River Landscapes Flashcards
What do the following mean: Drainage basin Weathering Mass movement Erosion
Drainage basin - an area drained by a river and its tributaries. Weathering - the breakdown of rock in-situ. Mass movement - once the rock has been broken down it moves downslope under gravity. Erosion - the wearing away of the land
What are the different types of erosion in a river?
Corrasian/abrasion - material carried by the river smashes against the banks wearing them away Attrition - rocks smashing into each other gradually become smaller and rounder Solution/corrosion - where water has a chemical reaction with the rock and dissolves it Hydraulic action - the force of the water and/or forces air into cracks making them wider
Name two types of weathering and two types of mass movement
Weathering types: chemical, physical or biological Mass movement: soil creep slumping
Describe how a river changes from upper to lower course
River becomes wider - as a river reaches its lower course lateral erosion becomes more common, as gradient decreases, widening the river. Discharge increases - as more tributaries join the river amount of water increases. Velocity increases - as bedload has become smaller and banks and bed smoother friction decreases therefore increasing velocity. Gradient decreases - due to meander migration widening the valley floor
How is a waterfall formed?
Waterfalls: Hard, more resistant rock overlays softer less resistant rock. Soft rock is eroded more rapidly through hydraulic action/corrasion undercutting the hard rock creating an overhang. The force of the water creates a plunge pool. The hard rock collapses under its own weight and the process repeats, retreating upstream to create a gorge.
Give five physical causes of flooding
Any of the following: heavy rainfall long periods of rain snowmelt steep slopes impermeable rock (doesn’t allow water through) very wet, saturated soils compacted or dry soil
Give two human causes of flooding
urbanisation, because towns and cities have more impermeable surfaces deforestation, because removing trees reduces the amount of water intercepted and increases run-off
Describe how a meander can move over time
A meander is a bend in the river. Meanders usually occur in the middle or lower course, and are formed by erosion and deposition. As the river flows around a meander, centrifugal forces cause the water to flow fastest around the outside of the bend. This creates erosion on the outside and deposition on the inside of the bend, which means that the meander slowly moves.
Explain how a V-shaped valley is formed
When a river is near its source, it often develops a V-shaped valley as the river erodes down (this is called vertical erosion). At the same time, weathering breaks up material on the valley slopes.
What are they planning to do in Oxford to protect the city from flooding in the future?
Building a flood relief channel. A separate channel will be built. It will bring water from the north of the city to near Sandford Lock. It will keep water away from the city
Give some impacts of the floods in Oxfordshire in the winter of 2013/14
Trains cancelled on route to Reading Major routes into Oxford (Abingdon Road and Botley Road) were closed. This meant that many people could not get into work and businesses lost money Hundreds of homes evacuated Loss of electricity - on Christmas Eve - for hundreds of homes Military called in to help give out sandbags Hundreds of homes flooded and damaged
What temporary measure is put in place when the river levels get high on the River Severn in Shrewsbury?
Demountable barriers made from aluminium barriers. Slotted together prior to floods arriving. They can hold back 1.9m of flood water
