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Surface Water Earth Science- Chapter 13 Mr. Hendricks and Mr. McMahon

Mar 29, 2015




  • Slide 1

Surface Water Earth Science- Chapter 13 Mr. Hendricks and Mr. McMahon Slide 2 Chapter Outline Streams and River Erosion and Deposition River Valleys Floodplains and Floods Slide 3 Streams and Rivers River Systems Vocabulary - Continental Divide: - Water Shed aka Drainage Basin: - River system - Tributary Slide 4 River System Slide 5 Definition- A river and all of its tributaries (feeder river or connecting rivers) Example: Mississippi River System Slide 6 Drainage Basin or Watershed Drainage Basin or Watershedall is all the land that drains into the river directly or through its tributaries. Example: green area is Mississippi R. Basin Slide 7 Continental Divide Defined as the highland that separates one drainage basin from another. Usually a mountain range Sub-Continental divide in Men. Falls Slide 8 Tributary A tributary is a feeder river/ creek/ stream that flows into a large parent river. There are some 250 tributaries of the Mississippi which drain a total area of more than 1,247,000 square miles--one third of the nation's landmass! Slide 9 River Characteristics Channelized flow- water flows in a chanel Velocity- how fast a river is flowing Gradient- how steep a river is Discharge- how much water is flowing Slide 10 Velocity How fast something is moving High velocity = high speed Low velocity = low speed Slide 11 Channelized Flow Cross section of river displaying channelized flow Rivers are Confined by their channel Affects Velocity of water Slide 12 Gradient Slope of a stream Rise over Run A river may drop 10 feet over a distance of 100 feet Gradient is 1/10 or 10% Slide 13 Discharge Cross Sectional Area = Width * Depth 5 ft * 100 ft = 500 ft 2 Velocity = 1 foot / second Discharge = 500 ft 2 * 1 ft/sec = 500 ft 3 / second Slide 14 Discharge Volume of water that passes a point over an amount of time How much water is flowing in a river Cross sectional area * Velocity Slide 15 Stream Discharge Slide 16 How to determine discharge Discharge = Cross sectional area * Velocity Determine the discharge of a stream with the following characteristics: Confined by two vertical walls. The average depth of water is 5 feet. The channel is 100 feet wide Average velocity = 1 foot per second Slide 17 Discharge Discharge is not constant. Depends on conditions Increased down river Increased during times of high precipitation or melt Spring = High Discharge Slide 18 Yearly Discharge Slide 19 Erosion and Deposition How does it happen? Mechanical Weathering- Abrasion Running water What does it produce? Sediment Rounded rocks Potholes Slide 20 Erosion, Transport, and Deposition Whether sediment is being eroded, transported, or deposited depends on the size of the particle and velocity of water Hjulstrom Curve Slide 21 Color Hjulstrom Slide 22 Transportation of Sediment Load: material transported by river Bedload: moved along bottom, rocks, gravel, pebbles Suspension: clay- silt muddy water Solution: material dissolved in water Capacity: total amount of sediment a stream can carry Competence: Maximize size particles a steram can carry Slide 23 Stream Load Slide 24 Slide 25 Deposition Sediment is deposited when the velocity of the current can no longer transport material Examples: A boulder will not be transported by a trickling crick A rapid river will move particles of all sizes because of the high V Silt and Clay is deposited in the deep ocean because there is barely a current (low V) Slide 26 Color Hjulstrom Slide 27 Depositional Feautres Delta Sandbars Deposit Bank Slide 28 Delta A fan-shaped deposit that forms when a river flows into a quiet or large body of water Where do you think clay particles are deposited on the diagram? Slide 29 Sand Bars Wisconsin River- How do they form? -Discuss for 2 mins Slide 30 Sand Bar Formation Current carries sediment Sediment is deposited when current is slowed down Sediment begins to pile up and catch more sediment Bars constantly move to change in current and water depth Slide 31 River Deposit Slide 32 River Valleys Toad River, Canada Slide 33 Why do some rivers grow so big? All rivers start on a small scale Rainstorm forms a valley in loose soils called a gullie Rainstorm ends, water evaporates, but depression remains Next rainstorm, erosion continues As time goes on, a gullie increases length, width, and depth Continuous erosion of land Slide 34 Headward Erosion The process by which land is worn away at the head of a stream or gully Head: An abrupt drop in elevation Waterfall Erosion opposite the direction of waterflow Slide 35 Canyons Canyon- river valley with steep vertical sides Form in areas with low rainfall Factors in formation: Type of rock, amount of water, climate Colorado R. -Grand Canyon) Slide 36 V-Shaped Valleys Rain erodes the sides of a valley which forms a V shape Deeper channel = greater width Ex: Yellowstone River Slide 37 Base Level Streams cant cut any deeper than the body of water they flow into Ultimately, all rivers only can cut to sea level Slide 38 Rapids and Waterfalls Water flowing over a cliff or steep, jagged slope forms rapids and waterfalls High rate of erosion at Rapids and WF Undermining Temporary features Slide 39 Undermining 1) Waterfall creates pool 2) Undercuts the waterfall 3) Creates overhang 4) Overhang collapses 5) Recession upstream Slide 40 Niagara Falls Slide 41 Dry Niagrara Falls? Slide 42 Floodsplains and Floods Features of a Floodplain: Meanders Oxbow Lake Natural Levees Slide 43 Floodplain Features Meander-River winding back and forth with broad curves Slide 44 Features Oxbow Lake- A curved body of water that separates a meander from its river Formed due to erosion of river banks Slide 45 Oxbow Lake Slide 46 Floodplain Feature Natural Levee- thick deposits alongside stream banks Elevated ridges Slide 47 Floods Naturally occurring event after heavy or long-lasting rains Positive and Negative Effects Recent Flooding? Slide 48 Flood Effects Positive Relieve water and sediment overload of the channel Floods deposit minerals on floodplains making these areas fertile for agriculture Negative Destructive for people near rivers Cause damage to buildings, farmland, and other properties Dangerous water levels/velocity Slide 49 Flood Causes For large rivers, like the Mississippi, floods occur after many days of heavy, steady rainfall- No flash floods Spring melt Dam failures- Ex: Lake Delton Slide 50 Lake Delton Slide 51 Flood Control and Prevention People rely on controlling and preventing floods Communities built on flood plains are of special concern Any time a flood occurs their property and their life is at risk Slide 52 Flood Prevention/Control Means: 1.Restore natural flood protections Replanting removed vegetation Urbanization = problem 2.Dams Creates reservoir Risk of failure Lake Delton Eventually fill up with sediment Slide 53 Flood Prevention Continued 3. Artificial Levees- sandbags Deeper river holds more water May create erosion downstream 4. Spillways Channels parallel to river to collect water Slide 54 Floodgates Slide 55 Artificial Levee Slide 56 Stream Stages ________: Rapids Waterfalls Fast-moving water Steep slope _______: Broad floodplain Meanders Oxbow lakes Meander Scars YouthfulOld Slide 57 ________ the bends and curves of a stream Meanders Slide 58 Oxbo w lake depositi on erosio n Slide 59 ____________ deposit formed when a stream spreads out onto a less steep area Slide 60 _____ where a stream empties into a larger body of water Delta Slide 61 ____________ when an old age stream downcuts to make it new again Rejuvenation