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VI. 1 VI. River Engineering And Geomorphology For Transportation Design.

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Presentation on theme: "VI. 1 VI. River Engineering And Geomorphology For Transportation Design."— Presentation transcript:

1 VI. 1 VI. River Engineering And Geomorphology For Transportation Design

2 VI. 2 VI. River Engineering And Geomorphology For Transportation Design Lecture Overview ASedimentation and Scour BDynamic Nature of Streams in the Arid West C Sediment Transport Models Next Lecture Section VII – Effects of Transportation Structures on Stream Systems

3 VI. 3 VI. River Engineering And Geomorphology For Transportation Design A.1.Sedimentation And Scour: Basic Sediment Transport Theory a) Sediment Continuity b) Sediment Transport Capacity c) Sediment Load d) Sediment Transport Functions e) Sediment Yield

4 VI. 4 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory a)Sediment Continuity Equation Storage change = erosion or deposition Streams naturally balance sediment load Imbalances cause adjustments to occur Fixing one problem may cause another Sediment in – Sediment out = Storage Change

5 VI. 5 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory c)Sediment Transport Capacity The amount of sediment a stream can move Basic Principles: Streams carry as much sediment as they can Streams deprived of sediment will find some Streams with excess will lose some There are several types of sediment transport

6 VI. 6 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory c)Sediment Load Types of Sediment load Bed-material load Wash load Total load Types of Sediment Movement Sliding, rolling, saltation, suspension, solution

7 VI. 7 A.1.Basic Sediment Transport Theory c)Sediment Load: Classification Sediment Load Classification Schemes. (After SCS, 1983, Figure 4-2.) Wash Load Suspended Bed-Material Load Bed Load Suspended Load Bed Load Wash Load Bed-Material Load TOTALTOTAL LOADLOAD VI. River Engineering And Geomorphology For Transportation Design

8 VI. 8 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory d)Sediment Transport Equations Key References: ADWR, 1985 – Design Manual for Engineering Analysis of Fluvial Systems ASCE Publications Sediment Transport Textbooks Variables: shown on next slide

9 VI. 9 Vegetation Cover Slope Drainage Area Elevation Geology Valley Slope Sediment yield Human Impacts – Urbanization Grazing Practices Watershed Characteristics Vegetation Type Root Depth Root Density Branch/Foliage Density Trunk Pliability Growth Rate Germination Cycle Grazing Practices Channel Vegetation Engineering (short-term) Geologic (long-term) Time Scale Precipitation Type (snow?) Precipitation Intensity Precipitation Duration Seasonal Distribution Temperature/Evaporation Climate Mean Diameter Size Distribution Armoring Potential Cohesion Stratigraphy Streambed and Bank Sediment Magnitude (peak) Duration (flashy?) Ratio of Peak to Base Flow Ratio of Rare to Frequent Floods Channel Capacity Losses Reservoirs/Flood Storage Flood Characteristics Width Depth Hydraulic Radius Friction Factor Velocity Topwidth Turbulence Temperature Transmission Losses Flow Channel Width Channel Depth Bank Height Bank Slope Bank Materials Bank Stratification Stream Pattern Bed Forms Meander Amplitude Meander Wavelength Sinuosity Floodplain Width Depth of Floodplain Flow Stream Terraces Channel Slope Aggradation Degradation Local Scour Bed Sediment Bar Sediment Pool & Riffle Sequence Armoring Bedrock Outcrop & Control Human Modifications Bank Protection Grade Control Roadway Crossings Utility Crossings Dominant Discharge Mean Annual Discharge Flow Duration Statistics Variation with Season Diversions and Storage Flow Source Hydrology River CharacteristicsVariable SubgroupVariable Some Variables Affecting River Behavior and River Characteristics That Can Change With Time

10 VI. 10 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory d)Sediment Transport: Typical Equation Zeller-Fullerton (Einstein/Meyer-Peter Muller) Qs = W n 1.77 V 4.32 G 0.45 Y -0.3 D Einstein’s suspended bed-material integration Meyer-Peter, Muller bedload equation Total bed-material discharge

11 VI. 11 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory d)Sediment Transport: Function Considerations Type of Load Variability Spatial variation Within channel, along stream Geographic regions Temporal Flow rates during hydrograph Seasonal Initiation of Sediment Movement Source Data for Empirical Equations

12 VI. 12 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory d)Sediment Transport: Yield Definitions Erosion: soil loss Delivery: sediment yield Factors Influencing Sediment Yield Climate, geology, vegetation, land use, topography, soils, runoff, channel conditions

13 VI. 13 Sediment Yield Over Time

14 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory e)Sediment Yield: Methodologies PSIAC Planning Level Average Annual Yield (Delivery) Total Load MUSLE/USLE/RUSLE Soil Loss Event Based Model (MUSLE/RUSLE) Suspended Load

15 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory e)Sediment Yield: Methodologies Reservoir Data BUREC Equation (Design of Small Dams) Total Load Average Annual Sediment Delivery Many Regional Methodologies Total Load Average Annual Sediment Delivery

16 VI. River Engineering And Geomorphology For Transportation Design A.1.Basic Sediment Transport Theory e)Sediment Yield: Implementation Rules Real World: Yield Varies Widely Rules of Thumb Average annual is poor predictor in Arizona For larger watersheds, use transport methods Sediment delivery is generally underestimated 10% sediment concentration

17 VI. 17 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion a)Types of Scour b)Scour Prediction c)Scour Equation d)Scour Mitigation

18 VI. 18 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion a)Types of Scour Short-Term Scour Scour is “lowering of a channel bed.” City of Tucson Manual, p “Short-term changes in channel bed elevation.” Long-Term Scour Lateral Erosion

19 VI. 19 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion a)Types of Scour Components of scour General Bend Thalweg Bed form Local [Long-term]

20 VI. 20 Scour Components

21 VI. 21 Scour Components

22 VI San Juan River Near Bluff, UT Example of Scour During a Flood

23 VI. 23 Natural Local Scour

24 VI. 24 Field Evidence of Scour Depth

25 VI. 25 Local Scour (PHOTO)

26 VI. 26 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion a)Types of Scour (CONTINUED) Long-Term Scour (Degradation) Time Scale Causes Geologic forces Hydrologic regime change Sediment supply Slope adjustments Change in erodibility PROCESS-BASED

27 VI. 27 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion b)Scour Prediction: Factors That Influence Scour Hydraulics Velocity, Depth, Slope Bend angle Obstructions Piers, walls, natural – shape, width, encroachment Other factors Flow rate Material characteristics

28 VI. 28 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion c)Scour Equations: Estimating Long-Term Scour Arroyo Evolution Model (AMAFCA Manual) Equilibrium Slope (ADWR and COT Manuals) State Standard 5-96 Field and Historical Data

29 VI. 29 Field Evidence Of Scour

30 VI. 30 Field Evidence Of Long-Term Scour

31 VI. 31 Field Evidence Of Long-Term Scour

32 VI. 32 Field Evidence Of Long-Term Scour

33 VI. 33 Field Evidence Of Long-Term Scour

34 VI. 34 VI. River Engineering And Geomorphology For Transportation Design A.2.Scour and Erosion d)Scour Mitigation Measures Resistant Materials Non-Transportable Materials Change Hydraulics Monitor and Maintenance References: Highways in Riverine Environment HEC-18/HEC-20

35 VI. 35 VI. River Engineering And Geomorphology For Transportation Design A.3. Recurrence Intervals Small flows Large floods Sediment transport Scour Lateral erosion Peak vs. Volume

36 VI. 36 VI. River Engineering And Geomorphology For Transportation Design B.Dynamic Nature of Streams in the Arid West 1.Humid vs. Arid Environments 2.Alluvial Streams 3.Ephemeral vs. Perennial Streams 4.Lateral Erosion, Avulsion and Meandering 5.Aggradation/Degradation 6.Flash Floods 7.Flood Ratios, Flood Volume 8.Alluvial Fans

37 VI. 37 Humid Region Streams Perennial Low Flood Ratio Long Durations Small Floods Dominate Meandering Slow Erosion Fast Recovery Free Flowing Low Sediment Load Resistant to Change Arid Region Streams Ephemeral High Flood Ratio Short Durations Large Floods Dominate Braided, Straight Fast Erosion Slow Recovery Dams and Diversions High Sediment Load Sensitive to Change B.1. Humid vs. Arid Environments

38 VI. 38 VI. River Engineering And Geomorphology For Transportation Design B.2.Alluvial Streams Formed by Materials it Carries Boundaries Subject to Transport Balance Between Transport/Deposition Change the Boundaries, Change the Stream

39 VI. 39 Perennial Equilibrium Non-flood recovery Defined banks Well vegetated Environmental protection Ephemeral Non-equilibrium Work only in floods Poorly defined banks Poorly vegetated Less environmental protection B.3. Ephemeral vs. Perennial

40 VI. 40 VI. River Engineering And Geomorphology For Transportation Design B.4.Lateral Erosion Bank Erosion Widening Meandering Avulsion

41 VI. 41 Mechanisms Of Bank Erosion

42 VI. 42 Bank Erosion

43 VI. 43 Bank Erosion

44 VI. 44 Bank Erosion

45 VI. 45 Widening Of Braided Streams

46 VI. 46 Meandering

47 VI. 47 Channel Avulsion

48 VI. 48

49 VI. 49 VI. River Engineering And Geomorphology For Transportation Design B.5. Aggradation/Degradation Aggradation – Bed Elevation Increases Some braided streams Alluvial fans Obstructions Degradation – Bed Elevation Decreases Urban rivers Encroachment In-stream mining

50 VI. 50 Field Techniques: Terraces/Headcuts

51 VI. 51 Channel Pattern Changes

52 VI. 52 VI. River Engineering And Geomorphology For Transportation Design B.6.Flash Floods Time to Peak Recession Time Transportation Issues: Response Time Observation of Floods Interruption Time Risk

53 VI. 53 VI. River Engineering And Geomorphology For Transportation Design B.7.Flood Ratio and Volume Examples of Flood Ratios Central Arizona Northern Arizona East Coast Annual Flow Volume vs. Flood Volume Salt River Skunk Creek Synthetic Hydrograph

54 VI. 54 VI. River Engineering And Geomorphology For Transportation Design B.8Alluvial Fans Depositional Landform Uncertain Flow Paths Channelized and Unchannelized Flow Avulsive Channel Change

55 VI. 55 Alluvial Fans

56 VI. 56 Alluvial Fans

57 VI. 57 Alluvial Fans

58 VI. 58 Arizona Alluvial Fans

59 VI. 59 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 1.Types of Models 2.Sediment Transport Computer Models 3.Evaluation of Results 4.Application of Sediment Transport Equations

60 VI. 60 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 1.Types of Models: Computer Models Mathematical Models Physical Models Qualitative Models

61 VI. 61 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 2.Sediment Transport Computer Models: Examples HEC-6, 6T Kovacs-Parker FLUVIAL-12 Darby-Thorne GSTARS Wiele STREAM2 Simon et. al. WIDTH Pizzuto RIPA Alonso-Co QUASED Many others

62 VI. 62 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 2.Sediment Transport Computer Models HEC-6 One dimensional Steady discharge Uniform scour or deposition Sediment continuity Initial conditions Time scale Sediment sources Sediment transport calculations Equilibrium Time step Bridges and culverts

63 VI. 63 C.Sediment Transport Models 2.Sediment Transport Computer Models Hydraulic modeling Gradually varied Steady flow One-dimensional Slope is low Discharge is known Loss coefficients are known Geometry is accurate Single channel – tributary pattern VI. River Engineering And Geomorphology For Transportation Design

64 VI. 64 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 2.Sediment Transport Computer Models Continuity principle: Inflow – outflow = change in storage Transport function selection Contribution of bank material Upstream control of sediment process Uniform sediment flux Ignores base level adjustments Channel vs. floodplain processes

65 VI. 65 C. Sediment Transport Models 2.Sediment Transport Computer Models: HEC-6 Assumptions HEC-6 Modeling Assumptions and Limitations Assumption/Limitation Assumption Generally Valid in Arizona? One Dimensional No. But probably gradually varied Uniform Scour or Deposition No. Braided system with bars No Bank Erosion No. Banks unstable in design flood Steady Flow Condition Modeled No. Flash flood hydrograph Sediment Continuity Initial Conditions for Suspended Sediment Yes. Ephemeral stream Time Scale of Hydrograph No. Flash flood conditions Sediment Sources Yes. Bed is primary source of sediment Sediment Calculations Yes. Equilibrium Achieved in Time Step No. Short duration hydrograph Time Step Length Adequate Yes. Scour limited in time steps No. Inadequate travel time through model No Bridges and Culverts No. Generally the point of investigation Low slope Yes. Single channel No. Braided, avulsive, sheet, distributary Accurate topographic mapping No. Accuracy within prediction range Know sediment size, hydraulic coefficients No. Varies temporally and spatially Yes.

66 VI. 66 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 2.Sediment Transport Computer Models: HEC-6 Results Uniform bed elevation change No bank erosion No scour in floodplain DOS Channel pattern adjustments Avulsive channel erosion Time scale: poor long-term modeling

67 VI. 67 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models

68 VI. 68 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 3.Evaluation of results Sensitivity analysis Calibration and verification Field data Historical data Comparative cross sections

69 VI. 69 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 4.Application of Sediment Transport Principles: Lane’s Relation Tool to evaluate / anticipate direction and nature of change from changes in sediment Q S  Q S D 50 Q = discharge S = energy slope Q S = sediment discharge D 50 = median sediment diameter

70 VI. 70

71 VI. 71 VI. River Engineering And Geomorphology For Transportation Design C.Sediment Transport Models 4.Application of Sediment Transport Equations: Zeller-Fullerton Equation Tool to evaluate / anticipate direction and nature of change from changes in sediment Qs = W n 1.77 V 4.32 G 0.45 Y -0.3 D If V increase, Qs ____________ If V decrease, Qs ____________ If n decrease, Qs ____________ If Y increase, Qs _____________ If D50 decrease, Qs ___________


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