Rivers

Question 1

definition

bed

Answer 1

bottom of river channel

Question 2

definition

bank

Answer 2

sides of river

each river has two banks

Question 3

definition

wetted perimeter

Answer 3

length of the bed and the banks in contact with the river.

Question 4

definition

channel

Answer 4

route course that a river flows. The flow of the river is often described as channel flow.

Question 5

definition

thalweg

Answer 5

fastest part of river, always near middle as there is less friction

Question 6

describe the river processes

Answer 6

Erosion: the process of wearing something away. The river erodes in four main ways; attrition, corrosion, corrasion and hydraulic action.

Transportation: The river can transport material when it has excess energy. The river transports in four main ways; traction, saltation, solution and suspension. Material carried by a river is know as load.

Deposition: When a river does not have enough energy, it will start putting down the load.

Question 7

describe the 4 types of river erosion

Answer 7

Corrasion (abrasion): load crashing and rubbing into a rivers’ banks and bed causing pieces to break off.

Corrosion (solution): water dissolving load, bed and banks.

Hydraulic action: Water and air getting into cracks in a rivers banks and bed causing erosion through increased pressure.

Attrition: Load crashing into each other in a river.

Question 8

describe the types of river transportation

Answer 8

Traction: large pieces of load rolling along a river bed.

Saltation: load bouncing a long a river bed.

Suspension: smaller pieces of load being carried in a rivers flow.

Solution: dissolved pieces of material being transported in a solution.

Question 9

what is the Hydrological Cycle (also known as the water cycle)?

Answer 9

continuous movement of water through the land, oceans and atmosphere. The hydrological cycle is known as closed system because water cannot be added or lost.

Question 10

difference between open/closed system

Answer 10

Open System: water can be added or lost. A drainage basin is known as open system because water can be added in the form of precipitation and lost in the form of evaporation and transpiration

Closed System: where water can not be added or lost. The hydrological cycle is known as a closed system because it includes all the water on our planet and no water can be added to it, or lost from it.

Question 11

what is:
Porous
Non-porous

Answer 11

Porous: An object (or ground) that can hold water i.e. it has pores where water can be stored.

Non-porous: An object (or ground) that can not hold water i.e. it does not have any pores

Question 12

equation for river discharge

Answer 12

velocoty x cross section area

= velocity (in cumers - cubic metres per second)

Question 13

what is river discharge?

Answer 13

amount of water flowing in a river at certain point

Question 14

how does a v-shaped valley form?

Answer 14

there is vertical erosion on a narrow channel
erosion caused by rain, wind, frost
gravity causes slope to slip downwards
debris left in channel

Question 15

how do potholes form?

Answer 15

material rubbed/thrown across river bed and banks and it becomes worn away
currents within river may swirl the material around the same spot to form a hole, known as pothole

Question 16

how do waterfalls form?

Answer 16

river flows over a layer of hard rock, then over soft rock

softer rock erodes faster, creating a step called a nick point

vertical erosion is created, making nick point deeper

water & stones will erode backwards underneath (undercutting) the hard rock

plunge pool created by hydraulic action

an overhang of hard rock is created

overhang eventually collapses and waterfall retreats

Question 17

formation of a meander and Ox -bow lake

Answer 17

river is flowing in a gently curving path as it enters the middle course

it flows faster and water is deepest outside the river bend

erosion and deposition cause bends to get bigger & are now called meanders

erosion on the outside creates a river cliff

deposition inside the bend creates a slip-off slope , it is like a small beach

as the meander develops the neck of the meander gets very narrow

eventually the river will break through the neck and the channel will straighten

very little water will flow around the meander loop and deposition will take place, creates ox bow lake

the ox bow lake will eventually dry out and may fill up in wet conditions

the meander process will begin again

Question 18

formation of a delta

Answer 18

all rivers eventually enter the sea
as it reaches the mouth, it will be carrying a lot of load

as it enters the sea the velocity reduces so it starts to deposit the load and it builds up so much the main channel might be blocked

the water forces through and creates distributaries (smaller rivers)

more material is deposited, making the delta bigger, creating moire distributaries

delta becomes more stablished and stronger and bigger
people start to form villages and farm on the fertile land

Question 19

conditions for a delta to occur

Answer 19

shallow sea shelf
no currents, no strong tides or waves
slow flowing river
large load
sheltered coastlines

Question 20

case study

flooding in ledc

Answer 20

ganges delta/river - bangladesh - bay of bengal

likely to flood:
over half of banglsdesh lies below 6m above sea level, water can spread easily

monsoon climate, lots of rain in short period

heavy rain at same time as highest temp. ice on himalayas melts and adds to discharge of the river

global warming

human mismanagment: building on flood plains, deforestation

problems:
transport links swept away
no electricity for several weeks
full hospitals, diseases (cholera, diarrhoea)
no safe drinking water

Question 21

how do waves form?

Answer 21

they are formed by the transfer of energy from the wind over the surface of the sea. It breaks because the top of the wave moves faster and the bottom is slower because of friction and the top eventually falls & wave begins to break

Question 22

4 processes by which waves erode land

Answer 22

Corrasion (abrasion): load crashing and rubbing into a cliff

Corrosion (solution): salts & acid dissolve a cliff.

Hydraulic action: Water and air getting into cracks in a cliff.

Attrition: Load crashing into each other in beach.

Question 23

formation of
headlands, caves, sea arches, stacks, and stumps

(landforms created by erosion)

Answer 23

coastline made up of different bands of hard rock and soft rock

soft rock will erode more quickly, creating bays
hard rock will stick out creating headlands

waves will hit headlands. Hydraulic action will erode more of any weaknesses in the rock, eventually creating a cave

the cave will eventually expand through the headland creating a sea arch

as the arch gets bigger gravity will cause the top to collapse, creating a stack

the stack will be worn away, creating a stump

this process will repeat leaving a series of arches stacks and stumps

Question 24

formation of
cliffs and wave cut platforms

(landforms created by erosion)

Answer 24

a cliff will erode between the low tide mark and the high tide mark, the undercutting will increase, creating a a wave cut notch

the top eventually falls and the cliff retreats

Question 25

formation of a spit

landforms created by deposition

Answer 25

prevailing wind is the direction the wind normally blows, waves hit the coast in that direction

longshore drift moves in the direction of prevailing winds, that also moves sand and stones

as the direction of the coast changes but winds stay the same direction, material will build up to form a beach that stretches out into sea, this is called a spit

the end of the spit often becomes hooked due to storms from the opposite direction

a salt marsh may develop behind the spit where there is less energy

grass may grow making the spit stronger and more permanent

Question 26

what causes rivers to flood or not to flood?

Answer 26

amount of precipitation
soil and underlying rock, (in)permeable
land use of river basin, e.g. vegetation
human activity, e.g. deforestation, concrete, (low infiltration and more run-off
steep/flat slopes
rainfall duration, e.g. fast & heavy (flood), long & light (no flood)
how deep soil is

Question 27

processes in upper/middle/lower course

Answer 27

upper: vertical erosion
middle: vertical + lateral erosion
lower: deposition

Question 28

valley shape in upper/middle/lower course

Answer 28

upper: v shaped
middle: }
lower: wider }

Question 29

velocity in upper/middle/lower course

Answer 29

upper: 2nd fastest (bc lots of friction)
middle: fastest (no friction)
lower: slowest (flat gradient)

Question 30

land forms in upper/middle/lower course

Answer 30

upper: waterfalls, rapids(small waterfalls), potholes, v shaped valleys, gorges
middle: erosion/deposition, meander, ox bow lakes, flood plain
lower: levees, flood plains, deltas, salt marshes

Question 31

what is

long profile

Answer 31

river from its source to mouth

Question 32

case study

river flood management

Answer 32

Danube, Ulm, Germany

cycle path on raised ground - levee

Friedrichschau - recreation, low value, not protected, used as place for flooding (spreading ground - flood without financial lost)

concrete flood protection wall (not everywhere bc it’s ugly & expensive

man-made piles of stones protects river bank from erosion (cheaper & prettier than a wall, & dissipation of energy)

dredging - making river deeper (reducing friction makes it faster)

cheap stone cages that prevent flood (gabian walls)

river is straightened (no meander) - protects buildings, gets water out quickly

thalfingen dam - controls water levels, electricity

Question 33

what is coral reef and coral?

Answer 33

coral reef: line of coral polyp in warm shallow seas

coral: tiny carnivore animals

Question 34

where is coral reef found?

Answer 34

within tropics
high sea temperature
shallow water
clear water (so sunlight reaches them)

Question 35

3 types of reefs

Answer 35

fringing reef: close to coast & only separated by small stretch of water

barrier reef: larger reefs, parallel to coast, and separated by shallow seas

atolls: near surface of sea when islands surrounded by reef subside

Question 36

why are coral reef so important?

Answer 36

support 25% of marine species
protect coastline from erosion
natural recycling agent from CO2
contribute as material to formation of beaches
raw material (jewellery, ornaments)
compounds useful in medicine

Question 37

how are coral threatened?

Answer 37

increase in tourism
people diving
motor boats
overfishing upsets food chain of choral
pollution disposed in sea, pesticides
global warming affects water temp and depth
hurricanes, storms

Question 38

how can we protect coral?

Answer 38

banning damaging fishing practices
conservation zones where tourism isn't allowed
no farming of coral
banning dropping of anchors near
reduce use of fertilisers near
educating people

Question 39

how do sand dunes & salt marshes form?

Answer 39

strong winds, large expanses id dry sand, and small grains cause saltation & sand moves up the beach

something stops sand from moving (seaweed, vegetation, or rubbish) and traps it

embryo dunes are the first, they are made stable by marram and lyme grass

they grow into yellow dunes (due to lack of humus) then into foredunes (great amount of humus)

sand dunes are destroyed by humans as they walk/build on them

dune slacks: depressions between dune ridges, damp in summer, & water-filled in winter

blow outs: holes, often evidence of over use by humans

Question 40

what are some cost management methods?

Answer 40

sea walls - ugly, expensive, strong

revetments - don’t last long, ugly, but wave will go through but lose energy & traps sand

breakwaters
gryones
gabions
rip rap