River Landforms Flashcards
what is an interlocking spur
- an interlocking spur is an acute, gently sloped valley with a deepened channel
how do interlocking spurs form
- potential and kinetic energy causes river to vertically cut into channel
- which creates a deep channel by hydraulic action and freeze thaw
- resistance along the way causes river to change direction and meander, making spurs of highland to interlock
what are rapids
areas of shallow, fast-flowing water in a stream
how are rapids formed
- they form downstream of a waterfall where water flow is straighter and quicker
- they mark the point of a previous waterfall
what is a waterfall
a waterfall is a cascade of water falling from a height
when are waterfalls formed
when a river flows over an area of hard rock followed by an area of softer rock
what is a gorge
- a gorge is a high valley side located directly downstream a waterfall
- it is a steep sided valley with rocky walls
how are gorges formed
- they are formed as waterfall retreats upstream
- it leaves a steep sided valley called a gorge
- every time over changing cap rock breaks off the gorge retreats and grows longer
what is an oxbow lake
an oxbow lake is a horseshoe shaped lake that was previously part of a river
how is an oxbow lake formed
- narrow neck of meander is laterally eroded
- narrower neck gets flooded by river to create shortcut to main channel
- process of flooding repeats and erodes narrow neck
- redundant loop cut from main channel
- high velocity river deposits material on the the outside
- creates a body of land between river and loop
- marsh plants colonise deposited material
what is the result of the process of an oxbow lake being formed
a straightened river channel and an isolated loop lake (oxbow lake)
the four simplified stages of oxbow lake creation
- erosion
- flooding
- new course
- oxbow lake
what is a flood plain
- a flood plain is made by a period of prolonged heavy rain
- causing an increase in rivers discharge
- so water rises over banks and floods surrounding land
- repetition builds up levees and flood plain
stage 1 of a flood plain
- before levee
- silt deposits on flood plain
stage 2 of a flood plain
- during a flood
- heavy deposited material nearer the river bed and fine sediment further on flood plain
stage 3 of a flood plain
- raised bank either side of river a natural levees
- river bed builds up bed load that deposits overtime
4 characteristics of flood plains
- large area of flat land
- layers of alluvium cover flood plain
- oxbow lakes
- reeds and marsh plants
where are levees found in a river
in the lower course
how is a waterfall formed
- softer rock is eroded by hydraulic action and abrasion more than hard rock
- creating a step
- as water goes over step it erodes more soft rock
- a steep drop is eventually created, forming the water fall
how is a gorge formed (after a waterfall is formed)
- hard rock is undercut by erosion
- it becomes unsupported and collapses
- collapsed rock is swirled around the floor
- eroding soft rock by abrasion, creating a deep plunge pool
- overtime, more undercutting causes more collapses
- and the waterfall retreats leaving a seep sided gorge
