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Natural Hazards Final Exam
Terms in this set (43)
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The energy to make liquid flow, controlled by the magnitude of the internal friction within a fluid. Thicker fluids have greater viscosities.
Extremely hot and rapid flow of eruptive material down the flank of a volcano consists of volcanic gases, ash and other material that move rapidly.
Flat topography adjacent to a stream produced by overbank flow and by lateral migration of the channel and associated sand to gravel bars, covered by a flood.
High water levels in a steam, lake, or ocean that may damage human facilities. A natural process, overbank flow.
Amount of water flowing through the stream
An area where surface water contributes into a certain river or steam network. (Area drained by a single steam)
Transfered materials within a river that flow with the water, these materials roll, slide, bunco along bottom.
The volume of water passing through a given cross sectional area per unit time.
intertwining of land and water, containing sand and gravel bars that divide and unite a single channel. Usually shallow and wide
Causes cutbanks (erosion on outside of curves, high velocity) and causes point bars (deposition on inside of curves, low velocity).
A steep slope on outside of a bend in a meandering steam, high velocity in this area.
Common bed form produced by scour in meandering and straight stream channels with relatively low channel slope. Near cut banks
A slight change in slope in a river, sort of like a tiny waterfall in a river, higher velocity movement in water.
A graph of stream discharge or water depth over time.
Average time between flood events of a certain size.
An area or center of low pressure with rotating winds. Counter clockwise in northern hemisphere, and clockwise in southern hemisphere
An effect from a cyclone by the water which creates waves due to the wind that a cyclone creates.
What are the challenges faced in Volcanic Hazard Forecasting?
-Difficult to forecast because of their infrequency.
-Even though we monitor seismic activity it still may not provide enough time for evacuation.
Discuss how monitoring the land surface helps us forecast volcanoes?
-Land surface monitoring allows us to monitor growth of bulges or domes. These growth shows that more magma is being produced making this bulge more dangerous.
The Japanese have built a channel to focus pyroclastic flows and lava flows into the sea. Discuss the merits and draw backs of such a design
-These channels are to control damage from pyroclastic flow, It try to contain it as much as possible. Providing these deep paths helps eliminate damage to farm land, housing and roads.
-Some draw backs are, these paths may flood because you can't estimate how much pyroclastic flow is going to occur. And also after the eruption, the pyroclastic flow must be cleaned out of these paths for the next time.
Define Discharge. What are the two factors that influence discharge and how do they affect the discharge of a stream.
-Discharge: The volume of water passing through a given cross sectional area per unit time.
-1. Velocity, if area decreases velocity increases
-2. Area, if area increases, velocity decreases
assuming the amount of water is constant
What are the characteristics of a meandering stream?
- Migrate back and forth within a floodplain
- Velocity is greater on the outside of curves causing erosion (Cut banks)
- Rivers slow on the inside of curves causing deposition (point bar)
- Contains pools and riffles
- Floodplains are created during over bank flow
What is a recurrence interval in the context of a flooding incident? What does recurrence interval and probability tells us about a flooding event?
- Recurrence internal in the context of a flood is how often a flood of a given magnitude will happen
-Recurrence interval will tell you the time interval that a flood would come again, meanwhile the probability tells you the chances of that flood occurring that specific year.
What is an extra-tropical cyclone?
-Form over land or water in temperate regions (30°-70°)
-Cool central cores
What is a tropical cyclone?
-Form over warm tropical or subtropical ocean water (5°-20°)
-Warm central cores
What are the common other natural hazards related to Volcanoes?
- Earthquakes, landslides, fire, climate change
What are some natural service functions of a volcano?
- Volcanic soils (goods for coffee, maize, sugarcane)
- Geothermal power (can create energy for nearby urban areas)
-Mineral resources (gold, silver) (soap, building stone)
-Recreation (heath spas and hot springs)
- Creation of new land
Silt and clay particles that are carried in the water (Increased downstream)
Materials carried as chemical solution (salt, carbon dioxide)
What factors does flooding depend on?
-amount and distribution of precipitation in drainage basin
-rate at which the precipitation soaks into the earth (decreases flooding)
- how quickly surface runoff reaches river
-amount of moisture in the soil, if its drier it will absorb more water
Velocity In stream
Velocity is higher upstream, and lower downstream
Calculating recurrence interval
- Find the number of events
-rank the events based on flood discharge
-Really quick and rapid
-Flashfloods are common upstream, because the channel widths are narrow so they flood more quickly.
-caused by intense rainfall over a short duration of time, and over a small area
-areas are usually have steep slopes, and little vegetation
Primary effects of flooding
- injury and loss of life
-damage caused by currents, debris, and sediments to farms, houses, buildings, railroads, bridges, roads
-erosion and deposition relates to loss of soil and vegetation
Secondary effects of flooding
-Short term river pollutions
-hunger and disease
Physical barriers to prevent flooding
-Concrete flood walls
-storm water retention basins
constant water flow can break down concrete flood walls
all physical barriers need to be maintained
Direction of rotations of cyclones in Northern hemisphere
Counter clock wise
Direction of rotations of cyclones in Southern hemisphere
Two factors in categorizing hurricanes
Wind Speed and Barometric Pressure
Environmental conditions for a hurricane
-Thick Layer of warm ocean water, Steep vertical temperature gradient, and weak vertical wind shear
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