president - nea-jc · 5 i forgot here that this message is intended for the readers of this...

NEA-JC Newsletter Volume 6, Issue 2

2

President

Er. Dr. Netra Prakash Bhandary

Secretary

Er. Dhruba Panthi

Treasurer

Er. Ram Pd. Dhungana

Vice President

Er. Dr. Madhu Sudan Kayestha

Member

Er. Satya Narayan Sharma

Member

Er. Hari Bdr. Pahari

Member

Er. Justin Shrestha

7th Executive Committee, NEA-JC


3

Professional Relation Committee (PRC)

Er. Dr. Netra Prakash Bhandary (Coordinator)

Er. Dr. Hari Ram Parajuli (Member)

Er. Dr. Tara Nidhi Lohani (Member)

Er. Dr. Ved Prasad Kafle (Member)

Er. Dr. Vishnu Prasad Pandey (Member)

Membership Management Committee (MMC)

Er. Ram Prasad Dhungana (Coordinator)

Er. Kamal Kumar Adhikari (Member)

Er. Dr. Madhu Sudan Kayastha (Member)

Web Page Management Committee (WPMC)

Er. Dr. Madhu Sudan Kayastha (Coordiantor)

Er. Krishna Kumar Bhetwal (Member)

Er. Ram Prasad Dhungana (Member)

Publication Committee (PC)

Er. Justin Shrestha (Coordinator)

Er. Dhruba Panthi (Member)

Er. Nabaraj Shrestha (Member)

Event Management Committee (EMC)

Er. Dhruba Panthi (Coordinator)

Er. Hari Bahadur Pahari (Member)

Er. Laxmi Prasad Suwal (Member)

Er. Rishi Ram Parajuli (Member)

Er. Satya Narayan Sharma (Member)


4

President's message President's Message Dear Engineer Colleagues and Readers:

On behalf of the whole Nepalese engineers community in Japan, I extend my warm seasonal

greetings and slightly belated Nepalese new year greetings to you all.

A complete one year term of my team in the NEA-JC office is going to end on 30th this month. As a

matter of fact, I also had an opportunity to serve NEA-JC at the time of its establishment back in

2003. After almost two-three years of continuous efforts to consolidate the base of Nepal Engineers

Association in Japan, it was in my time in the Ad hoc Committee that we finally established

NEA-JC through minimum requirements of preparing the working guidelines in the form of the

center statute and forming the first executive committee through the electoral procedures. It was

also under my leadership as the Coordinator of the Ad hoc Committee that considering various

factors we proposed a one-year term for the executive committee in NEA-JC. Now, after serving

NEA-JC again and not being fully accountable to what I promised to all NEA-JC members at the

time of my electoral manifesto, I felt that the very one-year term we established in this organization

is too short to accomplish too many promises! So, here again, I would like to express my greatest

apologies for all those unaccomplished promises.

Nevertheless, I and my team in the current executive committee have somewhat been able to set a

few new trends, which we suppose will greatly contribute to the development of NEA-JC into a

more professional and a strong organization in Japan. We do also hope that the activities we have

been regularly conducting for the past 5-6 years and the activities we have recently started will be

exemplary in the whole NEA community back home as well as abroad.

We still greatly suffer from some of our engineer colleagues’ choice to stay away from NEA-JC.

The current membership strength of about 65 is still less than the available number of all Nepalese

engineers in Japan. Many of our efforts to bring the non-member engineer colleagues in this com-

munity have failed because of unscientific and unjustifiable membership issuing criteria as well as

too primitive application procedures for a new membership set by our seniors in the parent

organization. I regret that we were not able to address this problem, but I do sincerely hope that the

next executive committee will look into the possibilities of easing the membership issuing method

through some concrete discussions with the executive committee of the parent organization.

I personally feel deep in my heart that I had a great team in this executive committee. Despite the

fact, however, that each of us in the executive committee was elected unopposed, I might have

probably developed a feeling of dictatorship while implementing my agendas of development and

activities as if I was the sole winner in the election and all team members had to listen to my plans.

I no doubt have a strong sense of democratic accountability, but I regret that I missed to put into

practice while working in NEA-JC this time. So, I also apologize though this message to my

executive committee colleagues although they might not have felt what I sometimes did in my way

of working in the committee.


5

I forgot here that this message is intended for the readers of this newsletter. Publishing two

newsletters in a year has been one of the regular activities of NEA-JC so far although I personally

feel that a readership survey may be helpful to evaluate the impact and significance of publishing

this material. I hope the next to-be-formed Publication Committee will take up this work and let us

know the importance of NEA-JC newsletter in terms of its role in professionalizing NEA-JC. The

current Publication Committee led by Er. Justin Shrestha has done a wonderful job by publishing

two newsletters and one Research Digest. I believe these publications truly represent professionalism

in NEA-JC, and I hope we will soon start a truly research publication in addition to these regular

materials.

Finally, please allow me to appreciate you all through this message for the support you extended to

the executive committee and sub-committees including the Publication Committee. Your continued

support to all office bearers in NEA-JC in the days ahead will certainly lead this organization to

greater heights.

Thank you.

Netra Prakash Bhandary

President

The 7th Executive Committee

Nepal Engineers Association Japan Center (NEA-JC)

The editorial team is very pleased to publish yet another issue of NEA-JC Newsletter for this

tenure. In this issue, we have included five research articles, four of which were presented in

the “Sixth NEA-JC Symposium on Current and Future Technologies”.

The Senior’s Insight section of the present issue features Dr. Dinesh Manandhar who has been

in Japan for his studies and professional career for more than 15 years. We believe that shar-

ing of his thoughts and experiences collected in Japan in different roles will be interesting and

useful to our readers.

We have also briefly included a summary of recent NEA-JC activities with some photographs.

We hope you will enjoy going through this issue.

With best regards,

Justin Shrestha

Dhruba Panthi

Naba Raj Shrestha

Editorial


6

Activity reports

Sixth NEA-JC Symposium on Current and Future Technologies….………..………...7

Participation in 8th NESAJ Symposium on

Knowledge Sharing for the Welfare of Nepal...…………………………………………... 9

Senior's insight

Er. Dr. Dinesh Manandhar…………..………………………………………………………..10

Research papers NUMERICAL APPROACH TO ANALYZE NATURAL DAM FAILURE BY SEEPAGE FLOW

BADRI BHAKTA SHRESTHA……………………………………………………………………..13

RAINFALL INTENSITY DURATION FREQUENCY CURVES UNDER CLIMATE CHANGE SCENARIO IN URBAN KATHMANDU VALLEY BINAYA KUMAR MISHRA AND SRIKANTHA HERATH……….…………………….……. …...19

EXPERIMENTAL EVIDENCES OF HYDRODYNAMIC INSTABILITIES IN AN AXIALLY ROTATING PIPE FLOW

K.SHRESTHA, L.PARRAS, C.DEL PINO……….………….……………….…………………….. 23

DYNAMICS OF ANTHROPOGENIC PRESSURE AND HABITAT QUALITY ASSESSMENT IN A MOSAIC LANDSCAPE USING REMOTE SENSING AND GIS- A CASE STUDY OF CHITWAN VALLEY, NEPAL

PRATIVA SAH……….………….……………….……………………………..………………....27

CHARACTERISTICS OF VIBRATION AND NOISE IN RESIDENTIAL ENVIRONMENT INDUCED BY ROAD TRAFFIC AND RAILWAY

SATYA NARAYAN SHARMA……….………….……………………………..………….………32

Congratulatory messages……………………….…………………..…. 36

Contents Page No.


7

As an annual event of the Japan Center of Nepal

Engineers’ Association (NEA-JC), the Event Man-

agement Committee (EMC) successfully organized

the Sixth Symposium on Current and Future Tech-

nologies in Tokyo on December 9, 2012 (Sunday).

The symposium was attended by about three dozens

of Nepalese academics, researchers, experts and

students from various engineering, natural science

and social science disciplines.

The symposium program was divided into five dif-

ferent sessions: Opening Plenary; Invited Lecture;

Information and Communication Technologies;

Ecology and Environment; and Hydraulics, Geo-

technology and Structures. The opening plenary was

kicked off with a welcome speech by the NEA-JC

President Er. Dr. Netra Prakash Bhandary. After the

welcome speech, an inaugural speech was delivered

by the chief guest H.E. Dr. Madan Kumar Bhattarai,

the Ambassador of Nepal to Japan. Guests of the

opening plenary Er. Dr. Ved Prasad Kafle and Er.

Rajan Bhattarai delivered greeting remarks on be-

half of the Non-Resident Nepali Association

(NRNA) Japan and Nepalese Students’ Association

Japan (NESAJ), respectively. The session was con-

cluded with vote of thanks by Er. Dhruba Panthi,

Coordinator of the Organizing Committee. Er. Hari

Bahadur Pahari, an executive committee member of

NEA-JC, was the MC of the session.

In the second session of the symposium, an invited

lecture was presented by Er. Dr. Ramesh Kumar

Pokharel, a professor at Kyushu University, on tech-

nology transfer with a special example of Egypt-

Japan University of Science and Technology (E-

JUST). In his lecture, Er. Dr. Pokharel also gave a

brief account of his own research that focused on

wireless communication technologies. Er. Dr. Netra

Prakash Bhandary had served as the chair of the

session.

The third session, chaired by Er. Dr. Ved Prasad

Kafle, included two papers on information and com-

munication technologies. Er. Chandi Subedi from

SoftBank Corporation made a presentation on

BYOD (Bring Your Own Device), an emerging ap-

proach to corporate computing, whereas Er. Kumar

Simkhada from KDDI Corporation discussed the

basic procedures involved in software development

with insights on skill requirements of successful IT

professionals.

In the fourth session, Er. Dr. Binaya Kumar Mishra

from United Nations University presented his re-

search on Rainfall Intensity Duration Frequency

Curves under Climate Change Scenario with a spe-

cial case of Kathmandu Valley. The second present-

er of the session Ms. Prativa Sah from The Universi-

ty of Tokyo talked about her case study of Chitwan

valley on the dynamics of anthropogenic pressure

and habitat quality assessment using remote sensing

and GIS. The session was chaired by Er. Dr. Ramesh

Kumar Pokharel.

Three papers from different fields of civil engineer-

ing were presented in the last session which was

chaired by Er. Dr. Dinesh Manandhar. Er. Kiran

Shrestha from Saitama University presented his ex-

perimental findings for an axially rotating Hagen-

Poiseuille (fully developed laminar) pipe flow,

whereas Er. Keshab Gyawali from The University of

Tokyo discussed his ongoing research on experi-

mental reproduction of mechanical weathering in-

duced in rocks. Er. Satya Narayan Sharma from

Saitama University talked about the effects of vibra-

tion and noise in residential environment as a result

of road traffic and railway.

At the end of the symposium, NEA-JC President Er.

Dr. Bhandary presented "President's Award" to Er.

Satya Narayan Sharma who was selected as the best

presenter among students. The award was initiated

this year with an aim to encourage young engineer-

ing students and recognize their contributions to the

field of engineering. The selection for the award was

made by an evaluation committee of five senior

NEA-JC members based on several criteria such as

presentation quality, scientific content, and time

management.

Acknowledgments

The organizing committee would like to express its

sincere gratitude to the Institute of Industrial Science

(IIS), The University of Tokyo for providing the

venue for the symposium.

Sixth NEA-JC Symposium on Current and Future Technologies

The University of Tokyo, Komaba Research Campus, 4-6-1 Komaba, Meguro-ku, Tokyo

9th December 2012 (Sunday)


8

Participant's opinion Er. Dr. Binaya Kumar Mishra

" It has been an excellent forum to meet and discuss different points of view on matters relating to technology transfer and global change processes towards sustainable development of Nepal. With a title of 6th NEA-JC symposium on “Current and Future Technologies”, it had speakers and participants from different educational background. I believe that the presentations and discussions will have positive impact for better future of the country. The symposium provided participants with the rich opportunity to explore relevant issues. Participants also commented on the value of connecting education and activities. There were many other highlights of the symposium, including invaluable networking, the high-quality and in-depth sessions, the innovative good practices. Excellent suggestions were made to session topics. "

Chief guest H.E. Dr. Madan Kumar Bhattarai, the Ambassador of Nepal to Japan, delivering his inau-

gural speech

A moment during the opening plenary

Er. Dr. Netra Prakash Bhandary presenting " President's Award" to Er. Satya Narayan Sharma

for the best presentation Time for photo session:

participants taking a group photo


9

In a cordial invitation from Nepalese Students Association in Japan (NESAJ), President Dr. Netra Prakash Bhandary represented NEA-JC in the 8th NESAJ Symposium on Knowledge Sharing for the Welfare of Nepal held in Nagoya. Dr. Bhandary delivered a speech in the inaugural session of the

symposium where he also proposed to organize a joint program by both NEA-JC and NESAJ in near future. The symposium was attended by about 40 participants including Nepalese professors, researchers, students and some Japanese guests.

Par�cipa�on on 8th NESAJ Symposium on Knowledge Sharing for the Welfare

of Nepal

Nagoya

13th

January 2013

We would like to extend our heartfelt congratulations and best wishes to the newly elected Eighth Executive Committee under the leadership Er. Dr. Achyut Sapkota. We are confident that the new executive team will be able to deliver its best for moving NEA-JC ahead.

Seventh Executive Committee

Nepal Engineers� Association�Japan Center �NEA�JC�


10

Namaskar!

Welcome to NEA-JC Newsletter.

Namaskar. Dhanyabad.

How long have you been staying in Japan?

Are you with your family here?

I have been in Japan for 15 years. I am staying

with my family; wife, daughter and son.

Why did you choose Japan?

I chose Japan because of my strong R&D inter-

est in Remote Sensing, GIS and Satellite Navi-

gation during my master studies at Asian Insti-

tute of Technology (AIT), Thailand. I found

The University of Tokyo was the most suitable

university for my studies from research view-

point. After completing my Ph. D. at the Uni-

versity of Tokyo, I got deeply involved in 3D-

Mapping and Satellite Navigation fields which

led me to be in Japan till now.

Where do you work at present?

I work at the University of Tokyo (Centre for

Spatial Information Science) and at GNSS

Technologies Inc., a Japanese company. At

both places my field and nature of works are

related with Satellite Navigation Technology.

The work at the university is more research ori-

ented and the work at the company is business

oriented research.

Did you have work experience in Nepal before

coming to Japan?

Yes, I worked at Nepal Telecom for about ten

years. I worked in Network Planning and devel-

oped AM/FM-GIS System for Telecommunica-

tion Network. This was the first system among

the SAARC countries at that time (early 90s).

Would you please give us some brief idea

about the nature of your current job?

My current working field is in Satellite Naviga-

tion. GPS, GLONASS, GALILEO, QZSS, and

BEIDOU are different types of Satellite Navi-

gation Systems developed by USA, Russia, Eu-

rope, Japan and China respectively. India is also

Senior’s Insight

Dr. Dinesh Manandhar

Dr. Dinesh Manandhar obtained Bachelor’s degree in Electrical Engineering from Punjab University, Chandigarh (India) in 1988. After working for Nepal Telecommunication Corporation (now Nepal Telecom) for almost 10 years, he joined Master’s degree at Asian Institute of Technology (AIT), Thailand in 1997 and graduated from the Space Technology Application and Re-search Program in 1998. He received his PhD from the Depart-ment of Civil Engineering at the University of Tokyo in 2001 with a dissertation on “Development of Vehicle-borne Laser Mapping System (VLMS) for Acquisition of Urban 3-D Data.” Dr. Manandhar is currently affiliated with the Center for Spatial Information Science, The University of Tokyo as well as with GNSS Technologies Inc. His broad areas of research include re-mote sensing, geographic information system (GIS), global navi-gation satellite system (GPS, QZSS, Galileo, Glonass, BeiDou etc), laser mapping, and image processing. Dr. Manandhar has been awarded with Mahendra Vidya Bhushan “Ka” and “Kha”, and Tim Kendall Memorial Prize from AIT.


11

going to develop their own systems called GA-

GAN and IRNSS. These systems are widely

used in navigation, mapping, surveying, moni-

toring, tracking and so many other applications

where position data are needed.

Currently, I am involved in R&D of Japanese

Navigation Satellite System, QZSS. I am in-

volved in signal design that is compatible with

GPS and QZSS satellite signals for indoor navi-

gation to be used by mobile phones and GPS

receivers. This allows one to know the location

of a mobile phone user even when the user is

inside the building, tunnel or underground areas

regardless of availability of communication or

satellite signals. This is a revolutionary technol-

ogy to provide location information that has

great business values.

At the university, I am working for authentica-

tion of GPS and QZSS satellite signals. Please

watch the James Bond movie “Tomorrow Never

Dies” to understand about this research. The

movie is about how a false GPS signal can be

generated to change the position of target vessel

or aircrafts that leads to a conflict between Chi-

nese and British military. My current research is

how to detect such fake (spoof) GPS signals.

Would you tell us something more about the

importance/scope of your research

activity? Is it applicable in context of

Nepal?

My research field and studies are very much

applicable in the context of Nepal. My research

has two parts. One part is developing the tech-

nology itself and the other part is developing the

applications to promote the technologies for the

social benefit. Of course, Nepal itself does not

need to launch satellites but it can receive satel-

lite data and use these data for social benefits.

Such data are used in infrastructure develop-

ment, planning and management. These days,

satellite data are available at very low cost and

affordable even to non-industrialized countries

like Nepal. Satellite Navigation (for example:

GPS) related technologies are used in many

fields like security (tracking, monitoring and

navigation), Surveying, Mapping, Atmosphere

observation and so on. These systems can also

be used for Search-And-Rescue (SAR), Broad-

casting of emergency messages, Route Guidance

to tourists and so on.

Early this year (January 2013), JAXA (Japan

Aerospace Exploration Agency) has assisted

Survey Department of Nepal to establish a

QZSS base station at Nagarkot, Nepal under my

coordination. This station monitors GPS (USA),

QZSS (Japan), GLONASS (Russia) data contin-

uously and provides services for surveying,

mapping and many other applications that need

position data. In the coming days, we are plan-

ning to provide capacity-building and academic

support in Space Technology Applications

through University Consortium. We would be

very happy to be in contact with academic and

research institutes as well as government organi-

zations that are interested in Space Technology

Applications. You can contact me at

[email protected] or

[email protected] if you are interested in

this program.

Would you please share with us about your

overall impression while studying and working

in Japan?

I found that higher education in Japan is more

research oriented. A huge research budget by the

government is made available for R&D to uni-

versities and research organizations every year.

However, due to Japanese language as primary

means of communication in universities and or-

ganizations, the available source of information

will be limited unless you can read, write and

speak Japanese to business level. For example, a

common e-mail send to the students, researchers

and staffs is available only in Japanese in most

of the cases. Nevertheless, Japan does provide

an excellent opportunity for top class research

and higher studies.

Working in Japan could be a very unique experi-

ence. I found that working in Japan is quite chal-

lenging unless you are accustomed to the Japa-

nese culture. Japanese work culture is bound by

the team. You have to be “compatible” with

your co-workers and work culture. Rules and

regulations are strictly followed. Strict disci-

plines, manners and behaviors are followed dur-

ing the business meetings and discussions. A

clear boundary between private and business

affairs are maintained. For example, never use

office phone for your private calls.

mailto:[email protected]

mailto:[email protected]


12

Do you have memorable moments in your pro-

fessional career, which you would like to

share with us?

Some of the memorable moments during the

professional career are:

Completion of Ph. D. Thesis: “Development of

Vehicle-borne Laser mapping System”. This

technology has become a base for today’s com-

mercial MMS (Mobile Mapping System) using

Laser Scanner).

Serving the US-JAPAN GPS-QZSS Sub-

Working Group Technical Committee to design

new signal for Indoor Navigation compatible

with GPS/QZSS system.

How do you see the role of engineers in

Nepal’s development?

The role of engineers in Nepal’s development is

extremely important. They shall not be under-

estimated at any stage. I think the Nepalese en-

gineers can best understand the Nepalese envi-

ronment. The Nepalese engineers are able to

plan and design infrastructure projects. During

my observation of the past fifteen years abroad

and ten years in Nepal (working with foreign

expats from JICA, DANIDA, FINIDA, GTZ,

WB and ADB), I have found Nepalese engi-

neers excellent in performing their jobs and

most of the times superior to their counterparts

from other countries. However, the Nepalese

engineers do need international exposure for

real experience to keep them updated with new

technologies.

What message do you want to convey to aspir-

ing young engineers entering Japan for high-

er studies or for research career?

Japan spends huge budget for R&D and top

level research are conducted in Japan in various

engineering and science fields. If you are really

interested in new and challenging research top-

ics, Japan is the best place for you. However, as

I mentioned above, the primary language of

communication in Japan is Japanese. Although,

lectures are given in English in many universi-

ties that target foreign students, most of other

resources are available only in Japanese. This

may limit you to get most of the information

that you would like to have unless you are flu-

ent in reading Japanese. If you want to have

your career in Japan, be ready to learn Japanese.

For higher studies, I recommend you (top level

students) to give priority to English Speaking

countries.

Would you please share your ideas about the

current activities of NEA-JC? Do you have

any suggestions for improvement?

I hear about NEA-JC few times a year. One

time is during the workshop/seminar, other time

is during the request for publication lists

(research digest?) and yet another one is during

the election (including the election of NEA

mother chapter). I get more e-mail during the

election period than other activities.

I would like to recommend the followings:

Conduct workshops/seminars at least

once in every two months

Conduct such programs together with

other institutes

Publish a Journal

Refrain from politically oriented issues

(especially during the election of mother

chapter).

Request the regular members to get in-

volved in various activities of NEA-JC

This makes the members to feel their responsi-

bilities for the organization. In most of our or-

ganizations, the executive members limit the

activities within their capabilities.

Final words.

Finally, I would like to thank all the executive

teams since its establishment to till now to bring

NEA-JC to today’s form.

Thank you very much.

NEA-JC Newsletter, Volume 6, Issue 2

13

NUMERICAL APPROACH TO ANALYZE NATURAL DAM FAILURE

BY SEEPAGE FLOW

BADRI BHAKTA SHRESTHA

International Centre for Water Hazard and Risk Management (ICHARM), Public Works Research Institute

(PWRI), Minamihara 1-6, Tsukuba, Japan

Abstract: The outburst discharge from the natural dam such as landslide dam or moraine dam can cause

catastrophic flood disasters along the river valley. It is thus pressing need development of numerical approaches

to analyze such catastrophic floods and debris flows caused by natural dam failures. In this paper, a numerical

approach to analyze natural dam failure by seepage has been discussed. The seepage and slope stability models

were integrated with a flood and debris flow routing model. The results of numerical simulation were compared

with results obtained from experiments. The numerical approach described in this paper could be useful tool for

risk assessment of potential outburst floods from natural dam failure.

Keywords: Natural dam; slope stability; seepage flow; failure of dam; numerical approach

INTRODUCTION

Floods and debris flows caused by natural dam

failure such as failure of landslides or moraine dams

are frequently occurred in the mountains areas [1]. A

usual natural dam such as landslide dam is especially

likely to occur at places where a construction in the

valley floors or lower valley sides and form by

landslide or slope failure mass in the river. However,

moraine dam lakes are normally formed near glacier

terminus by moraine debris lay down directly by a

glacier or pushed up by it at the point of its greatest

progress. Moraine dams are usually located down

slope from steep crevassed glaciers and vertical rock

slopes, and located upslope from steep canyons with

easily erodible materials. The material composition

of most natural dams is a heterogeneous

accumulation of unsorted soil, rock, boulder and

other materials [2].

To fail the natural dam, trigger mechanism is

normally required such as water level rising, seepage

flow/piping, rock fall/landslides into the upstream

reservoir and earthquake [1]. However moraine dam

can be burst also due to glacier/ice fall into the lake

and melting of dead ice inside the dam. The outburst

floods from natural dam failure can cause

catastrophic disasters along the river valley with

losses of lives and damage to properties. Thus it is

necessary to investigate failure mechanism of natural

dam in order to manage hazards and risk.

In this paper, a numerical approach to analyze natural

dam failure due to seepage flow is presented. The

seepage and slope stability models were integrated

with a flood and debris flow routing model. The

results of numerical simulation were compared with

results obtained from experiments.

NUMERICAL MODELS

Seepage Flow Model

The change in pore water pressure through

unsaturated-saturated soils of the natural dam was

computed by using Richards’ equation as follows [3]:

tC

zK

zxK

xzx

1

(1)

where is the water pressure head, xK and

zK are

the hydraulic conductivity in x and z directions, C

/ is the specific moisture capacity, is the

volumetric water content of the soil, x is the

horizontal spatial coordinate, z is the vertical spatial


14

coordinate taken as positive upwards and t is the

time.

The water storage coefficient and the coefficient of

permeability are required to solve transient seepage

problem associated with a unsaturated-saturated soil

system using Eq. (1). Thus, the constitutive

relationships given by van Genuchten [4] are used to

compute the water storage coefficient and the

coefficient of permeability as follows:

01

01

1

if

ifS

m

rs

re

(2)

0

0)1(12/15.0

ifK

ifSSKK

s

mm

ees (3)

whereeS is the effective saturation,

s andr are

saturated and residual moisture content of the

sediment mix respectively, and are parameters

related with matric potential of soil and are

determined by using a curve fitting of soil-water

retention curve, sK is the saturated hydraulic

conductivity and /11m . By differentiation of

Eq. (3), the relationship of the specific moisture

capacity can be described as

00

0)()()(1 11

if

ifm

C

rs

m

(4)

Slope Stability Model

A potential failure surface of the dam body can be

computed by equating the resisting forces and driving

forces applied along the failure surface. The factor of

safety sF for slip surface is defined by using the

simplified Janbu’s method as follows [3]:

i

i

sT

RF (i = 1, 2, 3, 4, ……..n) (5)

whereiR is the total normal force in each slice and

iT

is the mobilized shear force in each slice. These

forces can be expressed as follows:

sii

iiiiiii

F

luWclR

/tantan1cos

tancoscos2

(6)

iii WT tan (7)

in which c is the cohesion of the material of the dam

body, il is the length of the base of each slice,

i is

the slope of the bottom of each slice, iW is the

weight of each slice including surface water, iu is

the average pore water pressure on the bottom of

each slice and is the effective angle of internal

friction.

Figure 1 Experimental flume setup.

Figure 2 Particle size distribution curves of sediment

materials of the dam body.

Figure 3 Position of 1 to 9 WCRs in the dam body.

Fig. 9 Experimental flume setup

40

18

30 30

500254

50

65

180 VC-1

VC-2

PC

40

18

30 30

500254

50

65

180 VC-1

VC-2

PC

Servo type

water gauge

Load cell

Discharge

collection Sediment

collection

(All units in cm)

0

20

40

60

80

100

0.01 0.1 1 10

Diameter (mm)

Perc

en

t F

iner

by

Weig

ht

(%)

.

Sediment mix 1-6

Sediment mix 1-7

Fig. 24 Position of 1 to 9 WCRs in the dam body

All dimensions in cm

8 8 99

3 55

5

1

2

3

4

5

6

7

89

15

Figure 4 Comparison of the simulated and experimental moisture content profile, sediment mix 1-6 case.

EXPERIMENTAL ANALYSIS

The failure mechanism of natural dam due to seepage

flow was investigated through the flume experiments.

A 500cm long, 30cm wide and 50cm deep flume was

used for the experiments. The horizontal length of

upstream end of the lake reservoir from the axis of

dam crest is 254cm and the length of downstream

end of the flume from the axis of dam crest is 70cm

as shown in Fig. 1. A dam body was made by silica

sand (Sediment mix 1-6 and Sediment mix 1-7). The

sediment material of sediment mix 1-6 was prepared

by mixing uniformly distributed silica sand S1, S2,

S3, S4, S5 and S6 in equal proportion and sediment

mix 1-7 was prepared by mixing silica sand S1, S2,

S3, S4, S5, S6 and S7 in equal proportion. Fig 2

shows the particle size distribution curve of the

sediment materials. The mean diameter (md ) of

sediment mixes 1-6 and 1-7 are 1.4mm and 1.04mm,

respectively. The maximum particle size (maxd ) and

sediment density ( ) of both sediment mixes 1-6 and

1-7 are 4.75mm and 2.65g/cm3, respectively.

The lake/reservoir water was filled by supplying a

constant water discharge from the upstream end of

the lake. The lake water was filled up to about 16cm

in depth by supplying constant water discharge from

the upstream end of the lake. The moisture

movement in the dam body was measured by using

the Water Content Reflectometers (WCRs) (Figure 3).

RESULTS AND DISCUSSIONS

The simulated results of seepage analysis were

compared with the experimental results. The

moisture movement in the dam body was measured

by using 9 WCRs in different location as shown in

Figure 3. The parameters of numerical analysis are as

follows; the grid sizes cmdx 1 and cmdz 5.0 and

time interval sec004.0dt . The values of the soil

parameters of the constitutive relationships of van

Genuchten ( =6.3, 1.3 and =4.0, 3.2 for

sediment mixes 1-6 and 1-7) were determined by

using a curve fitting of soil-water retention curve of

the both sediment mixes. The measured values

sec/0005.0 mKs and 312.0s for sediment mix

1-6 and sec/00025.0 mKs and 296.0s for

sediment mix 1-7 were used. The equations of a

seepage flow model

Fig. 25 Comparison of the simulated and experimental moisture content profile, Case-VII

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tio

n (

%)

.

Exp (WCR-1)

Sim (WCR-1)

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tion (

%)

.

Exp (WCR-3)

Sim (WCR-3)

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tio

n (

%)

.

Exp (WCR-5)

Sim (WCR-5)

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tio

n (

%)

.

Exp (WCR-7)

Sim (WCR-7)

16

Figure 5 Comparison of the simulated and experimental moisture content profile, sediment mix 1-7 case.

Figure 6 Calculated temporal variations of moisture

movement inside the dam (0m=upstream end).

were solved by Line Successive Over Relaxation

(LSOR) scheme with an implicit iterative finite

difference schemes as used by Freeze [5,6]. The

simulated and experimental results of moisture

profile in the dam are shown in Figures 4 and 5. The

simulated results are agreeable with the experimental

results. The moisture movement in the dam body is

due to the depth of the lake water in the upstream.

The relationships of water storage coefficient and the

coefficient of permeability are very important to

compute the moisture movement in the unsaturated

region. The moisture movement in the earth soil

strongly depends on the saturated hydraulic

conductivity. Figure 6 shows the calculated temporal

variations of moisture movement in the dam.

Figure 7 shows the failure surfaces of natural dam

due to seepage flow in the experiments. Figures 8

and 9 show the comparison of the simulated and

experimental slip surface of natural dam failure due

to seepage. In case of sediment mix 1-6, the

simulated result of slip surface is very good

agreement with the experimental result. However in

case of sediment mix 1-7, there is some variation in

the simulated result with compared to the

experimental result, which may be due to the effect

of suction in the soil strength that is not considered in

the slope stability analysis and other factors. In

overall, the simulated slip surface of the natural dam

failure is fairly agreeable with the experimental slip

surface.

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tio

n (

%)

.

Exp (WCR-3)

Sim (WCR-3)

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tion (

%)

.

Exp (WCR-4)

Sim (WCR-4)

0

20

40

60

80

100

0 200 400 600

Time (sec)

Deg

ree

of

Sat

ura

tion (

%)

.

Exp (WCR-6)

Sim (WCR-6)

0

20

40

60

80

100

0 200 400 600Time (sec)

Deg

ree

of

Sat

ura

tio

n (

%)

.

Exp (WCR-8)

Sim (WCR-8)

Fig. 27 Comparison of the simulated and experimental moisture content profile, Case-VIII

50sec

125sec

100sec

150sec

175sec

50sec

125sec

100sec

150sec

175sec


17

Figure 7 Failure surfaces of natural dam due to

seepage flow.

Figure 8 Slip surface of dam failure due to seepage,

Sediment mix 1-6.

Figure 9 Slip surface of dam failure due to seepage,

Sediment mix 1-7.

CONCLUSIONS

The numerical approach to analyze natural dam

failure by seepage has been presented. The seepage

and slope stability models were integrated with a

flood and debris flow routing model. The calculated

results of moisture movement inside the dam and

failure surfaces of the dam were agreeable with

results obtained from experiments. The moisture

movement in the dam body strongly effects on the

stability of the dam by decreasing the shear strength

of the sediment mixture of the dam body. The

numerical approach described in this paper could be

useful tool for risk assessment of potential outburst

floods from natural dam.

REFERENCES

[1] Shrestha, B. B., Nakagawa, H., Kawaike, K.,

Baba, Y., and Zhang, H., Glacial hazards in the

Rolwaling valley of Nepal and numerical approach to

predict potential outburst flood from glacial lake,

Landslides, Springer publication, 2012. DOI

10.1007/s10346-012-0327-7

[2] Costa, J. E. and Schuster, R. L., The formation

and failure of natural dams, Geological Society of

America Bulletin 100:1054-1068, 1988.

[3] Shrestha, B. B., Nakagawa, H., Kawaike, K.,

Baba, Y., and Zhang, H., Glacial lake outburst due to

moraine dam failure by seepage and overtopping

with impact of climate change, Annuals of Disaster

Prevention Research Institute, Kyoto University, No.

53 B, pp.569-582, 2010.

[4] van Genuchten, M. T., A closed-form equation

for predicting the hydraulic conductivity of

unsaturated soils, Soil Science Society of America

Journal, Vol. 44, pp.892-898, 1980.

[5] Freeze, R. A., Influence of the unsaturated flow

domain on seepage through earth dams, Water

Resources Research, Vol. 7, pp.929-941, 1971.

[6] Freeze, R. A., Mathematical models of hillslope

hydrology, In M. J. Kirkby, (ed), Hillslope

Hydrology, John Wiley, pp.177-225, 1978.

AUTHOR’S PROFILE

Name: Badri Bhakta Shrestha

Affiliation: ICHARM, PWRI

Correspondence address:

1-6, Minamihara, Tsukuba-shi, Ibaraki-ken,

305-8516, Japan

Fig. 20 Moraine dam failure due to seepage and critical

failure surface, upstream water depth is about 16cm

Failure surface

(a) Case-VII, Sediment mix 1-6

(b) Case-VIII, Sediment mix 1-7

Failure surface

Fig. 26 Slip surface of moraine dam failure due to seepage, Sediment mix 1-6, Case VII

0

5

10

15

20

01020304050607080

Distance (cm)

Ele

vatio

n (c

m) .

Sim failure surface

Exp failure surface

Fig. 28 Slip surface of moraine dam failure due to seepage, Sediment mix 1-7, Case VIII

0

5

10

15

20

01020304050607080

Distance (cm)

Ele

vatio

n (c

m) .

Sim failure surface

Exp failure surface


18

Education background:

PhD (Engineering) (2009), Kyoto University, Japan.

M. Sc. in Water Resources Engineering (2004),

Institute of Engineering, Tribhuvan University, Nepal.

B. E. in Civil Engineering (2001), Institute of

Engineering, Tribhuvan University, Nepal.

Selected publications:

1. Shrestha, B. B., Nakagawa, H., Kawaike, K.,

Baba, Y. and Zhang, H.: Prediction of potential

outburst floods from glacial lake due to moraine

dam failure, Floods: from Risk to Opportunity,

IAHS Red book Series, IAHS publication, Vol.

57, pp.241-252, 2013.

2. Shrestha B. B., Nakagawa, H., Kawaike, K.,

Baba, Y., and Zhang, H., Glacial hazards in the

Rolwaling valley of Nepal and numerical

approach to predict potential outburst flood from

glacial lake, Landslides, Springer publication,

2012. DOI 10.1007/s10346-012-0327-7

3. Shrestha B. B., Nakagawa, H., Kawaike, K.,

Baba, Y., and Zhang, H., Driftwood deposition

from debris flows at slit-check dams and fans,

Natural Hazards, Springer publication,

61(2):577-602, 2012. DOI 10.1007/s11069-011-

9939-9

Professional affiliations:

- Nepal Engineers’ Association (NEA)

- Nepal Engineering Council (NEC)

- Japan Society of Civil Engineers (JSCE)


19

RAINFALL INTENSITY DURATION FREQUENCY CURVES UNDER CLIMATE CHANGE SCENARIO IN URBAN KATHMANDU VALLEY

BINAYA KUMAR MISHRA1 AND SRIKANTHA HERATH

2

1Research Associate, United Nations University, Tokyo, Japan

2Senior Academic Programme Officer, United Nations University, Tokyo, Japan

Abstract: Rainfall intensity duration frequency (IDF) curves, which provide information on maximum likely

rainfall intensities for different durations and return periods, are important in design of urban stormwater

management infrastructures such as flood detention reservoirs, sewer systems etc. One of the basic assumptions

in preparation of rainfall IDF curves is that historic extremes will characterize the extremes of future rainfall.

However, this stationary assumption is not valid under changing climate which is expected to increase

magnitude and frequency for extreme rainfall events. Objective of this study is to assess the change in rainfall

IDF curves under climate change scenario in urban Kathmandu valley, Nepal. The study area was found to have

very few sub-daily rainfall data, and hence a simple scaling theory was applied for deriving the sub-daily rainfall

intensities from daily rainfall data. The scaling behavior of observation rainfall intensities was examined and it

was revealed that the statistical properties of observation rainfall follow the assumption of simple scaling. The

research employed 20-km daily global climate model (GCM) rainfall output of Meteorological Research Institute

(MRI), Japan for investigating the climate change impact. Using regionalized quantile-quantile bias-corrected

annual maximum rainfall data of 1979-2003 and 2075-2099 periods as present and future climate respectively,

potential climate change impacts on rainfall IDF curves were assessed. A total of six different durations (1, 2, 3,

6, 12 and 24-hrs) for return periods of 2, 5, 10, 25, 50 and 100 years were analyzed for preparing the IDF curves.

Comparison of IDF curves for present and future climate indicated a significant increase in maximum rainfall

intensities which has major implications on planning and design of urban stormwater drainage systems.

Keywords: Bias correction; climate change; rainfall IDF curves; simple scaling.

INTRODUCTION

Rainfall intensity duration frequency (IDF) curves,

which provides an estimate of rainfall intensities for

different durations and return periods, are important

in design of urban stormwater management

infrastructures such as flood detention reservoirs,

sewer systems etc. One of the basic assumptions in

preparation of rainfall IDF curves is that historic

extremes will characterize the extremes of future

rainfall. This assumption is not valid under changing

climatic scenario which will bring change in the

magnitude and frequency for extreme rainfall. Such

changes in extreme rainfall pattern point out for new

design and regulations in urban stormwater

infrastructures management. Stormwater

management has been a major problem in urban

areas including Kathmandu metropolitan. Several

households in Kathmandu get flooded due to

inadequate drainage as storm water no longer drains

away as it used to and the technical systems put in

place are not sufficiently flexible to deal with a

changing climate (IIED report, 2009).

In this study, an assessment of climate change impact

on rainfall IDF curves in urban Kathmandu valley,

Nepal has been made. Kathmandu valley is situated

inside Bagmati river system. The valley has a

centripetal drainage system. The climate of the valley

is subtropical to monsoon with hot and wet summer

and cold and fairly dry winter. About 80% of the

total annual rainfall occurs during the months of June

to September. Average annual rainfall in the basin is

1650 mm. The assessment of climate change impact

on rainfall IDF curves includes these major steps: (i)

bias correction of global climate model (GCM)

rainfall projections for current and future climate

period; (ii) derivation of rainfall IDF relationships for

short-duration rainfall from daily rainfall data; and

(iii) comparative analysis for rainfall IDF curves.


20

Climate projections are widely used to assess likely

changes in rainfall pattern in future. Global climate

models (GCM) are currently the most credible tools

available for simulating the response of the global

climate system to increasing greenhouse gas

concentrations, and provide climatic variables such

as temperature, rainfall etc. These projections are

available for current and future climate. A very high

resolution global climate model (GCM) rainfall

projections of Meteorological Research Institute

(MRI), Japan has been employed for assessing the

climate change impact. Because of flaws in model

structure and coarse resolution input, GCM outputs

are found to have large biases when compared with

observation data. Therefore, direct use of GCM

precipitation outputs may not suitable for the climate

change impact assessment at basin level.

Bias correction techniques reduce error in GCM

outputs with added emphasis on statistical

characteristics of observation data. Rescaling is the

easiest bias-correction technique to rectify the

systematic error in the mean rainfall amount. Leander

and Buishand (2007) applied a power law

transformation to correct coefficient of variation and

mean of the rainfall values. Recently, quantile-

quantile bias correction technique is popular for

correcting biases in GCM rainfall. In this study,

correction of GCM rainfall data is based on

regionalized quantile-quantile bias correction

technique (Mishra et al. 2011).

Establishment of IDF relationships goes back to the

1930’s. Sub-daily rainfall data of longer periods,

which is important for preparing rainfall IDF curves,

is rarely available at most of the stations in many

countries including Nepal. Because daily rainfall data

is the most accessible and abundant source of rainfall

information, it is natural to develop and apply

methods to derive the IDF characteristics for short

durations events from the daily rainfall statistics. Use

of scaling properties for deriving IDF characteristics

of sub-daily rainfall from daily rainfall is largely

popular. Menabde (1999) applied simple scaling

theory to describe rainfall IDF in Australia and South

Africa. It was shown that the cumulative distribution

function for the annual maximum rainfall had a

simple scaling property over the range of 30 min to

24 hours and in some instances to 48 hours. Nhat et

al. (2006) derived rainfall IDF relationships for short-

duration rainfall from daily rainfall in Yodo river

basin, Japan. Bara et al. (2009) applied the simple

scaling theory to the intensity-duration-frequency

(IDF) characteristics of short duration rainfall in

Slovakia. In this study, scaling properties of extreme

rainfall are examined at Kathmandu airport in order

to establish scaling behavior of statistical moments.

Accordingly, rainfall IDF curves were prepared for a

period of 1979-2003 and 2075-2099 as current and

future climates respectively. Comparison of these

IDF curves provides information on changes in

extreme rainfall events in future which are

particularly important to the design, operation and

maintenance of municipal water management

infrastructure.

BIAS CORRECTION

Body text Daily observation rainfall data were

compared with corresponding GCM grid cell data for

identifying the bias pattern. Comparison of daily

rainfall series pointed significantly smaller peaks for

GCM data. GCM rainfall data were also found to

have significantly more wet days than that of

observation rainfall. It was also found that monsoon

months (June to September) had nearly all wet days

for GCM rainfall which is different than reality.

Other months were found to have 15 or more number

of wet days. However, in reality other months are

mostly dry. Mean monthly rainfall amount was more

or less similar for GCM and observation data series;

however rainfall intensity was significantly

underestimated in the GCM data series because of

too many wet days. In other words, GCM rainfall

consists of biases in rainfall frequency and intensity.

Rainfall frequency correction

Bias in number of wet days was corrected by

determining a threshold value such that GCM wet

days matches to observation wet days. In this study,

threshold value was obtained by linking the GCM

rainfall to non-exceedance probability of zero

observation rainfall value. Two-parameter gamma

distribution was fitted to both GCM and observation

rainfall values. Probability of non-exceedance for

zero GCM rainfall is significantly smaller than that

of historical data series. The GCM rainfall values

below threshold value were changed to zero i.e. dry

days. This enabled approximately similar number of

wet days in GCM and observation rainfall data series

(Figure 1).

Rainfall intensity correction

In no bias situation for present climate, the

distribution parameter values are expected to be

similar for observation and corresponding GCM

rainfall datasets. Considering this viewpoint, GCM

rainfall above threshold value is corrected by taking

inverse of GCM CDF with observation distribution

parameters (Figure 2). In relation to correction of

future GCM rainfall data series, a scaling factor is

derived for each of the quantile. The scaling factor is

ratio of inverse of CDF of future GCM rainfall to the

observation and present GCM rainfall datasets.


21

Figure 1: Comparison of wet days

Figure 2: Comparison of rainfall intensities

DERIVING SUB-DAILY RAINFALL

INTENSITIES

Scaling properties of extreme rainfall are examined

to establish scaling behaviour of statistical moments

over different durations. Such scaling or scale-

invariant models enable to scale data from one

temporal resolution to another, and thus help to

overcome the lack of extreme rainfall data of sub-

daily durations. Based on empirical evidence, it is

assumed and verified that random variable Id and ID

as annual maximum rainfall intensities over time

duration d and D respectively can have the following

scaling property (Menabde et al., 1999):

(1)

In equation 1, the equality refers to identical

probability distribution for both variables and η

represents the scaling exponent. In order to determine

if the data follows simple scaling or multi-scaling,

slopes K(q) of moment versus duration lines was

plotted against the moment order q. Figure 3 shows

linear dependence, thereby confirming about simple

scaling. Hence, simple scaling can be assumed for

estimation sub-daily rainfall intensity duration

frequency curves in urban Kathmandu valley. Scale

factor is estimated by slope of the regression line as

0.6761.

Figure 3: Simple scaling at Kathmandu airport

Applying scaling theory, IDF relationship with i as

rainfall intensity, T as return period and d as duration

of extreme event can be expressed in the following

form (equation 2):

(2)

where μ=μDDη and σ=σDD

η. Assuming Gumbel

distribution as suitable candidate, the following

simple rainfall IDF can be derived (equation 3):

(

)

(3)

Equation 3 enabled generation of rainfall IDF curves

for present and future climate over Kathmandu value

by smoothing maximum rainfall intensities over d =

1, 2, 3, 6, 12 and 24 hours. Figure 4 & 5 show

rainfall IDF curves estimated for 2-, 5-, 10-, 25-, 50-

and 100-years return periods. An important

observation is made by visual inspection for all

return periods, for all durations that rainfall

intensities are significantly greater for future climate

than present climate. Numerical analysis pointed out

that there will be an average increase of 18.9%

ranging from 10.9% to 22.2% in extreme rainfall

intensities. These observations have major

implications for the design, operation and

maintenance of storm water infrastructures in urban

Kathmandu valley.

Figure 4: Rainfall IDF curves for present climate


22

Figure 5: Rainfall IDF curves for future climate

CONCLUSIONS

Potential impact of climate change on rainfall

extremes have been studied by analysing rainfall IDF

curves for present and future climate at urban

Kathmandu valley, Nepal. The assessment has been

made by using 20-km daily MRI-GCM rainfall

projections over the Kathmandu valley. Regionalized

quantile-quantile bias correction successfully reduced

any significant biases in the MRI-GCM rainfall

projections. The properties of the time scale

invariance of selected rainfall quantiles were

investigated at Kathmandu airport. It has been

shown that the rainfall at Kathmandu airport follow

assumption simple scaling properties. Accordingly,

following the revision of Menabde et al. (1999), it

was possible to derive the rainfall IDF curves for

shorter durations from daily rainfall intensities.

Results of this study are of significant practical

importance for design, operation and maintenance of

storm water management infrastructures under

changing climate scenario.

REFERENCES

[1] Bara, M., Kohnova, S., Gaal, L., Szolgay, J. and

Hlavcoval, K., 2009. Estimation of IDF curves of

extreme rainfall by simple scaling in Slovakia,

Geophysics and Geodesy, 39(3), 187-206.

[2] IIED report, 2009. Climate change and the urban

poor: Risk and resilience in 15 of the world's most

vulnerable cities

(http://pubs.iied.org/pdfs/G02597.pdf).

[3] Kusunoki, S., Yoshimura, J., Yoshimura, H.,

Mizuta, R., Oouchi, K. and Noda A., 2008. Global

warming projection by an atmospheric global model

with 20-km grid, Journal of Disaster Research, 3(1),

4-14.

[4] Menabde M., Seed A. and Pegram G., 1999. A

simple scaling model for extreme rainfall, Water

Resour. Res., 35, 1, 335–339.

[5] Mishra, B.K. and Herath S., 2011. Climate

Projections Downscaling and Impact Assessment on

Precipitation over Upper Bagmati River basin, Nepal,

Proceedings of 3rd International Conference on

Addressing Climate Change for Sustainable

Development through Up-Scaling Renewable Energy

Technologies, 275-

281(http://cecar.unu.edu/groups/cecarweb/blog/?tag=

research+article).

[4] Nhat L. M., Tachikawa Y., Sayama T. and Takara

K., 2007. Regional rainfall intensity duration-

frequency relationships for ungauged catchments

based on scaling properties, Annuals of Disas. Prev.

Res. Inst., Kyoto Univ., 50B, 33-43.

AUTHOR’S PROFILE

Name: Binaya Kumar Mishra

Affiliation: Research Associate, Institute for

Sustainability and Peace, United Nations University,

Tokyo, Japan

Correspondence address: 53-70, Jingumae 5-chome,

Shibya, Tokyo 150-8925; Email: [email protected]

Education background: M.Sc. (Water Resources

Engineering), Ph.D. (Engineering)


1. Mishra, B.K. and Herath, S. (2011): Climate

Projections Downscaling and Impact Assessment

on Precipitation over Upper Bagmati River

basin, Nepal, Proceedings of 3rd International

Conference on Addressing Climate Change for

Sustainable Development through Up-Scaling

Renewable Energy Technologies, Kathmandu,

pp. 275-281.

2. Mishra, B.K., Takara, K., Yosuke Yamashiki

and Tachikawa, Y. (2010): An assessment of

predictive accuracy for two regional flood-

frequency estimation methods, Annual Journal

of Hydraulic Engineering, JSCE, vol. 54, 7-12.

3. Mishra, B.K. and Takara, K. (2009):

Implementation of folk-song program in flood

disaster awareness raising, Proceedings of the

International Conference on Hydrology and

Disaster Management in conjugation with 17th

regional steering committee for Southeast Asia

and the Pacific, UNESCO-IHP, Jakarta, pp. 101-

106.

Professional affiliations: Japanese Society of Civil Engineers (200600494

‘General’)

Nepal Engineering Council (1705 ‘Civil’)

Nepal Engineers’ Association (4366 ‘Life

member’)

The Institution of Engineers (India)

(A/524224/0)

http://cecar.unu.edu/groups/cecarweb/blog/?tag=research+article

http://cecar.unu.edu/groups/cecarweb/blog/?tag=research+article


23

EXPERIMENTAL EVIDENCES OF HYDRODYNAMIC INSTABILITIES

IN AN AXIALLY ROTATING PIPE FLOW

K.SHRESTHA1, L.PARRAS

2, C.DEL PINO

2

1Graduate School of Science and Engineering, Saitama University, 255, Shimo-Okubo, Sakura, Saitama 338-

8570, Japan 2 Fluid Mechanics, Universidad de Malaga, E.T.S. Ingenieria Industrial, Campus de Teatinos, 29071, Malaga,

Spain

Abstract: This paper describes an experimental study of flow instabilities in a pipe with a rotating Hagen-

Poiseuille flow (RHPF) by means of flow visualizations. Good agreement is found in a Reynolds number –Swirl

parameter (Re-L) plane, between the experimental values and the theoretical predictions for the onset of

convective hydrodynamic instabilities. As the Reynolds number or the swirl parameter were increased, the

transition from convective to absolute instabilities appeared, and one could observe a clear change in the flow

structure in the inlet region. Though absolute instabilities were related to negative axial velocities, we provide

here the experimental evidence on an onset of absolute instabilities in a pipe flow with the positive flow rate.

Keywords: Rotating Hagen-Poiseuille flow, Convective, absolute instabilities.

INTRODUCTION

Swirling flows are significant in many engineering

applications (combustion process, particle

transportation, etc.). In addition, there is some

problem within a certain piping facility where the

rotation is not introduced. This is the case of

nuclear and hydraulic power plants. For example,

there are cooling systems in nuclear plants which

are designed by Japanese companies using a main

pipe (bigger diameter) suppling water to several

pipes (smaller diameter). This system can be

considered as a sudden contraction. Though the

pipes are not rotating, a non-desired swirl could

appear due to the geometry. This case is briefly

described in Sanmiguel-Rojas & Fernandez-Feria,

2006 [3]. Due to high demand within the power

plant, sometimes it is required to supply high flow

rate. This high flow supplied in a sudden

contraction could promote the appearance of

fluctuations in the flow rate and it reached the

absolute unstable condition [2] & [4]. These

fluctuations are dangerous for the system because

they can introduce periodic changes in the power

supplied by the main reactor. On the other hand,

Pelton turbines with several jets are another

example of this sudden contraction. The spiral

camera must be well designed in order to avoid the

induced swirl in the jets.The small changes in the

jets even produce an unbalanced axial coupled

within the electric generator.

There are more theoretical details, fundamental

aspects, as well as practical applications in

Shrestha et al. 2012[5].

EXPERIMENTAL SETUP

We used the experimental setup depicted in figure

1, which allows us to obtain the base RHPF in a

horizontal pipe. The main parts were a head tank, a

condition chamber, where a diffuser and a

honeycomb were placed to reduce any disturbance

effect in the pipe inlet, a pipe, a DC motor and a

storage tank. A transparent perspex pipe was used

for proper visualization and was recorded by a

digital video camera (30 frames per second). A

small quantity of Mearlmaid AA was added to tap

water in the storage tank. These particles (flakes)

can highlight the flow pattern when a light sheet

strikes vertically onto the pipe. This allows flow

visualization. Videos were taken on a (r, x)-plane.


24

Figure 1. Sketch of the experimental setup

The Reynolds number is defined as Re = U.D/ ν ,

where U is the mean velocity, ν is the kinematic

viscosity and D is the diameter of pipe. On the

other hand, the swirl parameter is, L =Ω.D/(4.U) ,

being Ω the angular velocity. Several series of

experiments corresponding to Reynolds numbers

ranging from 50 to 450 have been performed and

the swirl parameters have been varied between 0

and 4. The pipe length was long enough to

achieve RHPF for the values of the control

parameters (Re and L ). [1], reported that the

minimum non-dimensional pipe length, L/R=0.

113Re, for achieving fully developed RHPF,

starting with a uniform flow. In our case, the

length and diameter of pipe were selected to

achieve the flow completely parabolic near by

the inlet region .

RESULTS AND DISCUSSION

Typical flow visualizations in two locations

along the pipe, one in the inlet region and the

other one in the downstream region were

performed. Qualitative and quantitative analyses

of flow visualizations for different values of Re

and L, allowed us to obtain the critical values of

Re and L for the onset of both convective and

absolute instabilities, as well as their

corresponding critical frequencies and wave

numbers (see Shrestha, K. et al for more details

of the comparison between the theoretical and the

experimental frequencies and the wavelengths).

Due to the configuration of the experimental

setup, the fluid entered the pipe without swirl,

which developed along the inlet region. Thus,

this first window always corresponds to this

entrance length where the RHPF is not fully

established, while the second is related, in all the

cases reported here, to the fully developed RHPF.

Figure 2. Flow visualization at inlet [a, b, c] and

downstream regions [d,e,f].

Figures 2 (a) and 2 (d) show the flow

visualization for a stable case, where one can

observe the rotating boundary layer development

region with an axisymmetric conical shape

(ACS) in the inlet region (a), and the downstream

region (d). As the Reynolds or the swirl

parameter were smoothly increased, new final

states were reached, so the frames highlighted

sinusoidal shapes in the downstream region (e)

which represent convective travelling waves. In

this case, one can observe the same ACS

structure of figure 2(a). However, the change

from 2(d) to 2(e) allow us the cut off criterion for

the onset of convective instabilities. When both

the Reynolds number and the swirl parameter

were increased, the perturbation downstream

affects the entire pipe and the cone in the inlet

[ACS, figure 2 (a)] is broken to a Steady Wavy

Cone (SWC), as it is shown in figure 2 (b),

though no changes are observed downstream

[figure 2 (e) and figure 2 (f)]. Therefore, the

transition from 2 (a) to 2 (b) allow us the cut off

criterion for the onset of absolute instabilities. As

one increased the swirl parameter, the SWC

changed to a Non steady wavy cone [figure 2 (c)].

RESULTS FOR THE INLET REGION

The analysis of the videos taken in the inlet

region of the rotating pipe is analyzed and two

different neutral curves were determined as

shown in figures 3. In the figure, the triangle

symbols represent the stable flow [ACS, figure 2

(a)], the green square symbols correspond to the

steady wavy cone [SWC, figure 2 (b)], and

diamonds are related to non steady wavy cones

[NSWC, figure 2 (c)]. The dashed and solid lines

in figure 3 represent the theoretical curve of R.

Fernandez-Feria and C. del Pino, 2002 for

convective and absolute instabilities, respectively.


25

Figure 3. Neutral curve in the (L, Re)-plane

RESULTS FOR THE DOWNSTREAM REGION

The experimental results show the different unstable

modes that exist when a solid body rotation is

superimposed into a Hagen-Poiseuille flow (HPF).

The experimental data is depicted in figure 4 as a

function of L and Re. The circle symbol in the figure

represents the stable flow [figure 2 (d)], whereas the

diamond symbol represents the convective unstable

flow [figure 2 (e)]. The experimental and the

theoretical data are in good agreement for the onset

of convective hydrodynamic instabilities.

Figure 4. Transition plot from stable to convective

instabilities

Figure 5 shows the neutral curve for the convective

to absolute unstable transition. The diamonds and

stars correspond to the experimental results of the

convective [figure 2 (a)] and absolute [figure 2 (b)]

instabilities. The experimental results show a good

agreement between the theoretical and the

experimental data. The absolute instabilities imply

small oscillations or perturbation which completely

changes the flow pattern within the system and may

be dangerous if it is not predicted properly.

Furthermore, non-linear effects appeared in the inlet

region as the Reynolds number was increased.

Figure 5. Transition plot from convective to absolute

instabilities

CONCLUSIONS

The experimental observations related to the sudden

rotation applied to Hagen Poiseuille flow have been

reported in this study. Good agreement has been

found with the predicted critical values of the

Reynolds number and the swirl parameter for both

the transition from stable to convectively unstable

flow and for the onset of absolute instability. A wide

range of Reynolds numbers and swirl parameters

have been tested, though there was a constraint in

this experimental study related to the length of the

pipe, which limited the fully developed RHPF to

swirl numbers, L<=2 for the Reynolds numbers

considered. Further theoretical and numerical works

about the absolute instability of the whole developing

flow that take into account non-linear and non-local

effects are required in a future research work. In

addition it should be needed to obtain the velocity

field by means of Particle Image Velocimetry.

REFERENCES

[1] Christiansen, E.B. and Lemmon, H.E. 1965

Entrance region flow AIChe Journal, 11 (6) 995-999

[2] Fernandez-Feria, R. & del Pino, C. 2002 The

onset of absolute instability of rotating Hagen-

Poiseuille Flow: A spatial stability analysis. Phys. of

Fluids 14 (9), 3087-3097.

[3] Sanmiguel-Rojas, E. & Fernandez-Feria, R. 2006

Nonlinear instabilities in a vertical pipe flow

discharging from a cylindrical container. Phys. of

Fluids 18, 024101

[4] Sanmiguel-Rojas, E. & Fernandez-Feria, R. 2005

Nonlinear waves in the pressure driven flow in a

finite rotating pipe. Phys. of Fluids 17, 014104.

10-1

100

50

100

150

200

250

300

350

400

450

L

Re

Experimental data for stable flow

Experimental data for convective instability

Theoretical curve

100

0

50

100

150

200

250

300

350

400

450

L

Re

Experimental data for convective instability

Experimental data for absolute instability

Theoretical curve


26

[5] Shrestha, K., Parras, L., del Pino, C., Sanmiguel-

Rojas, E. and Fernandez-Feria, R. 'Experimental

evidence of convective and absolute instabilities in

rotating Hagen-Poiseuille flow', J. Fluid Mech.,

Volume 716 / February 2013.

AUTHOR’S PROFILE

Name: Kiran Shrestha

Affiliation: Doctoral Student, Saitama University


International House Chamber, Sakura-ku, Saitama –

shi, Saitama 645 Shimookubo, 2211


Bachelor in Civil Engineering and Master of Science

in Water Resources Engineering from Pulchowk

Campus

2008-2012 Design Engineer in Chilime Hydropower

Company Ltd.


1. Shrestha, K., Parras, L., del Pino, C., Sanmiguel-

Rojas, E. and Fernandez-Feria, R. 'Experimental

evidence of convective and absolute instabilities

in rotating Hagen-Poiseuille flow', J. Fluid Mech

Volume 716 / February 2013.


Nepal Engineering Association (NEA)

Nepal Engineering Council (NEC)


29

DYNAMICS OF ANTHROPOGENIC PRESSURE AND HABITAT

QUALITY ASSESSMENT IN A MOSAIC LANDSCAPE USING

REMOTE SENSING AND GIS- A CASE STUDY OF CHITWAN

VALLEY, NEPAL

PRATIVA SAH

Institute of Environmental Science, The University of Tokyo

Abstract: Forest is one of the richest natural resources of the world. On top of that forest also has a unique

ability to capture and store carbon, and lessen the vulnerability of people and ecosystems to climate change.

However, ever increasing anthropogenic pressure is changing the pattern of landscape and threatening the

existence of biodiversity (flora and fauna). Such pattern and process also severely degraded habitat quality.

Therefore, understanding the natural process of a landscape and embedded forest ecosystem along with the

people living in and around it is essential to devise required counter measures. Satellite based earth observation

remote sensing, which have been started since 1970s, have wealth of spatial and temporal data that can be used

to assess the change of wildlife habitat worldwide. Analyzing such data in the GIS environment can reveal

spatio-temporal change pattern of such. Furthermore, remote sensing also captures anthropogenic activities,

which can be supplemented with the demographic statistical survey of a country. After assessing such changes

and under lying anthropogenic pressure may help to devise a sustainable landscape management.

Keywords: Anthropogenic Pressure, Habitat quality, Rhinoceros, Fragmentation, Mosaic landscape, GIS and

remote sensing

INTRODUCTION

Tropical forests contribute in mitigation of global

climate in several ways, such as CO2 sequestering,

biodiversity and human well beings (Banfai &

Bowman, 2008) According to WRI (1996), from

1980 to 1990, >6% of worldwide tropical forests and

10% of Asian tropical forests were converted to

shifting cultivation. The world’s forests, especially in

the tropic, are dramatically shrinking (Apan, 1999).

Tropical forests are being destroyed despite its

ecological, social and economic importance.

Deforestation is one of the invasive ecological

changes taking place in tropical regions (Lambin,

1994).

Globally, around 13 million hectares of forests were

converted to other uses or lost through natural causes

each year between 2000 and 2010 as compared to

around 16 million hectares during the 1990s (FAO,

2011). However the increasing rate of shifting

cultivation is increasing day by day, which is

severely affecting biodiversity. On another hand,

forest fragmentation is also pushing biodiversity to

be confined, impacting significantly on the species.

Overview and land Fragmentation in Nepal

Nepal’s geophysical location makes it one of the

world’s most diverse ecological zones in terms of

forest and biodiversity (FAO, 2000). Nepal

comprised only 0.1% of land area on a global scale,

but it possesses a disproportionately rich diversity of

flora and fauna. Nepal’s share of flora is 2.8% and

fauna is 1.23% of global totals (ICIMOD, 2007). Its

physiography extends from the Terai plains with a

27


28

minimum altitude of 60m above sea level in the south,

through to the Siwalik Hills, Middle mountains and

Himalayas (up to 8848m). The Terai region is

tropical lowland and a subtropical belt of flat land. It

covers 14% of total land area of country which is

under cultivation and extends from east to west along

the southern side of country (MPFS, 1988). 29% of

Nepal's land area is covered with forest and 23.23%

is under protected areas where around 9.6% of

Nepal's forest covers are estimated as relatively intact

primary forest (DNPWC, 2010). The total population

is estimated to 26 million, increasing from 23 million

(census 2011). Nepal has some 1,240 known species

of amphibians, birds, mammals,

Figure 1: Study Area, Chitwan

and reptiles, according to figures from the World

Conservation Monitoring Centre. Of these, 2.9

percent are endemic, meaning they exist in no other

country, and 5.6 percent are threatened. Nepal is

home to at least 6,973 species of vascular plants, of

which 4.5 percent are endemic. Officially, 7.6

percent of Nepal is protected under IUCN categories

I-V (BPP, 1995; HMGN/MFSC, 2002).

About 75% of households and 90% of rural

households rely on wood products for domestic

purposes for their daily basic needs of timber, fodder,

grasses, litter and traditional herbal medicines mainly

from forests (Hobley, 1996). According to FAO

(2011), the rate of deforestation decreased in 2000-

2010 by 0.7%, whilst previously (1999-2000) the rate

was 2.1% (92 ha). Despite of this decrease in

deforestation rate in past few years, is still continues

with alarming pace, and forests declining both

qualitatively and quantitatively. There are various

driver forces which causing the deforestation and

forest degradation. The main issues are legal and

illegal conversion of forest land into agriculture,

infrastructure development, unplanned use and

overexploitation of forest products, and uncontrolled

forest fire. These major contributors cause also


29

insufficiency of forest products, degrading soil

quality and accelerated soil erosion, downstream

sediments and decreased agricultural productivity

(HMG/DFRS, 1999; FAO, 2000). Thus, the aim of

this research is to present and discuss some aspects of

forest fragmentation in Chitwan valley, emphasizing

the fact that the underlying unplanned growing

activities of several human activities putting risk not

only the forest, but also on the indicator species

Rhinos.

Figure 2: Land Use and Land Cover change detection (1975-2009)

METHODOLOGY

The study was conducted in a mosaic landscape,

comprising of natural and commercial forest,

agricultural lands, protected area, and national forest

of Chitwan district, Nepal. The research

methodology has a trans- disciplinary approach with

a combination of land use and land cover (LULC)

change, socioeconomic analysis, and indicator

species analysis (Rhinoceros). Satellite imagery

analysis and Visual interpretation of Landsat images

were processed for evaluating LULC change

occurred. Anthropogenic analyses were performed by

demography trend followed by Socio-economic

Disadvantage (SED) index of socioeconomic

parameters. Rapid Rural Appraisal (RRA) was used

for household survey in five VDCs of Chitwan.

Finally, all the parameters were integrated to analysis

impact on indicator species.

RESULTS

Socio-economic Consequences

Anthropogenic reasons for deforestation and forest

degradation were observed, mainly from; population

factors, poverty, forest dependency (timber, fuel and

grazing), and LULC change (intensive agriculture).

The rapid population growth and in-migration in the

region contributing more or less risk in forest loss

and fragmentation on wildlife habitat. Similarly,

there are a numbers of inhabitants still dependent on

forests products which ultimately accounts for further

forest degradation. At the same time, agriculture

accompanied by livestock farming, brutally

encourages the deforestation in the region. However,

with the interventions of various conservations

measures; protected area, community forestry and

leasehold forestry programs and effectiveness of


30

forest polices in the recent decades has been playing

a positive role in forest management process.

Figure 3: Change detection analysis (1975-2003)

Land Use and Land Cover Changes

Three images; Earliest MSS 1975 image

(01/04/1975), middle ETM 2003 image (16/02/2003)

and final ETM 2009 image (22/10/2009) were

analyzed. Numbers of major and minor changes have

been concluded during 2009. From 1975-2003, a

heavy increment on agricultural land especially east

and west part of Barandabhar Corridor Forest (BCF).

Forests were also heavily degraded along CNP.

Furthermore, degradation of forest and conversion of

land legally or illegally for agriculture continued in

2003-2009. Even though there is heavy land

conversion, regeneration has been contributed a lot in

forest stability in some extend in the region. However,

LULC trend can be concluded as agricultural land is

increasing whereas forests were decreasing.

Figure 4: Change detection analysis (2003-2009)

Impact of anthropogenic activities on habitat

fragmentation

Loss of degradation of natural landscape especially

by human activities has given rise to reduction and

fragmentation of habitat. Fragmented land

exhilarated conflicts between wildlife and human

(Ogada et. al, 2003). Due to habitat destruction and

poaching, they are limited to few conservations areas.

Rise in rhinoceros population since 1973 which is

attributed to the proclamation of CNP along with

effective enforcement law by Nepal army (refer

figure 5). However, a noticeable drop out during

2000-2005 implies the impact of insurgency in the

Figure 5: Rhino trend and mortality rate

country security and excess of poaching (refer figure

5). With the stability of insurgency in the country,

rhinoceros trend is again in path of improvement.

This reveals the fact without enforcement of rules

and regulations, conservation of rhinoceros will be

on threat.

CONCLUSIONS

- Human dimensions such as demography,

poverty, agricultural expansion & infrastructure

development are major underlying factors for

deforestation & forest degradation.

- These triggering factors are further limiting

wildlife accessibility to habitat.

- Correlated dynamics of population growth,

LULC change & forest dependency have a great

influence on forest & wildlife.

- Demographic growth and the growing pressure

for access land, it is clear that human and

wildlife conflicts cannot be eradicated easily.

- Hence, fragmentation threat on the Chitwan

valley remains uncertain.


31

REFERENCES

[1] Apan A.A., 1999. GIS Application in Tropical

Forestry. Faculty of Engineering and Surveying,

University of Southern Queensland, Australia.

[2] Banfai D.S., Bowman M.J.S., 2008. Patterns

and Processes in Forest Landscapes. Springer

Science+ Business Media B.V

[3] CBS, 2011. Statistical Year Book of Nepal

2011. Central Bureau of Statistics, Kathmandu,

Nepal.

[4] DNPWC, 2010. Annual Report (2010/11).

Department of National Parks and Wildlife

Conservation, Ministry of Forests and Soil

Conservation, Kathmandu.

[5] FAO, 2000. Global Forest Resources

Assessment 2005(FRA 2005). Food and Agricultural

Organization of the United Nations, Rome, Italy.

[6] FAO, 2011. State of the World’s Forests. Food

and Agricultural Organization, the United Nations

(Rome).

[7] HMGN/MFSC, 2002. Nepal Biodiversity

Strategy. Government of Nepal, Ministry of Forests

and Soil Conservation, Global Environment Facility

and UNDP.132 pages.

[8] Hobley M., 1996. Participatory Forestry: The

Process of Change in India and Nepal. Overseas

Development Institute, London, UK.

[9] HMG/DFRS, 1999. Forest Resources of Nepal.

Department of Forest Research and Survey,

Kathmandu, Nepal.

[10] ICIMOD, 2007. Nepal Biodiversity Resources

Books. Protected Areas, Ramsar Sites and World

Heritage Sites,MOEST/GON.

[11] Lambin E.F., 1994. Modeling Deforestation

Process: A Review, Luxemburg. European

Commission.

[12] MPFS 1998. Master Plan for the Forestry

Sector, Nepal. His Majesty’s Government of Nepal/

Asian Development Bank/ FINNIDA.

[13] Ogada M., Wooroffe R., Frank G., 2003.

Limiting Depredation by African Carnivores: The

Role of Livestock Husbandary. Conservation

Biology, 17(6): 1521-1530.

[14] WRI, 1996. World Resources 1996-1997. The

United Nations Environment Programme, the World

Bank.

AUTHOR’S PROFILE

Name: Prativa Sah

Affiliation: Master Student, University of Tokyo


Hikonari 4-6-3-306, Misato, Saitama


2008-2009 Research Assistant, TU

2010 (Jan-Mar) Intern, IGES


32

CHARACTERISTICS OF VIBRATION AND NOISE IN RESIDENTIAL ENVIRONMENT INDUCED BY ROAD TRAFFIC AND RAILWAY

SATYA NARAYAN SHARMA Graduate School of Science and Engineering, Saitama University, 255, Shimo-Okubo, Sakura, Saitama 338-

8570, Japan

Abstract: Heavy machines or vehicles generate vibration and noise, which can be detected by the people and

can affect them in many ways such as their quality of life and working efficiency can be reduced. The

simultaneous effects of vibration and noise might lead to a total disturbance in residential environment. The main

objective of this study is to investigate the simultaneous effects of vibration and noise on subjective responses.

Measurements of building vibration induced by road traffic and railway were made by our research group at

several single-family Japanese houses. Vibration data were analyzed to understand the characteristics of

vibration and noise that occurs in real residential environments. The results show that dominant frequencies are

largely varied with location and source. Frequencies of the 10 Hz and 12.5 Hz are observed as highly dominant

in the substructure level and second floor for the vertical direction. However, the frequency of 5 Hz is found

dominant for both the substructure level and the second floor, where 6.3 Hz is found to be dominant for the

second floor for horizontal direction. The magnitude of the vertical vibration seemed to be generally higher than

that of the horizontal vibration recorded in all houses. The knowledge of the analysis result will be used to

investigate the combined effects of vibration and noise on the annoyance in residential environment.

Keywords: vibration, noise, dominant frequency, vibration magnitude, sound pressure level.

INTRODUCTION

Annoyance in residential environment due to the

combined effects of vibration and noise has been a

worldwide problem. In terms of building vibration

which may affect human occupants, vibration source

may be either external or internal. Vibrations induced

by external sources, such as road traffic and railway

may cause intolerable discomfort to humans in

residential environment. Vibrations in buildings due

to these sources are complex in nature such as

intermittent events characterizing pass-bys of road

traffic and train involve various directions,

magnitudes, frequencies, and durations of motion.

The vibration usually occurs simultaneously with

noise.

Previous studies concerned with simultaneous noise

and vibration have mainly dealt with the effect of one

stimulus on the another. Howarth and Griffin [1]

discussed the experimental results that the increase in

noise has a less effect on the annoyance rating at

higher magnitude of vibration and vice versa. Only

few studies have been concerned with the combined

effect of environmental stimuli. The combined

effects of vibration and noise on annoyance are

reported by Howarth and Griffin [2] and Paulsan and

Kastka [3]. It was reported by Howarth and Griffin

[4] that the total annoyance is the summation of the

individual effects of vibration and noise stimuli.

The objective of the present investigation is to

understand the characteristics of vibration and noise

in real residential environments so as to investigate

the subjective responses to simultaneous vibration

and noise experimentally.

METHODOLOGY

Measurements of environmental vibration and noise

were made at five single-family Japanese houses by

the side of a road and railway station. Vibrations

were measured simultaneously at the substructure

and the second floor in all three orthogonal directions.

Noises were measured at two locations that were

inside and outside of the house with the windows

closed. The duration of the measurement were over

40 minutes, which was long enough to record typical

vibration and noise induced by road traffic or railway.


33

The properties of source and house are given in Table

1.

Table: 1

House Type of

House

Source of

vibration

and noise

Location

A 2-Storey

wooden

house

Surface

railway

Near kitaurawa

B 2-Storey

wooden

house

Elevated

railway

Near

minamiyono

C 2-Storey

wooden

house

Undergro

und

railway

Along

musashino line

D 2-Storey

wooden

house

6-lane

road

traffic

Along kyu

nakasendo

E 3-Storey

wooden

house

2-lane

road

traffic

Along saitama

by-pass

Analysis results of vibration and noise presented in

this paper are based on frequency weighting (defined

as weighting characteristics of frequency). It means

some frequencies are given more weight or

importance than others. The Fourier transform was

applied to the vibration and noise records so as to

understand the frequency contents of the vibration

and noise from their spectra. For the evaluation of

vibration with respect to human responses, the

Vibration Level (VL in dB), Vibration dose value

(VDV in [ms-1.75

]) and Maximum transient vibration

value (MTVV in [ms-2

]) were calculated with the

data recorded. The Vibration Level is defined in the

Japanese Industrial standards (JIS) C 1510 [5] that

has been adopted in Japan as legal specifications for

vibration measurement and evaluation under the

vibration Regulation Law. The VL is defined as Eq.1

and Eq. 2

0

0

10log20a

taVL w

(Eq. 1)

2

1

2

0

0 0

1

t tt

ww dtetata

(Eq. 2)

where,

ao : reference acceleration, 10-5

[m/s2]

aw(t) : frequency weighted acceleration [m/s2]

τ : time constant : 0.63 sec

On the other hand, VDV and MTVV are defined in

the International standards (ISO 2631-1:1997) [6]

that have been adopted in worldwide as legal

specifications for vibration measurement and

evaluation under the vibration Regulation Law. The

VDV and MTVV are defined as Eq.3 and Eq. 4

respectively.

4

1

0

4

T

w dttaVDV (Eq. 3)

0

1max taMTVV w (Eq. 4)

2

1

2

10

10

1

0

1

t tt

ww dtetata

where,

T : duration of measurement

τ1 : time constant : 1 sec

The directions of vibration measurement defined in

the ISO 2631-1:1997 [6] are three orthogonal

directions related to structure rather than the human

body and similar to those for a seated person in Fig 1.

Fig.1: Principal basicentric axes for seated person.

RESULTS AND DISCUSSION

An example of the time history of vibration record

and its spectrum is shown in Fig. 2. The vibration

shown in Fig. 2 was recorded at the second floor in a

house. It can be seen that the vibration are of

transient nature. The dominant frequency presented

in this paper is defined as a frequency at which the

spectrum obtained by the Fourier analysis is greatest.

The data of one event for 16 seconds were analyzed

to make a comparison of amplitude spectra of signals

recorded at the substructure and the second floor.


34

(b)

(a)

Fig.2: Recorded signals at 2nd floor (a) in time

domain, and (b) in frequency domain.

Fig.3: Vibration magnitude in terms of VL, MTVV

and VDV for all five houses.

From Fig.3, it can be seen that the vertical (Z-axis)

vibration is higher in all the three orthogonal

directions for all houses. On the other hand, the

magnitude of vibration is the highest in surface

railway among all the five houses. Therefore, the

vertical vibration might induce intolerable annoyance

to humans inside buildings than the horizontal

vibration (X and Y axis).

It is seen from Fig. 4 (a) and (b) that the dominant

frequencies largely vary from 3.15 Hz to 80 Hz. To

summarize the results of dominant frequencies for

five houses, center frequencies in 1/3 octave band are

chosen as the reference values. The values of

dominant frequencies, which are closer to a 1/3

octave center frequency, are collected and gathered

into one group represented by that center frequency.

Number of appearances (NOA) of dominant

frequencies is counted. The normalized NOA is

defined as the ratio between NOA and the total

number of analyzed events at which the dominant

frequencies occur. The normalized NOA may reveal

how frequently those frequencies occur in the

analyzed set of field record.

For the evaluation of noise with respect to human

responses, 1/3 octave band are chosen to present

frequency content with the sound pressure level

(SPL). “A-weighting” frequency weighting are used

for the evaluation of noise of 16 second record for

house A. According to A-weighting, the human ear

has peak response around 2000 Hz to 3000 Hz and

has a relatively low response at the low frequencies.

From Fig. 5 it can be seen that the value of sound

pressure level is 41.94 dB (maximum) at 2 kHz and -

2.5 dB (minimum) at 20 kHz.

Fig.4: Normalized NOA. dominant frequencies of all

five house (a) substructure, and (b) second Floor.

Fig.5: Sound pressure level of 16 second noise

record for house A.

CONCLUSIONS

Road traffic and railway induced vibrations are

transient and intermittent. The duration of these

vibrations varies widely from 10 second for road-

induced vibrations to 30 second for train induced

0 500 1000 1500 2000 2500 3000 3500-0.1

-0.05

0

0.05

0.1

Time [sec]

accela

tion (

m/s

ec2

)

Time history of vertical vibration

0 5 10 15 20 25 30 350

20

40

60

Frequency(Hz)

Am

plit

ude s

pectr

um

Second floor

(a)

(b)


35

vibrations. Dominant frequencies in both the vertical

and horizontal directions are affected by several

factors such as frequency content of excitation forces,

dynamic characteristics of the ground, and dynamic

characteristics of the house structure. Frequencies of

10 Hz and 12.5 Hz are highly dominant in the

substructure level and the second floor for vertical

direction. However, the frequency of 5 Hz is found

dominant for both the substructure level and the

second floor, where 6.3 Hz is found to be dominant

for the second floor for horizontal direction.

The magnitude of vertical vibration seemed to be

generally higher than that of the horizontal vibration

recorded in all the houses. The magnitude of sound

pressure level is seen maximum at 2 kHz.

REFERENCES

[1] H. V. C. Howarth and M. J. Griffin (1990)

Applied Ergonomics 21(2), 129-134. The relative

importance of noise and vibration from railways.


Journal of Sound and Vibration 143, 443-454.

Subjective response to combined noise and vibration:

summation and interaction effects.

[3] R. Paulsen and J. Kastka (1995) Journal of Sound

and Vibration 181(2), 295-314. Effects of combined

noise and vibration on annoyance.


Journal of the acoustical Society of America 89(5),

2317-2323. The annoyance caused by simultaneous

noise and vibration from railways.

[5] The ministry of the Environment, Japan, Review

of the execution status of Vibration Regulation Law

in the fiscal year Heisei 20, 2009 (In Japanese)

[6] ISO 2631-1 (1997) Mechanical Vibration and

Shock – Evaluation of human exposure to whole

body vibration – part 1: General requirements.

AUTHOR’S PROFILE

Name: Satya Narayan Sharma

Affiliation: Graduate Student, Saitama University

Correspondence address: 338-0825 Saitama ken,

Saitama –shi, Sakura-ku, Shimo Okubo 738, Shimura

Kopo-106


Bachelor in Civil Engineering from Institute of

Engineering (IOE) Pulchowk Campus, Nepal and

Master of Science in Structure Engineering from

Saitama University, Japan

Work experience:

2008-2011 Design Engineer in Tisha Nirman Sewa

Pvt. Ltd Kathmandu, Nepal.


Nepal Engineering Association (NEA)

Nepal Engineering Council (NEC)


36

On behalf of NEA-JC, we would like to congratulate our graduate on the accomplishment of his PhD

degree in March 2013.

We wish him all the best for future endeavors. Mr. Laxmi Prasad Suwal

Department of Civil Engineering

The University of Tokyo

NEA-JC family would like to congratulate Ms. Ritu Bhusal Chhatkuli (The University of Tokyo) for receiving following

prestigious awards. We wish all the best in her research ahead.

Best Presenter Award (発表賞) at 9th Annual Conference of Japan

Society of Maintenolgy (July 2012).

&

Chairman’s Award (大会長賞) at 104th Scientific Conference of

Japan Society of Medical Physics (September 2012).


37

On behalf of NEA-JC, we would like to congratulate all the graduates on the accomplishment of their Master's degree in March 2013.

We wish them all the best for their future endeavors.

Ms. Alina Shrestha Suwal

Department of Civil and Environmental Engineering

Saitama University

Mr. Keshab Gyawali



Mr. Manoj Nakarmi



Ms. Ritu Bhusal Chhatkuli

Department of Bioengineering


Mr. Satya Narayan Sharma

Department of Civil and Environmental Engineering

Saitama University


38

Contact information:

For any comments and suggestions please contact any of the

following publication committee members.

Justin Shrestha ([email protected]) Dhruba Panthi ([email protected])

Naba Raj Shrestha ([email protected])

president - nea-jc · 5 i forgot here that this message is intended for the readers of this...

Documents