geography - rivers and coasts

groundwater flow

movement of water through rocks

overland flow

water flows in rivers and streams

throughflow

movement of water through soil

tributary

a small stream or river that joins a larger river

drainage basin

an area of land drained by a river and its tributaries

watershed

edge of river basin

substrate in friction

a larger,angular substrate causes more friction than a small, smooth substrate

relationship between high hydraulic radius and water in contact

the higher the hydraulic radius, the lower the amount of water in contact with the bed + banks which means less friction

river discharge

the volume of water flowing through a river channel

why does deposition happen?

when a river slows and velocity reduces the river doesn’t have the energy to carry particles and drops them.

centrifugal forces

push water to the outside of the bend

thalweg

fastest current

slip off slope

lots of material being deposited ( inside of bend )

lag time

the time between peak rainfall and peak discharge

rising limb

the increase in discharge once surface runoff and throughflow has reached the river

peak discharge

occurs when the river reaches it’s highest level

falling limb

discharge decreases and river levels fall

baseflow

the normal level of the river fed by groundwater

drainage density

how quickly the water takes to drain

how many inches of rainfall in boscastle

8 inches ( 440 million gallons)

how many people were rescued in boscastle

100

why did the flash flood in boscastle take place

lots of impermeable rock, more surface runoff

what causes a flash flood

saturated ground from previous rainfall, steep valley sides, lack of vegetation

Definition of a sand dune

A hill of loose sand formed by wind (aeolian) , these can be stabilised by vegetation, they form on the dry back shore of sandy beaches

What is a yellow dune?

Marram grass ( stabilises sand dune)

What is a grey dune?

Sea buckthorn, drewberry

What is a mature dune?

Oak, maple and ash (250 years old), Hawthorne

What are force dunes?

Sand couch grass, lime grass

What is an embryo dune ?

Prickly saltwart ( waxy leaves deep root)

Definition of spit

Depositional landform which connects to land and extends into the sea

Definition of attrition

When rocks knock against each other. They break and become more rounded

Definition of hydraulic action

The sheer power of the waves as they smash against the cliff

Definition of solution

Sea water dissolves cliffs eg . Limestone

Definition of abrasion

Pebbles grind along a rock , like sandpaper. Overtime, the rocks become smooth

What is a discordant coastline

Different types of geology. This can lead to the formation of headlands and bays

What is a concordant coastline

Same types of geology