Final Exam Review Pt 2 Flashcards
fluvial
stream-related processes
hydrology
the science of water and its global circulation, distribution, and properties.
What are the driving forces of fluvial systems?
Insolation and gravity. They power the hydrologic structure.
Drainage basins
Every stream has a drainage basin, or watershed, that acts as a collection system for water and sediment from many subsystems.
Sheetflow
AKA Overland flow. Any any drainage basin, water initially moves downslope in a thin film of sheetflow.
Continental divides
High drainage divides; extensive mountain and highland regions separating drainage basins. They form water-resource regions and provide a spatial framework for water-management planning.
Drainage pattern
The arrangement of channels in an area. Patterns are distinctive and determined by a combination of regional steepness, variable climate, variable hydrology, relief of the land, and structural controls imposed by the underlying rocks.
What is the most familiar drainage pattern?
Dentritic drainage, treelike pattern, similar to capilaries in the circulatory system. Its very efficient because the energy expended is minimal.
What characterizes the trellis drainage pattern?
Dipping or folded topography, like the eastern US. Here, the drainage patterns are influenced by rock structures
Base Level
A level below which a stream cannot erode its valley. The ultimate base level is sea level, the average between high and low tides. Not all landscapes degrade all the way to sea level.
Discharge
The stream’s volume of flow per unit of time.
How is discharge calculated?
Discharge (the streams volume of flow per unit of time) is calculated by multiplying three variables for a specific cross section of the channel:
Q=wdv
where: Q= discharge w= channel width d= channel depth v= stream velocity.
What happens as Q (discharge) increases?
As Q increases, some combination of channel width, channel depth and stream velocity must also increase.
Why does discharge change over time at any specific channel cross section?
Greater discharge increases the velocity and therefore the capacity of the river to transport sediment as the flood progresses. As a result, the river’s ability to scour materials from its bed is enhanced (example, San Juan River in Utah). This type of channel adjustment occurs as the system continuously works toward equilibrium in an effort to balance discharge and sediment load with channel form.
Streams that flow all year round are referred to as _______ streams.
Perennial.
What are perennial streams?
Streams that flow all year long that are fed by snowmelt, rainfall, or ground water.
Streams that flow only after precipitation events and are not connected to ground water systems are referred to as ______ streams.
Ephemeral.
What are ephemeral streams?
Streams that only flow after precipitation events that are not connected to groundwater systems. This means that years may pass between flow events in these usually dry stream channels.
What are intermittent streams?
Streams that flow for several weeks or months each year and may have some groundwater inputs (often in arid, desert environments).
Streams that flow for several weeks or moths each year and may have some groundwater inputs are called ________ streams.
Intermittent.
Flash flood
A rare or large precipitation event in a desert that can fill a stream channel with a torrent.
In most river basins in humid regions, discharge _________ in a downstream direciton.
increases. (Example, Mississippi River) In cases where a humid region flows through an arid region, this may change.
What happens to discharge in a downstream direction?
It increases. (Example, Mississippi River) n cases where a humid region flows through an arid region, this may change.
Exotic stream
A stream that originates in a humid environment and flows through an arid region. Instead of increased discharge in a downstream direction, the high potential evapotranspiration rate in arid regions causes discharge do decrease with distance downstream. (example, the Nile River– flows through deserts in Sudan and Egypt and loses water because of evaporation and agricultural use… the Colorado River is also an exotic stream).
What are the three measurements needed to calculate discharge?
Width, depth and velocity.
Hydrograph
A graph of stream discharge over time for a specific location.
Base flow
During dry periods, the low discharge is described as base flow on a hydrograph. It is largely maintained by input from local ground water.
