Chapter 14- Streams and Floods: The Geology of Running Water
Chapter 14- Streams and Floods: The Geology of Running Water Geology 101
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This 7 page Class Notes was uploaded by Alanna Wight on Monday November 2, 2015. The Class Notes belongs to Geology 101 at Washington State University taught by Wilkie in Fall 2015. Since its upload, it has received 21 views. For similar materials see Geology in Geology at Washington State University.
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Date Created: 11/02/15
Geology 101 Kurt Wilkie Lecture Notes Chapter 14 Streams and Floods The Geology of Running Water Key Points Understand the hydrologic cycle and be able to identify the different water reservoirs How does owing water move and deposit sediment How do rivers and streams evolve to form valleys and oodplains Chapter 14 Running Water The Geology of Streams and Floods The Water Cycle be familiar with the hydrologic cycle and the different reservoirs where water is stored The Earth s Water Cycle List the following water reservoirs from largest to smallest Salt water W Fresh water GlaciersPolar ice groundwater Lakes and Rivers 0 Atmosphere 0 Biosphere Initial runoff sheet ow thin sheets of water depends on intensityduration of rainfall soil textureprevious moisture hill slope vegetation next small channels develop which feeds streams Running water amp stream flow Tvpes of ow Water particles ow Laminar in straight paths parallel to channel slow speedssmooth channels turbulent erratic fashion swirling Whirlpool like erosive power Whitewater Highest velocity towards center of channel Know terms erosion transport and deposition Stream transport mechanisms in solution dissolved in water in suspension bed load along bottom Dissolved load is all the chemicals dissolved in the water Suspended load finer particles that are suspended in the water column ex natural arsenic in rivers draining the Yellowstone country Bed load Material the stream carries along the bed by sliding rolling and saltation Lower water velocities form ripples Higher water velocities form dunes types of sedimentary structures Stream velocity is not constant Deposition is more likely at lower velocities Settling deposition occurs when velocity slows grains in suspension are no longer supported and they settle to the bottom Different sized particles require different settling velocities Erosion is more likely at higher velocities the products are formed from chemical or physical weathering Abrasion Stream erosion Over time streams can erode rock just like sandpaper EX Slot canyon and potholes formed by abrasion Stream Any surface water whose ow is confined to a narrow topographic depression Stream channel Flood plain Stream Valleys are the most common surface landform on Earth there are 2 types Vshaped stream down cutting rapids waterfalls Wide valleys follows downcutting to base level energy directed sidetoside meanders Steams cut downward Ultimate base level where all rivers and streams erode toward sea level Stream Channel Patterns Straight 0 Braided Meandering Straight Channel single channel Forms on steep to low slopes usually comprise small segments associated with other channel types Braided Channel multiple channels Channels split apart and rejoin A braided stteam m Alaska Banded hauntIx Meandering Channel Meander to wander One main trunk channel 0 Forms on low slopes through easily eroded bedrock LOW SEDIMENT LOAD LOW VELOCIYY Development of a Meandering Stream Strongest currents occur at the outside of the curve erosion occurs forming a cut bank Velocity slowest on inside of curve so deposition occurs forming a point bar Meander cutoffs and Oxbow lakes Meanders migrate over time the rate depends on the erodibility of the sediments Incised river channels are formed when there was a change in base level to an established river system Base level can change by 1 Uplift of the land plate tectonics 2 Sea level drop period of glaciation Chapter 14 Running Water continued Key Points What are the different stream drainage patterns and what does each indicate about rock or material it erodes Flooding will it happen here Understand where not to build Drainage Networks Drainage basin area of land which funnels all the water into streams draining the area Divide ridge of high ground along Which rain runs off one side or the other Tributary streams feed trunk streams Drainage Patterns need to be able to recognize drainage pattern from photo or diagram Surface drainage is controlled by the underlying materials and structures that the water ows OVCI39 Dendritic at lying layers or similar rock type Trellis ooded rock layers Rectangular rock units cut by ioints and faults Radical high mountain Peak volcanoes Factors that In uence Stream Flow Velocity distance water travels divided by time fts ms speed ex slow 1 fts fast 35 ftsec Gradient change in elevation divided by distance ftmi slope Discharge volume of water passing a point on the stream bank per unit of time ft3s m3s Flooding Natural Levee ridges of coarse material built up during periods of ooding that act to confine the stream within its banks Recurrence interval The average time between two oods of a given magnitude Depends on Climate Width of Floodplain Channel Size Flood Frequency Curve 0 Probably the most misunderstood concept about oods A ood with a 10 year recurrence interval has a 1 in 10 chance of happening in y given year The occurrence of a 10 year ood does not mean there will be no ooding for 9 more years You have more than one 10year ood in a 10 year period Other Features of Streams Deltas Triangular shaped deposits of sediment deposited as streams enter the ocean and velocity slows Effects of Building a Dam a Original profile graded to regional base level b Dam forms new local base level c Deposition upstream and erosion downstream
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