Coarse Woody Debris in Streams of the Drift Creek Basin, Oregon by Curt N. Veldhuisen A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed February 20, 1990 Commencement June 1990 AN ABSTRACT OF THE THESIS OF Curt N. Veldhuisenfor the degree of Master of Science in Forest Engineeringpresented on February 27, 1990. Title: Coarse Woody Debris in Streams of the Drift Creek Basin. Oregon Abstract Approved: Robert L. Beschta This study examined the occurrence ofcoarse woody debris (i.e., pieces greater than 0.15m in diameter and 2.0 m in length) in first- through fifth-order streams located within the Drift Creek Basin of the Oregon Coast Range. Nine "tributary reachest were surveyed to determine how three land management treatments (undisturbed, patch clearcut with buffer strip, and entirely clearcut) and/or geomorphologywere associated with CWD loadings or piece characteristics. An additional 45 km of third- to fifth-order channelswere surveyed to identify CWD distribution patternsover changing stream size. All surveys recorded channel characteristics and the dimensions and attributes ofeach CWD piece. Coarse woody debris loadings varied greatly (11 to 62 pieces/lOOm, 0.3 to 4.3 m3/100m2 of inchannelvolume) between the tributary reaches, but were not significantly (p > 0.10) related to harvest treatment. However, reaches associated with clearcut treatment containedless hardwood CWD and pieces were significantly shorter, and more decayed than in the other treatments. This suggested that little CWD recruitment had occurred in the 15 to 20 years since harvest. The undisturbed and buffer strip tributaries contained CWD that reflected continued recruitment of both hardwood and conifer trees. Inchannel CWD loadings averaged 0.44 m3/100m2 and decreased significantly (p < 0.01, r2 = 0.68) with drainage area. Coarse woody debris frequency and total loadingaveraged 10 pieces/lOOm and 14 m3/lOOm, respectively, and were not significantly related to stream size. The percentage of total CWD volume within the channel increased with stream order and decreased with increasing channel gradient. "Large" debris pieces (i.e., pieces greater than 0.5 m in diameter and10 m in length) were particularly frequent in the gorge-like reaches of the Drift Creek Wilderness. Over one third of the CWD pieces in larger channels occurred within debris j ams. Coarse woody debris loadings in the Drift Creek Basin appear to be lower than other forested streams in the Pacific Northwest. It is concluded that past stream cleaning, harvesting, and basin geomorphology have influenced CWD loadings within the Basin. However, the effects of nineteenth century forest fires on stand characteristics and debris recruitment trendsappear to be a major cause of the observed CWD loadings. APPROVED: Professor of Forest Engineering in charge of major Head of department of Forest Engineering Dean of Graduate School Date thesis is presented February 27, 1990 Typed by ACKNOWLE DGEMENTS Many thanks are due to the directors of Coastal Oregon Productivity Enhancement (COPE) program for financial support and for selecting an intriguing study basin. Gordy Reeves, Jim Sedell, and Gordon Grant (from the PNW Forest Sciences Laboratory) were involved in conceiving the Drift Creek Basin survey, as were Tom McMahon and Stan Gregory (from OSU). The fisheries crew at the PNW did an outstanding job collecting and processing habitat survey data. Special thanks in particular go to Kelly Burnett for coordination and Miranda Raugh for her conscientious work on the CWD inventory. John Schwartz devoted enormous energy to the Drift Creek project, during our coordinated field surveys and interpreting observations from the Basin. You're almost there, John! Thanks go to Ray Ayers of Georgia Pacific Corpora- tion, the Waldport Ranger District, Hank Froehlich, and Jim Kiser for information and recollections regarding Basin history. Bob Beschta, as major professor, was tireless in his contribution of patience, support and enthusiasm. Thanks also to Bill Atkinson, who encouraged me to enjoy gradu- ate school and to the "Bob Squad" who helped me do it! TABLE OF CONTENTS SECTION PAGE INTRODUCTION 1 LITERATURE REVIEW 5 STREAM FUNCTIONS OF COARSE WOODY DEBRIS 5 COARSE WOODY DEBRIS LOADING PROCESSES 7 Inputs 8 Losses 9 COARSE WOODY DEBRIS DISTRIBUTION PATTERNS 11 EFFECTS ASSOCIATED WITH FOREST MANAGEMENT 13 Harvesting 13 Stream Cleaning 14 Long-term Effects is METHODS 18 STUDY AREA 18 Climate 18 Geology, Soils and Landforms 20 Vegetation 20 Resources and Management 22 SITE SELECTION 24 Tributary Reaches 24 Basin Survey Reaches 27 DATA COLLECTION 29 Channel Habitat Survey 29 Coarse Woody Debris Inventory 30 DATA ANALYSIS 35 RESULTS AND DISCUSSION 38 TRIBUTARY REACHES 38 Geomorphic and Vegetative Settings 38 Coarse Woody Debris 42 Spatial Distribution 42 Piece Characteristics 47 Forest Management and CWD in Tributaries 54 BASIN SURVEY 59 Geomorphic and Vegetative Settings 59 Coarse Woody Debris 61 Spatial Distribution 61 Piece Characteristics 64 Fluvial Influences on CWD Distribution 69 Forest Management and CWD in Survey 77 Reaches Effects of Valley Form on CWD 80 Distribution Comparing Drift Creek to other 86 Northwest Streams SECTION PAGE CONCLUSIONS 94 LITERATURE CITED 97 APPENDIX 103 LIST OF TABLES Table Page A 5-class system of log decay based on 33 fallen Douglas-fir trees (from Robison 1988) Physical characteristics of tributary 39 reaches, Drift Creek Basin Management history of tributary watersheds, 41 Drift Creek Basin Spatial distribution of CWD in tributary 43 reaches, Drift Creek Basin Mann-whitney results of CWD comparisons 46 between sub-basin tributaries Piece characteristics of CWD in tributary 48 reaches, Drift Creek Basin Mann-Whitney results of CWD comparisons 49 between treatments Physical characteristics of survey reaches, 60 Drift Creek Basin Spatial distribution of CWD in survey 62 reaches, Drift Creek Basin Piece characteristics of CWD in survey 67 reaches, Drift Creek Basin Loadings and piece characteristics of 75 "large" CWD in Drift Creek survey reaches Channel characteristics and spatial CWD 83 distribution for constrained and unconstrained stream segments, Drift Creek Basin Forest type and management history for 87 streams in the Pacific Northwest Al. Locations of Drift Creek survey reaches 103 A2. Coefficients and statistics of correction 104 equations for CWD piece dimension estimates Table Page A3. Elevations, low flows, and vegetation of 105 tributary reaches, Drift Creek Basin Additional piece characteristics of CWD 106 in tributary reaches, Drift Creek Basin Elevations and vegetation of survey 107 reaches, Drift Creek Basin Additional piece characteristics of CWD 108 in survey reaches, Drift Creek Basin Species categories of CWD in tributary 109 and survey reaches, Drift Creek Basin LIST OF FIGURES Figure Page Location of Drift Creek Basin, Oregon 19 Longitudinal profile for (a) Drift Creek, and 21 (b) Meadow Creek sub-basin streams (profiles developed from USGS quadrangle maps). Location of tributary reaches, Drift Creek 26 Basin Location of survey reaches, Drift Creek Basin 28 Coarse woody debris piece measurements 31 Coarse woody debris influence zones 34 Channel loading of CWD per bankfull area 44 in tributary reaches, Drift Creek Basin (UD = undisturbed, BS = patch clearcut with buffer strip, CC = entirely clearcut) Probability densities of CWD piece lengths 50 in (a) lower basin,(b) mid-basin, and (c) upper basin tributary reaches Mean decay of CWD vs. harvest treatment of 52 tributary reaches, Drift Creek Basin (UD= undisturbed, BS = patch clearcut with buffer strip, CC = entirely clearcut) Total volume loading of hardwood and conifer 53 CWD vs. harvest treatment of tributary reaches, Drift Creek Basin (UD = undisturbed, BS = patch clearcut with buffer strip, CC= entirely clearcut) Average decay vs. percent hardwood CWD pieces 56 in tributary reaches, Drift Creek Basin Relative frequency distribution for decay of 57 (a) hardwood and (b) conifer CWD pieces Channel loading of CWD per bankfull area vs. 63 drainage area, Drift Creek Basin Coarse woody debris volume in influence zones 65 vs. stream order, Drift Creek Basin Fiqure Page Eighty-fourth percentile CWD piece lengths 68 vs. drainage area, Drift Creek Basin Percent of CWD pieces with rootwads vs. 70 drainage area, Drift Creek Basin Percent of total CWD volume in Zones 1 and 71 2 vs. channel gradient, Drift Creek Basin Frequency of "large" CWD pieces (i.e., 76 pieces greater than 0.5 m in diameter and 10 m in length) and debris jams in Drift Creek reaches Longitudinal profile of channel unit CWD 78 loading per bankfull area along Drift Creek Cross-sectional view of typical (a) 81 constrained and (b) unconstrained valley forms Channel CWD loading per bankfull area for 84 constrained and unconstrained stream segments, Drift Creek Basin Channel loading of CWD for streams in the 88 Pacific Northwest (see Table 13 for stream descriptions) Hypothetical CWD loadings over time fora 91 second-order Oregon Coast Range stream COARSE WOODY DEBRIS IN STREAMS OF THE DRIFT CREEK BASIN, OREGON INTRODUCTION The presence of woody debris within Pacific Northwest streams has long been recognized, although perceptions of its function and value have changed. During the early years of settlement, waterways provided important avenues for transportation. Woody material in channels acted as an impediment to river navigation and the floating of logs to mills. In