Rivers and river management Flashcards

Question

How do dams and reservoirs effect the hydrological cycle?

Answer 1

Increased surface storage Increased evaporation The water in the river in front of the reservoir is decreased.

Answer 2

Impermeable surfaces such as concrete and tarmac Water cannot infiltrate which re-educated the amount of groundwater stored. Water flows over the surface as surface runoff, which can lead to flooding.

Answer 3

Prevents interception Means water hits the ground with more force, possibly leading to erosion. Water is less likely to infiltrate so there will be more surface run-off, this might lead to flooding.

Answer 4

A graph to show how a river reacts to a rainfall event.

Answer 5

The average or normal flow of the river.

Answer 6

The volume of water flowing through a given point on a river at a given time.

Answer 7

River velocity x cross sectional area | Cross sectional area is the width of the river x the average depth

Answer 8

How river discharge changes throughout the year/seasons.

Answer 9

Found in the upper course of a river. Started by vertical erosion of the river downwards. The sides of the river valley then break down due to weathering. Over time, the weathered rock falls into the river, causing the Valle sides to become v-shaped.

Answer 10

Formed in the upper course of the river. The river erodes the less resistant rock first (which is under the more resistant rock). This creates an overhang. As the river flows over the water fall and into the plunge pool, erosion occurs which makes the plunge pool larger. Eventually, the overhang above the plunge pool collapses and a result of undercutting. This way the waterfall retardants upstream creating a gorge.

Answer 11

Middle course of the river. The current swings to the outside of then bend and concentrates the erosion there. Deposition occurs on the inside of the bed where there is not enough energy to carry load. (It is LATERAL erosion).

Answer 12

Formed in a river on the inside bend. This is because the water has little energy so deposits any material her.

Answer 13

Formed on the outside bend in a river. The bank is undercut by LATERAL erosion because the water has lots of energy and the water flow is fastest here.

Answer 14

``` Estuary Flood plains Meanders Oxbow lakes Mud flats Salt marshes ```

Answer 15

``` Rock and soil type Land use Rainfall Relief - if the river valley is steep sided, when it rains the water will flow very quickly into the river leading to floods. Weather conditions. ```

Answer 16

Depressions that passed over the UK were very slow leading to huge amounts of rainfall. This meant the ground was very saturated and couldn’t hold anymore water resulting in large scale floods. The ocean temperature had been rising slowly causing an increase in evaporation and therefore rainfall. Also the confluence of the River Severn and Avon meet at Tewkesbury which leave it vulnerable to flooding. Most of the land around Tewkesbury is flat, low lying floodplain.

Answer 17

Urban creep - more and more houses built on flood plains in the last 60 years. People were also paving over their front gardens. This meant that more land is impermeable. Rain water flows straight into the rivers rather than soaking into the soil and this causes flooding. Field drains in the upland parts of the drainage basin. These drain farmland so that the soil is not too wet for crops, however they allow water to reach the river channel very rapidly.

Answer 18

Over 60mm of rainfall fell in two hours The ground was already saturated The drainage basin has many steep slopes, and has areas of impermeable slate causes rapid surface run off. Boscastle is at the confluence of three rivers. A large quantity of water all attained within a short space of time causing the rivers to overflow. The flooding coincided with a high tide, Laing the impact worse.

Answer 19

Monsoon climate brings heavy rain and snow. Souls are leaches and heavy runoff results in soil erosion. Spring snow melt Deforestation means less evapotranspiration. Landslides also occur. Rivers silt-up due to increased soil erosion. This raises the river bed and reduces the capacity of the channel resulting in increased likelihood of flooding. 80 percent of Bangladesh lies on a huge floodplain and delta, most of which is only 1m above sea level.

Answer 20

``` Short term 800 properties flooded Damage to possessions Property contaminated with dirty sediment Loss from business not operating. ``` ``` Long term Severn Trent water company had to spend £25 million on getting people fresh water and repairing the Mythe Water plant. Business out of operation for 8 months. £11 million of farm sets crops lost Damage to shop products Rise ins insurance premiums People not able to sell their houses Fall in house prices ```

Answer 21

Short term Schools temporarily closed Psychological impact of having your house flooded. 150000 homes with no water as Mythe Water treatment flooded. Long term Children taught in temporary classrooms while school buildings repaired. People homeless or in temporary accommodation for up to a year.

Answer 22

Damage to crops | Layers of contaminated silt on properties.

Answer 23

Recharging water sources Agriculture (farming) Fishery

Answer 24

River flood plains evoke inundated with flood water, the water will infiltrate the soil and recharge ground water. The groundwater stores are an important source of drinking water and it can also be essential for agriculture.

Answer 25

The water transports nutrients and sediments onto the surrounding flood plains where it is then deposited as a layer of alluvium. As this is rich in nutrients, it helps to enrich the surrounding soil. Rice paddies are flooded deliberately to take advantage of this natural fertilisation process.

Answer 26

A river basin is an ecological unit of interconnecting upstream spawning habitats with downstream rearing habitats for a variety of species and other aquatic systems. Seasonal habitats on the flood plain, created by variable flow regimes, are essential for various stages of the life cycle of species. Floods provide an ecological trigger for both the spawning and migration of certain species.

Answer 27

Generally defined as a controlled disruption of natural processes using man made structures.

Answer 28

Use of ecological practices to reduce erosion and achieve stabilisation while enhancing habitats and saving money.

Answer 29

Dams Flood shelters Embankments or levees River straightening

Answer 30

Walls built across river valleys to control the amount of water in the river. The prevent flooding and produce electricity. However, they are expensive and the reservoir floods large amounts of land.

Answer 31

Concrete shelters built to house people safely during times of flood.

Answer 32

Walls put either side of the river to keep it in its channel. If they fail they can make flooding worse. Also make flooding worse further downstream.

Answer 33

Meanders are straightened so that the river moves through towns more quickly and doesn’t flood. They do however sometimes make flooding worse downstream.

Answer 34

``` Do nothing Flood warning system Managed flooding Floodplain zoning Afforestation ```

Answer 35

Restricting certain activities to certain areas. Building houses would not be allowed on land that is frequently flooded.

Answer 36

Use of satellite imagery to detect storms and warn people of flooding so they can evacuate.

Answer 37

Allowing certain areas to flood where it doesn’t matter, to take pressure off the river.

Answer 38

Planting trees means there is more interception and rainfall takes longer to reach the river, so stops flooding.

Answer 39

Householders should be encouraged not to pave over their gardens. Make homes flood proof eg putting sockets higher up the walls and using yacht varnish to make wooden floors water proof. Restoring old peat bogs in the upper part of the river. Bigs act like sponges and soak up water meaning less water reaches the river.

Answer 40

The area in which the river begins.

Answer 41

Where a river ends its journey, flowing into the sea or a lake.

Answer 42

A smaller river that joins a larger river.

Answer 43

The point at which two rivers join.

Answer 44

The boundary between two drainage basins marked by a ridge of high land.

Answer 45

The area which is drained by a river and its tributaries.

Answer 46

The total length of all streams in the basin divided by the total area of the basin.

Answer 47

Buildings, towns and cities Dams and reservoirs Farming Deforestation

Answer 48

more interception more surface run off less infiltration less groundwater flow

Answer 49

Less surface run off more evaporation. lower channel flow infront of the dam more surface storage.

Answer 50

more transpiration more vegetation storage permeable - ploughed soil - more infiltration water can be removed from rivers to water crops.

Answer 51

``` less transpiration less interception more surface run off - no trees to slow down the rain less infiltration. less groundwater flow. ```

Answer 52

the volume of water flowing through a given point on a river at a given time.

Answer 53

discharge = river velocity x cross sectional area final answer is measured in cumecs

Answer 54

final answer is measured in cumecs. Cumecs are cubic meters per second.

Answer 55

``` gentle slopes light rain permeable rocks vegetation large drainage basin dry soil ```

Answer 56

``` steep slope - water will flow into the river easily heavy rain impermeable rocks ground surface frozen impermeable surfaces man made surfaces deforestation small drainage basin. ```

Answer 57

Attrition Hydraulic action Corrosion Corrasion

Answer 58

When rocks and material carried by the river grind into each other and wear down.

Answer 59

When the sheer force of the water wears away the river bank and bed.

Answer 60

When rocks in the river are dissolved by acid. (also solution)

Answer 61

When small particles of rock carried by the river rubs against the banks of the river. (also abrasion).

Answer 62

Traction Saltation Suspension Solution

Answer 63

Large rocks and boulders are rolled along the bed of the river.

Answer 64

Smaller stones are bounced along the bed of the river in a leap-frogging motion.

Answer 65

Fine material, light enough in weight to be carried by the river. This material causes the water to be discoloured.

Answer 66

Dissolved material transported in the river.

Answer 67

A river regime shows how river discharge changes through the year-seasons.

Answer 68

The breaking up of rock material (can be due to wind, rain, chemicals, freeze-thraw, biological etc).

Answer 69

When gravity pulls loose material down a slope (can happen quickly as a rock falls or slowly by slumping or soil creep).

Answer 70

As the river flows through the valley it is forced to swing from side to side around more resistant areas of rock (spurs). as there is little energy for lateral erosion, the river continues to cut down vertically flowing between spurs of higher land creating interlocking spurs.

Answer 71

Waterfalls form when a band of hard rock lies over a band of softer, less resistant rock is eroded more quickly than the harder, overlying rock, through abrasion and hydraulic action. This causes an overhang to form, which eventually collapses from the weight above it, creating a steep drop. A deep plunge pool will form at the bottom of the waterfall, and the water will continue to erode the soft rock through hydraulic power and abrasion creating another overhand. Over time the waterfall will recede due to repeated formation and collapse of overhangs, creating a steep-sided gorge.

Answer 72

A meander is a bend in the river. As the water flows around the bend the flow is fastest on the outside, where the river is deeper. Here, the processes of abrasion and hydraulic action erode the outside bank and undercut it to form a river cliff. On the inside of the river bend the flow is slow and the river is shallow. This causes deposition to take place and a slip-off slope is formed. As the water travels around the meander it moves in a circular motion like a corkscrew. This is called helicoidal flow. It helps erode and undercut the outside end and move the sediment to the inside bend where it is then deposited.

Answer 73

Ox-bow lakes form in the middle course of a river because the river meanders more vigorously. Continued erosion (eg abrasion) on the outside bend causes the neck of the meander to narrow. Eventually, the neck is broken through to form a straight channel. This often happens during floods when the river is very powerful. Continued deposition causes the old meander to be sealed off. Gradually the ox-bow lake will dry out.

Answer 74

unpredictable little time between rain fall and the flood drains couldn't cope fast flowing sudden rain fell 8 bours before the flood small, steep river infrequent

Answer 75

snowmelt in the Himalayas. cyclones 25% of Bangladesh is less than 1m above sea level. bad drainage systems slow flow monsoon- happens over a long period of time frequent

Answer 76

generally defined as a controlled disruption of natural processes using non man made structures

Answer 77

use of ecological practices to reduce erosion and achieve stabilisation while enhancing habitats and saving money.

Answer 78

Can be opened and closed to access roads. They stop any water from flooding into people homes. cheaper to run, easy access to rivers and roads, only a few people needed to shut them May be difficult to close the gates on time.

Answer 79

Act as a barrier to stop any excess water from flooding into peoples homes. However, it may remove areas of the floodplain.

Answer 80

Provides an area of land that the river can flood onto. Cheap. Can't use the land for anything else.

Answer 81

permeable ground provides a place for water to go. | Reduces surface run off.

Answer 82

Holds any extra water cost efficient safety hazard for young children.

Answer 83

tracking the river enables you to predict flooding. Severity.

Answer 84

Lighter furniture. Moving electrical appliances further up the wall. Home flood gates. Tiled floors. Cheaper to repair if the house does flood. Personal expense eg light furniture may be expensive.

Answer 85

Provide information and predictions of river flooding. Rainfall. Accurate predictions allows preparation time. someone has to man the office 24/7,

Answer 86

Flood alert - flood is possible. Flood warning - flooding is expected. Severe flood warning - danger to life.

Answer 87

Hard engineering High banks built on the river banks. The high bank stops water spreading into areas where it could cause problems. They can be made from earth which makes them look natural. Flood water may go over the top. They can also break and burst under pressure causing more problems as the gushing water is focussed.

Answer 88

Soft engineering. Areas which are allowed to naturally flood, these are on the flood plain. Water is allowed to naturally flood the flood plain meaning that it is inexpensive and the natural environment is left unspoilt. If the floodplain is allowed to be flooded, then it cant be used for anything else.

Answer 89

Hard engineering. A large artificial structure designed to hold back water creating a reservoir behind it. Water is held back before being released slowly to avoid large discharge and flooding. the are often multi-purpose and can provide electric and recreational facilities. Silt can build up behind the dam reducing capacity. a large area of land is flooded behind the dam which can destroy habitats and homes.

Answer 90

Hard engineering. Dredging the river (making it deeper) and/or straightening it. The deeper channel allows more water to run through it, straightening the channel allows water to pass through quicker. Th river has to be dredged every year, which is expensive. Water that passes through one area quickly can cause areas further downstream to flood.

Answer 91

Hard engineering. Extra channels built next to river to carry water. The relief channels take the extra water from the river when needed thus meaning the river is less likely o flood. Cutting a whole new relief channel can look ugly; they can also be very expensive to build.

Answer 92

Soft engineering River is watched, of the river rises settlements downstream are warned. people downstream can be warned and prepare to evacuate on the first sign of danger. it is not always possible to warn people, making it hard to save possessions.

Answer 93

Soft engineering. Areas of land are allocated different role depending on their flood risk. Major building zones are assigned low risk zones, other land use zones such as sports fields are assigned higher risk zones as when flooded they are less costly. The areas assigned for each zone may not be best for the public in terms of public use and accessibility.

Rivers and river management Flashcards

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