.

I remember well when I was introduced to Horton’s work and to geomorphology as a whole by Tom Dunne in the early 1970s. Geomorphology was considered by many then as an uncomfortable, backward cousin of Earth science, taught only in introductory classes, and lacking in quantitative accomplishments or rich research opportunities. Tom knew differently and opened the eyes of a generation of students.

Things could not be more different now. I have been witness to, and had some hand in, the rediscovery of geomorphology. Our field is populated with generous souls who collaborate closely, share their knowledge, and inspire their students. My colleagues have started new journals, organized new centers, invented new methods of observation, participated in committees and workshops, and written those reports that have created opportunity in our field. The Hydrology section of AGU in particular has been consistently supportive, encouraged new developments, and welcomed this emergence of geomorphology. I must note, too, that the section has been exceptionally kind to me throughout my career.

I thank my many collaborators who have continually challenged me, pulled me, and given me opportunities to learn from the best minds. Berkeley is a magnet for ambitious, creative students, and I have had the great fortune of working with many students with exceptional talent. When I opened a door to a room, they would fill it with intellectual furniture beyond my imagination. If chance favors the prepared mind, then I thank in particular Tom Dunne and Jim Smith, my graduate advisors at the University of Washington, for preparing me for what has been a surprising, exciting time of discovery. I share this medal with all of those from whom I have learned so much. And I must also share this medal with Mary Power, my wife, the warm soul who keeps me tethered as I wander this lovely field in search of the new.

—WILLIAM E. DIETRICH, Department of Earth and Planetary Science, University of California, Berkeley