SEDIMENT AND EROSION DESIGN GUIDE Prepared for Southern Sandoval County Arroyo Flood Control Authority 1041 Commercial Dr. SE Rio Rancho, New Mexico 87124 Prepared by 1730 S. College Ave #100 Fort Collins, Colorado 80525 November 2008 Acknowledgements This manual was compiled by Dr. Bob Mussetter, Mussetter Engineering, Inc. with assistance from the DPM Technical Committee (David Stoliker, Robert Foglesong, Trevor Alsop, Fred Aguirre, Howard Stone, Clint Dodge, Jeff Mortenson, and Randall Carroll). Much of the material in this manual was originally compiled for the Albuquerque Metropolitan Flood Control Authority (AMAFCA) Erosion and Sediment Design Guide that was published in 1994, modified and updated for applicability to the SSCAFCA jurisdictional area. Disclaimer This document is provided as a guidance document in the SSCAFCA and City of Rio Rancho area. The intent of this document is to assist regulatory authorities, engineers, developers, and other interested parties in understanding the dynamic behavior of arroyos and other natural or naturalistic drainageways, and identifying appropriate means of protecting people and property from flooding, erosion and sedimentation during storm events up to and including the 100-year event. The user should report any errors in this document promptly to SSCAFCA and the City of Rio Rancho. The user accepts full responsibility for application of the guidance information contained herein to their particular situations. 12603 SSCAFCA Sediment and Erosion Design Guide i TABLE OF CONTENTS Page Acknowledgements........................................................................................................................ i Disclaimer ...................................................................................................................................... i CONSTANTS AND CONVERSIONS............................................................................................ x LIST OF VARIABLES .................................................................................................................. xi INDEX ........................................................................................................................................ xiv 1. INTRODUCTION ................................................................................................................1.1 1.1. Purpose and Scope of Manual...................................................................................1.1 1.2. Arroyo Process—A General Statement of the Problem .............................................1.2 2. GEOMORPHIC AND WATERSHED PROCESSES IN TRIBUTARIES OF THE MIDDLE RIO GRANDE IN AND NEAR THE SSCAFCA JURISDICTIONAL AREA...........2.1 2.1. Geomorphology of the Area .......................................................................................2.1 2.1.1. Landforms ..........................................................................................................2.1 2.1.1.1. Alluvial Fans ...................................................................................................2.1 2.1.1.2. Pediments .......................................................................................................2.1 2.1.1.3. Alluvial Terraces..............................................................................................2.1 2.1.1.4. Floodplains of the Major Channels .................................................................2.2 2.1.1.5. The Ceja Mesa and Volcanic Plateau ............................................................2.2 2.1.2. Geomorphology of the SSCAFCA Area ...............................................................2.2 2.2. Rainfall-Runoff Processes..........................................................................................2.4 2.3. Sediment Yield............................................................................................................2.5 3. CHANNEL DYNAMICS.......................................................................................................3.1 3.1. Arroyo Geomorphology ..............................................................................................3.1 3.1.1. Channel Incision.................................................................................................3.1 3.1.2. Channel Widening ..............................................................................................3.2 3.1.3. Arroyo Evolution .................................................................................................3.2 3.2. Hydraulic Factors and Principles .................................................................................3.4 3.2.1. Introduction.........................................................................................................3.4 3.2.2. Uniform Flow Relationships................................................................................3.5 3.2.3. Hydraulics in Steep, Alluvial Channels.................................................................3.6 3.2.3.1. Bedforms and Flow Regime ...........................................................................3.6 3.2.3.2. Resistance to Flow—General ..........................................................................3.7 SSCAFCA Sediment and Erosion Design Guide ii 3.2.3.3. Resistance to Flow in Sand-bed Channels.....................................................3.9 3.2.3.4. Normal Depth Calculations ............................................................................3.13 3.2.3.5. Water-surface Profiles..................................................................................3.14 3.2.3.6. Superelevation of Water Surface at Bends ....................................................3.14 3.2.3.7. Supercritical Flow in Natural Channels.........................................................3.15 3.3. Sediment Transport in Steep, Erodible Channels ....................................................3.16 3.3.1. Introduction.......................................................................................................3.16 3.3.2. Analysis of Bed and Bank Material...................................................................3.18 3.3.3. Bed Material in the SSCAFCA Area.................................................................3.19 3.3.4. Incipient Motion and Armoring..........................................................................3.22 3.3.5. Methods for Computing Bed Material Transport Capacity................................3.22 3.3.6. Bulking Factors for the SSCAFCA Area...........................................................3.23 3.4. Evaluation of Channel Adjustments .........................................................................3.27 3.4.1. Sediment Continuity .........................................................................................3.27 3.4.2. The Equilibrium Concept ..................................................................................3.27 Annual Sediment Yield and Dominant Discharge............................................. 3.28 3.4.3. Evaluation of Vertical Stability ..........................................................................3.29 3.4.3.1. Equilibrium Slope..........................................................................................3.30 3.4.3.2. An Alternative Approximation of the Equilibrium Slope ................................3.31 3.4.3.3. Contraction Scour.........................................................................................3.33 3.4.3.4. Antidune Scour.............................................................................................3.33 3.4.4. Sediment Transport and Channel Stability at Culverts.....................................3.34 3.4.4.1. Sediment Deposition Upstream of Culverts..................................................3.35 3.4.4.2. Sediment Transport in Culverts ....................................................................3.35 3.4.4.3. Degradation from Culverts............................................................................3.36 3.4.5. Evaluation of Lateral Stability and the LEE Line...............................................3.36 3.4.5.1. Bank Erosion Processes ..............................................................................3.36 3.4.5.2. Bank Stability Analysis Techniques..............................................................3.39 3.4.5.3. Lateral Erosion Envelope (The LEE Line) ....................................................3.43 3.4.5.4. Guidelines for Aggradational Channels ........................................................3.48 3.5. Local Scour...............................................................................................................3.49 3.5.1. Pier Scour at Bridge Crossings ........................................................................3.49 3.5.2. Scour at Grade-control Structures....................................................................3.53 3.5.3. Scour at Revetments, Spurs, and Abutments ..................................................3.55 3.5.4. Scour along a Floodwall ...................................................................................3.56 3.5.4.1. Flow Parallel to the Wall ................................................................................3.56 3.5.4.2. Flow Impinging on the Wall at an Angle .......................................................3.57 3.5.4.3. Scour along a Floodwall in Relation to Unconstrained Valley Width ............3.57 SSCAFCA Sediment and Erosion Design