Chapter 5: Running Water and Ground Water Flashcards
The process of the Hydrologic Cycle?
Precipitation Evaporation Infiltration Runoff Transportation
(this cycle illustates the unending circulation of Earth’s water supply)
What is a Drainage Basin?
specific land area that contributes water to a river system
a Divide separates separate drainage basins.
The beginning of water being added to the surface is called what?
Streamflow
Stream flow begins as moving what?
Sheet wash:
thin surface layer of water
moves down steepest slope
erodes substrate
What creates tiny rill channels when forming streams?
sheet wash erosion
Rills the deepen and down cut into channels
The three factors to determine water velocity
1) Gradient/ slope of channel (vertical drop of steam over distance)
2) Channel characteristics (shape, size, roughness of channel bed)
3) Stream discharge (volume of water flowing in stream)
What is the Stream Longitudial Profile?
Cross-sectional view of stream across landscape.
It is a smooth curve.
Gradient decreases from the head to the mouth.
The two factors that increase downstream?
Discharge- volume of water in stream increases
Channel size- width changes from narrow to wide
The two factors that decrease downstream?
Gradient (slope)- channel becomes less steep
Channel roughness- channel smooths out
When the sediment is deposited in the opposite bank, it is called what?
point bar
When fast water erodes one stream bank is called what?
cut bank
The most common natural hazard _____.
Floods
Three causes to flooding?
1) Weather.
heavy rainfall/ rapid snow melt/ several days of rain
2) Human interference.
interference w/ stream system
3) Ground too dry to adsorb participation.
runs over land instead of infiltrating/ can result in flash flooding
Missouri and Mississippi Rivers near St. Louis facts
*Regional flooding last for 70 days!
*50 people died
*Property loss was over $27 billion
Normal Stage: 1988
Flood Stage: 1993
Big Thompson River Flood of 1976, Estes Park, Colorado facts
- Within 4 hrs 12 inches fell
- Rock and soil stripped away and added to the flow
- Wall of water was 20 ft deep in 30 min
- Houses, bridges, roads, and people vanished.
- At least 144 peoples died
The two efforts of flood control?
1) Engineering efforts to reduce flooding
2) Non-structural approach through sound floodplain management
The engineering efforts to reduce flooding?
Artificial Levees: earthen mounds built on river banks to increase the volume of water the channel can hold
Flood-control Dams: built to store floodwater and then let it out slowly
Channelization” altering stream channel in order to spread the flow of water to prevent from reaching flood height
What is one flood-controlled dam?
Hoover Dam
built in 1931 - 1936
What running water “work” streams involves what?
1) Erosion
2) Transportation
What is running water stream load?
An amount of transported material carried by the stream
Three types of stream load?
1) Dissolved load: ions from weathering of minerals
2) Suspended load: fine particles (slit or clay) in the flow
3) Bed load: larger particles roll, slide, and bounce along stream bed
Transportation - Depositional features include…
Deltas- exist at mouth of stream that enters ocean or lake. Form when sediment from a stream, drops out due to lock of water velocity.
Natural Levees- form parallel to the stream channel due to flooding along stream bank.
What are stream deposited sediments?
Deposits are known as alluvium
They are well-sorted deposits
Sediment deposition is caused by what?
A decrease in velocity
The lowest point to which a stream can erode, is what?
Base level
Two types of base levels?
1) Ultimate base level- refers to sea level
2) Local base level- a lake, river, ect; this stream base level is temporary
The changing of the base level of a stream causes what to happen?
A readjustment of a stream:
results in either the deposition of sediment OR erosion of bedrock
Valley sides are shaped by the process of what?
A) Weathering
B) Overland steam flow
C) Mass wasting -landslides, slumps, ect
The characteristics of a narrow stream valley
V-shaped
Always down-cutting towards base level
Features: rapids and waterfalls
The characteristics of a wide stream valley?
Downward eroison is less dominants
Stream energy directed from side to side Floodplain develops and grows wider with age
Features: meanders, cutoffs, and oxbow lakes
Groundwater:
Zone of Aeration
unsaturated zone
pore spaces are filled mainly with air
Groundwater:
Zone of Saturation
All pore spaces in the sediment are filled with water.
What is a water table?
the upper limit of the zone of saturation.
AKA the boundary between the saturated and unsaturated zones.
What is Porosity?
Percentage of pore spaces in a sediment
Determines possible storage of groundwater
What is Permeability?
Ability of sediment to transmit water through connected pore spaces.
Aquitard- an impermeable layer of material
Aquifer- a permeable layer of material that can move through sand/gravel
Two features that are associated with groundwater?
1) Wells
- pumping of groundwater can draw down water table. pumping can cause “cone of depression” is groundwater is removed too quickly than it can be recharged.
2) Artesian Wells
- water in well rises high that initial groundwater so it will flow out freely. No pumping required!
What is a geological role and what does is produce?
An erosional agent, groundwater dissolves soluble rock and produces…
A) Sinkholes
B) Caverns
A void underground, usually created from the dissolution of bedrock, causes the surface to sink, is called what?
A Sinkhole
What is a Cavern?
Caves originally formed within the zone of saturation.
They are formed by dissolving rock beneath Earth’s surface
What is the geologic work of groundwater?
- Groundwater is often acidic
- It contains carbonic acids (H2CO3)
- It dissolves the calcite in limestone
Common cave features include what?
Stalactites- hang down
Stalagmites- grow upward
Columns- stalactites and stalagmites have grown together
