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DEPARTMENT OF CIVIL AND ENVIRNMENTAL ENGINEERING
FACULTY OF ENGINEERING
UNIVERSITY OF RUHUNA
CE6322: ENGINEERING HYDROLOGY
FLOOD DAMAGES IN AMPARA DISTRICT 2011
(02/01/2011 to 07/02/2011)
NAME : BANDARA K.A.J.M.
REG No : RU/E/2008/014
DATE : 13/06/2011
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 2
ACKNOWLEDGEMENT
I have taken efforts in this project. However, it would not have been possible without the kind support and help of many individuals and organizations. I would like to extend my sincere thanks to all of them. I am highly indebted to Dr. Amila De Silva for their guidance and constant supervision as well as for providing necessary information regarding the report & also for their support in completing the report. I would like to express my gratitude towards my parents & member of Faculty of Engineering for their kind co-operation and encouragement which help me in completion of this report. I would like to express my special gratitude and thanks to Eng. Saman S.L. Weerasinghe, Regional Director of Irrigation of the Ampara Range for giving me such attention and time. Bandara K.A.J.M
RU/E/2008/014
Faculty of Engineering
University of Ruhuna.
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 3
CONTENT Page No
ACKNOWLEDGEMENT i
CONTENT ii
1.0 SUMMARY 1
2.0 INTRODUCTION TO THE GAL OYA BASIN 1
2.1.1 PHYSICAL FEATURES OF SENANAYAKA TANK 1
3.0 FLOOD DAMAGES 3
3.1.1 OPERATIONAL ISSUES 4
4.0 DATA ANALYZING 6
5.0 CONCLUSIONS 11
REFERENCES 11
ANNEXES 12
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 4
1.0 SUMMARY
This report presents the results of an impact in flood during at January 2011 in Ampara District. Due
to heavy rains in Ampara District has become inaccessible through the Inginiyagala, Mahaoya and
Kalmunai routes, which have been submerged, access has been cut off to all Division. This is the
most devastating floods that hit the Eastern part of the country especially Ampara since 1913.
2.0 INTRODUCTION TO THE GAL OYA BASIN
Gal Oya, a reservoir-based irrigation system, lies on the eastern coastal plain of Sri Lanka (fig. 1).
Originally proposed just after Sri Lanka’s independence in 1948, the main reservoir was completed
in 1960, and the full irrigation system was transferred from the Gal Oya Development Board to the
Irrigation Department for routine operation and maintenance. The reservoir, Senanayake Samudra,
has a capacity of 979 million cubic meters. Immediately below the dam is a trifurcation that controls
water deliveries into the main divisions of the system: the Right side (11,741 ha), the River Division
(8,502 ha), and the Left side (16,328 ha). Its combined irrigated area makes Gal Oya the largest
contiguous irrigation system in Sri Lanka.
2.1.1 PHYSICAL FEATURES OF SENANAYAKA TANK
The reservoir has been classified as “deep, encompassing many valleys” as the wetland is a multi-
fingered lake with 4 major basins and surrounded by hills. The reservoir is located in the Gal Oya
basin, which covers an area of 179,200 ha. The catchment area of the reservoir alone covers about
100,000ha. The main river feeding the reservoir is the Gal Oya River. In addition to this, the
reservoir is fed with water from seven main tributaries and 23 unnamed minor seasonal streams. The
profusion of bays gives the reservoir an estimated shoreline of about 130 km at full supply level. The
capacity of the reservoir is 949x106 m3 with a maximum depth of 33m and an average depth of 12m.
The water level in the reservoir is subject to wide seasonal and annual fluctuations and is directly
related to rainfall in the region. The lowest level recorded in the recent past was 28m below spill
level in 1989; maximum depth in the reservoir at that time was 5m. The length of the dam is 1,093m
with a crest at 83 m above sea level. The entire reservoir area is situated in the Vijayan series, a
Precambrian formation prevailing in the eastern part of the country. The reservoir is situated in the
dry zone of the eastern low country of Sri Lanka in the agro-ecological region DL2, which is defined
as an area with a 75% expectancy of annual rainfall exceeding 900mm. Most rainfall is normally
recorded in the period October-February; the period May-September is usually dry. Mean annual
temperature is around 27.7 0C.
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 5
Figure No 01
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 6
3.0 FLOOD DAMAGES
The floods in Sri Lanka are most likely to occur in the months of May in the first cycle and in
December in the second cycle. With respect to spatial distribution floods are most frequent in the
districts of Ampara. Due to floods in Ampara at January,
24 dead,
4 lakhs destitute,
1 ½ lakhs acres paddy field destroyed.
This damage’s occur after 1984 later year ago. People have become increasingly affected by floods
with the highest number recorded in 2011. Further, people located in the division of Ampara District
have been most affected by floods. However, the occurrence of deaths due to floods is quite high
except for the last years where it reached nearly 15 persons. Destruction and damage to houses and
buildings also appear to follow a similar pattern with most damage occurring in the districts of
Ampara. Damage to paddy has taken place mostly in the earlier years with the highest impact
recorded in 1984, while spatially the highest damage has incurred in the districts of Ampara.
Due to torrential rain resulting from recent weather condition, nearly 10 Divisional Secretariat
Divisions of Ampara district have been experiencing flooding since the 6th January 2008. The most
affected D.S. Divisions are Akkaraipattu, Aalayadivembu, Ninthavur, Thirukkovil, Pottuvil,
Sammanthurai, Saithamaruthu, Karaitivu, Addalaichenai and Kalmunai.
Over 70,000 children are among the affected. While some schools in the flooded areas are being used
as temporary camps, many of the school going children’s educational activities have been disrupted
due to present weather condition/flood situation. Most of the affected families are depending on
fisheries and daily earnings for their livelihood. As the heavy rain disrupted these families’
livelihood, children in the families are affected by shortage of food, drinking water and proper
sanitary care.
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 7
Table No 01
3.1.1 OPERATIONAL ISSUES
The torrential rains have caused main roads to be submerged reducing access to affected areas.
Additionally, heavy rains also resulted in the intermittent opening of sluice gates of tanks and reservoirs. Transport and telecommunications are disrupted across the districts.
All schools in the affected areas have been declared closed by the Government throughout the week and most of the displaced are accommodated in most of these sites.
0
50
100
150
200
250
300
350
400
450
500
1st Flood 2nd Flood
181159
497.8
248.9 No of Damages
Tentative EstimateCost(Million)
743512
816
207430
0 15 52
1285
2670 2580
39 95 15 12 27 0 2 0 18 3 20
500
1000
1500
2000
2500
3000
Partially DamagedHomes
Fully Damaged Homes
Funds required for the repairs the Damages in
2011
Rs. 300.0 Million
Table No 02: Homes Damaged During Flood
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Faculty of Engineering Page 8
Population Density & Flood Preparedness
Figure No 02
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 9
4.0 DATA ANALYZING
Spatial Distribution of Rainfall D
ate
Am
para
Uha
na
Him
idur
awa
Wee
rago
da
Ann
amal
ai
Gon
agol
la
Blo
ck”J
”
Sina
wat
htha
Bok
keba
da
Dam
ana
Palla
noya
Nam
aloy
a
Am
bala
noya
Ekga
loya
Pann
alga
ma
1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
2 13.9 3.8 7.6 8.1 17.7 3.0 8.8 _ 22.8 17.2 5.0 21.0 5.0 _ 31.7
3 33.0 45.7 27.9 48.2 50.0 82.5 40.6 78.0 27.6 29.2 10.0 17.7 21.5 6.3 17.7
4 7.6 11.4 7.6 36.8 40.1 22.8 24.1 41.9 30.4 9.1 7.0 19.3 15.2 3.8 7.6
5 19.8 29.7 36.8 13.9 10.1 12.7 16.5 22.8 33.0 26.4 17.0 23.6 44.1 10.1 30.4
6 11.4 11.4 15.2 10.1 8.8 14.4 7.6 8.0 8.1 10.1 5.0 16.0 7.6 3.8 5.0
7 21.5 _ _ _ _ _ _ _ _ 34.2 10.0 16.5 12.7 _ _
8 228.0 124.4 116.8 200.6 124.4 254.0 185.4 254.0 251.4 _ 122.0 193.0 190.0 139.7 119..3
9 21.5 27.9 27.9 47.7 53.3 44.4 24.8 41.1 50.8 20.3 20.0 22.8 12.7 7.6 22.8
10 63.5 54.6 55.8 _ 48.2 74.9 62.2 _ 33.0 55.1 46.0 40.6 33.0 27.9 27.9
11 236.2 165.1 124.4 144.7 200.6 143.5 201.0 _ 88.9 214.1 65.0 53.0 231.0 78.7 78.7
12 66.0 62.2 64.7 27.9 30.4 83.8 _ 68.5 60.9 _ 67.0 66.0 83.8 40.6 60.9
13 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
14 6.3 10.1 7.6 7.6 _ 21.3 6.3 _ 22.8 _ 5.0 10.1 _ 3.8 2.5
Table No 03: Rain fall data from 1st of January in mm (1st Flood)
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 10
=
15
Average Annual rain fall in Ampara District is 1250mm -1600 mm
By considering the daily rainfall data of January in 2011(1st flood)
Mean rainfall in the Ampara district (1st flood)
728.7
546.3
492.3
545.6583.6
757.3
577.3
514.3
629.7
415.7379
499.6
656.9
322.3
404.5
0
100
200
300
400
500
600
700
800
Figure No 04: Total Rainfall 1st flood (mm)
{728.7+546.3+492.3+545.6+583.6+757.3+577.3+514.3+629.7+415.7+379+499.6+656.9+322.3+404.5} mm
= 536.9 mm
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 11
D
ate
Am
para
Uha
na
Him
idur
awa
Wee
rago
da
Ann
amal
ai
Gon
agol
la
Blo
ck”J
”
Sina
wat
htha
Bok
keba
da
Dam
ana
Palla
noya
Nam
aloy
a
Am
bala
noya
Ekga
loya
Pann
alga
ma
25 68.5 93.9 55.8 _ 25.4 45.7 _ 49.5 40.6 39.3 30.0 22.8 27.9 12.7 3.8
26 16.5 49.5 38.1 7.6 17.7 30.4 _ _ 73.6 27.9 35.0 80.0 53.3 10.1 53.3
27 30.4 28.0 20.3 26.6 12.7 25.4 24.1 _ _ 25.4 20.0 12.7 33.0 7.6 28.0
28 36.8 49.5 54.6 49.5 20.3 25.4 50.8 20.3 27.9 _ _ 45.7 38.1 44.4 53.3
29 27.9 22.9 33.0 17.7 17.7 30.4 8.8 27.4 38.1 _ 10.0 31.7 5.0 8.8 8.8
30 3.8 4.5 8.8 5.0 _ 11.4 _ _ 15.2 _ 30.0 30.4 10.1 6.3 6.5
31 25.4 29.2 17.7 29.2 20.3 _ 24.8 _ 10.1 _ _ _ _ _ 3.8
1 217.4 167.6 187.9 111.7 114.3 330.2 204.4 _ _ 203.0 160.0 168.9 142.2 71.1 119.9
2 104.1 128.2 114.3 119.3 114.3 203.2 102.8 _ 200.6 114.3 187.9 138.4 134.6 177.0 97.7
3 33.0 30.4 _ 58.4 66.0 53.3 44.4 45.7 17.7 30.4 32.0 30.4 15.2 5.0 5.0
4 52.0 34.2 46.7 54.6 53.3 65.0 50.2 76.2 76.2 _ 19.0 39.3 40.6 11.4 6.3
5 9.6 15.2 11.4 5.0 3.8 _ _ _ _ 5.8 6.0 13.9 2.5 _ _
6 30.4 32.7 33.0 35.0 33.0 38.8 39.3 35.0 43.1 31.7 29.0 30.4 38.1 11.4 25.4
7 11.1 8.8 _ 10.1 15.2 5.5 5.0 15.2 17.7 28.7 21.0 _ 53.3 11.4 30.4
Table No 05: Rain fall data from 25th of January in mm (2nd Flood)
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 12
By considering the daily rainfall data of January and February in 2011(2nd flood)
Mean rainfall in the Ampara district (2nd flood)
1395
1241
11141075 1098
1622
1132
784
1191
922959
1144
1251
700
847
0
200
400
600
800
1000
1200
1400
1600
1800
Figure No 04: Total Rainfall 2nd flood (mm)
(1395+1241+1114+1075+1098+1622+1132+784+1191+922+959+1144+1251+700+847) mm
= 15
1098.3 mm =
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 13
Figure No 05: Flood damage map
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 14
5.0 CONCLUSIONS
The incidence of flooding seems to be most frequent in the latter years, with the most flooding
occurring in the year 2011 in Ampara District. Further, the floods in Sri Lanka are most likely to
occur in the months of May in the first cycle and in December in the second cycle. With respect to
spatial distribution floods are most frequent in the divisions of Ampara. People have become
increasingly affected by floods with the highest number recorded in 1984.. However, the occurrence
of deaths due to floods is quite high except for the latter years where it reached nearly 24 persons.
Destruction and damage to houses and buildings also appear to follow a similar pattern with most
damage occurring in the division of Thirickovil and Adalachchinei. Damage to paddy has taken
place mostly in the earlier years with the highest impact recorded in 1984, while spatially the highest
damage has incurred in the districts of Ampara. In some instances with respect to DS divisions, some
impacts have been reflected as low (Table No02).
REFERENCES http://www.rdiampara.weebly.com/ampara-division.html
http://www.dmc.gov.lk
http://www.meteo.gov.lk
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 15
Aligalge Tank Konduwattuwana Tank
Alahena Tank Weeragoda Tank
ANNEXES
6.1.1 Spilling Tanks during flood period
Ekgaloya Tank Pannalgamuwa Tank
CE6322: ENGINEERING HYDROLOGY
Faculty of Engineering Page 16
6.1.2 Flood Damages Area’s
Senanayaka Tank Nawagiri Tank
Ampara Town Ampara municipal building
Gemunupura Area Rajawewa Tank