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POLITECNICO DI MILANO

SCHOOL OF CIVIL, ENVIRONMENTAL AND LAND MANAGEMENT ENGINEERING

MASTER IN CIVIL ENGINEERING FOR RISK MITIGATION

A.Y. 2013-2015

DAMS FAILURE IN EUROPE

MSc. Graduate : TIANJI LI

Student ID : 10445449/816414

Supervisor : Prof. BOLZON GABRIELLA

OCTOBER, 2015

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ABSTRACT

In the European continent, as everywhere in the world, dam building has been very common for

centuries and millenniums. It used to be small dams built with basic means. With industrial

revolution, development of fluvial transport and agricultural improvements, needs became more

and more important.

In this document, I have collected the available information about European dams and their main

failures, depending on their typology, and I have introduced the present data-based models for the

prediction of dam behaviour.

Keywords: Dam; Europe; Typology; Failure

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SOMMARIO

Sul continente europeo, come ovunque nel mondo, la costruzione di dighe è stata un’attivit{ molto

comune per secoli. Inizialmente, si trattava di piccoli sbarramenti costruiti con mezzi elementari.

Con la rivoluzione industriale, lo sviluppo del trasporto fluviale e i miglioramenti agricoli, i bisogni

divennero sempre più importanti.

Questo documento raccoglie le informazioni disponibili sulle dighe principali presenti in Europa, e

sul loro eventuale collasso in relazione alla loro tipologia. Infine si introducono i modelli correnti di

previsione del comportamento delle dighe fondati su data-base.

Parole chiave: Dighe; Europa; Tipologia; Collasso

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Acknowledgements

Firstly, I would like to express my sincere gratitude to my supervisor Prof. Bolzon Gabriella for the

continuous support of my tesina study, for her patience, motivation, and immense knowledge. Her

guidance helped me in all the time of my work and writing of this tesina. I could not have imagined

having a better advisor and mentor for my tesina study. Without her precious support it would not

be possible to conduct this work well organised and timely.

I thank my friends for the believing in me and supporting me throughout the tesina work. I am glad

to have encouraging friends.

Last but not the least; I would like to thank my family: my parents for supporting me spiritually

throughout writing this tesina and my life in general.

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Table of Contents

INTRODUCTION ................................................................................................................................................................ 8

History of the dams in Europe: .................................................................................................................................. 8

Roman engineering ................................................................................................................................................ 8

Middle Ages ............................................................................................................................................................... 9

Industrial era .............................................................................................................................................................. 9

Large dams ............................................................................................................................................................... 10

CHAPTER: 1 – Functions of Dams ................................................................................................................................. 12

1.1 Irrigation ................................................................................................................................................................ 13

1.2 Hydropower ........................................................................................................................................................... 14

1.3 Water supply for domestic and industrial use ....................................................................................................... 15

1.4 Inland navigation ................................................................................................................................................... 15

1.5 Flood control .......................................................................................................................................................... 16

1.6 List of Functions with its purposes ......................................................................................................................... 17

CHAPTER: 2 – Type of Dams in Europe ........................................................................................................................ 18

2.1 List of Dams in Europe ........................................................................................................................................... 18

2.2 Height of Dams in Europe ...................................................................................................................................... 19

2.3 Type of Dams in Europe ......................................................................................................................................... 20

2.4 Different types and number of Dams in Europe ..................................................................................................... 22

CHAPTER: 3 – Major Dam Failures & Reasons (Europe) ............................................................................................ 23

3.1 List of Major Dam failures in Europe ..................................................................................................................... 23

3.2 Reasons of Dam failures in Europe ........................................................................................................................ 23

3.3 TYPES OF DAMS FAILED IN EUROPE: ...................................................................................................................... 28

3.4 REASONS OF DAMS FAILURE IN EUROPE: .............................................................................................................. 29

3.5 Final Results comparison of type of dams with the reasons of Failure in Europe:................................................. 30

CHAPTER: 4 – Data-Based Models for the Prediction of Dam Behavior .................................................................. 31

4.1 Introduction ........................................................................................................................................................... 31

4.2 Statistical and Machine Learning Techniques Used In Dam Monitoring Analysis ................................................. 31

4.3 Hydrostatic-Seasonal-Time (HST) Model ............................................................................................................... 32

4.4 Models to Account for Delayed Effects .............................................................................................................. 33

4.5 Other ML Techniques ......................................................................................................................................... 34

4.6 Methodological Considerations for Building Behaviour Models ............................................................................ 35

4.6.1 Missing Values ................................................................................................................................................ 35

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4.6.2 Practical Application ....................................................................................................................................... 36

CONCLUSION .................................................................................................................................................................. 38

BIBLIOGRAPHY ................................................................................................................................................................ 39

PHOTOS REFERENCES: ................................................................................................................................................... 41

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FIGURES & TABLES

S.No Description Page No

Fig-1 Grande- Dixence Dam in Switzerland 9

Fig-2 Chile’s South Atacama Dam 9

Fig-3 The Roman at cornalvo in Spain 10

Fig-4 Masonry arch wall, Parramatta, new south wales 11

Fig-5 The kolnbrein dam in the hohle tauern range within Carinthia, autria

12

Fig-6 Aldeadavila dam in spain 14

Fig-7 Irrigation plan 14

Fig-8 Lipno dam in Czech republic 14

Fig-9 Hydroelectric dam 15

Fig-10 Industry facilities 16

Fig-11 Large shipment of goods moves the locks and dams 17

Fig-12 Flood can cause major damage to human lives, property and livestock’s

17

Fig-13 Gravity dams: lyln stwlan dam in wales 21

Fig-14 El Atazar dam in spain 22

Fig-15 Embankment dam 22

Fig-16 Number of incidents Vs age of all dams (curve) 25

Fig-17 Incident rates of dams (curve) 25

Fig-18 Gleno Dam in Italy 26

Fig-19 Malpasset Dam in France 27

Fig-20 Vajont Dam in Italy 28

Fig-21 Type of dam failure 30

Fig-22 Reasons of dam Failures 30

Table-1 List of functions of dams 18

Table-2 Number of dams in Europe 19

Table-3 Height of dams in Europe 20

Table-4 Type of dams in Europe 21

Table-5 Type and number of dams in Europe 23

Table-6 Major dam failure in Europe 24

Table-7 Number of dam failure in Europe 24

Table-8 Comparison of results 31

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INTRODUCTION ---------------------------------------------------------------------------------------------------------------------------------- A dam is a barrier that impounds water or underground streams. The reservoirs created by dams not

only suppress floods but provide water for various needs to include irrigation, human consumption,

industrial use, aquaculture and navigability. Hydropower is often used in conjunction with dams to

generate electricity. A dam can also be used to collect water or for storage of water which can be

evenly distributed between locations. Dams generally serve the primary purpose of retaining water,

while other structures such as floodgates or levees (also known as dikes) are used to manage or

prevent water flow into specific land regions. [1]

Fig-1: Grande Dixence Dam in Switzerland Fig-2: Chile’s South Atacama Dam

History of the dams in Europe:

In the European continent, as everywhere in the world, dam building has been very common for

centuries and millenniums. It used to be small dams built with basic means. [2]

Roman engineering

Roman dam construction was characterized by "the Romans' ability to plan and organize engineering

construction on a grand scale". Roman planners introduced the then novel concept of large reservoir

dams which could secure a permanent water supply for urban settlements over the dry season. Their

pioneering use of water-proof hydraulic mortar and particularly Roman concrete allowed for much

larger dam structures than previously built, such as the Lake Homs Dam, possibly the largest water

barrier to that date, and the Harbaqa Dam, both in Roman Syria. The highest Roman dam was

the Subiaco Dam near Rome; its record height of 50 m (160 ft) remained unsurpassed until its

accidental destruction in 1305.

Roman engineers made routine use of ancient standard designs like embankment dams and masonry

gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the

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other basic dam designs which had been unknown until then. These include arch-gravity dams, arch

dams, buttress dams and multiple arch buttress dams, all of which were known and employed by the

2nd century AD (see List of Roman dams). Roman workforces also were the first to build dam bridges,

such as the Bridge of Valerian in Iran.

Middle Ages

In the Netherlands, a low-lying country, dams

were often applied to block rivers in order to

regulate the water level and to prevent the sea

from entering the marsh lands. Such dams often

marked the beginning of a town or city because it

was easy to cross the river at such a place, and

often gave rise to the respective place's names in

Dutch.

F

Fig: 3 - The Roman dam at Cornalvo in Spain

For instance the Dutch capital Amsterdam (old name Amstelredam) started with a dam through the

river Amstel in the late 12th century, and Rotterdam started with a dam through the river Rotte, a

minor tributary of the Nieuwe Maas. The central square of Amsterdam, covering the original place of

800 year old dam, still carries the name Dam Square or simply the Dam.

Industrial era

The Romans were the first to build arch dams, where the reaction forces from the abutment stabilizes

the structure from the externalhydrostatic pressure, but it was only in the 19th century that the

engineering skills and construction materials available were capable of building the first large scale

arch dams.

Three pioneering arch dams were built around the British Empire in the early 19th century. Henry

Russel of the Royal Engineers oversaw the construction of the Mir Alam dam in 1804 to supply water

to the city ofHyderabad (it is still in use today). It had a height of 12 metres and consisted of 21 arches

of variable span. [3]

The first such dam was opened two years earlier in France. It was also the first French arch dam of

the industrial era, and it was built by François Zola in the municipality of Aix-en-Provence to improve

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the supply of water after the 1832 cholera outbreak devastated the area. After royal approval was

granted in 1844, the dam was constructed over the following decade. Its construction was carried out

on the basis of the mathematical results of scientific stress analysis.

Many medium size dams in Europe that have been built from the beginning of the century to the end of

World War II are now reaching the end of their lifetime. Most of these dams are located in

mountainous areas and especially in the Alps (Switzerland, Italy, France, Austria) and in Norway. They

are 3 to 25 meters high or more and were built for electricity or, less often, for water - supply.

After WWII, dam projects were more and

more important and were located both in

mountainous areas and on lower parts of

rivers (and even sometimes on

estuaries). In most European countries

(with the exception of some Eastern

countries, and the ex-Soviet Union)

almost every dam is under a concession

which lasts from 40 to 60 years. This

period is usually smaller than the

physical lifetime of the building.

Fig: 4 - Masonry arch wall, Parramatta, New South Wales

The construction of reservoirs in Europe can be illustrated using the UK and Spain as examples. In the

UK, the number of large dams grew rapidly during the 19th century from fewer than 10 to 175 at a rate

of 1.7 per year. By 1950, the rate had almost doubled. After 1950, construction took place at a rate of

5.4 dams per year before slumping to zero by the late 1990’s. Today, the UK has a total of 486 dams.

By contrast, Spain saw the number of reservoirs grow at the rate of more than 4 per year between

1900 and 1950, before almost doubling and reaching 741 units by 1975. By 1990, this figure had more

than doubled again (19.5 per year). Today, there are 1172 large dams. [4]

The total number of dams in Europe is now growing very slowly, as suitable sites becomer fewer and

environmental concerns become greater.

Large dams

The total European reservoir surface area covers more than 100 000 km2; 50% of which lies in the

European part of Russia. Although there are only a few reservoirs in this area, they are very large. The

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six largest reservoirs are located in the Volga river system in Russia. The Kuybyshevskoye (6450

km2) and Rybinskoye (4450 km2) are the two largest reservoirs. Of the 13 European reservoirs with

an area exceeding 1000 km2, only the Dutch reservoir Ijsselmeer lies outside Russia and the Ukraine.

The member state with the largest number of reservoirs is Spain (approx. 1200), Turkey (approx.

610), Norway (approx. 364) and the UK (approx. 570). Other countries with a large number of

reservoirs are Italy (approx. 570), France (approx. 550) and Sweden (approx. 190).

Fig-5: The Kölnbrein Dam in the Hohe Tauern range within Carinthia, Austria

Now, let’s understand some functions and importance of the dams in the next chapter. As we

understand the functions and types of dams, we can investigate the main reasons and factors behind

the collapse of any dam in further chapters.

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CHAPTER: 1 – Functions of Dams

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In ancient times, dams were built for the single purpose of water supply or irrigation. As civilizations

developed, there was a greater need for water supply, irrigation, flood control, navigation, water

quality, sediment control and energy. Therefore, dams are constructed for a specific purpose such as

water supply, flood control, irrigation, navigation, sedimentation control, and hydropower. A dam is

the cornerstone in the development and management of water resources development of a river basin.

The multipurpose dam is a very important project for developing countries, because the population

receives domestic and economic benefits from a single investment. [5]

Demand for water is steadily increasing throughout the world. There is no life on earth without water,

our most important resource apart from air and land. During the past three centuries, the amount of

water withdrawn from freshwater resources has increased by a factor of 35, world population by a

factor of 8. With the present world population of 5.6 billion still growing at a rate of about 90 million

per year, and with their legitimate expectations of higher standards of living, global water demand is

expected to rise by a further 2-3 percent annually in the decades ahead.

But freshwater resources are limited and unevenly distributed. In the high-consumption countries

with rich resources and a highly developed technical infrastructure, the many ways of conserving,

recycling and re-using water may more or less suffice to curb further growth in supply. In many other

regions, however, water availability is critical to any further development above the present

unsatisfactorily low level, and even to the mere survival of existing communities or to meet the

continuously growing demand originating from the rapid increase of their population. In these regions

man cannot forego the contribution to be made by dams and reservoirs to the harnessing of water

resources.

Seasonal variations and climatic irregularities in flow impede the efficient use of river runoff, with

flooding and drought causing problems of catastrophic proportions. For almost 5 000 years dams have

served to ensure an adequate supply of water by storing water in times of surplus and releasing it in

times of scarcity, thus also preventing or mitigating floods

With their present aggregate storage capacity of about 6 000 km3, dams clearly make a significant

contribution to the efficient management of finite water resources that are unevenly distributed and

subject to large seasonal fluctuations.

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Most of the dams are single-purpose dams, but

there is now a growing number of multipurpose

dams. Using the most recent publication of the

World Register of Dams, irrigation is by far the

most common purpose of dams. Among the

single purpose dams, 48 % are for irrigation,

17% for hydropower (production of

electricity), 13% for water supply, 10% for

flood control, 5% for recreation and less than

1% for navigation and fish farming.

Fig-6: Aldeadávila Dam in Spain

1.1 Irrigation

Presently, irrigated land covers about 277 million hectares i.e. about 18% of world’s arable land but is

responsible for around 40% of crop output and employs nearly 30% of population spread over rural

areas. With the large population growth expected for the next decades, irrigation must be expanded to

increase the food capacity production. It is estimated that 80% of additional food production by the

year 2025 will need to come from irrigated land. Even with the widespread measures to conserve

water by improvements in irrigation technology, the construction of more reservoir projects will be

required. [6]

Fig: 7 – Irrigation Plan Fig-8: Lipno Dam in Czech Republic

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1.2 Hydropower

Hydroelectric power plants generally range in size from several hundred kilowatts to several hundred

megawatts, but a few enormous plants have capacities near 10,000 megawatts in order to supply

electricity to millions of people. World hydroelectric power plants have a combined capacity of

675,000 megawatts that produces over 2.3 trillion kilowatt-hours of electricity each year; supplying 24

percent of the world’s electricity. [7]

In many countries, hydroelectric power provides nearly all of the electrical power. In 1998, the

hydroelectric plants of Norway and the Democratic Republic of the Congo (formerly Zaire) provided

99 percent of each country’s power; and hydroelectric plants in Brazil provided 91 percent of total

used electricity.

Electricity generated from dams is by very far the largest renewable energy source in the world. More

than 90% of the world’s renewable electricity comes from dams. Hydropower also offers unique

possibilities to manage the power network by its ability to quickly respond to peak demands.

Pumping-storage plants, using power produced during the night, while the demand is low, is used to

pump water up to the higher reservoir. That water is then used during the peak demand period to

produce electricity. This system today constitutes the only economic mass storage available for

electricity.

Fig-9: Hydroelectric Dam

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1.3 Water supply for domestic and industrial use

It has been stressed how essential water is for our civilization. It is important to remember that of the

total rainfall falling on the earth, most falls on the sea and a large portion of that which falls on earth

ends up as runoff. Only 2% of the total is infiltrated to replenish the groundwater. Properly planned,

designed and constructed and maintained dams to store water contribute significantly toward

fulfilling our water supply requirements. To accommodate the variations in the hydrologic cycle, dams

and reservoirs are needed to store water and then provide more consistent supplies during shortages.

Fig-10: Industry facilities like this power plant need million of litters per day. A city like Paris in France needs some 700 millions lpd, water would not be provided without dam

1.4 Inland navigation

Natural river conditions, such as changes in the flow rate and river level, ice and changing river

channels due to erosion and sedimentation, create major problems and obstacles for inland navigation.

The advantages of inland navigation, however, when compared with highway and rail are the large

load carrying capacity of each barge, the ability to handle cargo with large-dimensions and fuel

savings. Enhanced inland navigation is a result of comprehensive basin planning and development

utilizing dams, locks and reservoirs which are regulated to provide a vital role in realizing regional and

national economic benefits. In addition to the economic benefits, a river that has been developed with

dams and reservoirs for navigation may also provide additional benefits of flood control, reduced

erosion, stabilized groundwater levels throughout the system and recreation. [8]

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Fig: 11 - Large shipment of goods moves the locks and dams on inland waterways, such as this tow, on the lower part of the picture.

1.5 Flood control

Dams and reservoirs can be effectively used to regulate river levels and flooding downstream of the

dam by temporarily storing the flood volume and releasing it later. The most effective method of flood

control is accomplished by an integrated water management plan for regulating the storage and

discharges of each of the main dams located in a river basin. Each dam is operated by a specific water

control plan for routing floods through the basin without damage. This means lowering of the

reservoir level to create more storage before the rainy season. This strategy eliminates flooding. The

number of dams and their water control management plans are established by comprehensive

planning for economic development and with public involvement. Flood control is a significant

purpose for many of the existing dams and continues as a main purpose for some of the major dams of

the world currently under construction. [9]

Fig: 12 - Floods can cause major damage to humans lives, property, and livestock’s.

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1.6 List of Functions with its purposes

Functions Purposes/Examples

Power generation Hydroelectric power is a major source of electricity in the world. Many countries that have rivers with adequate water flow, that can be dammed for power generation purposes.

Water supply

Many urban areas of the world are supplied with water abstracted from rivers pent up behind low dams or weirs. Examples include London – with water from the River Thames and Chester with water taken from the River Dee. Other major sources include deep upland reservoirs contained by high dams across deep valleys such as the Claerwen series of dams and reservoirs.

Stabilize water flow / irrigation

Dams are often used to control and stabilize water flow, often for agricultural purposes and irrigation. Others such as the Berg Strait dam can help to stabilize or restore the water levels of inland lakes and seas, in this case the Aral Sea.

Flood prevention Dams such as the Blackwater Dam of Webster, New Hampshire and the Delta Works are created with flood control in mind.

Land reclamation Dams (often called dykes or levees in this context) are used to prevent ingress of water to an area that would otherwise be submerged, allowing its reclamation for human use.

Water diversion

A typically small dam used to divert water for irrigation, power generation, or other uses, with usually no other function. Occasionally, they are used to divert water to another drainage or reservoir to increase flow there and improve water use in that particular area. See: diversion dam.

Navigation

Dams create deep reservoirs and can also vary the flow of water downstream. This can in return affect upstream and downstream navigation by altering the river's depth. Deeper water increases or creates freedom of movement for water vessels. Large dams can serve this purpose but most often weirs and locks are used

Recreation and aquatic beauty

Dams built for any of the above purposes may find themselves displaced by time of their original uses. Nevertheless, the local community may have come to enjoy the reservoir for recreational and aesthetic reasons. Often the reservoir will be placid and surrounded by greenery, and convey to visitors a natural sense of rest and relaxation.

Table:1 : List of Functions of Dams

Some of these purposes are conflicting and the dam operator needs to make dynamic tradeoffs. For

example, power generation and water supply would keep the reservoir high whereas flood prevention

would keep it low. Many dams in areas where precipitation fluctuates in an annual cycle will also see

the reservoir fluctuate annually in an attempt to balance these difference purposes. Dam management

becomes a complex exercise amongst competing stakeholders.

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CHAPTER: 2 – Type of Dams in Europe

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Dam failures are generally catastrophic if the structure is breached or significantly damaged. There are

several reasons behind dam failure. The main causes of dam failure include inadequate spillway

capacity, piping through the embankment, foundation or abutments, spillway design error, geological

instability caused by changes to water levels during filling or poor surveying, poor maintenance,

especially of outlet pipes, earthquakes and human, computer or design error.

Firstly, let’s understand the condition in our case study ‘Europe’, this chapter is divided in to two major

aspects, one to understand the dams in Europe and the second one two understand the major failures

and its reasons.

2.1 List of Dams in Europe:

Below are the list of countries included in European Union, I have considered all the dams in this

Continent to do my study.

EUROPE

Albania Estonia Lithuania Russia

Armenia Finland Macedonia Slovakia

Austria France Netherlands Slovenia

Azerbaijan Georgia Norway Sweden

Belgium Germany Serbia Switzerland

Bosnia-Herzegovina Greece Spain Turkey

Bulgaria Hungary Poland Ukraine

Croatia Iceland Portugal United Kingdom

Czech Italy Republic of Ireland

Denmark Latvia Romania

Analyzing the data of number of dams using “Hydropower & Dams in Europe” published to

commemorate the 79th Annual meeting of ICOLD Lucerne, Switzerland, 2011. We obtain the below

mentioned details:

Number of dams were built in different years according to the data

Before 1960 Between 1960 and 2000 After 2000

82 213 18

Table: 2 – Number of Dams in Europe

This table shows us the number of dams which were built in different years according to the data, and

we can see that most of dams in Europe are built between 1960 and 2000, the second is before 1960,

so dam for the past year is a common construction, and it lasts for many years. The situation is

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changing after the year of 2000, there are only 18 Dams built and few among them are still under

construction. I think there are several reasons behind constructing much lesser dams than earlier.

Reasons behind why now-a-days dams are built less than earlier:

1. There are already many dams built in Europe and most of them are still in good working

condition, so we don’t need to build more dams.

2. As we are developing Diversification of Energy, Dams sometimes are not our first choice

to produce Energy.

3. More importantly, huge adverse effect of river impoundments causing disruption of

ecosystem, decline of fish stock, forces resettlement, and spreading different diseases.

4. Also building a dam is very expensive in terms of construction.

5. Dam Construction may cause some issues, as it is expensive in terms of construction and

due to corruption and greed, construction are done with below standards causing soon

failure of the huge dam structure and effecting damage to ecosystem causing economical

crisis.

Finally we can’t say dam are less useful now but in some cases and situation they are dangerous and

mostly depend on the environment conditions. So there is no doubt that why there are less dam’s

built in Europe now-a-days.

2.2 Height of Dams in Europe:

According to the data we have from “Hydropower & Dams in Europe” published to commemorate the

79th Annual meeting of ICOLD Lucerne, Switzerland, 2011, we obtain the below mentioned data:

Height of dams according to the data

0 ～ 29 m 30 ～ 99 m Over 100m

100 205 172

Table: 3 – Height of Dams in Europe

We can observe that major numbers of dams are of height 30 to 99m, which is shown as 205. And over

100m height, they are 172 in number and the least of 100 numbers for 0-29m height. This shows that

on an average there are dams, which have taller heights. So in this case huge amount of water in cubic

meters can be stored for irrigation purpose, extracting energy, for livelihood and for general needs.

These dams in some places are taken care and some places they are in bad conditions, which can have

major failures. And they are dangerous to the ecosystem.

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2.3 Type of Dams in Europe:

According to the data we have from “Hydropower & Dams in Europe” published to commemorate the

79th Annual meeting of ICOLD Lucerne, Switzerland, 2011, we obtain the below mentioned data:

Type of dams according to the data

Arch Dam Gravity Dam Embankment Dam Others

(Buttress, Barrage…)

117 110 185 33

Table: 4 – Type of Dams in Europe

We can see from the table that mainly 3 types of dams were built in Europe, Embankment Dams, Arch

Dams and Gravity Dams. That’s the reason why when we discuss dam failure type, they are also the

mainly 3 type, because of the number of dams existing. Let’s discuss further more about these dams.

a) Gravity Dam:

It is a masonry or concrete dam which resists the forces acting on it by its own weight. Its c/s is

approximately triangular in shape. Most gravity dams are straight solid gravity dams. [10]

Fig: 13 – Gravity Dams: Llyn Stwlan dam in Wales

b) Arch Dam:

It is a curved masonry or concrete dam, convex upstream, which resists the forces acting on it by

arch action.

Arch shape gives strength

Less material (cheaper)

Narrow sites

Need strong abutments

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These type of dams are concrete or masonry dams which are curved or convex upstream

in plan

This shape helps to transmit the major part of the water load to the abutments

Arch dams are built across narrow, deep river gorges, but now in recent years they have

been considered even for little wider valleys.

Good for narrow, rocky locations.

They are curved and the natural shape of the arch holds back the water in the reservoir.

Arch dams, like the El Atazar Dam in Spain, are thin and require less material than any

other type of dam.

Fig: 14– El Atazar Dam in Spain

C) Embankment Dam:

It is a non-rigid dam which resists the forces acting on it by its shear strength and to some extent also by its own weight (gravity). Its structural behavior is in many ways different from that of a gravity dam.

Fig: 15– Embankment Dam

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2.4 Different types and number of Dams in Europe:

According to the data we have from “Hydropower & Dams in Europe” published to commemorate the

79th Annual meeting of ICOLD Lucerne, Switzerland, 2011, we obtain the below mentioned data:

Main Type and Number of dams in different regions of Europe according to the data

EUROPE Eastern Southeastern Southern Central Western Northern

Number 51 93 204 148 86 155

Main Type Embankment

/Gravity

Embankment

/Gravity

Embankment

/Arch Gravity/Arch Barrage/Arch

Embankment

/Gravity

Large Dams

Number (Height

over 100m)

3 23 81 10 22 7

Ratio

(Large

dams/dams)

5.80% 24.70% 39.70% 6.76% 25.58% 4.51%

Table: 5 – Type & Number of Dams in Europe

When we separate the whole Europe into 6 parts, we can find some interesting information. First let’s

discuss about the ‘Large dams’, we can see from the table that Southern Europe, Southeastern Europe

and Western Europe host the majority number of large dams, and the ratio between Large dams and

dams are, 39.70%, 24.70% and 25.58% respectively. From geographic view, these three regions are

along The Mediterranean Sea. They owned more large rivers and the histories of these countries

building dams are all quite older than other inland countries. We can’t say they have better advanced

technology than others. However, they obviously need more large dams to support them.

Secondly, we can find that for the east part of Europe, the main types of dams are Embankment and

Gravity Dams. When it turns to South Europe, they are Embankment and Arch dams, and Arch Dams

are very popular in the Central Europe and Western Europe as well. And for the north part of Europe,

It also turns out to be Embankment and Gravity Dams like Eastern Europe. So for the type of dams in

Europe we can simply divide the Europe into two parts. North & East as one part, Central, South &

West parts as one part.

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CHAPTER: 3 – Major Dam Failures & Reasons (Europe)

------------------------------------------------------------------------------------------------------------------------------------------------------------

3.1 List of Major Dam failures in Europe:

Apart vigorous study on the different dam failures in Europe, we obtained the below data:

S.No Dam Failures

1 Puentes Dam

2 Bilberry reservoir

3 Dale Dike Reservoir

4 Gleno Dam

5 Llyn Eigiau dam and Coedty reservoir

6 Secondary Dam of Sella Zerbino

7 Nant-y-Gro dam

8 Edersee Dam

9 Möhne Dam

10 Vega de Tera

11 Malpasset dam

12 Kurenivka mudslide

13 Mina Plakalnitsa

14 Certej dam failure

15 Tous Dam

16 Val di Stava dam

17 Doñana disaster

18 Ringdijk Groot-Mijdrecht (nl)

19 Sayano–Shushenskaya Dam

20 Niedow Dam

21 Ajka alumina plant accident

22 Ivanovo Dam Table: 6 – Major Dam Failure in Europe

Numbers of dams fail in Europe

Sub-standard

construction War

Geological

instability

Extreme

outflow or Rain Long-term use

9 3 2 4 1

Table: 7 – Number of dam failures in Europe

3.2 Reasons of Dam failures in Europe:

Europe ranks in second place in reported accidents (18%), more than one third of them in dams 10–

20 m high. In Europe, the most common cause of failure is related to unusual rain, whereas there is a

lack of occurrences associated with seismic liquefaction, which is the second cause of tailings dam

breakage elsewhere in the world. Moreover, over 90% of incidents occurred in active mines, and only

10% refer to abandoned ponds. Lets discuss all the failure reasons one after the other below:

Page 24 of 41

a) Long term Use:

It is generally assumed that the initial years of a dam's life are the most dangerous and the data

bears out this assumption. About 31 percent of the dam safety incidents analyzed for this paper

occurred during construction or the first five years of a dam's life. Among dam types, there was

a statistically significant variation in certain types of dams with 18 percent of gravity dams and

29 percent of arch dams experiencing incidents within the first five years, while 42 percent of

both earthen dams and rock-fill dams suffered incidents during construction or within the first

five years. [11]

The high percentage of dam safety incidents occurring within the first five years of operation

points out the importance of thoroughly examining a potential dam site, making sure that the

dam's design accounts for site-specific conditions that could result in the initiation and

development of a potential failure mode, constructing the dam carefully in order to minimize

the potential for a failure mode to initiate, and implementing a focused surveillance and

monitoring program to examine how the dam is behaving.

The second half of the first question was examined by considering only the data for those dams

where the incident occurred after five years of operation.

Fig: 16 –Number of Incidents Vs age of all dams (curve) Fig: 17 – Incident rates of dams (curve)

When the data for incidents that occurred after the first five years of operation for each type of

dam is plotted as an exceedance graph, the graph shows some distinct variations in the longer-

term performance of dams.

Page 25 of 41

b) Sub-Standard Construction:

For sub-standard construction, there are several reasons, use of materials an use of different

techniques during construction. And also depends on the designers design and process of how

the workers and working to construct during construction stage.

Let’s take a specific example to show the reason, Gleno Dam in Italy. The dam was originally

permitted as a gravity dam with a slight curvature, but was changed to a multiple arch dam by

the client to save money. The permit was not revised for this change until after the dam was

completed. The failure of the multiple arch dam was attributed to many aspects of its

construction, ultimately poor workmanship. The concrete in the arches was of a poor quality

and it was reinforced with anti-grenade scrap netting that had been used during World War I.

There were also indications that the dam was poorly joined with its foundation. Additionally,

the concrete was believed to not be completely cured when the reservoir was filling.

Reportedly, workers who complained about the construction techniques were fired. Today a

memorial exists in the failed gap along with a much smaller dam and reservoir within the old

reservoir zone. [12]

Fig: 18 - Gleno Dam in Italy

Page 26 of 41

c) Geological Instability:

For Geological instability, let’s take two examples. First is Malpasset Dam, Geological and

hydrological studies were conducted in 1946 and the dam location was considered suitable.

Due to lack of proper funding, however, the geological study of the region was not thorough.

The lithology underlying the dam is a metamorphic rock called gneiss. This rock type is known

to be relatively impermeable, meaning that there is no significant groundwater flow within the

rock unit, and it does not allow water to penetrate the ground. On the right side (looking down

the river), was also rock, and a concrete wing wall was constructed to connect the wall to the

ground. [13]

A tectonic fault was later found as the most likely cause of the disaster. Other factors

contributed as well; the water pressure was aimed diagonally towards the dam wall, and was

not found initially. As a consequence, water collected under a wall and was unable to escape

through the ground due to the impermeability of the gneiss rock underneath the dam. Finally,

another theory quotes a source stating that explosions during building of the highway might

have caused shifting of the rock base of the dam. Weeks before the breach, some cracking noises

were heard, but they were not examined. It is not clear when the cracking noises started. The

right side of the dam had some leaks in November 1959.

Between November 19 and December 2, there was 50 cm of rainfall, and 13 cm in 24 hours

before the breach. The water level in the dam was only 28 cm away from the edge. Rain

continued, and the dam guardian wanted to open the discharge valves, but the authorities

refused, claiming the highway

construction site was in danger of

flooding. Five hours before the breach,

at 18:00 hours, the water release

valves were opened, but with a

discharge rate of 40 m³/s, it was not

enough to empty the reservoir in time.

Fig: 19 - Malpasset Dam in France

Page 27 of 41

Second one is Vajont Dam. On 9 October 1963, engineers saw trees falling and rocks rolling

down into the lake where the predicted landslide would take place. Before this, the alarming

rate of movement of the landslide had not slowed as a result of lowering the water, although the

water had been lowered to what SADE believed was a safe level to contain the displacement

wave should a catastrophic landslide occur. With a major landslide now imminent, engineers

gathered on top of the dam that evening to witness the tsunami. [14]

At 10:39 P.M., a massive landslide of about 260,000,000 cubic metres (340,000,000 cu yd) of

forest, earth, and rock fell into the reservoir at up to 110 kilometres per hour (68 mph),

completely filling the narrow reservoir behind the dam. The landslide was complete in just 45

seconds, much faster than predicted, and the resulting displacement of water caused

50,000,000 cubic metres (65,000,000 cu yd) of water to overtop the dam in a 250-metre

(820 ft) high wave.

The flooding from the huge wave in the piave valley destroyed the villages, killing around 2,000

people and turning the land below the dam into a flat plain of mud with an impact crater 60

metres (200 ft) deep and 80 metres (260 ft) wide. Many small villages near the landslide along

the lakefront also suffered damage from a giant displacement wave. Estimates of the dead range

from 1,900 to 2,500 people, and about 350 families lost all members. Most of the survivors had

lost relatives and friends along with their homes and belongings.

The dam was largely undamaged. The top 1 metre (3.3 ft) or so of masonry was washed away,

but the basic structure remained intact and still exists today.

Fig: 20 - Vajont Dam in Italy

Page 28 of 41

d) War:

A notable case of deliberate dam failure (prior to the Humanitarian Law rulings) was the British

Royal Air Force Dam Busters raid on Germany in World War II (codenamed "Operation Chastise"),

in which three German dams were selected to be breached in order to impact on German

infrastructure and manufacturing and power capabilities deriving from the Ruhr and Eder rivers.

Such wars resulted in failure of dams causing major impact over the country. So in Olden days, it

was a strategy to paralise a country during war by damaging it most important infrastructure and

dams. [15]

e) Human Factors:

As part of a comprehensive review of its dam safety program, Swedish utility Vattenfall reviewed what is

known about human factors in dam safety. “Human factors” refers to a multidisciplinary knowledge domain

involving the study of human characteristics and actions in relation to technology (i.e., machines, tools,

equipment, computers, etc.) and to the organizational/cultural context in which the human is embedded.

The utility discovered that little has been studied about human factors in the context of dam safety when

compared to other industries such as nuclear power, transportation, and medicine. That may be because the

human and organizational issues related to dam safety events typically are not revealed in such a public way as

they are in events or accidents such as a reactor failure at a nuclear power plant or an airplane crash. Yet,

learning more about how human factors affect the safety of dams, and then sharing that knowledge with dam

safety professionals could enhance both worker productivity and dam safety. [16]

Now, let’s see these types of dams which are failed in Europe and their reasons over the Map to have a

better idea.

3.3 TYPES OF DAMS FAILED IN EUROPE:

This is the map showing the types of the dams in Europe. We can see from the map that Embankment

dam has the largest number of failures. Then follows Arch dam and other dam (barrages, etc.), and the

last one is gravity dam.

Page 29 of 41

Fig: 21: Type of dam failures

3.4 REASONS OF DAMS FAILURE IN EUROPE:

This map shows the reasons of failure of different type of dams in Europe:

Fig: 22: Reasons of dam failures

Page 30 of 41

3.5 Final Results comparison of type of dams with the reasons of Failure in Europe:

If we combine the above two maps together, we can see a very interesting result. Let’s forget about

war for now (as any type of dams can be destroyed in the war). For Gravity dam the most important

reason is extreme outflow or rain. For Arch Dam, the main reason is extreme outflow or rain then

follows sub-standard construction. On the contrary, for embankment dam, the main reason is sub-

standard construction, second is extreme outflow or rain. As for the other dams, since the number for

other dams are small, the reason is only extreme outflow or rain.

Type Total Number of

Dams in Europe

Number dams

failure in Europe Reason behind the failure

Embankment Dam 185 10 FIRSTLY: Sub-standard construction

SECONDLY: Extreme outflow or rains

Arch Dam 117 3 FIRSTLY: Extreme outflow or rains

SECONDLY: Sub-standard construction

Gravity Dam 110 2 Extreme Outflow rains

Other Dams 33 3 Extreme Outflow rains

Table: 8:Comparison of results

Page 31 of 41

CHAPTER: 4 – Data-Based Models for the Prediction of Dam Behavior

------------------------------------------------------------------------------------------------------------------------------------------------------------

4.1 Introduction

Behaviour models are a fundamental component of dam safety systems, both for the daily operation

and for long- term behaviour evaluation. They are built to calculate the dam response under safe

conditions for a given load combination, which is compared to actual measurements of dam

performance. The result is an essential ingredient for dam safety assessment, together with visual

inspection and engineering judgement. [17]

Numerical models based on the finite element method (FEM) are widely used to predict dam response,

in terms of displacements, strains and stresses. They are based on the physical laws governing the

involved phenomena, which gives them some interesting features: (a) they are useful for the design

and, more importantly, for dam safety assessment during the first filling, and (b) they can be

conveniently interpreted, provided that their parameters have physical meaning. [18]

On the contrary, some relevant indicators of dam safety, such as uplift pressure and leakage flow in

concrete dams, cannot be predicted accurately enough with numerical models. In addition, the

knowledge of the stress strain properties of the dam and foundation materials is always limited, and so

is the prediction accuracy of FEM models.

4.2 Statistical and Machine Learning Techniques Used In Dam Monitoring Analysis

The aim of these models is to predict the value of a given variable aspect (e.g. displacement, leakage

flow, crack opening, etc.)

The inputs may be of different nature, depending on the method:

Raw data recorded by the monitoring system, which in turn can be:

o External variables: reservoir level (h), air temper- ature (T), etc.

o Internal variables: temperature in the dam body, stresses, displacements, etc.

Variables derived from observed data. For example:

o Polynomials

o Moving averages

o Derivatives

Page 32 of 41

4.3 Hydrostatic-Seasonal-Time (HST) Model

The most popular data-based approach for dam monitoring analysis is the hydrostatic-seasonal-time

(HST) model. It was first proposed by Willm and Beaujoint to predict displacements in concrete dams,

and has been widely applied ever since. It is based on the assumption that the dam response is a

linear combination of three effects [19] :

A reversible effect of the hydrostatic load which is commonly considered in the form of a

fourth-order polynomial of the reservoir level (h).

A reversible influence of the air temperature, which is assumed to follow an annual cycle.

Its effect is approximated by the first terms of the Fourier transform.

An irreversible term due to the evolution of the dam response over time.A combination of

monotonic time-dependant functions is frequently considered.

The method makes use of strong assumptions on the response of the dam, which might not be fulfilled

in general. In particular, the three effects are considered as independent, although it is well known that

certain collinearity exists. The reservoir level affects the thermal response of the dam, provided that

the air and water tem- peratures differ. In some cases, the reservoir operation follows an annual cycle

due to the evolution of the water demand, so there is a strong correlation between h and the air

temperature. Collinearity may lead to poor prediction accuracy and, more importantly, to

misinterpretation of the results. [20]

Another limitation of the original form of HST model is that the actual air temperature is not

considered. On one hand, this makes it more flexible, because it can be applied in dams where air

temperature measurements are not available. On the other hand, it reduces its prediction accuracy for

particularly warm or cold years.Several alternatives have been proposed to overcome this

shortcoming. Penot et al. introduced the HSTT method, in which the thermal periodic effect is

corrected according to the actual air temperature. This procedure has been applied at Electricite de

France (EDF) with higher accuracy than HST, especially during the 2003 European heat wave.

Although the proposal of this method has been frequently attributed to Penot et al., Breitenstein et al.

applied a similar scheme 20 years earlier. [21]

Page 33 of 41

Tatin proposed further corrections of HSTT. The HST-Grad model takes into account both the mean

and the gradient of the temperature in the dam body, considered as a one-dimensional domain. They

are estimated from the air temperature in the downstream face, and from a weighted average of the air

and water temperatures in the upstream one. A similar and more detailed approach was applied by the

same authors, called the SLICE model . It considers different thermal conditions for the portion of the

dam body located below the pool level to that situated above, which is not affected by the water

temperature. [22]

Other common choice is to replace the periodic function of the thermal component by the actual

temperature in the dam body, resulting in the hydrostatic-thermal-time (HTT) method. One difficulty

of this approach is how to select the appropriate thermometers among those available. In arch dams,

some authors only consider the thermometers in the central cantilever, assuming that it represents the

thermal equilibrium between cantilevers in the right and left margins. Mata et al. solved this issue by

applying principal component analysis (PCA), while other authors considered all the available

instruments. Li et al. proposed an error correction model (ECM), featuring a term which depends on

the error in the estimation of previous output values.

Although HST was originally devised for the prediction of displacements in concrete dams, it has also

been applied to predict other variables. Simon et al. estimated uplifts and leakage with HST, although

they obtained more accurate results with neural networks (NN). Guedes and Coelho ´built a model for

the prediction of leakage in Itaipu Dam the average reservoir level between 6 and 11 days before the

measurement. Breitenstein et al. also studied leakage, although they discarded both the seasonal and

the temporal terms. Yu et al. combined HST with PCA to predict the opening of a longitudinal crack in

Chencun Dam.

4.4 Models to Account for Delayed Effects

It is well known that dams respond to certain loads with some delay. The most typical examples are:

The change in pore pressure in an earth-fill dam due toreservoir level variation.

The influence of the air temperature in the thermal field in a concrete dam body.

Other phenomena have been identified which are governed by similar processes. For example,

Lombardi noticed that the structural response of an arch dam to hydrostatic load comprised both

elastic and viscous components.Hence, the displacements not only depended on the instantaneous

reservoir level, but also on the past values.Simon et al. reported that leakage flow at Bissorte Dam

responded to rainfall and snow melt with certain delay. [23]

Page 34 of 41

Several approaches have been proposed to account for these effects. The most popular consists of

including moving averages or gradients of some explanatory variables in the set of predictors. In the

above mentioned study, Guedes and Coelho predicted the leakage flow on the basis of the mean

reservoir level over the course of a fivedays period. Sa´nchez Caroincluded the 30 and 60 days

moving average of the reservoir level in the conventional HST formulation to predict the radial

displacements of El Atazar Dam. Popovici et al. used moving averages of 3, 10 and 30 days of the air

temperature, together with the pool level in the previous 3 days to the measurement in order to

predict displacements in a buttress dam with neural networks (NN). Cre´pon and Lino reported

significant improvement in the prediction of piezometric levels and leakage flows by considering the

accumulated rainfall and the derivative of the hydrostatic load as predictors.

This approach requires a criterion to determine which moving averages and gradients should be

considered for each particular case. Demirkaya and Balcilar performed a sensitivity analysis to select

the number of past values to include both in an MLR and in a NN model. They used the same period

for the external and internal temperatures, as well as for the reservoir level, and found that the most

accurate results were obtained with an MLR model considering data from 30 previous days. Although

their results compared well to those proposed by the participants in the 6th ICOLD Benchmark

Workshop, they lacked physical meaning: they would imply that the dam responded with the same

delay to the water level, the air temperature, and the internal temperature field. Santilla´n et al.

proposed a methodology to select the optimal set of predictors among various gradients of air

temperature and reservoir level. They used the gradients instead of the moving averages to ensure

independence among predictors (moving averages are correlated with the original correspondent

variables). They combined it with NN to predict leakage flow in an arch dam.

4.5 Other ML Techniques

There is a wide variety of ML algorithms which can beuseful for dam monitoring data analysis. Their

accuracydepends on the specific features of every prediction task.Given that research on ML is a highly

active field, thealgorithms are constantly improved and new practicalapplications are reported each

year. Some of them have been applied to dam monitoring analysis. They are considered in this section

more briefly than others, in accordance with their lower popularity in dam engineering so far. This

does not mean that they can not offer advantages over the methods described previously. [24]

Support vector machines (SVM) stand among the mostpopular ML algorithms nowadays. They

combine a nonlinear transformation of the predictor variables to a higherdimensional space, a linear

regression on the transformedvariables, and ane-insensitive error function that neglectserrors below a

Page 35 of 41

given threshold. Cheng and Zheng used SVM in combination with PCA for short-term prediction of the

response of the Minhuatan gravity dam. Although the results were highly accurate, the computational

time was high. Rankovic et al. built a behaviour model based on SVM for predicting tangential

displacements.

K-nearest neighbours (KNN) is a non-parametric method which requires no assumptions to be made

about the physics of the problem; it is solely based on the observed data. The KNN method basically

consists on estimating the value of the target variable as the weighted average of observed outputs in

similar conditions within the training set. The similarity between observed values is measured as the

Euclidean distance in thed-dimensional space defined by the input variables.

A clear disadvantage of this type of model is that if the Euclidean distance is used as a measure of

similarity, all the predictors are given the same relevance. Hence, including a low relevant variable

may result in a model with poor generalisation capability. As a consequence, variable selection is a

critical aspect for fitting a KNN model. [25]

Salazar et al. performed a comparative study amongvarious statistical and ML methods, including HST,

NN, and others which had never been used before in dam monitoring, such as random forests (RF) or

boosted regression trees (BRT). It was reported that innovative ML algorithms offered the most

accurate results, although no one performed better for all 14 outputs analysed, which corresponded to

radial and tangential displacements and leakage flow in an arch dam.

4.6 Methodological Considerations for Building Behaviour Models

While each model has specific issues to take into account, there are also common aspects to consider

when developing a prediction model, regardless of the technique. It is not an exhaustive review: the

studies were selected on the basis of their relevance and interest, following the authors’ criterion.

4.6.1 Missing Values

There are several potential sources of data incompleteness, such as insufficient measurement

frequency or fault in the data acquisition system. Although there is a tendency towards increasing the

quality of measurements and the frequency of reading, there are many dams in operation with long

and low-quality monitoring data series to be analysed. According to Lombardi, only a small minority of

the world population of dams feature adequate, properly-interpreted monitoring records. Curt and

Gervais showed the importance of controlling the quality of the data on which the dam safety studies

are based, although they focused on proposing future corrective measures rather than on how to

improve imperfect time series.

Page 36 of 41

However, the vast majority of published articles overlooked this issue. They limited to the selection of

some specific time period for which complete data series were available. For example, Mata et al. only

considered the period 1998–2002 for their analysis of the Alto Lindoso dam, due to the absence of

simultaneous readings of displacements and temperatures in subsequent periods. In general, the need

for simultaneous data of both the external variables and the dam response reduces the amount of data

available for model fitting and limits the prediction accuracy. [26]

If the missing values correspond to one of the predictors, these models are inapplicable, which limits

their use inpractice. If lagged variables are considered, there is also a need for equally time spaced

readings. The above mentioned adaptive system proposed by Stojanovic et al. can be applied in the

event of failure of one or several devices.

Faults in the data acquisition process can also result inerroneous readings which should be identified

and eventually discarded or corrected. During model fitting, this would improve the model accuracy

and increase its ability to interpret the dam response. Once a behavior model is built, it can be used for

that purpose

Numerous statistical techniques have been developed to impute missing values. Their review is

beyond the scope of this work, as they were not employed in the papers analysed. Moreover, their

application should be tailored to the specific features of the problem, as well as to the nature of the

variable in question. For example, missing values of air temperature can be reasonably filled from the

average historical temperature for the period, or interpolated from available data. By contrast, daily

rainfall may change largely between consecutive readings, so that one missing value cannot be

imputed with similar confidence.

4.6.2 Practical Application

Despite the increasing amount of literature on the use of advanced data-based tools, very few

examples described their practical integration in dam safety analysis. The vast majority were limited

to the model accuracy assessment, by quantifying the model error with respect to the actual measured

data. Only a few cases dealt with the interpretation of dam behaviour, by identifying the effect of each

of the external variables on the dam response.

A more accurate analysis could be based on the consideration of the major potential modes of failure

to obtainthe corresponding behaviour patterns and an estimate of how they would be reflected on the

monitoring data. Mata et al. employed this idea to develop a methodology that includes the following

steps:

Page 37 of 41

Identification of the most probable failure mode.

Simulation of the structural response of the dam in normal and accidental situations

(failure) by means of finite element models.

Selection of the set of instruments that better identify the dam response during

failure.

Construction of a classification rule based on linear discriminant analysis (LDA) that

labels a set of monitoring data as normal behaviour or incipient failure.

This scheme can be easily implemented in an automatic system. By contrast, it requires a detailed

analysis of the possible failure modes, and their numerical simulation to provide data with which to

train the classifier.[26] Moreover, the finite element model must be able to accurately represent the

actual behaviour of the dam, which is frequently hard to achieve

Page 38 of 41

CONCLUSION

------------------------------------------------------------------------------------------------------------------------------------------------------------

In conclusion, I would like to add some of my observation and some of the preventive measures to stop

the failure of dams to a relative percentage. It is more evident from my study that most of European

dams were affected due to couple of reasons such as sub-standard construction, geological instability,

wars, extreme outflow or rain and long term use of the dam. Dams are like a back bone to the world,

supplying the needs to livelihood. It is very important to maintain these dams in good conditions. Due

to major failures in past which effect the ecosystem, leads us not to have a major dams constructions,

but in reality we do need such dams for storing water and producing electricity for the human lives.

We know in the future due to Ozone depletion, we may have huge lack of water supply so keeping that

in view, it is important to store the rain water for future need and irrigation.

I agree, if dams are not well maintained then disaster is expected, but we as humans will face much

disaster in future due to lack of water and which results in major lose of human era. Based on which,

we have to take major actions in restoring and maintaining these dams in a very effective way, by

having good standards while construction and appointing well educated professional workers to

maintain these dams. Sometimes these dams act as the protective barrier from other countries as well,

so it is also important to safely maintain these dams. We must appoint good engineers, who

understands, how to balance the water level in the dams, such as for electricity purposes and also

keeping in view the flood disaster due to heavy rainfall.

Overall I can conclude by saying, dams are one of the major need to the human lives and whereas

safety is very important to human from dams under failure. Though dams seems less important than

before, they are still widely used and brings us lots of benefits and they will support human lives much

more in the future.

Page 39 of 41

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PHOTOS REFERENCES:

S.No Reference Links

Fig-1 http://images.gadmin.st.s3.amazonaws.com/n49467/images/buehne/grande-dixence_3.jpg

Fig-2 http://www.ceati.com/images/dam.jpg

Fig-3 https://en.wikipedia.org/wiki/Dam#/media/File:Roman_Cornalvo_dam,_Extremadura,_Spain._Pic_01.jpg

Fig-4 https://en.wikipedia.org/wiki/Dam#/media/File:Lake_Parramatta,New_South_Wales.jpg

Fig-5 https://en.wikipedia.org/wiki/List_of_dams_and_reservoirs#/media/File:Presa_Aldead%C3%A1vil

a_desembalsando.JPG

Fig-6 https://en.wikipedia.org/wiki/List_of_dams_and_reservoirs#/media/File:Presa_Aldead%C3%A1vil

a_desembalsando.JPG

Fig-7 http://www.oas.org/DSD/publications/Unit/oea59e/p073a.GIF

Fig-8 https://en.wikipedia.org/wiki/Lipno_Dam#/media/File:Lipno1.JPG

Fig-9 https://upload.wikimedia.org/wikipedia/commons/thumb/5/57/Hydroelectric_dam.svg/2000px-

Hydroelectric_dam.svg.png

Fig-10 http://www.icold-cigb.org/GB/Dams/role_of_dams.asp

Fig-11 http://www.icold-cigb.org/GB/Dams/role_of_dams.asp

Fig-12 http://www.icold-cigb.org/GB/Dams/role_of_dams.asp

Fig-13 https://en.wikipedia.org/wiki/Ffestiniog_Power_Station #/media/File:Stwlan.dam.jpg

Fig-14 https://upload.wikimedia.org/wikipedia/commons/a/a5/El_Atazar_dam_view01.jpg

Fig-15 http://www.simscience.org/cracks/advanced/image/e_section.gif

Fig-18 https://en.wikipedia.org/wiki/Gleno_Dam#/media/File:Gleno_Dam_02.JPG

Fig-19 http://www.webpages.uidaho.edu/~simkat/geol345_files/malpasset_front.jpg

Fig-20 https://s-media-cache-ak0.pinimg.com/736x/e8/a0/08/e8a008acb65cb97a621a7e08562942cd.jpg