rivers Flashcards
(20 cards)
what is a levee and how is it formed?
a raised embankment on either side of a river to prevent flooding
formed through deposition, large material is dropped first which slows water down.
drainage basin
an area drained by a river and its tributaries
PISS IS PG
Precipitation Interception Stem-flow Surface Storage Infiltration Soil moisture Percolation Groundwater storage
explain the formation of a flood plain
a flat area of land adjacent to a river, it is covered in water at times of flood
wide=erosion on outer banks of meander
flat=repeated deposition of alluvium
levee=raised bank at the edge of the river
water cycle
the continuous circulation of water of evaporation from the sea, through the air and back to the sea by flowing through rivers or the ground.
precipitation
INPUT. any water falling from the sky: rain, hail, sleet, snow
Interception,
STORE. where water is prevented from reaching the ground by vegetation. it can slow run-off and reduce the risk of flooding.
watershed
the boundary between two drainage basins. usually a ridge of high land.
tributary
a smaller river flowing into a larger river
confluence
a place where two streams / rivers meet.
mouth
where a river flows into the sea.
evapotransporation
OUTPUT. Water turning from liquid into gas (water vapour) in the air by plants through their leaves.
gradient
the steepness of the slope down which a river flows. it will usually become less steep from source to mouth.
load
material carried/transported by a river e.g rocks, pebbles, sand, mud.
discharge
the amount of water passing a point in a river every second. measured in cumecs or cubic metres per second.
types of erosion
attrition (the load hit against each other and become smaller and fine)
hydraulic action(force of moving water)
abrasion/corrasion(load carried by a river grinds against the bed and banks of the river
corrosion(water dissolves minerals in the rock)
types of transportation
traction(largest material are rolled along the river bed)
saltation(pebbles bounce along the river bed)
suspension(small material are carried along in the water)
solution(rocks are dissolved into river water)
Land use zonation
soft engineering strategy to designate high flood risk areas not to be built on and others to be forested to increase interception.
how is a meander formed?
centrifugal forces push most of the water to the outside this creates fast flowing water
this creates erosion (hydraulic action)
this erosion is responsible for creating a river cliff on the inside of the bend there is less water and the water flows slowly. this creates deposition and a shallow river bed and a feature called slip-off-slope
how is a waterfall formed?
water flows over an area of hard rock and soft rock. the soft rock is eroded first due to hydraulic action and abrasion. this treated a step in the river. the soft rock continues to erode and undercuts the hard rock creating an overhang. the overhang is unsupported and it collapses into a plunge pool. overtime this process continues and retreats back and creates a gorge.
