Rivers Flashcards
national levees
these are raised banks of sedinment parallel to a river channel formed by deposition of coarser sediment during floods §
draingage basin
also known as watershed is the highest land bordering the basin. rivers are the main features of a drainage basin
processes- drainage basin
interception- precipitation falling into the drainage basin can be intercepted by leaves and ground vegetation
infiltration- some of the precipitation that reaches the ground continues downward through soil
overland flow- some of the precipitation reaching the ground flows over the surface until it reaches a river channel
evaporation- water on vegetation or in river channel get evaporated back into the atmosphere
through flow- infiltrating water continues down slopes through the soil towards the river channel
groundwater flow - some infiltrating water continues into pores and cracks in the underlying rock and cracks in the underlying rock and flows towards the river as groundwater.
river processes
source- upper
–> highland- middle
—> lowland- lower
—> mouth
transportation
rivers carry eroded material :boulders, pebbles, sand, silt. this is caller a river’s load this can be don in several processes:
- traction
- saltation
- suspension
- solution
traction
rolling large particles along the riverbed
saltation
bouncing of smaller particles along the riverbed
suspension
carrying fine particles in the water collumn
solution
dissolving soluble materials
alluvial plains
these are flat areas of land adjacent to rivers, fomred by the deposition of sediment carried by the river overtime.
deltas
form at the mouth of a river where it meets a body of water, such as a sea or lake. sediment carried by the river is deposited, creating a fan-shaped landforms with multiple distributions
meanders
are bends or curves in a river’s course, formed through the lateral erosion of the riverbanks and the deposition of sediment on the inside of bends
hydraulic action
force of the water knocks particles off the sides
corrasion
wearing down of rock by the river’s load(abrasion)
attrition
waering down of big rocks by colliding together and breaking in the river
solution/corrosion
acids in the river dissolve the rocks that make up the bed + banks
erosion and speed
as the speed of the river increases, so does the amount of erosion and load in a river
river deltas
formed at the mouth of a river where sediment is deposited, creating a network of distributariesfl
floodplanes
are flat area of land adjacent to rivers, periodically inundated to the formation and replenishment of floodplains
river course
goes through three stages : upper, middle, lower
length of these depends on type of rock, landscape, climate
refers to its journey from source to mouth
upper course
river has a V-shaped valley with a steep gradient, water in river channel occupies most of the valley floor
load is large bc not enough time to erode
load found at bottom
lots of friction between water and bed-load = decease velocity
common features: waterfalls, rapids, potholes
waterfalls
occur where the river crosses resistent rock and the softer rock downstream is eroded more rapidly
under waterfall is plunge pool is formed when erosion by hydraulic action and abrasion is greatest.
potholes
if riverbed is uneven, pebbles become trapped and swirl currents cause pebbles to rotate and erode circular holes in riverbeds
alternating hard and soft rock forms uneven bends and areas of rapids