1. Integrated Water Induced Vulnerability Assessment of Lothar
Watershed, Chitwan/Makawanpur, Nepal.
A Dissertation work
For the partial fulfillment of requirements for completion of
Master Degree in Environmental Science
Submitted by
Niroj Timalsina
TU Regd No: 5-1-283-42-2002
Roll No : 6410

2. INTRODUCTION
 Landslide, debris flow and flood are prominent water induced
hazards of Nepal.
 Total 7,809 people’s were killed by flood and landslide in
between (1983-2010), (DWIDP, 2010).
 Landslide and debris are prominent in mountainous parts and
while reaching plains of Terai it created wide spread flood.
 Disaster preparedness plan can be implemented on the basis of
Vulnerability assessment.
 Integrated water induced vulnerability assessment aims to
integrate physical vulnerability (flood, landslide and debris
flow) with social vulnerability.

3. STATEMENT OF THE PROBLEM
 Disaster occurred in 1993 reflected that high intensity rainfall
have high implication for triggering the flood, landslide and
debris flow.
 Many times these hazard (Flood, landslide and debris flow)
became the dependent event.
 Eg:
 Khosi flood caused by huge amount of sediments derived
from upper catchment (Dixit, et al., 2009).
 Seti flood was caused from debris mixed snow avalanches
(Dahal, et al., 2012).
 Individual vulnerability assessment of respective hazards in a
single watershed would insufficient.

4. RESEARCH OBJECTIVES
The general objective of the study is to assessing the overall water
induced vulnerabilities of Lothar watershed.
The specific objectives are as follows:
 To prepare hazard zonation maps of flood, landslide and debris flow
of Lothar watershed in 1:25000 scales.
 To create flood, landslide and debris flow vulnerability index in the
ward level (lowest local governmental administrative units).
 To prepare composite physical vulnerability map by combining flood,
debris flow and landslide vulnerability index.
 To estimate and map social vulnerability as directed by water induced
hazard.
 To prepare the overall vulnerability map by integrating physical
vulnerability and social vulnerability index.

5. SCOPE OF STUDY
 Varnes (1984): “the past & present are keys to the future”
 If GCMc projection holds true, it can easily excepted that water
induced hazards will take more often & with more
consequences.
 This integrated vulnerability map of places can easily be
understood.
 Place based vulnerability map will fruitful to concern agencies
tasked with DRR.

6. METHODOLOGY
Collection of Maps and Imageries
Desk Topographic maps (Sheet numbers 2784 -08A, 07D, 07B and
08C at a scale of 1:25,000) and Google images 2012
Study Collection of Hydro-Meteorological Data
Collection of Socio-economic Data
Local consultation
Walk over Previous debris flow boundary and
survey cultivation land loss were recorded
Field
Old flood marks, old river course, channel shifting,
Study old and young river terraces, and flood deposits
were collected
Active and old landslide were
marked on the GPS

7. ANALYSIS AND INTERPRETATION
The overall analysis consists of creating the indexes and summing with
certain weight.
Flood Vulnerability
index (FVI, w=0.5)
Combined physical
Landslide Vulnerability Vulnerability index
index, (LVI, w= 0.25) (PhyVI), w=0.5
Debris flow
vulnerability index Integrated Vulnerability
(DVI, w-0.25) index
Previous loss index
(PLIward), w=0.25 Social Vulnerability index
Potential loss index (SoVI), w=0.5
(PoLIward), w=0.25
Vulnerability index derived by
Composite/multiple adoptive
capacity index (ACI), w=0.5

8. In Brief:
Flood Vulnerability Assessment
Flood frequency analysis Maximum instantaneous flow by WECS/DHM method
DoS + Additional
Houses unit of
Google image
Flood hazard
units from
mapping
Flood depth (m) Hazard level
<.05 Low
0.5-2 Moderate
2-4 High Returning
>4 Very high period: 5, 10,
50 &100 yr

9. Houses units located in more
than 0.5 m flood depth from
each wards
Flood vulnerability index
Calculated as (Rod et al., 2010):
FloVI=
Where r are the return intervals, Hr are the houses within inundated zones of
a 1/r flood and Hward are the total houses in each wards within Lothar
watershed.

10. Landslide Vulnerability assessment
 Landslide Hazard mapping: Statistical bivariate was performed
Selected eight Parameter taken are:
Land use/land cover Slope angle

11. Relief Factor Internal relief Distance from thrust
Aspect
& Faults
Geology of Lothar watershed
Distance from Stream

12. Classified eight
Landslide obtained from field
parameter
+
Landslide from Google (100 of
landslide having more than
400 m2 )
Landslide index method
Digitalized (Arc GIS
9.3)
Density Map = the landslide density within the
Where,
entire map.
Wi = Weight assigned to certain parameters
A (Si) = Area, which contain landslide, in a
class.
certain parameter class.
Density Class = the landslide
A (Ni) = Total area, in a certain parameter class.
density within the parameter class.

13.  LHI is determined by summation of each factor’s ratings using
equation (Lee and Min, 2001; Lee and Pradhan, 2006):
LHI =
Where,
Wi = Weight assigned to each i parameters
N= Total number of parameters
 Classification of landslide hazard zones: low, moderate, high with
predictive rate evaluation.
 Then returning period was assigned as 50 and 100 yrs in regard to high
hazard zone and moderate hazard zone respectively as a fictive
probability.
 Similar to FoVI at a ward level, the landslide vulnerability index is
calculated as:
LVI =
Where, Hr is the number of houses within hazard level r.

14. Debris flow vulnerability assessment
DEM SINMAP Saturation Saturation
zonation map zone= Debris
hazard zone
Validation
Houses unit

15. Combined physical Vulnerability index (PhyVI)
Calculated as done by Rod and et al. (2010):

16. Social vulnerability assessment
Socially vulnerability, SoVI calculated as:
SoVI = ½ (PLI +PoLI) + ½ Vulnerability index derived from capability index (ACI)
Previous lost index (PLI):
PLIward = (Flood damaged + Landslide damages + Debris flow
damaged)ward/Total Cultivation land ward
Potential loss index (PoLI):
Vulnerability index derived by Composite/multiple adoptive capacity index
(ACI) from climate change vulnerability mapping for Nepal, MoEn,2010.:
 In accordingly each ward of respective VDC of Chitwan districts was
assigned with 16.66 vulnerability indexes and that of Makawanpur was
33.67

17. Integrated vulnerability index
Integrated vulnerability index was calculated by adding together
the min-max transformed index of combined physical
vulnerability and social vulnerability with giving weighted of 0.5
to each:
Int VI = PhyVI + SoVI (Rod et al, 2010)

18. Study Area
District VDC Wards Area (sq. km) of VDC
Chitwan Piple 6 8.74
Chitwan Korak 1,2,3,4,5 23.41
,6&7
Chitwan Lothar 1,2,3,4,5 61.95
,6,7,8 &
9
Makawanpur Kakanda 1,2,3,4,5 62.32
,6,7,8 &
9
Makawanpur Manaha 1,2 11.95
ri
Chitwan/Mak 5 VDC 28 168.37
awanpur wards

19. Results
1. Hazard Assessment
1.1 Flood hazard assessment
Flood frequency analysis
Table : Flood discharge with respect to returning period of tributaries of
Lothar Khola
S.N Lothar Reach/ Instantaneous Flood discharge (m3/s)
Tributaries
Returning 5Yrs 10yrs 50yrs 100yrs
period
1 Upper reach 119 145 199 222
2 Reuti 83 111 184 219
3 Middle reach 190 240 383 408
4 Panthali 71 95 159 191
5 Lower reach 273 351 542 632

20. Some HecRAS Export
Geom: Geometry data Flow: Lother flow data
RS = 2997.765
.035 .035 .035
390 Legend
EG 100yrs
380
WS 100yrs
EG 50yrs
370
WS 50yrs
E levation (ft)
360 EG 10yrs
WS 10yrs
350 EG 5yrs
WS 5yrs
340 EG 2yrs
WS 2yrs
330 Ground
Bank Sta
320
0 50 100 150 200 250
Station (ft)
Water surface profile of reach station
Cross section develop from (2997.766) with respect to returning period
HEC- GeoRAS

21. Flood inundated map with respect to returning period 5yrs,
10yrs, 50yrs and 100yrs were prepared:

22. Relation of Flood inundated area with returning period
50
Total flood inundated area(ha)%
45
40
35
30
25
20
15
10
5
0
5 years flood 10 years flood 50 years flood 100 years flood
Returning Period
Low (<.5)m Moderate (.5-2)
High (2-4)m Very high (>4m)
Flood inundated area with respect to hazard level and returning
period

23. 1.2 Landslide hazard assessment
 Total weight is positive, the factor is
favourable for landslide
 Class with lesser distance from
drainage (50m) has only assured the
positive weight.
 Elevation (1000-1500m) and south
and south-west facing slope of
study area were landslides prone
 Distance from the faults and thrust
have positive weight so it reveals
the situation of places nearby the
trust and faults to be more
susceptible towards landslide
Landslide index in according to different
classes of respective parameters

24.  Quantitative bivariate analysis was done to obtain hazard map, which
is then reclassified into three hazard zones

25.  118.544 km2, 40.668 km2 and 8.6504 km2 located under low, moderate and
high zone respectively.
Probability rate
Percentage of obsorbed 100
90
80
70
landslides
60
50
40 78.67%
30
20
10
0
0 20 40 60 80 100
Percentage of pridicted landslides from
high to low hazard
Figure : Predictive rate of landslide occurrence
 The probability rate was calculated by trapezoid rule, resulted with
78.67% .

26. 1.3 Debris flow hazards assessment
Table : Saturation zonation areas with debris flow occurrences areas
Saturation Area on Percen Debris flow Percentage of Cumulative Cumulative
Zonation zonation tage of occurrences Debris flow summation of % summation of % of
(km 2) Area (%) area (km 2) area (%) of zonation area debris occurrences
area
Saturation 16.97 10.50 0.88 78.67 10.50 78.67
Threshold 2.51 1.49 0.026 2.28 11.99 80.95
Saturation
Partially 46.83 27.87 0.16 14.18 39.86 95.13
weighted
Low 101.94 60.19 .05 4.85 100 100
moisture
Total 168.25 100 1.12 100

27. 100
Percentage of obsorbed debris
90
80
70
flow area
60
50
40
30
20
10
0
0 20 40 60 80 100
Percentage of pridicted Saturation zone
from high to low hazard
 Debris flow hazard zonation map and
occurrences of previous debris flow
recorded area to respective zonation
resulted 88.53% of success .

28. 2. Vulnerability assessment
Table : Digital representation of Houses unit with respect to wards of
concern VDC within Lothar watershed
VDC Ward No Total Number of VDC Ward No Total Number
houses of houses
Korak 1 261 Manahari 1 68
Korak 2 56 Manahari 2 230
Korak 3 94 Piple 6 352
Korak 4 70 Lothar 1 231
Korak 5 169 Lothar 2 85
Korak 6 54 Lothar 3 157
Kakanda 2 63 Lothar 4 122
Kakanda 3 12 Lothar 5 122
Kakanda 4 585 Lothar 6 115
Kakanda 5 131 Lothar 7 155
Kakanda 6 81 Lothar 8 153
Kakanda 7 180 Lothar 9 97
Kakanda 8 125
Kakanda 9 133
Total 3901

29. Physical vulnerability index
VDC- Landslide Debris flow Flood Combined
Ward vulnerability vulnerability vulnerability physical
index index index vulnerability
index
Korak-1 84.27 34.39 0.52 29.93
Korak-2 41.78 14.57 0 14.08
Korak-3 99.57 2.89 0 25.61
Korak-4 47.8 11.65 0 14.61
Korak-5 91.38 9.65 0 25.26
Korak-6 10.83 10.07 0 5.22
Kakanda-2 5.57 12.95 0 4.63
Kakanda-3 0 0 0 0
Kakanda-4 100 16.74 14.64 36.51
Kakanda-5 31.25 2.07 0 8.33
Kakanda-6 15.88 23.51 0 9.85
Kakanda-7 40.3 3.02 0 10.83
Kakanda-8 3.74 6.52 0 2.56
Kakanda-9 3.51 16.36 0 4.97
Manahari-1 0 100 100 75
Manahari-2 60.53 14.19 4.92 21.14
Piple-6 42.87 22.41 53.31 42.98
Lothar-1 33.93 6.87 19.03 25.36
Lothar-2 6.88 6.4 0 3.32
Lothar-3 20.86 27.72 3.17 13.73
Lothar-4 4.79 2.23 0 1.75
Lothar-5 7.67 0 0 1.91
Lothar-6 24.41 0 0 6.1
Lothar-7 3.02 1.75 0 1.19
Lothar-8 23.7 21.33 13.63 18.07
Lothar-9 2.8 2.8 0 9.14

30. Fig: Physical Vulnerability index spider chart

32. Social vulnerability index
 Social vulnerability map was prepared on the basis of natural break
(Jenks) classification with basic statistical value:
Count: 26 Mean: 20.09 Vulnerability Value
Classes
Minimum: Median: 16.60 Low <15
8.58
Maximum: Standard deviation: Moderate 15-23.38
52.65 111.84
Sum: 522.49 High >23.38

34. Integrated water induced vulnerability index
 Integrated water induced vulnerability map was prepared on the
basis of natural break (Jenks) classification with statistics as:
Count: 26 Mean: 18.15 Vulnerability Value
Classes
Minimum: Median: 15.86 Low <13.04
5.17
Maximum: Standard deviation: Moderate 13.04-27.88
56.76 12.13
Sum: 471.85 High >27.88

36. DISCUSSION
 Integrated water induced vulnerability assessment was based on the use of
indices.
 HDI of UNDP, Indicator of development of districts of Nepal created by
the ICIMOD (2003), Climate change vulnerability mapping for Nepal,
MoEn (2010) has been an inspiration sources for such calculation.
 Lothar watershed characterized by the higher threat of landslide and debris
flow in hill parts which also possesses serious risk of flood in lower reach
(DWIDP, 2011).
 Proper water induced hazards preparedness in this watershed would only be
possible when three prominent hazards are focused at once.

37. o Since people of Lothar watershed has prioritized the disaster prevention as
development issues (DWIDP, 2011), previous agricultural loss and
potential loss were incorporated here for SoVI calculation.
o Integrated vulnerability map displayed here reliable for judging the place
based vulnerability and helpful for disaster preparedness within study
areas.
The map display here indicated
that Panthali watershed needs
emergency response for DRR.

38. CONCLUSION
 Flood inundated area will increase with returning interval.
 118.544 km2, 40.668 km2 and 8.6504 km2 of watershed is under low, moderate
and high landslide hazard zone respectively with probability rate 78.67%.
 Debris flow hazard is also prominent in the study area which was mapped with
having success rate 88.53%.
 Ward no:1 of Manahari VDC and ward no:6 of Piple VDC are more vulnerable
towards flood while ward no: 4 Kakanda VDC, wards no: 3,1 and 5 of Korak
VDC and ward no: 2 of Manahari VDC are vulnerable to landslide.
 Ward no: 1 of Manahari VDC which together with higher potential flood
inundation and debris flow made the place to assure higher physical
vulnerability.
 Panthali and Retuti Khola possesses higher influence on social vulnerability
index.
 Integrated vulnerability map revealed that wards no: 1 and 2 of Manahari VDC,
ward no: 4 of Kakanda VDC, and ward no: 1 of Korak VDC are most water
induced vulnerable places within Lothar watershed.

39. RECOMMENDATIONS
This study offers several practical applications:
 Lothar bazar area including the places of Panthali watershed needs immediate
planning of risk management and lower reach of Reuti as well as places nearby
Ganawachok Khola should prioritize for disaster preparedness.
For further study:
 To overcome from the deficiency of digital terrain data, new technology such
as LIDAR (Light Detection and Ranging), which improves the quality of the
digital terrain representations can be used for further study.
 Digital data layers which has dynamic characters should be updated
continuously and thus study strongly suggests to responsible Governmental
agencies for regular updates the houses unit, road coverage, landcover etc.
Moreover, GPS could use for further study to delineate household units and
wards boundary.
 Assessment is recommended to be carried out for formulating the returning
period of landslide.
 Detail study of Social vulnerability assessment needs to incorporate the lowest
scale (wards) and more concisely at households level.

40. References
 Dahal R.K., Bhandary N.P. and Okamura, M., 2012. Why 1255
flash flood in the Seti River? Retrived from www.ranjan.net.np. In
July, 2012.
 DWIDP: Department of Water Induced Disaster Prevention, 2011.
Study of Lothar watershed, Chitwan/Makawanpur District.
 NAPA: National adaptation programme of Action, 2010. Climate
change vulnerability mapping of Nepal.
 Lee, S., and Pradhan, B., 2006. Probabilistic landslide hazards and
risk mapping on Penang Island, Malaysia, Earth System Science, v.
115(6), pp. 661-672.
 Rod, J. K. and et.al (2010). Mapping Climate Change , Natural
Hazards, and the vulneability of Districts in Central Norway.
Norwegian University of Science and Technology (NTNU), pp. 6-
12.

41. ACKNOWLEDGEMENT
I express my heartiest gratitude to :
 Associate Prof. Kedar Rijal, Ph.D., HOD of CDES
 My thesis supervisor, Mr. Ananta Man Singh Pradhan
 My co-supervisor Mr. Gyan Kumar Chhipi Shrestha
 All the members of Central Department of Environmental
Science, TU.
 My family, friends and everybody who was important to the
successful realization of research.

42. Some Photo Plate
Photo Plate: Local Consultation During field Visit

43. Photo Plate: Place where 15 persons of single family were killed by debris
flow

44. Photo Plate: Google View of Reuti Landslide (Source: Google Earth image: 2012)