Chapter 15: River Systems and Geomorphology Flashcards
Identify all the parts of the hydrologic cycle and give definitions for each.
- Evaporation - Process in which water, from a wet surface, changes from a liquid to gas/vapor as it moves into the air. (occurs over water bodies)
- Transpiration - water moves into air and changes into gas/vapor from land environment (from leaves and stem of plants)
-Precipitation - the release of condensed water vapor in form of rain, snow, hail, or sleet from clouds in atmosphere - Cloud formation - Occurs when warm air containing water vapour rises, expands, and cools, causing the water vapor the expand into tiny droplets or ice crystals around microscopic particles in the air
- Surface runoff - the flow of water over land surfaces when the soil is saturated and can’t absorb any more water. It eventually flows into streams, lakes, oceans, or rivers, replenishing surface water bodies
- Ground water flow - the movement of water beneath the Earth’s surface through permeable rocks and soil layers. it occurs when precipitation infiltrate the soil and goes down until it reaches the water table, which also eventually discharges into water bodies.
Briefly describe the origin of earth’s waters, and list the locations of Earth’s freshwater supply in order of
relative volume
The origin of Earth’s water’s seemed to come from:
-comets made of ice and rocky material during Earth’s early formation stages
-Hydrogen and oxygen laden debris
-Extraterrestrial collisons, like massive collisons w/ water-rich celestial bodies could have also contributed
Locations of Earth’s freshwater supply:
-Glaciers and ice caps - the largest volume of freshwater
- Groundwater - second-largest
- Rivers and lakes
- atmospheric water
Describe the two pathways for precipitation that reaches Earth’s surface as rain, considering infiltration,
overland flow and streamflow.
Rain either:
1.) flows overland
-overland flow (surface run off) - water that flows across land and into stream channels; this occurs when soil is impermeable or infiltrated to full capacity
-Streamflow - occurs when run off becomes channelized; surface water that flows into streams, rivers, and other channels
2.) soaks into soil
- infiltration - the process in which water soaks into the subsurface; this needs the surface material to be permeable
Describe the three main surface water resources.
1.) Snow and ice
- the largest freshwater store
- seasonal melting of snow and ice are captured in reservoirs behind dams
2.) Rivers and lakes
- they are fed by precipitation, stream flow and groundwater
-many rivers are dammed to create reservoirs
3.) Wetlands
- areas that are seasonally or permanently saturated w/ water (marshes, swamps, bogs, peatlands)
-They improve water quality by trapping sediment and filtering nutrients and pollutants
Define groundwater, zone of aeration, zone of saturation, water table, aquifer and drawdown and be able
to locate all of these on a diagram.
- Groundwater - water beneath the surface that’s beyond the soil-root zone; it’s also a large potential freshwater source on earth
- Zone of aeration - pore spaces that contain air, and where soil and rock aren’t saturated
- Water table - upper limit of zone of saturation
-Aquifer - a subsurface layer of permeable rock or sediment through which groundwater can flow
-Drawdown (cone of depression) - the lowering of a water table due to the excessive pumping of water from the aquifer
Define stream, river, drainage basin. How do drainage basins form? What are the topographic features of a
drainage basin?
- Stream - any surface water flow confined to a channel regardless of size
-River - trunk, or main stream of network of tributaries forming a river system
Drainage basin - portion of landscape that holds river systems and the land that feeds them.
Drainage basins form by:
Water first moves downslope as sheet flow (thin film of water that’s spread over ground surface), which concentrates into rills (small grooves in landscape made by downslope movement of water), then develop into gullies (deeper grooves in landscape), which feed into streams.
Topographic features of drainage basin:
-Valley -elongated depression in a landscape
-Interfluve - high ground that separates one valley from another; helps directs sheet flow direction
-Ridge - narrow, linear crest along top of interfluve
-drainage divide - ridge that separates one basin the surface run off drains
-Catchment - water-receiving area of a drainage basin
Describe the seven most common drainage patterns in terms of their shape as well as the type of
landscape they tend to form in. Be able to sketch an example of each or label a diagram.
1.) Dendrite drainage
-common in gentle-to- moderate sloping landscapes
-it’s shaped in a tree-like pattern
2.) Trellis drainage
- pattern is characteristic of folded or tilted topography
- common at the nearly parallel mountain folds of the Ridge and Valley Provinces in the US
3.) Radical drainage
- pattern: branch lines that are all flowing out from a central point in all directions
- occurs maybe on a volcanic mountain
4.) Parallel drainage
- Pattern: branch lines are all lined up, parallel to one another
-common in steep slopes
5.) Rectangular drainage
-Pattern: branch lines are sometimes turned 90 degrees, making sharp corners that look rectangular
-commonly formed by faulted and jointed landscapes, which direct stream courses in patterns of right-angle turns
6.) Annular drainage
- Pattern: branch lines form a circular pattern around a central point
- common in landscapes where there’s a layer of less resistant rock on a hill
7.) Deranged drainage
- Pattern: unclear or no true pattern
-common in areas with disrupted surface patterns (ex. glaciated shield regions of Canada)
Where would you expect to find a low drainage density vs. a high drainage density?
-A typical desert has a low drainage density
-an area w/ humid climate is associated w/ a high drainage density
Explain the concepts of stream gradient and base level, and describe the relationship between
stream velocity, depth, width, and discharge.
- Stream gradient is the drops in elevation per unit distance; a steep gradient means there’s a large elevation change over a distance while a gentle means there’s a small elevation change
-Base level - the lowest level to which as stream can’t erode its valley
-If the width, depth, and velocity increase, then discharge increases; if they all decrease, then discharge also decreases.
How does discharge change with distance downstream? How does this change depending on
climate or human activity?
-It may decrease due to the high potential of evapotranspiration, which occurs due the arid climate in some regions
- on the other hand, impermeable man-made surfaces, like concrete or tarmac, can cause discharge to increase due to higher amounts of surface runoff
Explain the processes that produce fluvial landscapes, including stream channel flow, hydraulic
action, abrasion, and corrosion.
-The process that produce fluvial landscapes include:
- Stream channel flow - its unsystematic, irregular, has different directions and speeds, which are affected by friction (caused by the width and depth of the channel, as well as the roughness of the channel floor)
- Hydraulic action - the type of erosion work performed by flowing water alone; it has a squeeze and release action that loosens and lifts the rock
- Abrasion - physical erosion of the stream bed by rock and sediment grinding and carving the stream bed
-Corrosion - chemical erosion of the stream bed by slightly acidic water, which reacts w/ certain rocks a part of the stream bed and dissolves them
Explain what processes might cause fluvial incision.
Fluvial incision is the process in which rivers cut into its stream bed, deepening the channel. These processes might cause it:
-Erosion - the primary process, where the force of flowing water wears away at the bedrock of a river channel. this happens through the processes of hydraulic action, abrasion, and corrosion
-Tectonic uplift - the uplift could increase the gradient of the river, causing it to flow faster and erode more aggressively leading to a deeper incision
Describe the erosional and depositional landforms associated with meandering stream environments.
Erosional landforms:
-Point bars - small bar made of sediment along inner bank
-Cut banks - outside bank of a curve; forms when water hits walls of the channel on the outside and erosion occurs
- Oxbow lake - ‘U’ shaped lake or pool that forms when a wide meander of a river is cut off, making a free-standing water body
Depositional landforms:
-Alluvial deposits - Material deposited in river beds; consists of silt, sand, clay, and gravel or organic matter
-Natural levees - deposit of sand and mud built up along and sloping away from, either side of the floodplain of a river/stream
-Terraces - flat or gentle sloping landforms found alongside rivers and streams; generally appear as paired steps on either side of the river valley
-Alluvial fan - Cone/fan shaped deposits of fluvial sediments; commonly occurs at the mouth of a canyon where ephemeral stream exits mountain into a flatter valley
-Delta - level (or nearly level) depositional plain that forms at mouth of river (where it reaches base level)
Describe the different ways that stream sediment load is transported.
-Coarse sand - deposited closer to river’s mouth
-Finer materials (clay, silty mud) are carried further and form extreme end of the deposit
Describe the common stream channel patterns, and explain the concept of a graded stream.
-Multiple-thread channels - braided or ana branching patterned stream; occurs when sediment load increases and discharge lowers, thus reducing the ability of a stream to transport its sediment load
-Single-thread channels - either it’s straight or meandering stream; perfectly straight streams are rare. more common are meandering stream. The stream form a more snake-like form; wavy
Graded stream - streams in which a state of equilibrium between gradient and sediment load has been reached; the channel slope has adjusted so stream velocity is just enough to transport the sediment load.
