Effects of Vegetation in Channels
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EFFECTS OF VEGETATION IN CHANNELS A summary of findings regarding vegetation interactions with channel processes and potential application to the lower Boise River Picture courtesy of Frauke Koenig Report Prepared For: Boise River Flood Control District #10 Report Facilitated By: Dr. David R. Tuthill Jr., PhD, PE Idaho Water Engineering, LLC Dr. Peter Goodwin, PhD, PE; Dr. Daniele Tonina, PhD, PE; Dr. Rohan Benjankar, PhD University of Idaho, Boise, Idaho Dr. Frauke Koenig, PhD Karlsruhe Institute of Technology, Karlsruhe, Germany Report Prepared By: CE504: Effects of Vegetation in Channels Engineering Class Spring 2011 Christopher Campbell Kresta Davis-Butts Frank Gariglio William Jeffery Reeder May 13, 2011 - ACKNOWLEDGEMENTS - The work to produce this report was guided by many helpful participants. Their suggestions and input greatly improved this manuscript. We would like to extend particular appreciation to David Tuthill of Idaho Water Engineering, LLC for inviting the University of Idaho to participate in this unique project and for providing overall project guidance. We are grateful to Steve Sweet of Flood Control District 10 for providing history of maintenance activities on the lower Boise River. Chuck Ferguson of Flood Control District 10 provided valuable insight into operational logistics and a wealth of knowledge of the river system. We are thankful to Sandra Schneider and Frauke Koenig of the Karlsruhe Institute for Technology for presenting their work regarding riverine vegetation in Germany. Peter Goodwin, Daniele Tonina, and Rohan Benjankar of the Center for Ecohydraulics Research at the University of Idaho provided valuable research insights and reviews of the manuscript drafts. - DISCLAIMER - This report is intended as an objective summary of a literature review and research effort by University of Idaho students. It does not recommend any action alternative nor does it represent the official stance of the University of Idaho. Effects of Vegetation in Channels TABLE OF CONTENTS Executive Summary ...................................................................................................................................... 1 Chapter 1: Introduction ................................................................................................................................. 4 1.0 Introduction ......................................................................................................................................... 4 Chapter 2: Hydraulics, Dynamics, and Morphology of Vegetation in Channels .......................................... 6 2.0 Introduction ......................................................................................................................................... 6 2.1 Hydraulics of Rooted Vegetation in Rivers ........................................................................................ 6 2.2 Hydraulics of Uprooted, Mobile Vegetation in Rivers ....................................................................... 8 2.2.1 Single LWD Hydraulics ............................................................................................................... 8 2.2.2 Aggregate LWD (Log Jam) Hydraulics ..................................................................................... 10 2.3 Hydraulics of Uprooted, Stable Vegetation in Rivers ....................................................................... 11 2.3.1 Single LWD Hydraulics ............................................................................................................. 11 2.3.2 Aggregate LWD (Log Jam) Hydraulics ..................................................................................... 14 2.4 Morphology and Vegetation in Rivers .............................................................................................. 16 2.5 Management of Vegetation in Rivers – Management Implications .................................................. 17 Chapter 3: Ecology of Vegetation in Channels ........................................................................................... 18 3.0 Riparian Vegetation .......................................................................................................................... 18 3.1 Vegetation and stream ecology/biology (habitat diversity, species diversity) .................................. 18 Chapter 4: Case Studies .............................................................................................................................. 20 4.1 The Effect of Artificial Placement of LWD in the River Y Fenni, in the Great Triley Wood, Near Abergavenny in South Wales .................................................................................................................. 20 4.1.1 Introduction ................................................................................................................................ 20 4.1.2 Results ........................................................................................................................................ 21 4.2 Large Woody Debris in Streams of the Pacific Northwest ............................................................... 23 4.2.1 Introduction ................................................................................................................................ 23 4.2.2 Durability of Pacific Northwest Instream Structures Following Floods (40) ............................... 24 4.2.3 Effectiveness of large woody debris in stream rehabilitation projects in urban basins (50) ......... 26 4.2.4 Density and size of juvenile salmonids in response to placement of large woody debris in Oregon and Washington streams (52) ................................................................................................... 27 4.3 The Response of Engineered Log Jams Introduced Into the Williams River, New South Wales, Australia .................................................................................................................................................. 28 4.3.1 Introduction ................................................................................................................................ 28 4.3.2 What are engineered log jams? .................................................................................................. 28 4.3.3 Types of Engineered Log Jams .................................................................................................. 28 Final Report Page i May 13, 2011 Effects of Vegetation in Channels 4.3.4 ELJs on the Williams River ....................................................................................................... 32 4.4 Riparian Restoration on the River Enz, Germany ............................................................................. 34 Chapter 5: Example Calculations ................................................................................................................ 36 5.1 Hydraulic Methods ............................................................................................................................ 36 5.1.1 Composite Roughness ................................................................................................................ 36 5.1.2 Subarea Partitioning ................................................................................................................... 37 5.1.3 Gravel Bed ................................................................................................................................. 37 5.1.4 Bends.......................................................................................................................................... 38 5.1.5 Vegetation .................................................................................................................................. 38 5.1.6 Large Woody Debris .................................................................................................................. 39 5.2 Example Calculations of LWD Effects ............................................................................................. 39 Chapter 6: Adaptive Management .............................................................................................................. 45 6.1 Introduction ....................................................................................................................................... 45 6.2 What is Adaptive Management? ....................................................................................................... 45 Chapter 7: Conclusions ............................................................................................................................... 47 7.0 Introduction ....................................................................................................................................... 47 7.1 Hydraulics ......................................................................................................................................... 47 7.2 Ecology ............................................................................................................................................. 47 7.3 Management ...................................................................................................................................... 47 7.4 General .............................................................................................................................................. 48 References ..................................................................................................................................................