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20 Cards in this Set
- Front
- Back
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hdrologic cycle
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The hydrologic cycle is a summary of the circulation of Earth’s water supply
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Processes Involved
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Processes involved in the hydrologic cycle
-Evaporation -Transpiration -Precipitation -Infiltration -Runoff |
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running water - begins as sheet flow
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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 -Sheet flow develops into tiny channels called rills |
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Running water - drainage networks
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Drainage networks
-The land area that contributes water to a stream is called the drainage basin -The drainage pattern consists of the interconnected network of streams in an area -A drainage basin of one stream is separated from the drainage basin of another by an imaginary line called a divide |
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running water - streamflow
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Streamflow
-Two types of flow determined primarily by velocity -Laminar flow -Turbulent flow -Factors that determine velocity -Gradient, or slope -Channel characteristics including shape, size, and roughness -Discharge – the volume of water moving past a given point in a certain amount of time |
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factos that increase downstream
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-discharge
-channel size |
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factors that decrease downstream
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-gradient
-channel roughness |
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base level and graded streams
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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 |
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stream erosion
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Lifts loosely consolidated particles by
Abrasion Dissolution Stronger currents lift particles more effectively |
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transport of sediment by streams
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Transported material is called the stream’s load
Types of load Dissolved load Suspended load Bed load Capacity – the maximum load a stream can transport Competence - the maximum particle size a stream can transport Determined by the stream’s velocity |
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Deposition of a sediment by a stream
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Deposition of sediment by a stream
Caused by a decrease in velocity Competence is reduced Sediment begins to drop out Stream sediments Generally well sorted Stream sediments are known as alluvium Channel deposits Bars Braided streams Deltas Floodplain deposits Natural levees – form parallel to the stream channel by successive floods over many years Back swamps Yazoo tributaries Alluvial fans Develop where a high-gradient stream leaves a narrow valley Slope outward in a broad arc Deltas Form when a stream enters an ocean or lake Consist of three types of beds Foreset beds Topset beds Bottomset beds May develop distributaries |
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stream valleys
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The most common landforms on Earth’s surface
Two general types of stream valleys - wide and narrow |
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incised meanders
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Meanders in steep, narrow valleys
Caused by a drop in base level or uplift of the region |
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terraces
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Remnants of a former floodplain
River has adjusted to a relative drop in base level by downcutting |
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narrow valleys
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Narrow valleys
V-shaped Downcutting toward base level Features often include rapids and waterfalls |
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wide valleys
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Wide valleys
Stream is near base level Downward erosion is less dominant Stream energy is directed from side to side forming a floodplain Features of wide valleys often include Floodplains Erosional floodplains Depositional floodplains Meanders Cut bank and point bar Cutoffs and oxbow lakes |
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drainage patterns
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Drainage patterns are formed by the network of streams in a given area
Common drainage patterns Dendritic Radial Rectangular Trellis |
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floods and flood control
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Floods are the most common and most destructive geologic hazard
Causes of flooding Result from naturally occurring and human-induced factors |
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types of floods
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Types of floods
Regional floods Flash floods Ice-jam floods Dam failure |
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flood control
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Flood control
Engineering efforts Artificial levees Flood-control dams Channelization – Mississippi River flow path shortened by more than 240 km. Nonstructural approach through sound floodplain management |
