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GEO 110 (47)
Chapter 10


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GEO 110
David Atkinson

Chapter 14 river systems and landforms • Rivers shape land by removing products of weathering, mass movement and erosion and transporting them downstream • Stream related processes  FLUVIAL • River – truck or mainstream • River system – network of tributaries • Stream – general term • Hydrology – science of water and its global circulation, distribution and properties • Discharge- streamflow volume past a point in a given unit of time (GREATEST IN AMAZON OF SOUTH AMERICA • Insolation and gravity power the hydolica cycle – driving forces of fluvial systems • Deposition – when materials are laid down by another process • Alluvium – clay, silt, sand, gravel and mineral fragments deposited by running water • Base level- level below which a stream cannot erode its valley (ultimate = sea level) usually curves upward from the sea • landforms are produced either by EROSIVEACTION OF FLOWING WATER or DEPOSITION OF STREAM TRANSPORTED MATERIALS DRAINAGE BASINS • aka watershed • RIDGES form DRAINAGE DIVIDES define the water receiving area sepeartes the basin from other basins • Sheet flow a thinfilm in which water initially moves downslope aka overland flow • Interfluvehigh ground that separates one valley from another and directs sheetflow • Surface water concentrates in gills then GULLIES • Drainage basin system  small rills and gullies main tributaries & stream trunk dispersing lower extremeties mouth where the river meets another water body • Continental divides  high drainage basins – in Canada ad the us • Each contributing tributary adds its flow and sediment load to the larger river – sediment accumulates in the lakes • OPEN SYSTEMS – inputs precipitaion, minerals, rocks. ENERGY and MATERIALS redistributed as stream adjusts to landscape outputs water and sediment disperse though the mouth of the river into another waterbody • INTERNALDRAINAGE  water doesn’t reach another water body but drains internally through evaporation or subsurface gravitational flow • Ie. Great basin of the western united states OR dead sea in middle east have no outlet to the ocean DRAINAGE DENSITYAND PATTERNS • Number and length of channels in a given area reflect climate and landscapes regional geology and topography • Drainage pattern  arrangements of stream channels in the area • Common pattersn (SEE PICTURE PG 427) • Dendritic like tree or capillaries • Trellis drainage  bunch of parallel lines of dendritic  dipping or folded topography • Radial big empty circle in the middle 00 from stream flowing off a central peak • Parallel steep slopes • Recrangular pattern • Annular • Derangaed –canada – no pattern FLUVIAL PROCESSESAND LANDFORMS Water above base level = energy flows down = converts to kinetic energy Stream Discharge • Discharge: streams volume of flow per unit of time • Depends on stream channel WIDTH and DEPTH and VELOCITY of flow • Discharge = width * depth * velocity • Discharge increases in downstream direction with inflow from tributaries –“ one of ht three variables has to increase as well • Discharge also changes over time at any specific chanel cross section • Flood  Greater discharge  more velocity more capacity to transport sediment as the flood progresses (CLEARING OF SEDIMENTS) • Discharge back to normal less kinetic energy bed filled with sediments again as restored • System works towards EQUILIBRIUM to balance discharge and sediment load with channel form • Dam controlled discharge dams control discharge and block sediments Exotic Streams • Usually in river basins in humid climate discharge increases donwnstream • If going from humid to arid  evapotranspiration may cause it to decrease downstream ie. Nile river Stream erosion and transportation • Streams erosional turbulence and abrasion carve the shape the landscope through which it flows • Hydraulic action  work of flowing water alone • Squeeze and release of running water on rocks debris moves along erodes streambed (abrasion)*** rock particles grind and carve • Usually up stream small discharge, high energy, high turbulence, SOO maximm hydraulic action • Downstream high vlume,larger loads of sediment • Competence –streams ability to move particles of a cer
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