Freshwater Flashcards
What are the inputs of a drainage basin?
Precipitation of varying type and intensity
What are the processes of a drainage basin?
Interception surface runoff infiltration throughflow percolation groundwater overland flow base flow vegetation soil cryosphere aquifers
What are the outputs of a drainage basin?
evapotranspiration
river runoff
What is discharge?
the volume of water that passes through a cross section per unit of time
what is occupied channel width?
the distance across the actual channel measured at the water surface; it increases because of input from tributaries etc.
what is channel depth?
the height from the water surface to the stream/river bed channel depth - increases further downstream along with the size of the river. A line connecting all places of greatest depth all along the river is called the ‘thalweg’
what is average velocity?
the speed of the water flow (distance travelled per unit of time),
- it increases steadily further downstream
- further downstream, the river becomes more efficient with proportionally less contact with its bed and banks
what is load quantity?
the capacity of the river including the river load and it increases with large discharge and velocity.
- load particle size decreases considerably downstream and the more angular pebbles become more rounded due to attrition.
what is channel bed roughness?
a measure of how rough the bed of a river is. It decreases significantly downstream because of fewer and smaller stones, this is due to erosion.
- channel bed roughness decreasing allows much faster water flow.
What is the slope angle (gradient)?
How steep the river is.
- The gradient decreases downstream
What is hydraulic radius?
The efficiency of a stream’s shape is measured by its hydraulic radius (the cross sectional area divided by the wetted perimeter.
- the higher the ratio, the more efficient the stream is and the smaller the friction loss is.
what is cross sectional area?
the area of water in a channel cross section multiplied by the average velocity of the water in that cross section
What is abrasion or corrasion?
the wearing away of the bed and bank by the load carried by a river
what is attrition?
the wearing away of the load carried by a river = smaller, rounder particles
what is hydraulic action?
the force of the air and water on the sides of rivers and in cracks
solution or corrosion
the removal of chemical ions, especially calcium, which causes rocks to dissolve
what are the factors affecting erosion?
load velocity and discharge gradient geology pH human impact seasonality
how does load affect erosion?
the heavier and sharper the load, the greater potential for erosion
how do velocity and discharge affect erosion?
the greater the velocity and discharge, the greater the potential for erosion
how does gradient affect erosion?
increased gradient, increases the rate of erosion because of faster speeds.
how does geology affect erosion?
soft, unconsolidated rock, such as sand and gravel are easily eroded.
how does the pH of water affect erosion?
rates of solution are increased when the water is more acidic
how does human activity affect erosion?
deforestation, dams, and bridges interfere with the natural flow of the river and frequently end up increasing the rate of erosion
how does seasonality affect erosion?
more precipitation during rainy/monsoon seasons leads to a faster rate of erosion