CHAPTER 1: INTRODUCTION TO

HYDRAULIC STRUCTURES, HISTORY,

DESIGN, RISK, UNCERTAINTY AND

SUSTAINABILITY

DR. MOHSIN SIDDIQUE

ASSISTANT PROFESSOR

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0401544-HYDRAULIC STRUCTURES

University of Sharjah

Dept. of Civil and Env. Engg.

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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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 Hillshttp://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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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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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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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

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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HISTORY

Schematic representation of the major components of a Hohokam irrigation system in the Phoenix Basin. (Masse, 1991) 8

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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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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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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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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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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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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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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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

Conventional procedure for

hydraulic design and analysis.

(Mays and Tung, 1992) 18

ROLE OF ECONOMICS IN HYDRAULIC DESIGNEngineering 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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ROLE OF ECONOMICS IN HYDRAULIC DESIGN

20Flowchart for a benefit-cost analysis. (Mays and Tung, 1992)

ROLE OF OPTIMIZATION IN HYDRAULIC DESIGNOptimization 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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ROLE OF OPTIMIZATION IN HYDRAULIC DESIGNAn 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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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.23

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.

24In math, the complement is the amount you must

add to something to make it "whole".

ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNUncertainty can be defined as the occurrence of events that are beyond one’s control. The uncertainty of a hydraulic structure is an indeterministiccharacteristic 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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ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNUncertainties 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.

ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNHydrologic 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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ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNHydraulic 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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ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNStructural 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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ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNEconomic 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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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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ROLE OF RISK ANALYSIS IN HYDRAULIC DESIGNRisk 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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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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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

ELEMENTS OF SUSTAINABILITY•Environment•Society•Economy

35(Wikipedia)

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

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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THANK YOU

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