Geological Hazards Final Flashcards
Why do people choose to live near rivers?
Fertile soil
Transportation
Food source (fish)
Trade
What are the dangers of rivers?
Susceptible to flash flooding
Fast flowing water
What is the ‘hydrologic cycle’ and how can it be altered?
The natural cycle that circulates water throughout the environment to maintain an overall balance between water in the air, on the surface and in the ground.
Human activities that can alter the hydrologic cycle include:
Agriculture
Industry
Alteration of the chemical composition of the atmosphere
Construction of dams
Deforestation and afforestation
Removal of groundwater from wells
Water abstraction from rivers
Urbanization
What affects stream flow?
Weather
Snow accumulation and melting
Rainfall and snowmelt
Evaporation
Water use by plants
Vegetation
Subsurface water flows
Water withdrawal for irrigation and municipal water needs
Diversion for hydropower generation
Urbanization
What causes streams to either erode or deposite sediment?
Adequate stream flow
How do people mitigate against flooding dangers?
Levees
Dams
Channel straighening
Inundation maps
Transpiration (hydrologic cycle)
Water inside of plants in transferred from the plant to the atmosphere as water vapor.
Condensation (hydrologic cycle)
Vapor to liquid
Forms clouds
Precipitation (hydrologic cycle)
Rain or snow
Evaporation (hydrologic cycle)
Occurs when the physical state of water is changed froma liquid to a gaseous state.
Water comes from lakes or oceans
Run-off (hydrologic cycle)
Rivers or streams
Infiltration (hydrologic cycle)
The physical process involving movement of water through the boundary area where the atmosphere interfaces with the soil. The surface phenomenon is governed by soil surface conditions. Water transfer is related to the porosity of the soil ad the permeability of the soil profile. Water that is infiltrated and stored in the soil can also become the water that later becomes subsurface runoff.
Percolation (hydrologic cycle)
The movement of water through the soil, and its layers, by gravity and capillary forces.
Stream profile: head, mouth, gradient

Discharge
The volume of water flowing through a channel in one second.
Drainage area
Drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody such as a river, lake, reservoir, estuary, wetland, sea, or ocean.
Local base level
Where a stream’s gradient temporarily approaches or reaches zero before increasing again.
Can be a lake or reservoir or a layer of rock that is highly resistant to the stream’s erosive force.
Ultimate base level
All rivers and streams erode toward sea level, which is also known as the “ultimate base level.”
Capacity
The total amount of load that the stream can move.
Controlled largely by discharge.
Competence
Measures the largest particles that the stream can transport.
Controlled largely by velocity.
Hydrosphere
Water
- Oceans
- Lakes
- Rivers
- Groundwater
- Ice
What percentage of the hydrosphere is fresh water?
2.8%
Drainage systems
Defined by topography
Streams and mass wasting influencing topography
Stream processes (x3)
Sediment production
Sediment transport
Sediment deposition
