Hydraulic structures have been developed for thousands of years to control water flow for irrigation and water supply. Early examples include canals, dams, and irrigation networks developed by ancient Egyptians and Mesopotamians. Conventional hydraulic design is an iterative process relying on an engineer's experience. Optimization and economic analysis can lead to more optimal designs. Risk analysis is also important as hydraulic structures always face uncertainties and risks of failure from hydrologic, hydraulic, structural, and economic sources. Assessing load and resistance with reliability and safety factor analysis allows quantification of risks.

1. CHAPTER 1: INTRODUCTION TO
HYDRAULIC STRUCTURES, HISTORY,
DESIGN, RISK, UNCERTAINTY AND
SUSTAINABILITY
DR. MOHSIN SIDDIQUE
ASSISTANT PROFESSOR
1
0401544-HYDRAULIC STRUCTURES
University of Sharjah
Dept. of Civil and Env. Engg.

2. HYDRAULIC STRUCTURE
A hydraulic structure is a structure submerged or partially submerged
in any body of water, which disrupts the natural flow of water. They can
be used to divert, disrupt or completely stop the flow. A hydraulic
structure can be built in rivers, a sea, or any body of water where there is
a need for a change in the natural flow of water.
Example of hydraulic structures:
1. Canals or drainage (lined and unlined), canal falls (Drops),
regulators, outlets
2. Head-works: Weirs, Barrages
3. Cross drainage works (aqueduct, siphon)
4. Culverts, Bridges and Causeway
5. Dams, spillways, outlet works
6. Stilling basin, energy dissipaters
7. Breakwater, jetties, groins, headlands etc
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3. HISTORY
Irrigation in Egypt and Mesopotamia
Since the Egyptian’s and Mesopotamian’s first successful efforts to
control the flow of water thousands of years ago, a rich history of
hydraulics has evolved.
Hydraulic design handbook, Larry W. Mays, Mcgraw Hills
http://www.waterencyclopedia.com/Hy-La/Irrigation-Systems-Ancient.html
Humans have spent most of their history as hunters and food-gatherers. Only in the
past 9,000 to 10,000 years have humans discovered how to raise crops and tame
animals. Such changes probably occurred first in the hills to the north of present-
day Iraq and Syria.
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4. Comparative irrigation networks in
Upper Egypt and Mesopotamia. A.
Example of linear, basin irrigation in
Sohag province, ca. AD 1850. B.
Example of radial canalization system
in the lower Nasharawan region
southeast of Baghdad, Abbasid (A.D.
883–1150). Modified from R. M.
Adams (1965, (Fig. 9) Same scale as
Egyptian counterpart) C. Detail of
field canal layout in B. (Simplified
from R. M. Adams, 1965, Fig. 10).
Figure as presented in Butzer (1976).
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5. HISTORY
Irrigation in Prehistoric
Mexico
Regional chronology and dates of developments in various aspects of canal
irrigation technology in Mexico. (Doolittle, 1990)
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6. HISTORY
Map of fossilized canals on the Llano de la Taza in the
Tehuacan Valley Mexico. (Woodbury and Neely, 1972, as
presented in Doolittle, 1990) 6

7. HISTORY
Irrigation in North America: Chaco and Hohokam Systems
FIGURE Canal building in the Salt River Valley with a stone hoe held in the hand without a handle. These were the original
engineers, the true pioneers who built, used, and abandoned a canal system when London and Paris were a cluster of wild
huts. Turney (1922) (Courtesy of Salt River project Pheonix Arizona)
Although the Indians
of Arizona began
limited farming nearly
3000 years ago,
construction of the
Hohokam irrigation
systems probably did
not begin until the
first few
centuries A.D.
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8. HISTORY
Schematic representation of the major components of a Hohokam
irrigation system in the Phoenix Basin. (Masse, 1991)
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9. HISTORY
Dams
Mesopotamia
Located in modern-day Jordan, the
Jawa Dam was originally constructed
around 3,000 BCE in what was then
Mesopotamia.
In its prime, the Jawa Dam was 15 feet
tall, 80 feet long, with a base of 15 feet.
It created the Jawa Reservoir that had
a capacity of 1.1 million cubic feet.
http://www.tataandhoward.com/2016/05/a-history-of-dams/
Remains of the Jawa Dam
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10. HISTORY
Dams
Egypt
Sadd-el-Kafara dam in Egypt,
http://www.tataandhoward.com/2016/05/a-history-of-dams/
Approximately 400 years after the
construction of the highly successful Jawa
Dam, Egyptians built the Sadd el-Kafara,
or Dam of the Pagans, most likely to
supply water to the local quarries outside
of Cairo rather than for irrigation, since the
flooding Nile would have supplied plenty of
water to the farmers.
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11. HISTORY
Dams
Roman empire: The Romans,
highly regarded for their advances
in hydraulic engineering, were
prolific in dam construction during
the height of the empire. In addition
to the vast network of aqueducts,
the Romans built a plethora of
gravity dams, most notably the
Subiaco Dams, which were
constructed around 60 AD to create
a pleasure lake for Emperor Nero.
The Romans also constructed the
world’s first arch dam in the Roman
province of Gallia Narbonensis, now
modern-day southwest France, in
the 1st century BCE.
The Cornalvo Dam, a Roman gravity
dam in built in the 1st or 2nd century
AD, still supplies water to the people of
Meriden, Spain.
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12. HISTORY
Dams
Asia: As early as 400 BCE, Asians
built earthen embankments dams to
store water for the cities of Ceylon,
or modern-day Sri Lanka
Japan and India also contributed to
early dam engineering, with much
success. In fact, five of the ten
oldest dams still in use are
located in these two countries. The
oldest operational dam in the world,
the Lake Homs Dam in Syria, was
built around 1300.
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13. HISTORY
Urban Water Supply and Drainage Systems
Knossos, approximately 5 km from Herakleion, the modern capital of
Crete, was among the most ancient and unique cities of the Aegean and
Europe.
Anatolia, also called Asia Minor, which is part of the Republic of Turkey,
has been the crossroads of many civilizations during the past 10,000
years. During the last 4000 years, going back to the Hittite period (2000–
200 B.C.) many remains of ancient urban water supply systems have
been found, including pipes, canals, tunnels, inverted siphons,
aqueducts, reservoirs, cisterns, and dams. (see Ozis, 1987 and Ozis and
Harmancioglu, 1979).
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14. HISTORY
Water distribution pipe in Knossos, Crete.
(Photograph by L.W. Mays)
Urban drainage system in Knossos,
Crete. (Photograph by L.W. Mays)
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15. HISTORY
A drainage channel on the floor of
the Great Theater at Ephesus,
Turkey. (Photograph by L. W.
Mays)
View of the baths at Perge, Anatolia,
Turkey. (Photographs by
L.W. Mays)
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16. 16

17. CONVENTIONAL HYDRAULIC DESIGN
PROCESS
Conventional procedures for hydraulic
design are basically iterative trial-and-
error procedures.
The effectiveness of conventional
procedures depends on an engineer’s
intuition, experience, skill, and
knowledge of hydraulic systems.
An advantage of the conventional
process is that engineers use their
experience and intuition to make
conceptual changes in the system or to
change or add specifications.
The conventional procedure can lead to
non-optimal or uneconomical designs
and operation policies. Also, the
conventional procedure can be
extremely time consuming.
Conventional procedure for
hydraulic design and analysis.
(Mays and Tung, 1992)
17

18. Conventional procedure for
hydraulic design and analysis.
(Mays and Tung, 1992) 18

19. ROLE OF ECONOMICS IN HYDRAULIC
DESIGN
Engineering economic analysis is an evaluation process that can be used
to compare alternative hydraulic designs and then apply a discounting
technique to select the best alternative.
Benefit-Cost Analysis
Water projects extend over time, incur costs throughout the duration of the
project, and yield benefits. When selecting a set of projects, one rule for
optimal selection is to maximize the current value of net benefits. Another
ranking criterion is to use the benefit-cost ratio (B/C), PWB/PWC:
B/C= PWB/PWC > 1
The B/C ratio is often used to screen unfeasible alternatives with B/C
ratios less than 1 from further consideration.
Selection of the optimum alternative is based on the incremental
benefit-cost ratios, ∆B/∆C.
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20. ROLE OF ECONOMICS IN HYDRAULIC
DESIGN
20Flowchart for a benefit-cost analysis. (Mays and Tung, 1992)

21. ROLE OF OPTIMIZATION IN HYDRAULIC
DESIGN
Optimization eliminates the trial-and-error process of changing a design
and re-simulating it with each new change. Instead, an optimization model
automatically changes the design parameters.
An optimization procedure has mathematical expressions that describe
the system and its response to the system inputs for various design
parameters.
Every optimization problem has two essential parts:
(1). the objective function and
(2). the set of constraints.
The objective function describes the performance criteria of the system.
Constraints describe the system or process that is being designed or
analyzed
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22. ROLE OF OPTIMIZATION IN HYDRAULIC
DESIGN
An optimization problem in water resources can be formulated in a
general framework in terms of the decision variables (x), with an objective
function to optimize
f(x)
Subject to constraints
g(x)=0
and bound constraints on the decision variables
X’<x<X’’
where x is a vector of n decision variables (x1, x2, …, xn), g(x) is a vector
of m equations called constraints, and x’ and x’’ represent the lower and
upper bounds, respectively, on the decision variables.
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23. ROLE OF OPTIMIZATION IN HYDRAULIC
DESIGN
f(x), g(x)=0, X’<x<X’’
A feasible solution of the optimization problem is a set of values of the
decision variables that simultaneously satisfies the constraints. The
feasible region is the region of feasible solutions defined by the
constraints.
An optimal solution is a set of values of the decision variables that
satisfies the constraints and provides an optimal value of the objective
function.
Depending on the nature of the objective function and the constraints, an
optimization problem can be classified as
(1) linear vs. nonlinear,
(2) deterministic vs. probabilistic,
(3) static vs. dynamic,
(4) continuous vs. discrete, or
(5) lumped parameter vs. distributed parameter.
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24. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Uncertainties and the consequent related risks in hydraulic design are
unavoidable.
Hydraulic structures are always subject to a probability of failure in
achieving their intended purposes.
Procedures for the engineering design and operation of water
resources do not involve any required assessment and
quantification of uncertainties and the resultant evaluation of a risk
!!!
Risk is defined as the probability of failure, and failure is defined as an
event that causes a system to fail to meet the desired objectives.
Failures can be grouped into either structural failures or performance
failures.
Reliability is defined as the complement of risk: i.e., the probability of
non-failure.
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In math, the complement is the amount you must
add to something to make it "whole".

25. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Uncertainty can be defined as the occurrence of events that are beyond
one’s control. The uncertainty of a hydraulic structure is an indeterministic
characteristic and is beyond rigid controls. In the design and operation of
these systems, decisions must be made under various kinds of
uncertainty.
The sources of uncertainties are multifold.
Natural uncertainties are associated with the random temporal and
spatial fluctuations that are inherent in natural processes. Model
structural uncertainties reflect the inability of a simulation model or
design procedure to represent the system’s true physical behavior or
process precisely. Model parameter uncertainties reflect variability in
the determination of the parameters to be used in the model or design.
Data uncertainties include inaccuracies and errors in measurements,
inadequacy of the data gauging network, and errors in data handling and
transcription. Operational uncertainties are associated with human
factors, such as construction, manufacture, deterioration, and
maintenance, that are not accounted for in the modeling or design
procedure.
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26. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Uncertainties fall into four major categories:
(i). Hydrologic uncertainty,
(ii). Hydraulic uncertainty,
(iii). Structural uncertainty, and
(iv). Economic uncertainty.
Each category has various component uncertainties.
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Hydrologic: The science dealing with the occurrence, circulation, distribution, and
properties of the waters of the earth and its atmosphere.

27. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Hydrologic uncertainty can be classified into three types: inherent,
parameter, and model uncertainties.
Various hydrologic events, such as streamflow or rainfall, are considered
to be stochastic processes because of their observable natural (inherent)
randomness.
Because perfect hydrologic information about these processes is lacking,
informational uncertainties about the processes exist. These uncertainties
are referred to as parameter uncertainties and model uncertainties.
In many cases, model uncertainties result from the lack of adequate data
and knowledge necessary to select the appropriate probability model or
from the use of an oversimplified model, such as the rational method for
the design of a storm sewer.
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28. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Hydraulic uncertainty concerns the design of hydraulic structures and
the analysis of their performance.
It arises mainly from three basic sources: the model, the construction
and materials, and the operational conditions of flow.
Model uncertainty results from the use of a simplified or an idealized
hydraulic model to describe flow conditions, which in turn contributes to
uncertainty when determining the design capacity of hydraulic structures.
Because simplified relationships, such as Manning’s equation, are
typically used to model complex flow processes that cannot be described
adequately, resulting in model errors.
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29. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Structural uncertainty refers to failure caused by structural weakness.
Physical failures of hydraulic structures can be caused by saturation and
instability of soil, failures caused by erosion or hydraulic soil, wave action,
hydraulic overloading, structural collapse, material failure, and so forth.
An example is the structural failure of a levee system either in the levee
or in the adjacent soil; the failure could be caused by saturation and
instability of soil. A flood wave can cause increased saturation of the
levee through slumping. Levees also can fail because of hydraulic soil
failures and wave action.
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30. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Economic uncertainty can arise from uncertainties regarding
construction costs, damage costs, projected revenue, operation and
maintenance costs, inflation, project life, and other intangible cost and
benefit items.
Construction, damage, and operation or maintenance costs are all
subject to uncertainties because of fluctuations in the rate at which
construction materials, labor costs, transportation costs, and economic
losses, increase and the rate at which costs increase in different
geographic regions.
Many other economic and social uncertainties are related to
inconvenience losses: for example, the failure of a highway crossing
caused by flooding, which results in traffic related losses.
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31. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Risk-Reliability Evaluation
Load resistance: The load for a system can be defined as an external
stress to the system, and the resistance can be defined as the capacity
of the system to overcome the external load.
If we use the variable R for resistance and the variable L for load, we can
define a failure as the event when the load exceeds the resistance and
the consequent risk is the probability that the loading will exceed the
resistance, P(L >R).
Composite Risk: Hydrologic and hydraulic uncertainties being the
resistance and loading uncertainties leads to the idea of a composite risk
Safety factor The safety factor is defined as the ratio of the resistance to
loading, R/L. Because the safety factor, SF, R/L is the ratio of two
random variables, it also is a random variable. The risk can be written as
P(SF <1) and the reliability can be written as P(SF>1)
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32. ROLE OF RISK ANALYSIS IN HYDRAULIC
DESIGN
Risk assessment Risk assessment requires several phases or steps,
which can vary for different types of water resources engineering
projects: (1) identify the risk of hazard, (2) assess load and resistance,
(3) perform an analysis of the uncertainties, (4) quantify the composite
risk, and (5) develop the composite risk-safety factor relationships.
A model for risk-based design The risk-based design of hydraulic
structures potentially promises to be the most significant application of
uncertainty and risk analysis. The risk-based design of hydraulic
structures integrates the procedures of economics, future uncertainty
analysis, and risk analysis in design practice.
When risk-based design is embedded in an optimization framework, the
combined procedure is called optimal risk-based design. This approach
to design is the ultimate model for the design, analysis, and operation of
hydraulic structures and water resource projects that hydraulics
engineers need to strive for in the future.
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33. SUSTAINABILITY
Sustainability
In ecology, sustainability (from sustain and ability) is the property
of biological systems to remain diverse and productive indefinitely.
(Wikipedia)
Sustainable development**
…meeting the needs of the present without compromising the
ability of future generations to meet their own needs.
**World Commission on Environment and Development (1987): Our Common Future
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34. ELEMENTS OF SUSTAINABILITY
•Environment
•biodiversity
•materials
•energy
•biophysical interactions
•Society
•human diversity (cultural,
linguistic, ethnic)
•equity (dependence /
independence)
•quality of life
•institutional structures and
organization
•political structures
•Economy
•money and capital
•employment
•technological growth
•investment
•market forces 34

35. ELEMENTS OF SUSTAINABILITY
•Environment
•Society
•Economy
35(Wikipedia)

36. SUSTAINABILITY: PROBLEMS
Depletion of finite resources
• fuels, soil, minerals, species
Over-use of renewable resources
• forests, fish & wildlife, fertility, public funds
Pollution
• air, water, soil
Inequity
• economic, political, social, gender
Species loss
• endangered species and spaces
- WCED, 1987 36

37. SUSTAINABILITY: SOLUTIONS
Cyclical material use
– emulate natural cycles;
– Safe reliable energy
– conservation, renewable energy, substitution, interim
measures
Life-based interests
– health, creativity, communication, coordination,
appreciation, learning, intellectual and spiritual
development
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38. THANK YOU
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