Guidebook for Hydrogeomorphic (HGM)–based Assessment of Oregon Wetland and Riparian Sites I. Willamette Valley Ecoregion Riverine Impounding and Slope/Flats Subclasses Volume IB. Technical Report Oregon Division of State Lands Guidebook for Hydrogeomorphic (HGM)–based Assessment of Oregon Wetland and Riparian Sites I. Willamette Valley Ecoregion Riverine Impounding and Slope/Flats Subclasses Volume IB. Technical Report Prepared for: Oregon Wetland-Riparian Assessment Project Oregon Division of State Lands by: Paul R. Adamus Adamus Resource Assessment, Inc. Corvallis, OR 97330 February 2001 ii Summary This technical report describes the development of the wetland and riparian assessment methods presented in an accompanying document (Volume IA). Those methods are largely based on characteristics we observed at 109 wetland and riparian sites in the Willamette Valley region. This report describes the selection of those reference sites, the selection of least-altered (reference standard) sites, the selection of indicators of functions, and protocols used to assess those indicators at the reference sites. This report summarizes much of the field data, and describes preliminary results of testing the comparability and consistency of assessments using the indicators. The results cannot be statistically extrapolated to all wetlands of the Willamette Valley ecoregion, because private property issues make it impossible to select sites in a statistically random manner from the population of all sites in the ecoregion, and then visit and assess these. Nonetheless, the reference data set will be useful for helping develop performance standards for mitigation wetlands in the region. This report also describes initially promising results of use of some floristic (plant community) indicators of wetland condition. With continued testing and evaluation, these and other biological indicators may improve our knowledge of ecological condition in the region’s riverine impounding and slope/flats wetland subclasses. This document should be cited as: Adamus, P.R. 2001. Guidebook for Hydrogeomorphic (HGM)–based Assessment of Oregon Wetland and Riparian Sites. I. Willamette Valley Ecoregion, Riverine Impounding and Slope/Flats Subclasses. Volume IB. Technical Report. Report to Oregon Division of State Lands, Salem, OR. iii Acknowledgments Many people participated in this project. Jim Good proposed the idea of adapting HGM methods to Oregon (Good & Sawyer 1997). Financial support from the USEPA was initiated by Joel Shaich and later administered by Yvonne Vallette. Participation of the Oregon Division of State Lands (DSL) was spearheaded by Janet Morlan, and Dana Field contributed significantly during all phases of the project. This project would not have been possible without the participation and suggestions of the following individuals: Policy Advisory Committee: Roger Borine, Larry Devroy, Bob Frenkel, Jim Goudzwaard, John Marshall, Dennis Peters, Barbara Priest, Patty Snow, Yvonne Vallette Water Technical Committee: Michelle Girts, Steve Griffith, Herbert Huddleston, Richard Novitzki, Malia Kupillas Biodiversity Technical Committee: Mike Adams, Ed Alverson, Pete Bayley, Bob Frenkel, Ralph Garono, Esther Lev, John Marshall, Kathy Pendergrass, Ralph Rogers, Lynn Sharp, Chris Thoms, Yvonne Vallette Assessment Teams: Tim Acker, Danielle Aleshire, Will Austin, Janet Barnes, Elaine Blok, Tonia Burns, Lori Campbell, Dan Cary, Anita Cate, Kimberly Conley, Matt Cox, Larry Devroy, William Fletcher, Ken Franklin, Valanne Glooschenko, Alex Gonyaw, Jennifer Goodridge, John Gordon, Jim Goudzwaard, Sharon Gutowsky, Jeff Handley, John Hawksworth, Pat Hendrix, Mike Holscher, Nancy Holzhauser, Herb Huddleston, Malia Kupillas, Matt Kuziensky, Annette Lalka, Chris Lett, Larry Lodwick, John Marshall, Colin MacLaren, Ryan Makie, Katie McKenzie, Rebecca Miller, Sarah Miller, Janet Morlan, Sarah Mullins, Christina Nelson, Dick Novitzki, Barbara Priest, Phil Quarterman, Nancy Rorick, Ethan Rosenthal, Emily Roth, Bill Ryan, Tiffany Ryan, Mary Santelmann, Daniel Sarr, Shon Schooler, Joel Shaich, Belinda Shantz, Mika Snowbarger, Phil Stallings, Heather Stout, Ed Strohmaier, Chris Thoms, Yvonne Vallette, Kathy Verble, David Weatherby, Loverna Wilson In addition, thanks are due to several landowners who allowed access to their wetlands, to resource managers in other agencies who replied to our letter request for information on ecological benchmarks and standards they use, and to Heidi Brunkal, David Budeau, John Christy, Esther Lev, Alan Mackinson, Jon Titus, Lynne McAllister, Chris Pearl, Phil Scoles, Mike Shippey, Greg Sieglitz, Steve Smith, Pat Thompson, and Randy Wildman who assisted in the selection of reference sites. Agencies represented by some of the above individuals include: Oregon Departments of Environmental Quality, Fish & Wildlife, Transportation; U.S. Army Corps of Engineers, U.S. Environmental Protection Agency, U.S. Fish & Wildlife Service, USDA Natural Resources Conservation Service. iv Contents Section 1. Introduction................................................................................................................... 1 1.1 Project Background............................................................................................................. 1 1.2 Purpose................................................................................................................................ 1 1.3 Developing the Willamette Valley HGM Guidebook......................................................... 2 Section 2. Developing the Classification.......................................................................................3 Section 3. Selecting Reference Sites.............................................................................................. 5 3.1 Concepts for Selecting Reference Sites ............................................................................... 5 3.2 Process Used for Selecting Reference Sites......................................................................... 8 3.3 Highlights of the Reference Sites......................................................................................... 9 3.4 Selecting Least Altered Sites ............................................................................................. 15 Section 4. Selecting Functions and Indicators ............................................................................. 17 Section 5. Collecting Reference Data .......................................................................................... 22 Section 6. Calibrating Scoring Models ........................................................................................ 23 Section 7. Verifying Consistency ................................................................................................ 27 Section 8. Towards Bioassessment.............................................................................................. 29 8.1 Background ....................................................................................................................... 29 8.2 Exploring a Bioassessment Protocol Featuring Wetland-associated Plants ..................... 31 Section 9. Towards Performance Standards ................................................................................ 41 9.1 Background ........................................................................................................................ 41 9.2 Information Relevant to Performance Standards for Plant Communities.......................... 43 9.3 Information Relevant to Performance Standards for Fish Habitat..................................... 48 9.4 Information Relevant to Performance Standards for Amphibian and Invertebrate Habitat50 9.5 Information Relevant to Performance Standards for Bird Habitat..................................... 52 9.6 Information Relevant to Performance Standards for Water Storage Functions................. 56 9.7 Information Relevant to Performance Standards for Nutrient Processing......................... 57 Section 10. Performance Standards in the Context of Watersheds and Landscapes ................... 58 Section 11. Literature Cited ......................................................................................................... 61 APPENDICES A. Evidence Supporting Selection of Least-Altered Sites B. Fish Species That Use Willamette Valley Wetland/Riparian Habitats C. Bird Species That Use Willamette Valley Wetland/Riparian Habitats D. Sites Ranked According to Plant Metrics E. Distributions of Standardized Function Scores, by Subclass and Function v List of Tables Table 1. Reference sites whose functions were assessed............................................................. 10 Table 2. Comparison of 2 wetland/riparian subclasses using indicators of function................... 14 Table 3. Willamette Valley sites selected as reference standards................................................ 17 Table 4. Functions and their definitions, quantification, and associated values.......................... 18 Table 5. Indicators assessed and the functions to which they pertain ......................................... 20 Table 6. Comparison of means of standardized function scores, least-altered vs. other sites..... 25 Table 7. Correlations among function capacity scores, riverine impounding sites (n = 54) ....... 26 Table 8. Correlations among function capacity scores, slope/flats sites (n = 55).......................... 26 Table 9. Types of procedures commonly