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Lecture – 01: Introduction

Welcome, all of you to these interesting lectures on river engineering. This is an introductory lecture on river engineering. You all know about river engineering and you all have seen rivers in a different part of your life, but today we are going to start the engineering aspect of river concept that what we are looking at and today’s lecture just being an introductions lectures, I
will just talk about a brief note on hydrological issues.
What are the issues are there in Indian basins? The basic idea is that what problems are there
and what are the reference book and eminent scientists on this subject. Then, also I will talk
about major river projects which are constructed and what is their performance, how they are
fulfilling their major objective and the recent area if you talk about the physical,
mathematical modeling, some of the case studies I will show.
And then I will tell you so what is the planning of lecture series for this course. So, that is
what I will discuss in today’s lecture.
(Refer Slide Time: 02:08)Look at the eminent river scientist. Let me have Albert F Shield, very beginning, considering
the fluvial experiment in the flume and tried to understand the concept of incipient motion.
How the sediment particles are moving from the bed? that is what you try to understand and
try to have a knowledge on the sediment transport because if you talk about the rivers, we
have to talk about the sediment, we have to talk about energy dissipation.
So, the famous Albert F Shield developed the sediment transport formulas or the sediment
curves which is Shield’s curve or Shield number and that is what is very early studies makes
us understanding the complex process between water and sediment transports in regional
river systems. Then Professor W. L. Graf looking for beyond this rivers, looking for the
human impacts on the rivers, morphology.
The process of contaminated transport, riparian habitat changes in the rivers that is what is
the present issues. Today for most of the Indian rivers, we have the issue of water qualities,
river health. These are studies which are started by professor W. L. Graf and that is what is
the fluvial process in dryland rivers, dam removals science and decisions. An Indian
scientists you know it, Professor R. J. Garde, he was a professor in IIT, Roorkee.
He has contributed on turbulent flow, river morphology and the fluid mechanics. He tried to
combine the morphology, turbulent flow, fluid mechanics and tried to understand the water
sediment transport process and established very unique lab set ups in IIT, Roorkee. It was
established to study the process of the fluvial hydraulics. So if you look at this, there are
many scientists in this field, I just want to highlight it from Albert F Shield to R. J. Garde.So, a lot of experimental studies were conducted, very precisely tried to understand water and
sediment transport process which is the complex processes. As well as professor W. L. Graf,
he tried to understand human impacts on the river morphology process.
(Refer Slide Time: 05:10)
Now, if you look it today what challenge you have? Very interesting challenge what we have
today, especially Indian river basins, today there is not having an independent process we will
look it like hydrodynamic process separately, sediment transport process differently,
morphology process differently, hydrology process are different and the society the human
being interventions, all we look it in separate entity that does not happen it, all are very much
integrated concept.
If you talk about the river dynamic cycles, how the rivers are changing? it is so dynamic, it is
interlinked with hydrology, fluvial processes, the long-term morphology change and also the
driving factors like society or the human beings. The river dynamic process are linked to
hydrology, fluvial process, morphology, and society. Now, if you look at that, what it
happens is, in the last few decades that we have an alternative concept like a river modelling.
There is lot of mathematical modeling concept has come out and tools are available, models
are available, helpful to look at the similar behavior what it happens in natural rivers that
what we can represent mathematical models. There are lot of significant development
happening, physical modellings that is what I will show it. There are good setup of physical
model of river models are there.Not only that there are lot of advanced measurements are happening today, which it was not
possible maybe 20 years back, but now it is possible to do the data collection at the river
levels. It is a possible that is what I will show some photographs for you. The advanced
measurement of the hydraulic parameters are also possible, so that way there are significant
development happens in these 3 directions.
Mathematical models, physical models are interacting each other or each one is a
complementary to each other’s. There is no superiority of physical model or mathematical
model along the field data, all are interlinking each other’s to enhance the knowledge of the
river mechanics. Try to understand the sediment transport process, the hydrodynamic process,
the turbulent process in rivers with respect to energy dissipation, nutrient transport.
All we have to try to look it as a river. We try to look at how the process happens it. So, for
that reasons, we need to have all these 3 tools i.e. physical modelling, mathematical modeling
and also the advanced measurement, all they are complementing to each other’s to have a
knowledge on the river. The river morphology is also a part of planning in present days
which earlier is considered to be a long-term purpose.
But now the river morphology also is considered as a part of planning in river health and the
river engineering. So, if you look at this, all are interlinking each other's at applications level.
It is an advancing levels of modeling, river mathematical modeling, physical modeling,
advanced measurement, similar way if you look at the planning, planning also we should look
at river health, I am talking about water quality which is a major issue in our countries.
So river health, the ecological health of rivers, river engineering as well as the morphology
all are linked to each other. If you look at these 6 blocks, it is changing its that also we have
linked with this part because as we have a knowledge about the rivers that is what will be
give us a confidence or to take appropriate decisions on what type of river engineering we
should implement it.
So, that is the reasons if you look at that, both the things are happening and as you implement
the river engineering, any projects like maybe a barrage project, maybe a river trainingworks, you have to try to understand using the advanced equipments what is the performance
of that structures if that is what you can also look it.
So if you try to look at these figures the river modeling, physical modeling, advanced
measurement, morphology, river health and river engineering. And I can bracket into the
society, they are the socio-economical benefits that is what is the basic things. Mostly, we
ignore one part of the river, which helps us to maintain big cycles at the society point of view,
which is water-food-energy nexus. The river also play major roles to make it sustainable, or
socio-economic benefits. Let us try to manage, or try to understand how the water-foodenergy nexus is happening in a particular river systems, which varies from river to river.
Like the concept what do I develop for the Brahmaputra River, I cannot apply the same
things for the Godavari rivers or the same things for the Narmada river. So, all this concept
we have to understand locally, at the regional levels and also you should have the broad
knowledge at the global scales. That is my concept to bring you this course and based on that
concept I have designed this course for you to go next levels.
(Refer Slide Time: 11:46)
Now if you look at the books what I am going to follow it is, River Mechanics by Pierre Y.
Julien which is a very interesting book. Also fluvial hydrodynamics looking at new modeling,
new measurement technique, discussing on hydrodynamics and sediment transport
phenomena that is what we will follow by the book authored by professor Subhasish Dey.
Then we will have a very interesting book looking for ecologist point of view is a Stream
Hydrology: An introductions for ecologist.A group of professors have written this book, very interesting book. So, what I have to tell
you that, it is a combination of, one side is river mechanics, the fluvial hydrodynamics and
the steam hydrology: an introduction for ecologist, not only that we have to follow some of
reputed journals like journal of hydrology, journal of hydraulic engineering and journal of
sediment research.
(Refer Slide Time: 13:06)
Now, if you look at some major projects in our country the Hirakud dam projects which is
located on Mahanadi river in Odisha. We can look at the dam projects here in this Figure. If
you can see this bird's eye view of Hirakud dam project, this project is a one of the projects
what was initiated in 1956, way back close to 70 years back. Longest major earthen dam of
the world which is having closely 26 kilometers.
The biggest artificial lake in India which covers 745 km2 approximately, close to 750 km2
area of artificial lake that is what is to create for the flood management, water balance and
also nowadays this is a major source for water supply for industry and the domestic purpose.
So if you look at this project which is 70 years old projects still it is running it with a
hydropower, the irrigations.
And the project cost in 1957, it was 100 crores. In the last year I just discussed with river
project authorities, The annual return from hydropower and the water supplies is coming very
close to 100 cores for years, so that is what I have to tell you that these big projects what is
there we can look in 1956 that is 100 crores, now the annual return of this project is comingfrom water supply to industry, the domestic and the hydropowers that is what is close to
cores.
This is the lifeline for the water resources in the state of Odisha. So if you look at that, this is
what one of the major interventions we did.
(Refer Slide Time: 15:29)
Same way if you look at this Bhakra Nangal project which is the interesting projects we will
be having. The reservoir of 166 km2. It is began in 1963 and is constructed basically to
prevent the floods and provide the water for irrigations requirements and the hydropower
projects, that is what if you look at that how basic features, the power generation part as well
as this is the projects part.
If you look at that what I have to say that there are the projects existing in our countries and
that is the interventions we have done for the rivers.
(Refer Slide Time: 16:13)Same way if you look at very interesting project which is the Farakka Barrage project.
That is the bridge connecting between northeast and the West Bengal. So, this bridge is there
and four lane bridge with a barrage structures is known as Farakka Barrage. If you look at the
major objective of this barrage is, to divert around 800 cumecs of the waters from Ganga to
Hooghly rivers which was a dying river before this project’s implementation.
Before the implementations of the diversions projects, the Hooghly river which was earlier
known as the Ganga river, many of the people also believe that is a part of the ganga systems.
Hooghly river is regenerated by this Farakka Barrage project, which have been providing 800
cumecs of discharge diverting from Ganga to the Hooghly river systems.
It is a quite successful projects, no doubt there are disadvantage and advantages, but because
of this projects Kolkata city is sustained today because the existence of the Hooghly river
talks about the existence of the Kolkata city. This project is implemented in 1970s and it is
really a big project helped our country to survive a dying river like Hooghly river just about
in 1975, just 50 to 60 years back.
And this is what helped us to survive the Kolkata city as well as the Hooghly river. So if you
look at that all the projects tells us a successful stories on how we managed our river systems.
(Refer Slide Time: 18:35)Same way if you look at this another interventions what we did, it is Koshi Barrage, just it is
situated at the border of India and Nepal and this barrage help us to mitigate the floods, which
was earlier is annual floods, because of that the Koshi’s was known to sorrow of Bihar. It has
been successfully managing these floods but still the issues are there to how to manage the
floods.
The barrage and the embankments are helping to reducing the floods in the Bihar where
earlier it was known as sorrow of Bihar. So if you look it that way, the 50 or 60 years back
we are supposed to a leader on river interventions, leader on the knowledge of river, the
sediment transport, river dynamics, the sediment transport, the nutrient transport and we are
well managing with the rivers with some intervention structures.
So if you look at this Koshi barrage, the details, information on how we have done the
interventions of the major rivers in India, like Koshi barrage, the Farakka barrage, Mahanadi
Hirakud Dam project, all it says that there are certain amount of knowledge we had and we
also tried to do managing the river in different ways in having understanding about the river
systems.
It is necessary to develop knowledge pillars on river mechanics, the sediment transports and
the nutrient transport or the energy dissipation. The course is meant for that giving it to you
the glimpses.
(Refer Slide Time: 20:35)More interestingly, now you look at like national waterways. So, there is national waterway-1
which is connecting from Allahabad to Sundarbans, Haldia port, national waterway-2. We
have a national waterway-5. So if you look it like a national highways, we have a national
waterways. There are lot of issues, lot of improvement we can do to make this river navigable
and what is the advantage to have a river navigable?
You can go through the websites of Inland Waterways Authority of India which will talk
about how we should develop national waterways and how we can develop the tourist, the
river will be navigables. We can develop the tourist, we can have a goods movements and we
can think in the transport mechanisms what we presently have road network based transport
mechanisms or the railway networks.
The inland waterways also can play the major roles for us in these centuries, and thus still we
have lot of challenges to implement as a waterways of national waterways-2, 5 and other
case. So what my point is that there are a lot of opportunities for us to understand the rivers
now and try to have this the best options what is available to us.
(Refer Slide Time: 22:12)Now you look at very interesting photographs of 1893s. If you look at this cable connected
with that and person is sitting on this, holding the current meters. This is what the current
meters and the persons are collecting the data, so you can see that how much of risk the
person took to just do a survey in rivers, but today we have a much more technology-driven
river surveys.
Like if you have the river vessel survey, it can equipped with GPS, global positioning
systems to know where it is, you can have an Acoustic Doppler Current Profilers, for
measurement of 3-dimensional velocity components. You can measure the sediment
concentrations, you can measure the flow depth, you can have an Echo-Sounder, you can
have a side sonar profiler and there are the software inbuilt.
We can also look at that with the previous data of flood plains and river courses, all these
informations can integrate it and that is what you can do it with having a very good facilities
like the river survey vessels. So, we have transformed ourselves from these manual device of
velocity measurement in the river to a very advanced equipments with a survey vessels, GPS,
Acoustic Doppler Current Profiler, Echo-sounder, side sonar and river software, the many
mores.
Nowadays, the technology are coming to inbuilt, make a river surveys much simpler as
compared to earlier.
(Refer Slide Time: 24:10)I will show what we did it as a water resource fluvial group. We conducted river surveys in
these stretches, 3 locations, and if you look at the Brahmaputra rivers as the google earth
images showing it that this width itself will be more than 10 kilometers. So, that is the
reasons we cannot do a traditional survey. This width could be more than 3 kilometers.
This would could be more than 4 kilometers. Just look at the dimensions of the rivers. So if
you look at this river and if you do the survey with this type of survey vessels integrated with
advanced river surveying equipments, very interesting knowledge we get it. Just trying to
show you the velocity distributions.
(Refer Slide Time: 25:07)
If you look at the data of river survey what we have done it and this is the bed and you can
understand in the high velocity zones and low velocity zone, there are the secondary currentformations are happening. The vertical circulations are also happening. This is what the field
level of measurements. The primary velocities are varying from 0.5 to 2 m/s.
The vertical velocity is not that higher, it is cm/s and there are the vertical circulations you
can see. So if you look at today we can measure at the river levels, how these velocity
distributions are happening. Not only that you can also have a sediment concentrations
variability. If you can look at the sediment concentrations variability in the rivers in some
cases it can go as high as it is about 1500 mg/L.
And in some cases, in average conditions the sediment concentrations can be 300 to 400
mg/L. So what I am telling you that if you do a river surveys you can understand it, how the
transport mechanisms are happening, how the velocity fields are happening, the primary
velocity, the vertical velocities, secondary currents, vertical circulations all the informations
now today we can get it if you do a thorough survey in a river like Brahmaputra where we
have a lot of challenging tasks.
(Refer Slide Time: 26:56)
Same way if you look it if I replicate the river into my fluvial-hydro ecology lab. So if you
look at the river meanders with the floodplains and we can use an instrument like Acoustic
Doppler velocitymeter and with a colored dye, you can see how the turbulent structures are
happening in it, all these energy dissipations are happening in it. So this is the scaled down
model flume experiment. Now if you look at we have real field conditions, also we have the
lab conditions.
(Refer Slide Time: 27:43)The same way if you look at another lab setup which is the physical river modeling at NIT,
Rourkela. See if you look at the river meanders, and you can have these instruments to
measure it exactly how the velocity distributions are happening, how the secondary current
formations are happening. I tried to tell you that once we have the laboratory setups, we can
understand the river mechanics at the flume level.
(Refer Slide Time: 28:18)
The same way if you look the study we have done for Brahmani river, which is shown in this
photographs. The barrage and detailed river cross sections were incorporated in mathematical
modeling. With a very detailed cross sections data, and with mathematically putting this same
barrage structures here and the cross sections are this like this.
(Refer Slide Time: 28:52)If you look at that, we also got very interesting results by conducting this mathematical
models. This is what the observed velocity distributions. This is the real field conditions and
that is what mathematical model simulations. So, you can try to combine mathematical
models with the real field conditions and understand the model predictions performed with
some sort of approximation in mathematical models, which we will discuss in detail later on.
And we have the velocity measurements at the field levels as well as the mathematical
models. I just tried to show you that how the advanced tool of river models can be used to
predict how the flow behaviors are there.
(Refer Slide Time: 29:35)
Same way also we conducted the Dam Break analysis for Kopili river in Assam. If you look
at the river model setup photographs and by considering the dram breaks, we tried to lookhow the flood is propagating downstream and with help of HEC-RAS and the GIS we can
able to show these type of photographs.
(Refer Slide Time: 30:00)
This type of maps clearly indicating to the people, the planners, the flood inundation map for
dam break conditions and flood depth variations and the velocity variations. So if you look at
these figures, the flow depth variations are there with a 100 year return period flood, design
flood and dam break flood. So, you can prepare this type of flood zoning map by conducting
a mathematical modeling with detailed cross section informations.
And then if you prepare this type of the data, I think this will be really great help for planning
the flood management strategies which we generally do it. So, my point is that we can look at
this way, how efficiently data we are getting and what will happen even if there is a dam
break, 100 years flood or the design flood which can be obtained by conducting the dam
breaks artificially.
(Refer Slide Time: 31:16)So, in similar way, I can have lot of examples which I will be discussing in my lecture
thoroughly. So if you look at that part I need to design the course layouts in the 3 ways. One
is basic knowledge. Second is advanced knowledge we should have. Third is that you should
have a design practice, what is the design practice happening because we have to protect the
river bank, we have to have the planning of the floodings.
Also we have to look for the water qualities from the ecologic point of view. Looking at the
first few lectures we will discuss physical properties of the sediment where we talk about
shape of the sediment particles, size distributions, terminal fall velocity, suspended sediment
mixtures which is a basic knowledge of sediments.
Then, we will talk about hydrodynamics. Here I will go for mass conservation equations,
momentums and energy kind of equations. From 3 dimensional to 2 dimensional
approximations like Saint-Venant equations part.
So basically we will go for 3-dimensional to the 1 dimensional with a simplifications for river
models, so which is advanced knowledge and that will be discussed. The river floodwaves
which is very critical which we talk about celerity, diffusive waves, loop rating curves with
advanced knowledge on the flood waves that is what will be there.
Then we will discuss sediment transports in the rivers. So, basically we will talk about near
bed hydraulics, bed load, suspended sediment concentrations, turbulence bursting, this is a
very interesting problems, the knowledge recently last two decades what has happened, theturbulent characteristics, the sediment transport which are all advanced knowledge in this
subject, that will be discussed.
Then we have river equilibrium and river dynamics which is required for designing a stable
alluvial channels. We will be discussing regime relationship, channel stability, particle
stability, river meanderings. Same way we have a river dynamics, which is morphological
knowledge, necessary for appropriate river training work.
(Refer Slide Time: 33:53)
Not only that there are very interesting river bank stability concept. In this we will talk about
bank erosion process, river bank riprap, revetment which is a design concept, river
protections work, river flow control structures which all will be discussed for river bank
protections. River bank stabilization, mostly the design concept, the difficulties and the
designing will also be discussed.
Then we will come to river engineering where we will talk about more interestingly bridge
scour, navigations waterways and discussion on national waterways, locks and dams,
dredging. So, this is the advanced level of designing and planning for the rivers. Then we will
have the physical river models which will have a one lecture talking about the difference
between rigid bed models and mobile which is part of the design. Whenever you do any big
projects, we do mathematical model as well as we do the physical river models
We plan all these topics in 24 lectures including today’s introduction lectures.(Refer Slide Time: 35:13)
Before leaving for today, I just want to show you that whenever you try to understand the
rivers, first try to sketch a river. When you sketch a river, you will have a knowledge about
the rivers, just a preliminary sketching is what I am doing. The river if you look at the plan
form it never follows straight path.
The concept is that as it never follows a straight path. I take the cross sections at the different
points, point A and the point B. The cross sections of A because of centrifugal forces you will
have these values. If you look at that you will have a cross section shape like this, so that
means you will have, this is the outer bend and this is the inner bend.
And you will have this super elevations, you will have secondary current formations, at
section A and to A, same way if you talk about B and B you can have a simple parabolic
cross-section shape with having smaller current profiles. So here, at A-A, the centrifugal
forces is making a strong secondary currents, the same way at B-B secondary currents will be
there here but that strength will be much lesser than A-A.
So, similar way if you always sketch like this, same river if I have the floods, that means the
river and the water will be there in floodplain regions. See if I just sketch it, the cross sections
will be same way and here, there will be the vegetations in the floodplain area and here if you
have a bed materials and you have vegetations here and this is the flood levels.So if you sketch a river, you can try to understand how the river processes are happening. So,
what I am trying to say it whenever you have not understanding the river mechanics, I try to
encourage you to sketch a river. If you are sketching a river, then you can try to understand
what is happening. You just try to make it a sketching practice as a river engineering
specialist, you can do a sketching and can try to understand it how the river process is
happening.
(Refer Slide Time: 38:23)
With this, let me conclude today’s introduction class by talking these quotations which is
given by Mohandas K. Gandhi. The earth provides enough to satisfy every man's need, but
not every man's greed. That is the basic understanding we should have for a river
management concept. They are Ph.D. students who are helping for preparing these course
materials and I would thank you for them to be part of this, but with this let me conclude this
lecture. Thank you.