GLY1000 Final Review Mass Wasting Streams Groundwater and Global Climate Factors that affect the stability of a slope Factors that affect the velocities of streams Key Points Darcy s Law Mass Wasting 1 Mass wasting the down slope hill movement of rock soil or sediment under the influence of gravity a Occurs depending on materials involved rock soil earth mud or debris AND the motion involved fall slide flow 2 Landslide all falls slides and flows that occur at a fast or moderately fast rate Falls landslides that involve collapsing material from steep slopes o Typically involve free falling bouncing or rolling sediments that deposit at base of slope Slides downslope movement of soil rock that occurs primarily on the surface of rupture or on thin areas of great shear strain Flows Turbulent motion of sediments downhill motion Types of Types of Falls 1 Rock Fall 2 Earth Fall www bgs ac uk www bgs ac uk 3 Debris Fall www bgs ac uk Falls occur with the detachment of soil rock from steep slope Secondary Falls involve rocks already detached from cliff just lodged upon the cliff GLY1000 Final Review Mass Wasting Streams Groundwater and Global Climate Types of Slides surface 1 Translational slide mass displaces along a wavy surface of rupture sliding out over original 2 Rotational Slide move along surface of rupture that is curved concave www saarc sadkn org 3 Slump breaks off of a steep surface Material moves as coherent mass along curved surfaces www saarc sadkn org Types of Flows www geocaching com 1 Debris Flow turbulent flow of debris cars scrap trees etc a Fast moving destroy objects in their paths strike without warning b Materials vary greatly in size c Often triggered by heavy rains on steep slopes d Famous debris flows Venezuella December 1999 Mt Mayuyama Japan 1992 e Includes Debris Avalanche 2 Creep Flow slow flow downhill grain by grain through freeze thaw cycles freezing melting between grains of rock Slowly creep 1 cm year or less a Biological agents also important in creep process insects small animals and plants move soil around b Oddly enough results in most damage costs per year among landslides 3 Mud Flow very rapid flow of saturated plastic debris in a channel a Caused by high intensity rainfall b Contains a great water content 4 Earth Flow very thick soil that accumulates and creates a flow slow to rapid GLY1000 Final Review Mass Wasting Streams Groundwater and Global Climate a Type of earth flow Colorado Landslide 5 Rock Flow extremely slow movements of bedrock Factors that influence Mass Wasting the stability of slopes Materials involved rocks soil sediment etc Steepness of slope Water Vegetation Heights Climate freeze thaw cycles Presence and orientation of planes of weakness upon the zones of weakness of a slope Human Activities Streams a example a dipping diagonal foliation can result in landslides and damage to buildings built Stream water that flows in channels o Carries water and sediments o Ability to erode pick up sediments Erosion depends on VELOCITY Difference between capacity of stream and competency of stream o Capacity of stream amount of particles stream can carry per unit time o Competency of stream largest particle it can carry Depends on velocity Factors that affect velocities of stream very important Depends on discharge amount of water flowing past a certain point of stream o Gradient of stream or slope of surface over which it flows elevationdistance horizontal distance Steeper the slope of stream faster the water flows GLY1000 Final Review Mass Wasting Streams Groundwater and Global Climate o Channel shape and size move faster with more water ie Added pressure Channel bed walls vegetation roots etc slow velocity by drag effects friction www meted ucar edu o Channel roughness o Discharge also known as flow Can be affected by Human activities ex Vegetated areas being cleared to bare soil increases run off creates flashy streams Channelization when a channel is straightened by removing debris and large obstructions to increase discharge velocity o This increases erosions and can increase flooding downstream Dams change the discharge by detaining the flow Alters conditions of the stream upstream and downstream Velocity and discharge increase along the outside of the meander curve bend creating cut banks from erosion Because of this deposition occurs on the INSIDE of the meander where velocity slow forming point bars Both deposition erosion of meanders make them more sinous having many curves Graded stream very important carries the amount of sediments it can given the velocity and discharge Over years slope is gradually adjusted to yield for the available discharge velocity An asymmetrical stream channel is deeper near the cut bank and shallower near the point bar Alluvium any stream deposited sediment Meander cutoff where two meanders converge as a result of cut banks eroding back and point bars advancing o Widest part of stream cutoff Long Profile of stream represents the elevation point along the length of a stream GLY1000 Final Review Mass Wasting Streams Groundwater and Global Climate o Closer to source steeper the gradient Base level the level below which a stream cannot erode o Sea level ultimate base level for all streams o Characteristic of streams V shaped valleys Steep valley walls base level far above Where mass wasting is faster valley walls become less steep Actively downcutting channel and valley Absent to narrow flood plain Fairly straight channels Steep stream gradients o Remember high mountain streams can have local base levels therefore take the characteristics of streams close to base level o Characteristics of streams base level near Contained in broad valleys Very low stream gradients flat long profile Broad complex meander belts with cutoff andoxbow lakes Flood plains much wider than meander belt o Characteristics of lower course stream Deposition is dormant Oxbow lakes occur Estuaries deltas Valley floor had broad flat flood plain River banks or levees are marked Pronounce meanders o Rejuvenated stream When a stream was once close to base level but transitions to far above base level and its energy now down cuts rock Ex Green River Can occur either by changes in base level or tectonic changes in elevation of land o Entrenched incised meanders meanders that downcut into deep steep V shaped valleys o River Terraces what is left of the old flood plain of a stream Types of sediment transportation o Dissolved load in solution
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