physical landscapes Flashcards
what is a confluence?
where two or more streams/rivers meet
characteristics of the upper course?
- shallow
- narrow
- steep relief
- large, uneroded rocks
- rough riverbed and banks - high levels of friction - lower velocity
- primarily vertical erosion
formation of a waterfall
1) at an area of hard rock and soft rock, the soft rock erodes faster
2) the soft rock undercuts the hard rock, creating a plunge pool
3) this creates an overhang of hard rock, which due to weathering, weakens over time, and eventually collapses due to gravity, forming a waterfall
4) hydraulic action and abrasion attack the base of the cliff, creating another plunge pool, and so the process repeats again, causing the waterfall to retreat
what is a gorge?
a steep-sided, narrow valley is left where the waterfall once was, and the river runs through it
formation of a V-shaped valley
1) due to vertical erosion, the river bed deepens
2) the sides of the river bed are weakened due to weathering
3) material breaks off and slides down diagonally into the river, forming a V-shaped gap where they once were
4) the sediment added to the river causes further erosion, causing a steeper V-shaped valley
formation of a meander
1) the fastest flow of the river (the thalweg) is on the outside of the river
2) hydraulic action and abrasion therefore erode the outside of the river, forming a river cliff
3) the slowest flow of the river is on the inside of the river, therefore this is where the least energy is, and subsequently deposition of sediment occurs, forming a slip off slope
4) as this process repeats, the river moves across the floodplain, and become wider and more sinuous, forming meanders
formation of an oxbow lake
1) the erosion on the outside of meanders can create a meander neck
2) in the event of a flood, water may cut through the neck and take a straight route to the other side
3) the spreading of water causes a drop in energy, meaning that deposition occurs, leading to the meander being cut off from the lake, forming an oxbow lake
what is alluvium?
- rock particles (clay, silt, sand, etc.) deposited by a river
formation of floodplains and levees
1) high discharge causes flooding of the surrounding area
2) the spread out of water over a large area causes a drop in energy, causing deposition, gradually increasing the height of the floodplain
3) the heaviest material is deposited closest to the riverbanks, forming natural embankment called levees
what is an estuary?
where the river meets the sea
formation of mudflats and salt marshes
1) when saltwater meet freshwater at the mouth of the sea, this causes a drop in velocity
2) deposition occurs and builds up in layers to form mudflats
3) mudflats grow vegetation and form salt marshes
River Tees?
- NE England, 85 miles long
- Pennines to the North Sea
- High Force waterfall, highest in the UK
- meanders near Darlington, floodplains and levees
what is lag time?
time taken for the precipitation to reach river (shorter lag time = increased discharge = increased flood risk)
what are the factors that affect flood risk?
- human: deforestation (less interception), urbanization (impermeable materials), agriculture (soil become more compact), climate change (increase in precipitation)
- physical: steep relief (reduces infiltration), impermeable rock types, frozen/compacted soil, amount of vegetation/trees, amount of precipitation, antecedent conditions (recent rainfall that already saturated the ground)
dams?
- large concrete barrier, and there is a valley behind it, creating a reservoir to store floodwaters
- advantages: HEP source, drinking water source, highly effective, boosts tourism
- disadvantages: expensive (167 million pounds), harms habitats, displaces existing people, landslides often occur
raising embankments?
- impermeable soil/concrete embankments to contain floodwaters
- advantages: cheaper, earthen embankments provide habitats, attractive walkway
- disadvantages: requires lots of maintenance, displaces natural habitats when built, no easy access to fishing or boating, earthen ones prone to erosion, visually unattractive
channel straightening?
- meanders turned into wider, deeper channels
- advantages: water moves faster, improves navigation and increases trade, lower insurance costs
- disadvantages: expensive, constant maintenance, more energy which erodes banks runoff cannot drain into the river easily
flood relief?
- another channel built to divert flooded water
- advantages: completely removes risk, footpaths, cycle paths, etc. built along channel, lower insurance costs
- disadvantages: displaces people, causing distress, settlement downstream suffer from more flooding, constant maintenance, unattractive at low tide when concrete is exposed
river restoration?
- uses meanders to slow river flow
- advantages: - restores natural habitats, reduces flood risk downstream
- disadvantages: take time to be effective, expensive (1.1 million), loss of agricultural land
flood warnings?
- prediction of flood and issues warnings
- advantages: cheap, people feel more in control and secure
- disadvantages: only effective if people listen, not everyone has internet, flooding still damages properties, etc.
afforestation?
- planting trees to increase interception
- advantages: increases lag time, low-cost, nature is conserved, also reduces climate change
- disadvantages: limited impact, loss of agricultural land
floodplain zoning?
- buffer zone for flooding, protects high-value land
- advantages: decrease in impermeable surfaces, less flood risk, low cost, conserves nature
- disadvantages: lots of cities already built over floodplains
different types of erosion?
- hydraulic action - force of water hitting against cliff face
- abrasion - rocks from water being thrown at seawall
- attrition - rocks hitting each other
- solution - chemicals dissolving rocks
different types of transportation?
- saltation - rocks bouncing along the seabed
- suspension - small rocks floating
- traction - large boulders rolling along seabed
- solution - dissolved fine particles carried by water
reasons for deposition?
- water spreads out/increased surface area
- shade
- decrease in energy
- increase in sediment
- mouth reached
what is a concordant vs. discordant coastline?
- concordant - alternating layers of soft ad hard rock parallel to the coast - forms coves
- discordant - alternating layers of soft and hard rock perpendicular to the coast - forms headlands and bays
types of mass movement?
- sliding - rain infiltrates soil and makes it heavier, so large blocks of mud or rock slide downhill
- slumping - material travels down a concave slip plane, so it it rotates backwards into the cliff face as it slips, creating layers
- rock falls - bits of rock fall off from cliff face, and fan out at the base to form a scree slope
types of beaches?
- sandy beaches - flat gradient and constructive waves (low energy and relatively stronger swash)
- pebble beaches - steep gradient and destructive waves (high energy and stronger backwash, although swash is still stronger than that of a constructive wave)
formation of a cave, arch, stack, stump
1) wave is refracted by low energy/wind direction
2) hydraulic action and abrasion attack both sides of the headland
3) eventually, as rock pieces break off, a cave is formed
4) erosion continues until the caves on either side of the headland meet, breaking through the headland and forming an arch
5) the overhang weakens and collapses due to weathering, leaving an isolated rock column called a stack
6) hydraulic action and abrasion erode the base of the stack, leaving the top weakened by weathering and eventually collapses to form a stump
longshore drift?
1) waves driven onto the beach at an angle by the prevailing wind direction
2) therefore, swash carries sediment up the beach at an angle
3) materials travels straight down with backwash (due to gravity)
4) sediment continues to travel in the zigzag motion down the beach
formation of a spit?
1) when the coastline changes direction, LSD will continue into the sea
2) as it is now surrounded by water, the increase in surface area will cause deposition of sediment, forming a spit
3) recurve caused by prevailing wind direction
formation of bars?
1) at a bay, LSD will continue across the sea - the shade in the sheltered area means sediment is deposited
2) this will continue to the other side, forming a bar
3) the bay behind the bar is cut off from the sea, forming a lagoon
formation of sand dunes?
1) sand is blown against an obstacle (vegetation)
2) more plants and vegetation grow there which traps more sand, increasing the size of the dune
embryo vs. mature dunes?
- embryo dunes - yellow, more sandy, at the front of the beach
- mature dunes - grey, tall, more vegetation at the back of the beach
seawall?
- designed to absorb and reflect wave energy
- advantages: low maintenance, strong defense, provides a sense of security, can be used for social activities, doesn’t impede LSD
- disadvantages: very expensive, visually unappealing, restricts access to the beach, impacts nearby species
groynes?
- barriers perpendicular to the coastline to trap sediment from LSD
- advantages: maintained beaches are tourist attractions, cheaper than seawalls
- disadvantages: visually unappealing, restricts access, can rot/fall apart, more erosion in beaches further along the coast
rock armour?
- boulders act as barrier and dissipate energy
- advantages: can be used to protect seawall (less maintenance), quick and easy, does not impede LSD, relatively cheaper
- disadvantages: safety hazard, transport of rocks is expensive, restricts access
gabions?
- wire cages filled with rocks and pebbles, when waves energy their energy is dissipated
- advantages: least cost, long-lasting, looks somewhat natural
- disadvantages: safety hazard, can rust/degrade, easily destroyed by a storm
beach nourishment?
- sand taken from another beach and deposited, larger beach dissipates energy
- advantages: provides material for LSD and natural processes, increases tourism, looks natural, can be used to protect hard engineering
- disadvantages: closes beach for weeks, annoying to residents, expensive, deprives a beach somewhere else
beach reprofiling?
- reshaping beach for a steeper gradient for a higher, wider barrier
- advantages: protects home and sense of security, cheaper
- disadvantages: steep beach looks unnatural and uninviting to tourists, bulldozers make noise pollution, restricts access to beach
sand dune regeneration?
- planting vegetation to trap sediment and encourage sand dunes
- advantages: cheap, sheltered areas for picnics, natural, sustainable long-term solution
- disadvantages: fences deter visitors, needs to be constantly maintained, prone to damage, takes years to grow and establish
managed retreat?
- people are moved out and buildings demolished to protect from retreating coastline
- advantages: natural habitats, cheaper in the long-term, takes pressure off flooding in neighboring beaches
- disadvantages: distressed people, damages natural habitats by flooding, compensation costs make it expensive in the short-term
