rivers Flashcards
characteristics of rivers
- width
- depth
- speed of flow
- discharge`
width of river
the distance between to banks
depth of river
the distance between the surface of water and the riverbed
speed of flow of river
the velocity of water in the river
discharge of river
the volume of water in the river
characteristics of drainage basin
- watershed
- tributary
- confluence
watershed
marks the boundary of the drainage basin
tributary
small rivers joining into the main river
confluence
the point where the tributary joins the main river
process of erosion
- abrasion
- hydraulic action
- attrition
- solution (corrosion)
abrasion river
where sand and pebbles are dragged along the river bed, wearing it away
hydraulic action river
where fast-flowing water is forced into cracks, breaking up the bank over time
attrition river
where rocks and stones wear each other away as they knock together, becoming smaller and more rounded
solution river
where rocks such as limestone are dissolved in acid rainwater
process of transportation in a river
- traction
- saltation
- suspension
- solution
traction river
large stones are dragged along the river bed
saltation river
smaller stones or pebbles are picked up then dropped again in a “leapfrog motion”
suspension river
tiny particles of sediment are carried as a suspension in the river water making it look murky
solution river
dissolved salts and minerals are carried by the river water
what is a drainage basin
area of land drained by a river and its tributaries
what is interception in a drainage basin
leaves and branches of trees catch rainwater
what is infiltration in a drainage basin
rain soaks into the ground
what is throughflow in a drainage basin
some water flows through the soil
what is groundwater flow in a drainage basin
some water continues into solid rock to form groundwater
what is evaporation in a drainage basin
due to the sun’s heat. some river water evaporates
what is overland flow in a drainage basin
if the ground is very hard or very wet rain flows overground
upper course of the river characteristics
steep long profile with a steep and v-shaped cross profile (water flow is fastest here)
middle course of river
gentler long profile and cross profile
lower course of river
gentle long profile and almost flat cross profile (water flow is slowest here)
formation of waterfalls process
- alternating layers of hard and soft rock present
- hard rock resists erosion whereas softer rock is eroded rapidly
- plunge pool forms
- overhang develops
- plunge pool deepens
- process repeats causing waterfall to retreat
- gorge forms
formation of potholes process
- smooth rounded hollows formed in the river bed by vertical erosion
- formed by stones trapped in hollows on the river bed
- eddies in the water swirl the trapped stones around, causing abrasion
- this causes the stone to drill down into the riverbed
- hollows become deeper and wider and may join together to form larger potholes
formation of oxbow lake process
- river flows around a meander
- erosion on outer bends due to faster flowing water
- hydraulic action and abrasion involved
- helical flow of water adds to the faster erosion
- deposition on inside bends due to slower flowing water
- river becomes more sinuous, winding around meanders
- neck of meander reduced in thickness
- eventually river erodes across neck and river flows straight on
- during time of flood, deposition seals former meander
- oxbow lake formed
formation of delta process
- large amounts of sediment brought downstream
- deposition in lower course as speed of flow is reduced
- flocculation occurs due to salt in water
- deposited silt blocks course of river which splits into distributaries to reach the sea
- deposited materials are not washed away due to lack of current
- colonization by vegetation occurs and delta is formed
what are floodplains
- a wide and flat piece of land found on both sides of a river
- covered in alluvium (rock particles such as sand, clay and silt) deposited by the river
what are levees
naturally raised banks by the riversides made up of deposited coarser materials
hazards of living near rivers
- erosion
- marsh lands not suitable for firm houses
- mosquitoes contaminate and spread diseases
- difficulty to get to other side of river
- roads cant be built on rivers
- flooding
managing river flooding
- reservoirs/dams built upstream
- increase height of banks
- artificial levees
- afforestation
- overflow channels
- straighten channel
- dredging
- widening river
- warning systems
- land zoning
managing river erosion
- strengthen banks by adding hard rocks to banks or placing rock barriers infront of banks
- use gablons
- concrete river channel
