GEOG1710 1st Edition Lecture 17 Outline of Previous Lecture I Streams and Fluvial Processes II Drainage Basin Types III Stream Discharge Outline of Current Lecture I II III IV V VI Steam Energy Fluvial Erosion Fluvial Transport Fluvial Deposition Arid landscapes Arid Environment Current Lecture Stream Energy Capacity of a stream to do work Stream uses kinetic energy Energy is a function of three factors o Discharge gradient fiction Amount of energy determines streams ability to do work o Shape landscape erosion running water erodes stream channels and stream bed o Carry deposit stream load running water transports and deposits load High energy erosion and transportation Low energy deposition Fluvial Erosion Removal of rock material by flowing water physical Removal of dissolved ions chemistry Fluvial Transport These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Streams erode some sediments but larger proportion of stream load is delivered to channels by surface runoff and mass movement o Dissolved load solution chemical solution o Suspended load fine grained particles o Bed load coarser materials saltation traction Fluvial Deposition Sediments deposited when not enough energy to carry them Alluvium fluvial deposits regardless of size Watershed health can be assessed by monitoring river water chemistry V shaped valleys product erosion down cutting mass wasting Meandering stream and eventually slope flattens out and channel meanders back and forth eroding out banks and depositing point bars Floodplains flat with many stream channels subjected to recurrent flooding River deltas depositional plains at river mouths stream flow velocity and sediment load stream capacity Arid Landscape 35 40 of Earth s surface Home to two billion people 30 of world s cultural plants originated here Characterized by scarcity of water Sources of dust Arid lands lack water low and variable rainfall often very intense high potential evapotranspiration Paleo climatological and paleo botanical studies Arid Environment 1 Areas dominated by sub tropical high pressure 2 Leeward side of mountains 3 Area far from moist air masses extreme continentally Lack water but water often more important than wind in shaping arid landscapes how Low rain low npp low weathering low soil low infiltration low biomass low interception sudden runoff when rains Desert streams are ephemeral come and go Perennial flow year round sustained by ground water Intermittent flow parts of the year some ground water inputs Ephemeral but effective can have high drainage density Fluvial erosion Braided streams are common carry coarse sediments and gentle slopes transports Most desert streams don t make it to the ocean interior basin why Not a lot of water evaporation seeps into the ground Dry lake beds are common playa dry lake bed in a basin of interior basin salina dry lake bed with high concentrations of salt in lake bed sedimets Permanent lakes are rare covered most of Utah 32 000 14 000 years ago high salinity Some desert streams do make it to the ocean exotic streams but originate in humid areas run through acid regions
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