Geology- mass wasting and rivers
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- Types of motion (mass wasting)
-
-falling
-flowing
-sliding - Mass wasting
- the downslope movement of Earth's materials due to gravity
- Factors that cause mass wasting
-
-rainfall
-construction
-undercutting by waves
-type of material that makes up ground
-angle of repose - Which process of mass wasting causes most economic damage?
- surface creep
- slump
- when Earth's materials move along a curved surface
- Processes of Mass wasting
-
-rock fall
-rock avalanche
-landslide
-slump
-earthflow
-mudflow
-surface creep
-solifluction - Which processes of mass wasting cause the most damage?
- surface creep and solifluction
- Human activities that enhance mass wasting
-
-increased runoff leads to slumping in river bends
-building roads, retaining walls
-lawn (watering, spectic tanks)
-vegetation (limits how hard water falls, roots hold soil in place, slows runoff process, helps soil process)
-unnatural drainage
-urban areas - What does running water do?
-
-erode
-sculpt the land
-build up landscapes - angle of repose
- steepest angle at which material remains stable
- rockslides
- when blocks of bedrock break loose and slide down a slope
- debris slide
- when involved material is largly unconsolidated
- Where do earthflows form?
- on hillsides in humid areas
- Creep
- involves gradual downhill movement of soil and regolith
- solifluction
- when soil is saturated with water and the soggy mass flows downslope
- Permafrost
- permanently frozen ground that occurs in association with Earth's harsh tundra
- Sheet flow
- broad, thin sheets across the ground
- runoff
- when the rate of rainfall is greater than the land's ability to absorb it, additional water flows over the surface into lakes and streams
- discharge
- total amount of water flowing past a certain point (Q= width x depth x velocity)
- erosion
- lifting of particles by turbulant flow
- stream capacity
- total amount of sediment
- stream competence
- maximum sized sediment in a stream
- What is the most common destructive geologic hazard?
- FLOODS!!!
- What causes flooding?
-
-more rainfall, snow melt
-natural part of the process - How often do rivers flood?
- About every two and a half years
- Where are flash floods most common?
- In deserts
- How does urbanization affect rivers?
-
1. decrease in lagtime
2. decreases infiltration
3.increases runnoff
4. reduces vegetation - Flood Control measures
-
- construct dams
-levees
-dikes
-straighten channels
- fill in wetlands
-riprap - laminar flow
- water particles move steadily downstream without mixing
- Turbulant Flow
- water moves in erratic fashion, swirling
- Factors in the Velocity of a river
-
-gradient
-shape, size, and roughness
-discharge - Gradient
- slope of stream
- longitudinal Profile
- cross section view of a river
- base level
- downward limit to stream erosion
- graded stream
- correct slope etc. necessary to maintain just velocity
- Oxbow Lake
- A curved lake produced when a stream cuts off a meander.
- Point Bar
- A crescent-shaped accumulation of sand and gravel deposited on the inside of a meander.
- Cut Bank
- the area of active erosion on the outside of a meander
- levees
- a dam along the river to force water into a channel (can be natural or artificial)
- Three Ways Streams Transport Things
-
1. solution
2. suspension
3.bedload (bottom of channel) - Settling Velocity
- speed at which a particle falls through a still liquid
- Mouth
- point downstream where it empties into another body of water
- bars
- coarser components of a stream's laod
- meanders
- when streams form in a series of bends
- floodplain
- part of a valley that is inundated during a flood
- Alluvial Fan
- forms when a high gradient stream leaves a narrow valley in a mountinous terrian and comes out suddnely onto a broad blat plain
- Delta
- forms when a stream enters a lake or an ocean
- distributaries
- smaller channels it is divided into
- What are some sources of pollution?
-
runoff
salts - Dams
-
-try to limit flooding
-source of hydtroelectric power
-affects the eco system
-organisms need annual rise in water - causes for pollution in sreams (urban areas)
-
1. excess sediment runoff
2. road runoff
3. trash, garbage from storm sewers
4. lawn chemicals
5. pathogens
6. agricultural runoff
7. stream pollution - Sustainable Remedies For Flood Management
-
- better floodplain management
-space for natural wetlands
-land use planning
-building restrictions - Remedies For Pollution
-
-restrictions on use of yard chemicals
-restrictions on use and application of agricultural chemicals
-pet waste - Thalwag
- region of maximal flow velocity
- riprap
- -rock or other material used to stabalize the shore