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River Notes

River Notes. Ch-13. What is the purpose of a river. To carry water down stream to base level Base level is the lowest body of still water The ultimate base level is the ocean. Parts of a river system. Drainage basins or watersheds The area drained by a river Divides

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River Notes

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  1. River Notes Ch-13

  2. What is the purpose of a river • To carry water down stream to base level • Base level is the lowest body of still water • The ultimate base level is the ocean

  3. Parts of a river system • Drainage basins or watersheds • The area drained by a river • Divides • Lines that divide drainage basins • ex) continental divide which splits water between Atlantic and Pacific

  4. Tributaries Water flowing to the base level Classifications #1 rill small nonpermanent #2 gully larger than rill but not permanent #3 stream Permanent #4 river Large with permanent tributaries

  5. Properties of a Waterway • Velocity - Speed of the water • faster = more erosion • Speed depends on slope or width • steeper = faster • narrower = faster • straighter = faster • Discharge - The amount of water flowing in a river per time unit • more = higher carrying capacity • Gradient – steepness • Steeper = faster

  6. Structures and Formations • Potholes • Water drills a round hole in the rock • Plunge pool • Deep pool at the base of a waterfall • Causes waterfall to erode back upstream • Delta • Fan shaped deposit at the end of a river • water slows and drops what it is carrying

  7. Meanders • Curves in a river • outside moves faster • outside erodes & inside deposits • outside deep & inside shallow • Oxbow lakes • Cutoff meanders • “V” shaped valleys

  8. Levees • mounds of dirt along the bank of a river • is where the soil was first dropped due to loss of speed for the water when it flowed over its banks • Floodplain • the part of the valley floor that gets covered by floodwaters • most towns it is a year flood range

  9. Transporting Material • Faster moving = more material moving • Transported materials is called load • Different ways of transporting material • Solution • material dissolved in the water & Does not settle • Example - Salts • Suspension • small particle held up by current • settle out when movement slows or stops • Example – silts and sands • Bed load • large particles that are rolled and bounced along the bottom • Example – Gravels and boulders

  10. Young stream Straight, steep, & fast Has waterfalls Narrow “V” shaped valley Mature Flatter & slower Starts to meander Creates a floodplain Old age Slow & flat Wide flood plain Has oxbow lakes Most rivers have all three stages Young at top due to headward erosion Old at bottom Stages of development

  11. Floods • Flash floods • Heavy single rain or quick snow melt creates flooding for a very localized and short time period • Occur on young streams • Floods • Long term rain • hurricanes • Snow melt with rain when water can not get into ground because it is frozen • ice dams • dam failures

  12. Prevention • Dams • Baltimore project - Hold back the water and let it go at a pace that will not flood • Problems • Creates floods back up stream • Can break • Hold back sediments • Spillways • open the sides of the levees to flood low lying lands • Controlling runoff • replanting lost vegetation

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