Ch16 surface water_fall2007-final

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  • Begins as sheetflow:
    Infiltration capacity is controlled by:
    Intensity and duration of rainfall
    Prior wetted condition of the soil
    Soil texture
    Slope of the land
    Nature of the vegetative cover
  • Ch16 surface water_fall2007-final

    1. 1. CHAPTER 16 SURFACE WATER
    2. 2. RIVERS & STREAMS • The Hydrologic Cycle • Water Reservoirs • Surface Water Systems • Surface Water Flow • Sediment Transport • Stream System Components • Floods and Flooding • Pollution
    3. 3. What is the Cycle of Water on Earth’s Surface? • The hydrologic cycle is a summary of the circulation of Earth’s water supply. • Processes involved in the hydrologic cycle: • Precipitation • Evaporation • Infiltration • Runoff • Transpiration
    4. 4. The Hydrologic Cycle • Infiltration = Groundwater System • Runoff = Surface Water System • Runoff = Precipitation – Evapotranspiration Figure 16.3
    5. 5. Where is the Water ? Figure 16.2
    6. 6. The World’s Largest Rivers by Length Largest Rivers of the World River Outflow mi. km Nile Mediterranean Sea 4,180 6,690 Amazon Atlantic Ocean 3,912 6,296 Mississippi-Missouri Gulf of Mexico 3,710 5,970 Yangtze Kiang China Sea 3,602 5,797 Ob Gulf of Ob 3,459 5,567 Huang Ho (Yellow) Gulf of Chihli 2,900 4,667 Yenisei Arctic Ocean 2,800 4,506 Paraná Río de la Plata 2,795 4,498 Irtish Ob River 2,758 4,438 Zaire (Congo) Atlantic Ocean 2,716 4,371 Heilong (Amur) Tatar Strait 2,704 4,352 Lena Arctic Ocean 2,652 4,268 Mackenzie Beaufort Sea (Arctic Ocean) 2,635 4,241 Niger Gulf of Guinea 2,600 4,184 Mekong South China Sea 2,500 4,023 Mississippi Gulf of Mexico 2,348 3,779 Missouri Mississippi River 2,315 3,726 Volga Caspian Sea 2,291 3,687 Madeira Amazon River 2,012 3,238 Purus Amazon River 1,993 3,207 São Francisco Atlantic Ocean 1,987 3,198 Yukon Bering Sea 1,979 3,185 St. Lawrence Gulf of St. Lawrence 1,900 3,058 Rio Grande Gulf of Mexico 1,885 3,034 Brahmaputra Ganges River 1,800 2,897 Indus Arabian Sea 1,800 2,897 Danube Black Sea 1,766 2,842 Euphrates Shatt-al-Arab 1,739 2,799 Darling Murray River 1,702 2,739 Zambezi Mozambique Channel 1,700 2,736 Tocantins Pará River 1,677 2,699 Approx. length
    7. 7. Discharge River m^3/sec mm/yr % of total entering oceans Runoff Ratio 1 Amazon, Brazil 190,000 835 13.0 0.47 2 Congo, Zaire 42,000 340 2.9 0.25 3 Yangtse Kiang, China 35,000 560 2.4 0.50 4 Orinoco, Venezuela 29,000 845 2.0 0.46 5 Brahmaputra, Bangladesh 20,000 1070 1.4 0.65 6 La Plata, Brazil 19,500 235 1.3 0.20 7 Yenissei, Russia 17,800 215 1.2 0.42 8 Mississippi, USA 17,700 175 1.2 0.21 9 Lena, Russia 16,300 210 1.1 0.46 10 Mekong, Vietnam 15,900 630 1.1 0.43 11 Ganges, India 15,500 455 1.1 0.42 12 Irrawaddy, Burma 14,000 1020 1.0 0.60 13 Ob, Russia 12,500 135 0.9 0.24 14 Sikiang, China 11,500 840 0.8 - 15 Amur, Russia 11,000 190 0.8 0.32 16 St. Lawrence, Canada 10,400 310 0.7 0.33 The World’s Largest Rivers by Discharge
    8. 8. U.S. Precipitation Map U.S. Runoff Map Notice the effect of the Rocky Mountains
    9. 9. What is the Function of Streams? (From the Geologic Perspective, of course)
    10. 10. The main function of a stream is to remove excess surface water from the continent.
    11. 11. How Do Streams Remove Water from the Continent? • Laminar Flow • Turbulent Flow • By Stream Flow – Two types determined primarily by velocity:
    12. 12. Near-Laminar flow in the center of a river channel Turbulent flow in the headwaters of a rushing mountain stream
    13. 13. Factors that Determine Velocity • Gradient, or slope. • Channel Characteristics including: – shape – size – roughness. • Discharge
    14. 14. So Where Does Streams Flow the Fastest (Highest Velocity)? • Headwaters move slowest. • Mouth of stream moves fastest. • Laminar flow is more efficient than turbulent flow. • Deeper streams move faster than shallower streams.
    15. 15. How much water do streams remove from a continent?
    16. 16. Discharge – the volume of water moving past a given point in a certain amount of time. • Highly variable in most streams. • When discharge increases, velocity and channel cross-sectional area both increase. Discharge (m3 /s) = channel width(m) X channel depth(m) X velocity(m/s)
    17. 17. - Velocity measurements V 0.6D D Pygmy Meter Price Meter ∫ ×= A dAVQ  Stream bank
    18. 18. RATINGS CURVE Collect stage data continuously, transform it to discharge data To get a bit of experience with stream gaging and analysis of stream data, visit http://vcourseware4.calstatela.edu/VirtualRiver/FloodingDemo/index.html and play with it!!!
    19. 19. World’s Largest Rivers Ranked by Discharge
    20. 20. How Do Streams: Affect the Land Surface (and Geology)?
    21. 21. While rivers are removing water from the continent: • They carve the landscape forming erosional geologic features. • The erode existing geologic formations (rocks). • Transport the sediments. • Deposit new geologic formations.
    22. 22. Streams Carve the Landscape by Erosion • Lift loosely consolidated particles by: • Abrasion (Mechanical Weathering) • Dissolution (Chemical Weathering) • Stronger currents lift particles more effectively. • Create stream valleys and other erosional features.
    23. 23. How Do Streams Transport Eroded Sediments to Deposit New Geologic Formations? • Types of Stream Load: – Dissolved Load – Suspended Load – Bed Load • Streams transport sediment via stream loads.
    24. 24. Movement of Bed Load by Saltation
    25. 25. Animation #75: Sediment Transport by Streams
    26. 26. – Capacity – the maximum load a stream can transport. – Competence • Indicates the maximum particle size a stream can transport. • Determined by the stream’s velocity.
    27. 27. How Do Streams: Affect the Land Surface (and Geology)?
    28. 28. Ultimately, Erosion by Surface Water Returns the Surface of the Continent to Equilibrium. (equilibrium being base level = sea level) In other words, what goes up (mountains) must come down.
    29. 29. Life Cycle of a Stream • Streams erode the highlands and deposits those sediments in the lowlands/ continental edge. • Begins with the Hydrologic Cycle. • As the stream evolves from young to mature, it shifts from being predominantly erosional to depositional.
    30. 30. Changes from Upstream to Downstream • Longitudinal Stream Profile: – Cross-sectional view of a stream. – Viewed from the head (headwaters or source) to the mouth of a stream. – Profile is a smooth curve. – Gradient decreases downstream.
    31. 31. Longitudinal Stream Profile Can be divided into 3 main parts Drainage System Transport System Distributary System
    32. 32. Functions of Three Stream Phases • Drainage (Tributary) Systems: – Collect water (and sediments) • Transport Systems: – Move water along (and sediments) • Distributary Systems: – Return water (and sediments) to the sea
    33. 33. • Factors that increase downstream – Velocity – Discharge – Channel Size Changes from Upstream to Downstream • Factors that decrease downstream – Gradient – Channel Roughness
    34. 34. Drainage System: Youthful Streams • Stream energy is spent eroding downward into the basement rock (downcutting toward base level) and... • Moving Sediment – Very Course- to Very Fine-Grained • Creates “V” Shaped Canyons and Valleys • Stream Occupies Entire Valley Floor • Smaller Channel Size • Greater Channel Roughness • Straighter Stream Path • Higher Gradient • Lower Velocity • Lower Discharge • Fewer Tributaries • Features often include rapids, waterfalls, and alluvial fans • Rock Types: Conglomerates, Breccias, Arkosic Sandstones, Graywacke Sandstones, etc.
    35. 35. The Drainage Systems of Youthful Streams End at the Base of the Mountains Where Alluvial Fans are Deposited.
    36. 36. • Alluvial Fans – When high-gradient streams emerge from the narrow valley of a mountain front, they often deposit some of this sediment forming alluvial fans. • Due to a dramatic decrease in velocity. • Causing Sediment to drop out of suspension. • Slopes outward in a broad arc similar to a delta. Alluvial Fans Transition from Drainage to Transport Systems
    37. 37. Coalescing Alluvial Fans
    38. 38. Transport System: Braided Streams • High sediment load. • Anastamosing channels. • Constantly changing course. • Floodplain completely occupied by channels. • Many small islands called mid-channel bars. • Usually coarse sand and gravel deposits.
    39. 39. Transport System Mature Streams: Meandering Rivers • Stream is near base level • Stream energy is spent eroding and depositing laterally • Downward erosion is less dominant • Constantly erode material - Cut bank • Constantly deposit material - Point bar • Channel changes course gradually as stream migrates from side-to-side (meanders) • Create floodplains (broad or U-shaped stream valley) wider than the channel (occupies small portion of valley floor) – Very Fertile soil – Subjected to seasonal flooding • Larger Channel Size • Smooth Channel Bottom • Wandering and Curved Stream Path • Low Gradient • Higher Velocity • Higher Discharge • Greater Number of Tributaries • Rock Types: Quartz Sandstones, Siltstones, Mudstones, Shales, Coal, etc.
    40. 40. Transport System Mature Streams: Meandering Rivers • Features of mature streams often include: • Floodplains
    41. 41. Animation #81: Stream Processes – Floodplain Development
    42. 42. Transport System Mature Streams: Meandering Rivers • Features of mature streams often include: • Meanders – Cut Banks and Point Bars – Cutoffs and Oxbow Lakes
    43. 43. Erosion and Deposition Along a Meandering Stream Figure 16.14
    44. 44. Formation of Meanders
    45. 45. Point bar deposits
    46. 46. Point Bar Deposits Point bar deposits grows laterally through time
    47. 47. Cut bank erosion Point bar deposits }Meander loop
    48. 48. Erosion of a Cutbank
    49. 49. Formation of an Oxbow
    50. 50. Meanders and Oxbow Lake Green River, Wyoming
    51. 51. Mississippi Meanders
    52. 52. Meandering stream flowing from top of screen to bottom
    53. 53. Maximum erosion Maximum deposition
    54. 54. Oxbow Lake Oxbow cuttoff Meander scars
    55. 55. Animation #83: Stream Processes – Floodplain Development and Oxbow Lakes
    56. 56. Transport System Mature Streams: Meandering Rivers • Features of mature streams often include: • Floodplain Deposits – Natural Levees – form parallel to the stream channel by successive floods over many years – Back Swamps – Yazoo Tributaries
    57. 57. • Deltas – Form when a stream enters an ocean or lake. • Characteristic of mature streams. Distributary System: Deltas • Consists of three types of beds: – Foreset Beds – Topset Beds – Bottomset Beds
    58. 58. Delta Shapes Fan Delta Bird-Foot Delta
    59. 59. Things to Remember • Streams area part of a larger hydrologic system. • The main function of a stream is to remove excess surface water from the continent. • Ultimately, erosion by surface water returns the surface of the continent to equilibrium (equilibrium being base level). • While rivers are removing water from the continent: – They carve the landscape forming erosional geologic features. – The erode existing geologic formations. – Transport the sediments. – Deposit new geologic formations. • Streams have three main components: – Drainage (Tributary) Systems – collect water – Transport Systems – move water along • Alluvial fans, braided streams, meandering streams – Distributary Systems – return water to the sea • Deltas • As the stream evolves from young to mature, it shifts from being predominantly erosional to depositional. • Summary of Stream Chacterisitics.
    60. 60. Summary Stream Characteristics Summary of Stream Life Cycle Characteristics Characteristic YOUNG OLD Valley Shape V-Shaped Broad or U-Shaped (Steep-Sided Channel Walls) (Gently-Sloped Channel Walls) Channel Size Smaller Larger River Occupying Valley Floor Occupies Entire Valley Floor Occupies Small Portion of Valley Floor Channel Roughness Rough Smooth Stream Gradient High Low Stream Velocity Lower Higher Stream Discharge Lower Higher Number of Tributaries Smaller Greater Erosional Style Downcutting and Headward Erosion Migration (Side-to-Side) and Meandering Proximity to Base Level Stream is above base level Stream is near base level Ability to Transport Sediment Very Course- to Very Fine-Grained Pebble--Sand--Silt--Clay (Finer-Grained) Rock Types Conglomerates Quartz Sandstones Breccias Siltstones Arkosic Sandstones Mudstones Graywacke Sandstones Shales Coal Energy (Due to Gradient) High (Dams for Power Supply) Low (Dams for Water Supply)
    61. 61. Summary Stream Characteristics Summary of Stream Life Cycle Characteristics Characteristic YOUNG OLD Erosional Features Wind Gaps Cut Banks Water Gaps Rapids Waterfalls Depsitional Features Alluvial Fans Deltas Flood Plains Natural Levees Incised Meanders (Rejuvinated) Meanders Point Bars Meander Scars Cutoffs Oxbow Lakes Terraces (Rejuvinated) Terraces Back Swamps Yazoo Tributaries Note: Braided Streams are Intermediate Features - Transitional Between Young and Old Streams
    62. 62. How Does Geology Affect Stream Development and Flow?
    63. 63. Drainage Networks • Land area that contributes water to the stream is the drainage basin. • Imaginary line separating one basin from another is called a divide.
    64. 64. Drainage Basin of the Mississippi River Figure 16.31
    65. 65. Drainage Patterns • Pattern of the interconnected network of streams in an area – Common drainage patterns • Dendritic • Radial • Rectangular • Trellis
    66. 66. Drainage Patterns Figure 16.32
    67. 67. Base Level and Graded Streams • Base level is the lowest point to which a stream can erode. – Two general types of base level: – Ultimate (sea level) – Local or temporary – Changing conditions causes readjustment of stream activities: – Raising base level causes deposition – Lowering base level causes erosion » Uplift of the region
    68. 68. Adjustment of Base Level to Changing Conditions Figure 16.9
    69. 69. Rejuvenated Streams • Incised Meanders – Meanders in steep, narrow valleys. – Caused by a drop in base level or uplift of the region. Incised Meanders of the Delores River in Western Colorado A Meander Loop on the Colorado River
    70. 70. Rejuvenated Streams • Terraces – Remnants of a former floodplain. – River has adjusted to a relative drop in base level by downcutting.
    71. 71. Floods and Flood Control
    72. 72. Floods and Flood Control • Floods are the most common and most destructive geologic hazard – Causes of Flooding: • Naturally occurring factors • Human-induced factors
    73. 73. Floods and Flood Control • Types of Floods – Regional Floods – Flash Floods – Ice-Jam Floods – Dam Failure – Levee Breach
    74. 74. Regional Flood Recurrence, Skykomish R. Want some stream flow data? Try: http://water.usgs.gov/
    75. 75. Flash Flooding & Sheetwash
    76. 76. Flash Flooding & Sheetwash
    77. 77. Floods and Flood Control • Flood Control • Engineering Efforts – Artificial Levees – Flood-Control Dams – Channelization • Nonstructural approach through sound floodplain management
    78. 78. Flooding, Sedimentation, and Natural Levee Formation
    79. 79. Formation of Natural Levees Figure 16.16
    80. 80. Natural Levees
    81. 81. Artificial Levee Diagram
    82. 82. Levee Breach
    83. 83. Floods and Flood Control • Causes of 1993 Mississippi Flooding • There were four principal reasons why flooding was so extensive: – The region received higher than normal precipitation during the first half of 1993. Much of the area received over 150% of normal rainfall and parts of North Dakota, Kansas, and Iowa received more than double their typical rainfall. – Individual storms frequently dumped large volumes of precipitation that could not be accommodated by local streams. – The ground was saturated because of cooler than normal conditions during the previous year (less evaporation) so less rainfall was absorbed by soils/air and more ran-off into streams. – The river system had been altered over the previous century by the draining of riverine wetlands (80% since the 1940s) and the construction of levees (many of which failed under the weight of the floodwaters). – Source:http://lists.uakron.edu/geology/natscigeo/lectures/streams/miss_fl ood.htm#sum
    84. 84. Satellite Views of the Missouri/Mississippi Flood in 1993.
    85. 85. 1993 Mississippi Flood
    86. 86. Mississippi Deltas over the Last 5000-6000 Years http://www.nola.com/speced/lastchance/multimedia/credits.swf
    87. 87. If the Mississippi changes course again, what will happen to the City of New Orleans?
    88. 88. New Orleans Levee System
    89. 89. New Orleans Levee System
    90. 90. New Orleans Levee System http://www.nola.com/katrina/graphics/flashflood.swf
    91. 91. Pollution and the Anacostia River: One of the Nation’s Most Polluted Rivers is in our Backyard http://www.nrdc.org/water/pollution/fanacost.asp • Anacostia River is eight miles long. • Severely polluted by sediment, nutrients, pathogens, toxins and trash. • Because the Anacostia is relatively flat and extremely tidal, it especially vulnerable to contamination. • It's unsafe to swim in the Anacostia, or to eat its fish. An aerial view of the Anacostia River (far right) at its confluence with the Potomac River. The dramatic difference in color is due to the high level of sediments from CSOs and stormwater runoff.
    92. 92. Pollution and the Anacostia River: One of the Nation’s Most Polluted Rivers is in our Backyard http://www.nrdc.org/water/pollution/fanacost.asp • The river's decline began as settlers cleared fields for agriculture (leading to heavy erosion and sedimentation). • Urbanization claimed forest and wetland habitat, altered stream flows, and fed ever- increasing flows of sewage and polluted runoff into the Anacostia. A river designated for swimming, fishing, and other recreation is instead an eyesore, as this floating debris testifies.
    93. 93. Pollution and the Anacostia River: One of the Nation’s Most Polluted Rivers is in our Backyard http://www.nrdc.org/water/pollution/fanacost.asp • Between 75 percent and 90 percent of the Anacostia's pollution is caused by stormwater runoff. • A problem closely tied to sprawl and overdevelopment throughout the watershed. • More development means more hard surfaces -- more roads, sidewalks, parking lots and rooftops. • As a result, water that was once absorbed and filtered by soil and plants now rushes across pavement, picking up nitrogen, phosphorous, oil, heavy metals, bacteria and viruses, which are dumped directly into the river.
    94. 94. Pollution and the Anacostia River: One of the Nation’s Most Polluted Rivers is in our Backyard http://www.nrdc.org/water/pollution/fanacost.asp • Stormwater also plays a role in combined sewer overflows (CSOs), which are the other major source of pollution to the Anacostia. • Like many older cities, Washington uses a sewer system that carries both sewage and stormwater in the same set of pipes. • When it rains, the system rapidly becomes overwhelmed and begins discharging untreated sewage into local waterways. • Along the Anacostia's short course, such overflows occur in 17 different places, spilling 2 to 3 billion gallons into the river each year. The District of Columbia's century- old sewage and flood control system is designed to overflow when it rains. As a result, untreated sewage and stormwater spills into the river at 17 different discharge points.

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