geography rivers (topic 2) Flashcards
give the features of the upper course
- narrow and v shaped valley
- steep sides
- shallow and narrow channel
give the features of the middle course
- flatter than upper course
- deeper and rounder channel than upper course
- steeper than lower course
give the features of the lower course
- wide and deep channel
- flat and flat valley
- u shaped valley
name all 4 erosional processes
- abrasion -> scrapes and bangs against the sides of river bank like sand paper
- attrition -> rocks hitting against together, becoming smaller, rounder, and softer
- hydrolic action -> water forces it into cracks to force them apart
- corrosion/solution -> slightly acidic water dissolves the chemicals in rocks into the river
name all 4 transportation processes
- solution - chemicals are dissolved in the river water
- suspension - particles and small rocks are light enough to float within the water
- saltation - pebbles and small rocks which are too heavy to be suspended bounce along the river channel
- traction - large rocks are rolled along the river bed
explain the formation of a meander and what course its found in .. (upper,middle or lower) lawwwl
- Meanders often occur in the middle course of a river as the water begins to move at a faster pace.
- As the water flows around a bend it is pushed towards the outer bank of the curve and this increases the levels of both abrasion and hydraulic action.
- middle course
explain the formation of a waterfall and what course its found in .. (upper,middle, or lower) lawwwl
- A waterfall is formed when a layer or hard rock lies on top of a layer of soft rock.
- As the river passes over the hard rock, the soft rock below is eroded more quickly than the hard rock so there is a step in the river bed.
- Eventually this becomes deeper causing a waterfall.
1.upper course
explain the formation of a floodplain and levee and what course its found in (upper,middle, lower) lawwwl
- Periods of continous heavy rainfall causes discharge in a river to rise, meaning that the river level will rise above the banks and flood the surrounding land.
- Over time repeated annual flooding will lead to sediment being deposited, forming levées and flood plains.
- lower course
name and explain the human factors that influence flooding
- urbanisation -> water cant go into impermeable surfaces like concreate in cities which forces the water to go into surface run off, causing the flood to occur quicker.
- Deforestation -> Trees intercept the rain and
so it takes longer for the water to travel through the leaves into the river. So cutting down trees will speed up the time taken for rainwater to flow into the river, increasing the risk of flooding.
name and explain the natural factors that influence flooding
- Geology - If the area has many impermeable rocks, the rainwater can’t run into the soil and goes into surface runoff, increasing the risk of flooding on bad weather days.
- Topography - The shape of the land will
determine how quickly rainwater flows into the
river. Steep hills with high gradients are
more likely to have flash floods than flatter gradients.
explain the features of a storm hydrograph
- Lag time – The time delay between peak rainfall and peak river discharge
- Peak Precipitation - The maximum rainfall that occurs, shown as bar charts at the start of the
graph
name and explain two soft river flood managements
- river channel restoration -> Concrete structures are replaced with natural sediment
- wetlands -> Vegetation is planted and legal
protection stops building on wetlands
name and explain two hard river flood managements
- dams -> Concrete blockade that stores
water in the upper course and can regulate
river flow - dredging -> Rubbish and sediment are dug
up from the bottom of the river
whats good and bad about damns and dredging
- dredging -> good =Widens the river channel and removes pollution from the water,
bad = Takes time to complete, and the river
must be dredged regularly
- damns -> good =Valves can control and release the right amount of water to avoid flooding
bad = Visually unappealing
what is good and bad about the wetlands and river channel restoration
- river channel restoration -> good = The natural environment benefits, as the ecology recovers
bad = Land will still flood, but often this is
parks and football fields
- wetlands -> good = Creates valuable habitats for river wildlife
bad = It takes a long time for wetlands to
establish and grow
