Practice UPload GEOL 101 001
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This 3 page Study Guide was uploaded by Kendrick Notetaker on Monday October 17, 2016. The Study Guide belongs to GEOL 101 001 at University of South Carolina taught by Scott White in Fall 2016. Since its upload, it has received 6 views. For similar materials see Introduction to the Earth in Science at University of South Carolina.
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Date Created: 10/17/16
Geology 101(Mr.White) Ch. 14 Highlight = Important Principle Highlight = Important Concept Highlight = Key Term [Chapter 14] [Streams and Floods] Stream Runoff Streams are channels of water that drain the landscape. Stream runoff, water in motion over the land surface, is crucial for humans. Streamflow is used for drinking water Transportation Water disposal Recreation Commerce Irrigation Energy Generation. Flowing water erodes, transports, and deposits sediments and sculpts landscapes. la Earth is the only planet in the Solar System with flowing water. Drainage Divides Watersheds are defined on a variety of scales. Tiny tributaries have tiny watersheds; large continental rivers have large watersheds. Continental divide separates flow to different oceans. Discharge is the amount of water flowing in a channel. Discharge measures the volume of water passing a point per unit of time. It is determined by measuring the crosssectional area of the channel multiplied by the flow velocity. Discharge varies seasonally due to changes in precipitation and runoff. A river with low crosssectional area and velocity has a lower discharge than a river with higher cross sectional area and velocity. Flood Hazard – flood risks are borne by homeowners, insurance companies, lenders, and government agencies Hydrologic data are used to produce flood risk maps, which allow regulatory agencies to better manage risks. Building in floodprone settings is tightly regulated. Flood Risks are calculated as probabilities. Discharges plotted on semi logarithmic paper against recurrence intervals yield a straight line. FloodFrequency Analysis They are based off Probability Stream Gage Records Peak Annual Discharge Rank Streamflow Largest to Smallest Recurrence Interval: Period of time elapsed between two events of same size Large events are rare; extrapolation necessary. Recurrence is based on stream gage records and topography. People live in floodplains face hard choices: move or realize eventual castastrophic loss. Why regulate the floodplain? Protect people and property Ensure that Federal Flood insurance and disaster assistance are available Save Tax dollars Important to Ecosystems Greatest Primary Productivity Buffer against Flooding Filter on Carbon Cycle and Nitrogen Cycle Filter Pollutants Recharge groundwater Critical Habitat Fish nursery Endangered Species Describing flow in channels Velocity is not uniform in a channel. Friction slows water along channel edges; water flows faster in the deeper center. In curved channels, the maximum velocity is swept to the outside curve, which is preferentially scoured and deepened. Streamflow is turbulent. It is chaotic and erratic, with abundant mixing via eddies, which scout sediment and bedrock. Sediment transport: the material moved by streams is sediment load. Dissolved loads consists of ions from mineral weathering. Suspended load is made of fine particles (silt and clay) entrained in the flow. Bed load is composed of the large particles that roll, slide, and bounce along the bed of the channel. Movement is called saltation. Sediment Transport Sediment transport changes with discharge. During high discharge, cobbles and boulders that are stranded at low discharge may be mobile. Competence is the maximum grain size transported. Capacity is the maximum load(coarse, fine, and dissolved material) transported by streamflow. Sediment deposition: How do streams deposite sediment? Competence decreases with velocity. Sediment grains drop out and the water sorts them by size. Gravel settles in the highest velocity setting channels Sands are deposited in slightly lower velocity settings( point bars and leeves) Muds(silts and clays) settle in slack water. 2 Main types of streams Meandering Single main channel Sinuous(“wiggly”) Low competence, steady discharge. Braided Multiple channels Straight High competence, flashy discharge. Meanders formation[meandering stream] Lowsediment load, Low velocity Lowvelocity, Lowsediment streams form meanders Meanders shift from side to side in a snaking motion. The current is faster at the outside of the banks, which are eroded Sediments get deposited in inside banks forming point bars. The bends grow closer and the point bars gets bigger. What happen after meanders grow. During a major flood the river cuts across the loop and the abandoned loop remains as an oxbow lake. Alluvial Fans and Delts[The end of the line] Alluvial Fan No Grav. Energy Sediment Dump Delta Underwater Lakes, Oceans
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