Specific volcanic hazards

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Specific volcanic hazards

• Largely f(velocity)
• Pyroclastic flow
• Also f(position)
• Tsunami (coastal)
• Thirdly f(snow/ice)
• Mudflow (lahar)
• Finally f(society)
• Famine, etc.

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Volcanoes of the western US

• Cascades
• Andesitic
• Most are dormant
• Clear Lake (transform?)
• Hot spots
• Rhyolitic
• May be dormant
• Snake RP
• Basaltic
• Historic

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Volcanism in Space (2)
Is this map complete?
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Plate settings of volcanoes
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Public Perception and Adjustment

• Perception of volcanic hazards
• Age and residence time affecting ones perception
• No other choices as where to live
• Optimistic and accepting risks
• Mitigation
• Public awareness
• Improvements in education
• Better scientific info dissemination
• Timely and orderly evacuation

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Forecasting Volcanic Activity
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Case Study (1)
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Case Study (2)
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(No Transcript)
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Case Study (2)
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Mount St. Helens
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RIVERS AND FLOODING
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Case History Mississippi River Floods

• Major recent floods, (1927) 1973, 1993 ( 2008)
• 1973 spring flood
• Evacuation of tens of thousands
• Inundation of thousands of km2 of farmland
• 1.2 billion in property damage
• 1993 summer flood
• Century flood in magnitude From climatic
  anomaly, unusual precipitation and snowmelt
• Lasted from late June to early August
• 50 deaths, 10 billion in damage
• Levees provided a false sense of security
• 2008 spring flood 13 deaths and 6 billion
  damages

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Case History Mississippi River Floods
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Streams and Rivers

• Part of the hydrologic cycle
• Streams Small rivers
• River components
• Watershed or drainage basin
• Network of streams
• Base level and gradient
• Longitudinal profile
• Latitudinal profile
• Grading processes

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Drainage Basins

• Rain
• Basin

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Drainage Basins

• Rain
• Basin
• Runoff

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Drainage Basins

• Rain
• Basin
• Runoff
• Erosion
• Evolution
• Streams

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River Dynamics Characteristics

• Continuity equation
• Discharge The volume of water passing through a
  given location of a river per unit of time
• Q W D V
• Gradient Vertical drop over horizontal flowing
  distance, expressed in percentage, ft/mi, or
  degree of the slope
• Stream velocity Largely depending on stream
  gradient, discharge, channel shape, and
  turbulence (channel roughness)

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Stream Discharge (Q)

• Fundamental stream variable
• Cubic feet/second(cfs, ft-3sec-1)
• QVA
• Velocity (ft/sec)
• Channel area (ft2)
• Instantaneous
• Cumulative

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Sediment in Rivers (1)

• Stream total load total amount of sediments
• Bed load Coarse particles moving along the
  bottom of river channel, often less than 10 of
  the total load
• Suspended load Accounts for about 90 of its
  total load and makes river look muddy
• Dissolved load Carried in chemical solutions,
  such as HCO3, SO42, Ca2, Na, Mg

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Stream Load
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Green and Colorado Rivers
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Seasonality of Work

• Only at high (Q) storms, snowmelt

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Sediment in Rivers (2)

• Stream competence and capacity
• Competence Measuring the maximum size of the
  sediments transported by a river
• Capacity Total amount of sediments a river is
  capable of transporting
• Riprap

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Stream Work

• Work
• Erosion
• Transport
• Deposition
• f(logQ)
• f(log particle size)
• Result stream load

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Figure 8.7
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Figure 8.5b