LONGITUDINAL PATTERNS IN STREAM CHANNEL GEOMORPHOLOGY AND AQUATIC ...

274 Pages·2008·5.55 MB·English

LONGITUDINAL PATTERNS IN STREAM CHANNEL GEOMORPHOLOGY AND
AQUATIC HABITAT IN THE LUQUILLO MOUNTAINS OF PUERTO RICO

Andrew Stephen Pike

A DISSERTATION

in

Earth and Environmental Science

Presented to the faculties of the University of Pennsylvania in partial fulfillment of the
requirements for the degree of Doctor of Philosophy

2008

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Supervisor of Dissertation – Dr. Frederick N. Scatena

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Graduate Group Chairperson – Dr. Gomaa Omar
ACKNOWLEDGEMENTS

This dissertation would not have been possible with the help and support of
numerous mentors, colleagues, and friends, all of whom deserve recognition here. First
and foremost, I would like to thank my advisor, Fred Scatena. Although his expectations
were high and his demands were challenging, his perpetual guidance from the field to the
office has been unparalleled. With his iron drive to help me succeed, and his deep breadth
of knowledge of the natural world, it has truly been an honor to have studied under Fred.
Second, I would like to thank each member of my graduate committee. I extend special
thanks to Art Johnson, for first launching me onto the scientific research course, and for
his continued mentorship throughout the years; I most certainly would not have made it
this far without him. I thank Todd Crowl for arranging for me to spend an enjoyable and
beneficial semester in his laboratory at Utah State University. I thank Dana Tomlin for
his lucid intellect and always enlightening discussions. Lastly, I am deeply appreciative
of Gomaa Omar not only for his support in handling logistical issues, but also for sharing
his unique talent of bringing out the buried spiritual essence in scientific work.
The field work required to survey tropical mountain rainforest streams was
inherently enjoyable, but it was not without its challenges. Yet I had the pleasure of
working with people who knew how to get a difficult job done, and have a good time
doing it. The assistance from the following people made four summers of stream surveys
possible, and all the more pleasant: Erik Drew, Tamara Heartsill-Scalley, Emmanuelle
Humblet, Kris Johnson, Kunal Mandal, José Marcial, Amanda Moyer, Pablo Piña, and of
course, Jennifer Schiffner.
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Housing and logistical support while in the field was made possible by the El
Verde Field Station (University of Puerto Rico), the Sabana Research Center (United
States Forest Service), and the International Institute for Tropical Forestry (IITF).
My colleagues on the Biocomplexity project were critical in the formulation of
this dissertation. I especially thank Katie Hein for her hard work collecting ecological
data, her insight throughout the project, and for two excellent field seasons that made this
collaborative project work. I also thank Drs. Ellen Wohl, Jorge Ramirez, Alan Covich,
Felipe Blanco, and all others involved with the project for their intellectual contributions.
I would like to thank numerous people around the department of Earth and
Environmental Science at Penn. A special thanks for Karen Taylor for her support in all
matters of life. Also, thanks to all the fellow grad students for their camaraderie, and to
all the faculty who I’ve studied with and learned from over the past years.
Funding for this dissertation was provided from the National Science Foundation
Biocomplexity Grant (NSF #030414) —Rivers, Roads, and People: Complex Interactions
of Overlapping Networks in Watersheds. Additional support was provided by the
University of Pennsylvania, and the Long-Term Ecological Research (LTER) Network.

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ABSTRACT

LONGITUDINAL PATTERNS IN STREAM CHANNEL GEOMORPHOLOGY AND
AQUATIC HABITAT IN THE LUQUILLO MOUNTAINS OF PUERTO RICO
Andrew S. Pike
Frederick N. Scatena

The hydrologic, geomorphic, and ecological dynamics of tropical montane
streams are poorly understood in comparison to many temperate and/or alluvial rivers.
Yet as the threat to tropical freshwater environments increases, information on the
dynamics of relatively pristine streams is important for understanding landscape
evolution, managing and conserving natural resources, and implementing stream
restoration. This dissertation characterizes the geomorphology and hydrology of five
adjacent watersheds draining the Luquillo Experimental Forest (LEF) in northeastern
Puerto Rico, and discusses implications on aquatic habitat. I performed several
interrelated studies, including: 1) formulating a geographic information systems (GIS)
framework to estimate hydrologic parameters from topographic information and
hydrologic records, 2) developing a method to determine active stream channel
boundaries (“bankfull” stage) that allows for comparison of channel geometry on the
basis of flow-frequency, 3) decoupling the relative influences of lithologic and hydraulic
controls on channel morphology using an extensive field-based stream survey and
analysis of stream profiles, channel geometry, and sediment dynamics, 4) linking
network- and pool-scale geofluvial dynamics to the abundance of migratory fish and
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shrimp through a collaborative analysis combining geomorphic surveys and aquatic
faunal sampling. This research indicates that these streams have some properties
resembling both temperate montane and alluvial rivers. Similar to low-gradient rivers
where floodplains mark channel boundaries, the active channel stage in these streams is
defined by the incipient presence of woody vegetation and soil development. Systematic
basin-scale geomorphic patterns are well-developed despite apparent non-fluvial and
lithologic control on local channel morphology. This implies that strong fluvial forces are
sufficient to override channel boundary resistance; a feature common in self-forming
“threshold” alluvial channels. Migratory aquatic fauna abundances are influenced by a
variety of geomorphic factors such as barrier waterfalls and suitable headwater habitat,
and are consequently highly variable and patchy. These results stand in contrast to the
notion that aquatic communities mirror systematic geomorphic gradients, but rather
acknowledges the influences of multiscale geomorphic processes. Ultimately, this
research provides baseline information on physical and biological processes in relatively
unaltered tropical streams and can be used to inform further studies that document human
interactions with stream networks.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS ii
ABSTRACT iv
LIST OF TABLES x
LIST OF FIGURES xii
CHAPTER 1: General Introduction
Introduction 1
Chapter Outlines 6
References 9
CHAPTER 2: Application of Digital Terrain Analysis to Model Surface
Water Flow in the Luquillo Mountains of Northeastern Puerto Rico
Abstract 15
Introduction 16
Study Area 17
Digital Elevation Model (DEM) Construction 18
Stream Network Extraction 22
Rainfall, Runoff, and Discharge 24
Conclusion 27
Acknowledgements 27
References 28
CHAPTER 3: Defining a Bankfull Analog for Tropical Montane Streams
Using Riparian Features
Abstract 31
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Introduction 33
Study Area 38
Northeastern Puerto Rico 38
Regional Stream Gages 41
Riparian Vegetation 42
Methods 50
Field Surveys 50
Estimation of Flow-Frequency 51
Multivariate Regression Trees 55
Effective Discharge 56
Results 60
Riparian Vegetation 60
Bankfull Discharge and Effective Discharge 61
Multivariate Regression Trees 61
Discussion 70
Riparian Features 70
Bankfull and Effective Discharge 73
Applicability to other stream systems 76
Conclusion 77
Acknowledgements 78
References 79
CHAPTER 4: Longitudinal Patterns in Stream Channel Geomorphology in
the Tropical Mountain Streams of the Luquillo Mountains, Puerto Rico
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Abstract 88
Introduction 89
Study Area 97
Methods 105
Results 109
Longitudinal Profiles 109
Hydraulic Geometry 113
Grain Size 116
Stream Power 127
Discussion 130
Conclusion 136
Acknowledgements 137
References 138
CHAPTER 5: Multiscale Linkages Between Geomorphology and Aquatic
Habitat in a Tropical Montane Stream Network, Puerto Rico
Abstract 149
Introduction 151
Study Area 156
Stream Community 161
Methods 164
Field Methods 164
Pool Length and Spacing 168
Statistical Analyses 168
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Principal Components Analysis 168
Non-Parametric Multiplicative Regression 169
Stepwise Multiple Linear Regression 171
Results 171
Species Distribution in Geomorphic Space 171
Longitudinal Trends of Species 183
Influence of Reach and Pool-Scale Geomorphology 192
Pool Size and Spacing 195
Discussion 195
Landscape Scale Patterns 195
Reach and Pool-Scale Patterns 201
Conclusion 204
References 205
CHAPTER 6: Conclusions and Future Research
Summary and Conclusions 216
Future Research 218
APPENDIX 222
Site Information 227
Baseflow Channel Geometry 234
Active Channel Geometry 241
Grain Size and Pebble Count Data 248
Additional Biocomplexity Pool Information 255
INDEX 259
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LIST OF TABLES

Table 3.1 Physiographic site information for the selected study gages. 44
Table 3.2 Riparian features (vegetation, substrate, and soil 52
characteristics) that were recorded at each survey point.
Table 3.3 For each study USGS gage, the time span of the discharge 54
record, flow parameters, and at station width and depth hydraulic
geometry coefficients and exponents.
Table 3.4 The median height above water table, unit discharge, flow 68
frequency, and recurrence interval of zones defined by the multivariate
regression tree analysis.
Table 3.5 The discharge, unit discharge, flow frequency, and 69
recurrence interval associated with the bankfull stage, the effective
discharge, and the bankfull analog at each study stream gage.
Table 4.1 Downstream hydraulic geometry coefficients and exponents 115
divided by watershed.
Table 5.1 Species identified during trapping and electrofish sampling. 166
Table 5.2 Principal component eigenvalues for 58 geomorphic 173-174
variables, using data from 113 pools throughout the study basins.
Table 5.3 Principal component eigenvalues for 20 geomorphic 181
variables measured for pools in the Quebrada Prieta.
Table 5.4 Landscape scale variables used to predict species 184
presence/absence using a NPMR 2-parameter model.
x