Part 630 Hydrology National Engineering Handbook Chapter 14 Stage Discharge Relations Rain clouds Cloud formation Precipitation n o i Evaporation t a n r n o i a i p t l e a i s t c e o n o s a g e r v T m m o m o n r o r f r o f f i s t n a o r m ti i a a p e r s r o n t p a s a r v T m Surface runoff E o r f Infiltration Soil Percolation Rock Ocean Groundwater Deep percolation (210–VI–NEH, Amend. 53, April 2012) 1 Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook Issued April 2012 The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all pro- grams.) Persons with disabilities who require alternative means for commu- nication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, SW., Washington, DC 20250–9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. (210–VI–NEH, Amend. 53, April 2012) Acknowledgments Chapter 14 was originally prepared in 1971 by Robert Pasley (retired), NRCS, Washington, DC, and Dean Snider (retired), NRCS, Fort Worth, Texas, and revised in 1972 by Owen P. Lee, (retired), NRCS, Washington, DC, and Edward G. Riekert (retired), NRCS, Washington, DC. This version was prepared by William H. Merkel, hydraulic engineer, NRCS, Beltsville, Maryland; Helen Fox Moody, hydraulic engineer, NRCS, Beltsville, Mary- land; Quan D. Quan, hydraulic engineer, NRCS, Beltsville, Maryland; Karl Visser, hydraulic engineer, National Design, Construction, and Soil Mechan- ics Center, Fort Worth, Texas; and Donald E. Woodward (retired), NRCS, Washington, DC, under the guidance of Claudia C. Hoeft, national hy- draulic engineer, NRCS, Washington, DC. The Technical Publications Team, NRCS, Fort Worth, Texas, prepared the final document. (210–VI–NEH, Amend. 53, April 2012) Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook 14–ii (210–VI–NEH, Amend. 53, April 2012) Chapter 14 Stage Discharge Relations Contents 630.1400 Introduction 14–1 630.1401 Development of stage discharge curves 14–3 (a) Direct measurement .....................................................................................14–3 (b) Indirect measurements ................................................................................14–3 (c) Slope-area estimates ....................................................................................14–6 (d) Synthetic methods ......................................................................................14–10 630.1402 Collection of field data 14–11 (a) Selecting Manning’s n values .....................................................................14–11 (b) Selecting cross section locations .............................................................14–11 (c) Selecting representative reach lengths .....................................................14–11 630.1403 Discharge versus drainage area 14–14 630.1404 Computing profiles 14–16 630.1405 Road crossings 14–24 (a) Bridges .........................................................................................................14–24 (b) Full bridge flow ...........................................................................................14–32 (c) Overtopping of bridge embankment .........................................................14–33 (d) Multiple bridge openings ...........................................................................14–35 (e) Culverts .........................................................................................................14–36 630.1406 References 14–48 Appendix A Estimating the Roughness Coefficientn for Use in 14A–1 Hydraulic Computations Associated with Natural Streams, Floodways, and Similar Streams (210–VI–NEH, Amend. 53, April 2012) 14–iii Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook Tables Table 14–1 Computation of discharge using velocity head rod 14–5 (VHR) measurements Table 14–2 Data for computing discharge from slope-area 14–9 measurements, example 14–1 Table 14–3 Hydraulic parameters for starting cross section 14–18 M–1, example 14–4 Table 14–4 Stage discharge for section M–1 with meander 14–19 correction, example 14–5 Table 14–5 Water surface profiles from cross sections, 14–22 example 14–6 Table 14–6 Backwater computations through bridges, 14–30 example 14–8 Table 14–7 Stage discharge over roadway at cross section 14–35 M–4 without submergence, example 14–9 Table 14–8 Headwater computations for eight 16- by 8-foot 14–45 concrete box culverts, headwalls parallel to embankment (no wingwalls), square-edged on three sides, example 14–10 Table 14–9 Stage discharge over roadway at cross section 14–47 T–3, figure 14–5, example 14–10 Table 14A–1 Examples of effect of vegetation on n 14A–5 Table 14A–2 Computations for example 14A–2 14A–11 14–iv (210–VI–NEH, Amend. 53, April 2012) Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook Figures Figure 14–1 Energy balance equation 14–2 Figure 14–2 Velocity head rod for measuring streamflow 14–4 Figure 14–3 High water mark profile and cross sections, 14–8 Concho River near San Angelo, Texas Figure 14–4 Reach length versus elevation, Little Nemaha, 14–13 section 35 Figure 14–5 Schematic of watershed outlet with cross sections 14–17 and floodplain for examples 14–4, 14–5, 14–6, 14–8 14–9, and 14–10 Figure 14–6 Cross section M–1, examples 14–4 and 14–5 14–17 Figure 14–7 Conveyance values section M–1, example 14–4 14–18 Figure 14–8 Stage discharge curve, section M–1, example 14–4 14–19 Figure 14–9 Conveyance values, section M–2, example 14–6 14–21 Figure 14–10 Conveyance values, section T–1, example 14–6 14–21 Figure 14–11 Stage discharge, section M–2, example 14–6 14–24 Figure 14–12 Stage discharge, section T–1, example 14–6 14–24 Figure 14–13 Water surface profiles, example 14–8 14–27 Figure 14–14 Stage discharge without embankment overflow, 14–28 section M–5, example 14–8 Figure 14–15 Bridge opening areas, example 14–8 14–28 Figure 14–16 M values for bridge, example 14–8 14–31 Figure 14–17 J values for bridge, example 14–8 14–32 Figure 14–18 Stage discharge with embankment overflow, 14–36 section M–5, example 14–9 Figure 14–19 Approach section for a bridge opening 14–37 Figure 14–20 Culvert flow conditions 14–38 Figure 14–21 Types of culvert inlets 14–39 Figure 14–22 Elements of culvert flow for outlet control 14–41 Figure 14–23 Plots of data for cross section T–3, example 14–10 14–42 (210–VI–NEH, Amend. 53, April 2012) 14–v Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook Figure 14–24 Stage discharge exit section T–2, example 14–10 14–43 Figure 14–25 Rating curves, cross section T–4, example 14–10 14–44 Figure 14A–1 Selection of Manning’s n for a cross section 14A–7 Figure 14A–2 Example of field notes describing roughness conditions 14A–8 Figure 14A–3 Hydraulic properties of a subdivided cross section, 14A–10 example 14A–2 Exhibits Exhibit 14–1 K values for converting cubic feet per second 14–51 per square mile to cubic feet per second Exhibit 14–2 Estimate of velocity head in bridges 14–52 Exhibit 14–3 Estimate of M for use in BPR equation 14–53 Exhibit 14–4 BPR base curve for bridges, Kb 14–54 Exhibit 14–5(a) Incremental backwater coefficients∆K and 14–55 J for the more common types of columns, piers, and pile bents Exhibit 14–5(b) Incremental backwater coefficientsσ and M 14–56 for the more common types of columns, piers, and pile bents Exhibit 14–6 Headwater depth for box culverts with inlet control 14–57 Exhibit 14–7 Headwater depth for concrete pipe culverts with 14–58 inlet control Exhibit 14–8 Headwater depth for oval concrete pipe culverts 14–59 long axis horizontal with inlet control Exhibit 14–9 Headwater depth for corrugated metal (C.M.) 14–60 pipe culverts with inlet control Exhibit 14–10 Headwater depth for corrugated metal (C.M.) 14–61 pipe-arch culverts with inlet control Exhibit 14–11 Head for concrete box culverts flowing 14–62 full—n = 0.012 14–vi (210–VI–NEH, Amend. 53, April 2012) Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook Exhibit 14–12 Head for concrete pipe culverts flowing 14–63 full—n = 0.012 Exhibit 14–13 Head for oval concrete pipe culverts long axis 14–64 horizontal or vertical flowing full—n = 0.012 Exhibit 14–14 Head for standard corrugated metal (C.M.) 14–65 pipe culverts flowing full—n = 0.024 Exhibit 14–15 Head for standard corrugated metal (C.M.) 14–66 pipe-arch culverts flowing full—n = 0.024 Exhibit 14–16 Critical depth—rectangular section 14–67 Exhibit 14–17 Critical depth—circular pipe 14–68 Exhibit 14–18 Critical depth—oval concrete pipe—long 14–69 axis horizontal Exhibit 14–19 Critical depth—standard corrugated metal 14–70 (C.M.) pipe-arch Exhibit 14–20 Critical depth—structural plate—corrugated 14–71 metal (C.M.) pipe-arch, 18-inch corner radius Exhibit 14–21 Entrance loss coefficients 14–72 (210–VI–NEH, Amend. 53, April 2012) 14–vii Chapter 14 Stage Discharge Relations Part 630 National Engineering Handbook