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January 1982 Final Report PB83-118190 STREA January 1982 final Report fi)e[:umEmi: is available to the U.S. public through till" NatioilCl! Technical information Service Sj)fr'ing'l'ieid, V~!'girli<J 22161 Prepared for REPRODUCED BY Deportment of Transportation NATIONAL TECHNICAL u.s. INFORMATION SERVICE ~~der@~ ";~gh\fj@Y Administration u.s. DEPARTMENT OF COMMERCE SPR'INGfIELD, VA. 22161 Offices of Research & Development Environmental Division Washington, D.C. 20590 FOREWORD '!his report provides a simple method for detennining relative stability of streams based on stream type. Four stream types are distinguished based on variability of width and presence of bars , These characteristics are readily observed on aerial photographs, supplerrented with field investigations.. The study is an outgrowth of previous research contracts "Countenneasures for Hydraulic Problems at Bridges" (Research Report Number: FHWA/RD-78/l62) and "Stability of Relocated stream Charmels" (Research Report Nmnber: FHWA/RD-80/158)" An understanding of the potential for stream instability hazards at a particular crossing is necessary for proper design and mai.ntenance, Research in highway drainage and stream crossing design is included in the Fed.eral Coordinated Program of Highway Research and Deve Iopmerrt; in Project 5H "Protection of the Highway System from Hazards Attributed to Flooding,," Roy E. Trent is the Projec-t Manager and Stephen A", Gilje is t::le Task Manager and the Contracting Officers & Tectillical Representa~cive for this eff'fort.. Sufficient copies of the report are being distributed to provide a mirrimum of one copy to each FHWA regional office, division office, and state highway agency e Direct distribution is being made to the division offices. /" / ~ // ;j I -. / ; J:_ -, '1/ . F' I ;()J)'''fi/''7 d5"O /fj" ~.,.._Charles F" Scheffey if Director g Office of Research NOTICE This document is disseminated under the sponsorship of the Department of Transportation in the interest of info~ma~i?n exchange. The United States Government assumes no l1abl11ty for its contents or use thereof. The contents of this report reflect the views of the contractor, who is responsible for the accuracy of the data presented herein. The contents do not necessarily reflect the official policy of the Department of Transportation. This report does not constitute a standard, specification, or regulation. The United States Government does not endorse products or manufacturers. Trade or manufacturers v names appear herein only because they are considered essential to the object of this document. Technical Report Documentation Page 1. Report No. 2. Governmen,t Accession No. 3. Recipient's Catalog No. F'ffi\1A/RD- 82/021 PB83 118190 4. Title and Subtitle 5. Report Date Januarv 1982 stream Channe L Stabili.ty Assessment 6. Performing Organi zation Code ------------------4 ~~~~~------------------------~8. Performing Organization Report No. 7. Author1s) L1 C Brice 9. Performing Organi zation Name and Address 10. Work Unit No. (TRAIS) u.S. Geological Survey, WRD FCP #35HI-032 345 Middlefield Road 11. Contract or Grant No. Menlo Park, California 94025 P.O. No. DTFH6l-8l-P-30085 r--------------------------------oj 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Final Peport. Office of Fesearch .Ian.. -Oct> 1981 Federal Highway Administration U•s. Deparbnent of Transportation Washinoton, D.C. 20590 15. Supplementary Notes FH\A.~ Contract Manager: Stephen A. Gilje (HRS-42) 16. Abstract Channel instability is manifested as lateral bank erosion, progressive degradation of the streambed, or natural scour and fill of the streambed. Lateral stability is related to stream type, and four major stream types having different stability characteristics are distinguished: equiwidth, wide-bend point. bar, braided point-bar I and braided. Measurements of bank erosion on a study group of 36 streams indicate that oquiwidth streams have the lOVJest lateral erosion rates and braided point-bar strearrs the highest. Also, erosion rates Increase with stream size. Significant degradation of the streambed can usually be detected from indirect field evidence. The sites of greatest potential scour along a channel can be identified from charmel configuration. 17. Key Words 18. Distribution Statement streams, Channel Morphology, Channel No restrictions. Thi.s document is Er'os.i.on, Scour I Channel Patterns, available to the public through the Stre2nbed Degradation. National Teclmical Information Service Springfield, Virginia 22161. 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price UNCLASSIFIED UNCIASSIFIED ' ' 45 \ \ Form DOT F 1700.7 (8-72) Reproduction of completed page authori zed NOT ICE THIS DOCUJ\tlENT HAS BEEN REPRODUCED FROM THE BEST COpy FURNISHED US BY THE SPONSORING AGENCY. ALTHOUGH IT IS RECOGNIZED THAT CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED IN THE INTEREST OF MAKING AVAILABLE AS wIUCH INFOR1'IATION AS POSSIBLE. CONTENTS Page Introduction 1 Airphoto interpretation of channel properties -------------------------------- 2 Major channel properties -------------------------------------------------- 2 Alluvial strea~ types ---------------------------------------------------__ 5 Lateral stability ------------------------------------------------------------ 14 Field assessment ---------------------------------------------------------- 14 Unstable banks, erosion rate moderate to high -------------------------- 15 Unstable banks, erosion rate slow to moderate -------------------------- 16 Stable banks, erosion rate very slow ----------------------------------- 16 Repetitive surveys of channel cross section ------------------------------- 18 Measurement on airphotos and maps ----------------------------------------- 18 Acquisition of maps ---------------------------------------------------- 18 Acquisition of airphotos ----------------------------------------------- 18 Reference points on time-sequential airphotos -------------------------- 19 Airphoto scale --------------------------------------------------------- 19 Methods of comparison -------------------------------------------------- 21 'Photographic enlargement ----------------------------------------------- 22 Reflecting projector --------------------------------------------------- 22 Graphical data transfer instrument ------------------------------------- 22 Direct projection of transparencies ------------------------------------ 22 Lateral stability in relation to channel type and size -------------------- 23 Estimation of future stability and behavior ------------------------------- 29 Bank erosion rates ----------------------------------------------------- 29 Behavior of meander loops ---------------------------------------------- 29 Effects of meander cutoff ---------------------------------------------- 29 Meander cutoff on the South Santiam River, Oregon ---------------------- 29 Channel degradation ---------------------------------------------------------- 31 Assessment of degradation ------------------------------------------------- 32 Field assessment of degradation ---------------------------------------- 32 Other methods of assessment -------------------------------------------- 33 Natural scour and fill ------------------------------------------------------- 33 Definition and measurement ------------------------------------------------ 33 Bed form migration -------------------------------------------------------- 34 Convergence and divergence of flow ---------------------------------------- 35 Scour in relation to channel configuration -------------------------------- 36 Shift of thalweg ---------------------------------------------------------- 36 Assessment of natural scour at a site ------------------------------------- 37 Bed form migration ----------------------------------------------------- 37 Convergence of flow ---------------------------------------------------- 37 Shift of thalweg ------------------------------------------------------- 38 Conclusions ------------------------------------------------------------------ 39 Recommendations -------------------------------------------------------------- 40 Selection of a crossing site ------------------------------------------- 40 Design of bridge ------------------------------------------------------- 40 Location of highway parallel to stream course -------------------------- 40 References ------------------------------------------------------------------- 41 ILLUSTRATIONS Page Figure 1. Major properties of alluvial channels ----------------------------- 3 2. Typical features of a laterally unstable stream ------------------- 4 3. Typical features of a laterally stable stream --------------------- 5 4. Alluvial stream types ------------------------------Q-------------- 6 5. Equiwidth stream incised into cohesive surficial materials -------- 7 6. Equiwidth stream incised into alluvium ---------------------------- 7 7. Equiwidth stream on a swampy, densely forested coastal plain ------ 8 8. Large equiwidth stream on a densely forested flood plain ---------- 8 9. Equiwidth stream on a swampy, forested glacial drift plain -------- 9 10. Equiwidth stream, locally anabranched, on a semiarid plain -------- 9 11. Wide-bend point-bar stream on a flood plain densely forested with hardwood -------------------------------------------------- 10 12. Wide-bend point-bar stream on a deforested flood plain ------------ 10 13. Wide-bend point-bar stream, incised, on a sparsely forested plain -------------------------------------------------
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