Hillslope and Watershed Hydrology FE 537 Syllabus Fall 2004 Four ...

Four Credits, Lecture (4 hours per week)
Hillslope and Watershed Hydrology FE 537
Syllabus Fall 2004
Instructor: Jeff McDonnell, Dept. of Forest Engineering
Office: Peavy 015
Phone: 737-8720
E-mail: jeff.mcdonnell@orst.edu
Class Schedule: Tuesday and Thursday, Peavy 276, 10:00 to 11:50am
Office Hours: Tues and Thurs following class 12-1pm.
Historical Context and Motivation for the Course:
Hillslope hydrology as a discipline has evolved from a set of agricultural and engineering
applications focusing on problems at distinct scales. The agricultural approach focused on issues
dealing with soil water availability and movement at the scale of the soil column. Detailed,
bottom up consideration of soil physical and chemical processes could be incorporated as the soil
column could be well described, and potentially extended to the level of an agricultural field as a
relatively homogeneous, basic unit of production and irrigation needs. Water resources
engineering issues of flood flow and water supply, on the other hand, generally dealt with
significantly larger catchments and traditionally took a top-down approach to the prediction and
understanding of runoff generation and flood frequency. Specific process observation, however,
was also necessarily limited to plots, and generally borrowed concepts drawn from the
agricultural community. Therefore, initial concepts used for runoff and streamflow generation in
hillslope hydrology were dominated by so-called “infiltration-excess” mechanisms. This is
exemplified by Horton's work in the New York City watershed in his descriptions of infiltration
and runoff generation. Significantly, this approach conceptually treated water movement through
a hillslope as a spatially uniform process. What we commonly refer to as Hortonian runoff was
incorporated into mathematical models that became widely used in the water-resources
engineering community. It is interesting to note that models that are essentially based on plot
scale infiltration excess concepts are still dominant for representing land surface hydrology in
atmospheric circulation models.
In the 1960s and 1970s, an accumulation of field observations at the hillslope and catchment
scale appeared to contradict previously held concepts of uniform precipitation excess
mechanisms and the models that had come into general use. Many of these observations were
made in forested and other less disturbed catchments where infiltration capacity was much
higher, and significant amounts of water entered the soil and moved laterally through the
subsurface to form distinct wetness zones. The variable-source area concept of streamflow
generation required a fuller treatment of soil water flowpaths at the hillslope scale than was
possible with the current generation of models. As a result, a set of mathematical models were
then refined or newly developed to accommodate these observations. These models first
concentrated on extending the equations for matrix flow in the soil column to include a lateral
flux (e.g. Freeze, 1972 WRR) often short of a full 3-dimensional model due to the limitations in
computing resources and in spatial information on soil properties required. A set of models that
sought to reproduce the effects of a full 3-d flow field were developed that coupled a vertical

infiltration model with a method for moving soil moisture downslope either by attempting to
trace topographically controlled flowpaths with a local Darcy flux or developing a conceptual
redistribution scheme (e.g. Topmodel).
During this time, a new set of scientific questions have evolved, separate in focus and
intermediate in scale to traditional agricultural and water resources engineering. These dealt with
problems in non-point source contaminants, acid rain, and other integrated watershed hydrologic
processes and required a fuller understanding of the vertical distribution of flowpaths through
hillslopes, their velocities and residence (or contact) times, and temporal dynamics on storm to
seasonal time scales.Partially in response to these emerging problems, in the 1980s and 1990s,
catchments (both hillslopes and streams) have been intensively studied by simultaneously
monitoring the distribution and flux of water and chemicals at many locations in space and time.
Technical advances in methods of measuring soil water distribution in the soil profile (TDR),
soil and substrate structure (ground penetrating radar), and the use of chemical and isotopic
tracers to source streamwater during this time have dramatically increased the amount of
information available to study basic processes by which water moves through hillslopes. The
information is not consistent in certain cases, between isotopic and chemical signals, with signals
derived from more standard hydrometric methods.
As our ability to measure hillslope flowpaths and the evolution of soil moisture patterns and
chemistry progressed, it was recognized that the concept of matrix flow as the dominant
subsurface pathway may not be universally applicable. It is now recognized that the process of
macropore flow and other preferential flowpaths through hillslopes are significant at least under
certain conditions. Over the last 10-15 years, their has been a rapid advance in our ability to
observe distributed processes in watersheds over a range of scales. The intensive monitoring of
catchments has been made possible by automatic sampling and remote sensing techniques. The
advent of isotopic methods to study the source and evolution of stormwater have added
significantly to our knowledge base, sometimes yielding information that appears to conflict
with previously held concepts and more traditional hydrometric data collection methods. These
observations have raised many questions and issues about all of our commonly held concepts of
streamflow generation and soil water dynamics.
Current model development continues to seek to incorporate the distribution and dynamics of
soil moisture and the set of possible flowpaths that become important under given conditions.
However, at present there does not appear to be either a general understanding or consensus on
how the dominant processes of water input, internal flow (pathway dynamics) and outflow
(including evapotranspiration) interact and evolve on different hillslopes. At the same time, an
understanding of these processes and their interactions have become critical to a set of pressing
scientific questions regarding flood generation, water supply, water quality and land/atmosphere
interactions. This course will explore the state of the art of Hillslope Hydrology as it forms the
foundation of the many water-mediated reactions that relate to it in the context of contemporary
environmental problems.
Learning Objectives of the Course:

The learning objectives of the course are to define a robust physical description of how water
moves into, through and out of hillslopes in the context of how this information can and should
be captured in model formulation, calibration and testing at small to large catchment scales.
More detailed learning objectives will accompany each of the 3 course sections
Course Description
FE 537 is a research-oriented course intended to provide students with an overview of hillslope
hydrology from a process perspective. The course will focus on processes and pathways of water
fluxes in catchments and how hillslopes modulate water transfers in the landscape. Runoff
production mechanisms will be reviewed and combined hydrometric and tracer techniques will
be explored in the context of quantifying the age, origin and pathway of subsurface stormflow.
The course will be evenly divided into lecture periods that address plot, hillslope and catchment
scales.
Course Grading
Completion of Rainfall Runoff Web material 15%
Quizzes 30%
Project Report 40%
Classroom Participation 15%
Course Text
No course text will be used. A reader of Benchmark Papers in Hillslope Hydrology will be used.
This is downloadable at the course web page at
http://www.cof.orst.edu/cof/fe/watershd/Documents/Teaching/FE605/INDEX.HTM
The Workbook by Tarboton to accompany the web module is at:
http://media.engineering.usu.edu/RRP/
Lecture Schedule:
Sept 28 Course introduction and overview
Sept 30 Field trip
Oct 5 Rainfall-Runoff process
Oct 7 Plot scale 1:
Oct 12 Plot scale 2
Oct 14 Plot scale 3
Oct 19 Discussion, Quiz
Oct 21 Hillslope scale 1
Oct 26 Hillslope Scale 2
Oct 28 Hillslope Scale 3
Nov 2 Discussion, Quiz
Nov 4 Catchment scale 1
Nov 9 Catchment scale 2
Nov 11 Veteran’s Day
Nov 15 Catchment Scale 3
Nov 18 Discussion, Quiz
Nov 23 Field Project Presentations and Discussion
Nov 25 Thanksgiving

Nov 30 Field Trip re-visit
Dec 2 Final lecture
Course Web Page
http://www.cof.orst.edu/cof/fe/watershd/Documents/Teaching/FE605/INDEX.HTM