AN ABSTRACT OF THE RESEARCH PAPER OF John T. Gabriel for the degree of Master of Science in Geography presented on September 20. 1993. Title: A Modified Synoptic Analysis of the Status of Oregon's Willametté Valley Wetlands Sound wetland management depends on an accurate comprehensive assessment of functional wetland values. This management should account for the cumulative impacts to regions and landscapes resulting from piecemeal destruction and degradation of wetland resources. A regional or watershed evaluation of wetland values can also make site-specific assessments more efficient. The purpose of this paper is to conduct a regional landscape assessment of Oregon's Willamette Valley wetlands. The information in this report is designed to augment site-specific wetland evaluations with information on 1) wetland loss, 2) habitat for listed wetland species and special wetland communities, 3) development threat, 4) threat to habitat, and 5) wetland restoration potential. I use a modified version of the U.S. Environmental Protection Agency's synoptic approach methodology to evaluate Willamette Valley wetlands based on these five "synoptic indices." The Willamette Valley was divided into seven subunits, each ranked relative to the synoptic indices. Based on current wetland area and the historic area of wetland soils, wetlands occupy between 8 and 13% of the area of each subunit; historically wetlands were not distributed so uniformly. Altogether, the Willamette Valley has lost about 41% of its original wetland area. Wetlands in urban subunits are under the greatest development pressure and disproportionately contribute habitat for threatened and endangered species. A Modified Synoptic Analysis of the Status of Oregon's Willamette Valley Wetlands John T. Gabriel A RESEARCH PAPER submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed September 20, 1993 Commencement June 1994 Research Paper Directed by Dr. Frenkel ACKNOWLEDGMENTS I wish to thank the U.S. Environmental Protection Agency and the Oregon Division of State Lands for funding this research. I would also like to express my appreciation to Ken Bierly, Scott Leibowitz, and Robert Frenkel for their review, comments and suggestions on drafts of this paper. Their comments have substantially improved and refined this research. A special thanks goes to Karen Gabriel for her support and encouragement. Although the research described in this report has been funded inpart by the U. S. Environmental Protection Agency agreement 1BO792NTTA to John T. Gabriel, it has not been subject to the Agency's review and, therefore, does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. TABLE OF CONTENTS Introduction 1 Background 2 The Willamette River Watershed 2 Settlement History 4 Prehistoric landscape 4 Willamette Valley Wetlands 6 Wetland Ecological Functions 11 Water Quality 12 Biodiversity/ Habitat 13 Hydrologic Function 13 Wetland Management 15 State Wetland Management 15 Wetlands Defined 15 Oregon's Removal-Fill Law 15 Statewide Planning 16 Local Wetland Management 17 Oregon's Wetland Conservation Strategy 18 Federal Wetland Regulation 19 Summary 20 The Synoptic Approach 21 EPA Methodology 21 Define Goals and Criteria 24 Define Synoptic Indices 24 Select Landscape Indicators 25 Conduct Assessment 26 Prepare Synoptic Reports 26 Summary of EPA Methodology 27 Criticism of Synoptic Approach 27 Delineating the study area 27 Oversimplification of complex ecological relationships 29 Methodology 32 Research Question 33 The Study Unit and Subunits 36 Long Tom Subunit 36 Molalla Subunit 37 Rickreal Subunit 37 Santiam Subunit 37 Scappoose Subunit 38 Tualatin Subunit 38 Yamhill Subunit 40 Landscape Indicators 40 Historic Wetland Area 40 Current Wetland Area 42 Listed Wetland Species and Special Wetland Communities 46 Removal-Fill Permit Applications 47 Unallocated Stream Water 49 Results and Discussion 51 Synoptic Indices 51 Wetland Loss 52 Development Threat to Wetlands 55 Habitat for Listed Wetland Species and Special Communities 58 Threat to Listed Wetland Species and Special Communities 61 Restoration Potential 64 Conclusion 67 Long Tom 67 MolaIla 69 Rickreal 69 Santiam 69 Scappoose 70 Tualatin 70 Yamhill 70 Willamette Valley 71 Works Cited 73 Appendices A. List of National Wetlands Inventory Maps Sampled 80 B. Subunit Area Information 81 C Subunit Shannon Index Data 82 D. Gray Scale Copies of Subunit Maps 83 LIST OF FIGURES Figure 1. The Willamette River Watershed 3 Figure 2. The Willamette Valley Study Unit and Subunits 39 Figure 3. Area of Hydric Soils 42 Figure 4. Dot-Grid Sampling Techniques 44 Figure 5. Current Wetland Area 45 Figure 6. Sites Supporting Listed Wetland Species and Communities 47 Figure 7. Removal-Fill Applications Per Subunit 48 Figure 8. Synoptic Index: Wetland Loss 53 Figure 9. Synoptic Index: Development Threat to Wetlands 57 Figure 10. Synoptic index: Habitat for Listed Wetland Species and Special 60 Wetland Communities. Figure 11. Synoptic Index: Threat to Wetland Habitat for Listed Wetland 63 Species and Special Communities. Figure 12. Synoptic Index: Restoration Potential 65 Figure 13. Summary of Synoptic Indices 68 LIST OF TABLES Table 1. Wetland Support of Listed Species 13 Table 2. The Synoptic Approach 23 Table 3. Research Questions, Synoptic Indices, Landscape Indicators 33 Table 4. Comparison of Dot-Grid Sampling to GIS 45 Table 5. Water Availability per Subunit 50 The Modified Synoptic Analysis of the Status of Oregon's Willamette Valley Wetlands INTRODUCTION The purpose of this study is to develop baseline information on Willamette Valley wetlands that can be used to guide wetland management decisions. Little is currently known about the status of Oregon's Willamette Valley wetlands; this study is a first attempt to gather regional information on this natural resource. The goal of the study is to place management decisions regarding individual wetlands in the context of the regional status of wetlands. Wetland managers may use information in this study to augment, rather than substitute for, site-specific wetland evaluations. A modified version of the synoptic approach methodology developed by the U.S. Environmental Protection Agency's Wetlands Research Program (EPA) in Corvallis, Oregon, is used to conduct this study (Leibowitz et al. 1992). 2 BACKGROUND The Willamette River Watershed Oregon's Willamette Valley is located in the western third of the state. It contains two-thirds of the state's total population, the major urban centers, and it is the state's most productive agricultural region. The valley is a structural trough which has been partially filled by alluvium from the Coast and Cascade Ranges and silts deposited by the Bretz or Missoula floods (Dart 1981). The eastern boundary of the Willamette River watershed (Figure 1) is formed by the Cascade Range, a strongly faulted anticline composed primarily of igneous rocks. The Cascades rise to a maximum height of about 3500m, but typical elevations range between 1000 and 1500m. Many of the rivers draining this range have headwaters in snow fields or glaciers. Snow melt in the spring and summer is stored in reservoirs and released throughout the year. This results in less variability in stream flows than prior to dam development, with lower flood peaks in the spring and higher flows in summer. The Coast Range forms the western boundary of the Willamette Valley watershed. It has less topographic relief, with maximum elevations in the north at Saddle Mt. at l000m and in the south at Marys Peak at 1250m. Typical elevations range from 550m to 1050m. This range is composed primarily of uplifted marine sediments. The range is more easily eroded than the Cascades and has a smaller snow pack and water storage capacity. The climate is humid temperate with average annual rainfall between 90 to 115 cm, approximately three quarters of it falling between October and March. The average annual temperature is between 4°C in January and 19°C July and August (NOAA 1978; Dart 1981).