Geaography - Rivers

what is an estuary?

where the tide meets the stream

what is a drainage basin?

ana rea of land drained by a river and its tributaries

features of upper course?

• low volume of water

• v-shaped valley

• interlocking spurs

• gorges

• high level of percepitation

features of the middle coarse

• wide valley

• flood plains

• meander

• oxbow lake

• more suspended sedement

what kind of erosion occurs on the upper coarse

vertica; erosion

what kind of erosion occurs on the middle coarse?

lateral erosion

features of the lower coarse

• levees

• deep and wide channels

• lots of deposition

what is hydraulic action

force of water foces air into crack which break the rock on the river bank away

requires high energy water

what is abrasion

eroding the river bed as big angular boulder roll across the river bed

what is attrition

when small sediment hit eachother as they are carriend in the river

what is solution

soluble material has been dissolved in the river by the mildly acidic river water

what is traction?

the moving of large rocks being rolled along the river bed

what is saltation?

small stones bouncing along the bed in a hopping motion

what is suspension?

carrying find river material within the water so it floats in the river and is moved as it flows

what is solution and an example

carrying dissolved soluble rocks e.g. limestone

how are v - shaped valleys formed?

• formed in the upper coarse where the river channel is narrow and fast-flowing

• abrasion cuts into the landscape

• over time the side of the valley are weekend by weathering

• mass movement causes material from the valley sides to fall into the river

• this material is transported downstream

how do interlocking spurs form?>

• the river cuts down into the valley

• if there are areas of hard rock the river will bend around it.

• creating interlocking spurs

how are waterfalls formed?

• when hard rock lays on top of soft rock

• the soft rock erodes faster

• this results in an overhand and undercut

• overtime the overhand collapses and the process repeats

• forming steep sided gorge

how do meanders form?

• a meander is a bend in the river

• mater moves faster on the outer backs due to obstacles

• the high velocity water has more energy to erode the rocks through hydraulic action

• this forms a river cliff

• water moves slowly on the inside of the bend and the river deposits load forming slip off slopes

• a meander will change over time

formation of an oxbow lake

• a meander forms on the river

• the neck joins.

• in times of flood the river takes the shortest path

• the river now uses the new path

• over time deposition occurs cutting of the neck of meander

• creating an oxbow lake

characteristics of flood plain?

• lots of vegetation

• arable farming

• fertile soil

formation of a flood plain

wide flat area casued by meanders shifting along the valley

formation of a levee

• before the flood the water is base leve

• during the flood the water overflows, loosing velocity and dropping heavier sediment

• further along the finnner sediment is deposited.

• after many floods a natural levee is built up

feature sof eastuariers

• large amount of deposition of muddle silt

• salt marshes and mudflats formed

uses of the estuariers

• oil industries,

• steel, cast iron factories

physical factors increase flood risk

• percipitation

• geology

• the shape of the land