0 10 km

15 km

5 km 20 km 25 km

Ja Ela

16

14

12

10

8

6

4 Elevation (m) 2 River Bed 0 Left Bank -2 Right Bank 5-year Flood Level -4 2-year Flood Level -6 0 5 10 15 20 25 30 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.1 for the Metropolitan Region River Longitudinal Profile (1/2) in the Democratic Socialist Republic of JAPAN INTERNATIONAL COOPERATION AGENCY (Ja Ela)

A8 - F20 15 km

10 km

20 km 0 40 km

5 km 25 km 35 km

30 km

Dandugam Oya

14

12

10

8

6

4

2 Elevation (m) 0 River Bed -2 Left Bank -4 Right Bank 5-year Flood Level -6 2-year Flood Level -8 0 5 10 15 20 25 30 35 40 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.1 for the Colombo Metropolitan Region River Longitudinal Profile (2/2) in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY (Dandugam Oya)

A8 - F21 6 km

4 km 8 km 14 km 2 km 10 km 12 km 0

Kalu Oya

12 River Bed 10 Left Bank Right Bank 8 5-year Flood Level 2-year Flood Level 6

4

Elevation (m) 2

0

-2

-4 0 2 4 6 8 10 12 14 16 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.2 for the Colombo Metropolitan Region Longitudinal Profile of the Kalu Oya in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY

A8 - F22 㪉㫂㫄 㪇 㪈㫂㫄

Wellawatta Canal

10 Bed Left Bank 8 Right Bank 25-year Flood Level 10-year Flood Level 6

4 Elevation (m) 2

0

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater Colombo in the Democratic Socialist Republic of Sri Lanka Basin (1/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Wellawatta Canal)

A8 - F23 㪊㫂㫄

㪉㫂㫄 㪈㫂㫄 㪇

Dehiwala Canal

6

5 Bed Left Bank 4 Right Bank 25-year Flood Level 10-year Flood Level 3

2

Elevation (m) 1

0

-1

-2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater Colombo in the Democratic Socialist Republic of Sri Lanka Basin (2/18) JAPAN INTERNATIONAL COOPERATION AGENCY ( Canal)

A8 - F24 㪇 㪈㫂㫄

㪉㫂㫄

Bolgoda Canal

6 Bed 5 Left Bank Right Bank 4 25-year Flood Level 10-year Flood Level 3

2

Elevation (m) 1

0

-1

-2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (3/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Bolgoda Canal)

A8 - F25 㪈㫂㫄 㪇

㪉㫂㫄 㪊㫂㫄

Kirillapone Canal

6.0

5.0 Bed Left Bank 4.0 Right Bank 25-year Flood Level 10-year Flood Level 3.0

2.0

Elevation (m) 1.0

0.0

-1.0

-2.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (4/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Kirillapone Canal)

A8 - F26 㪉㫂㫄 㪈㫂㫄

㪇

Heen Ela

6

5 Bed Left Bank 4 Right Bank 25-year Flood Level 3 10-year Flood Level

2

Elevation (m) 1

0

-1

-2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (5/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Heen Ela)

A8 - F27 㪈㪅㪌㫂㫄 㪇 㪈㫂㫄

Torrington South Canal

4

3

2

1 Elevation (m) Bed 0 Left Bank Right Bank 25-year Flood Level -1 10-year Flood Level

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (6/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Torrington South Canal)

A8 - F28 㪇㪅㪌㪢㫄 㪇

Torrington North Canal

4

3

2

1 Elevation (m) Bed 0 Left Bank Right Bank 25-year Flood Level -1 10-year Flood Level

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (7/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Torrington North Canal)

A8 - F29 㪉㫂㫄

㪈㫂㫄 㪇

Mahawatta Ela - Connection Canal to Heen Ela

4

3

2

1

Elevation (m) Bed 0 Left Bank Right Bank -1 25-year Flood Level 10-year Flood Level

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater Colombo in the Democratic Socialist Republic of Sri Lanka Basin (8/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Mahawatta Ela and Connection Canal to Heen Ela)

A8 - F30 㪊㫂㫄

㪉㫂㫄

㪈㫂㫄 㪇

Dematagoda Ela

4

3

2

1 Elevation (m) 0 Bed Left Bank Right Bank -1 25-year Flood Level 10-year Flood Level -2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (9/18) JAPAN INTERNATIONAL COOPERATION AGENCY ( Ela)

A8 - F31 㪈㪅㪌㫂㫄 㪈㫂㫄 㪇㪅㪌㫂㫄 㪇

St. Sebastian North Canal

4

3

2

1 Elevation (m)

0 Bed Left Bank Right Bank -1 25-year Flood Level 10-year Flood Level

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (10/18) JAPAN INTERNATIONAL COOPERATION AGENCY (St. Sebastian North Canal)

A8 - F32 㪇 㪈㫂㫄 㪉㫂㫄

St. Sebastian South Canal

4

3

2

1 Elevation (m) Bed 0 Left Bank Right Bank -1 25-year Flood Level 10-year Flood Level

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (11/18) JAPAN INTERNATIONAL COOPERATION AGENCY (St. Sebastian South Canal)

A8 - F33 㪇 㪇㪅㪌㫂㫄 㪈㫂㫄

St. Sebastian East Canal

4

3

2

1 Elevation (m) Bed 0 Left Bank Right Bank -1 25-year Flood Level 10-year Flood Level

-2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (12/18) JAPAN INTERNATIONAL COOPERATION AGENCY (St. Sebastian East Canal)

A8 - F34 㪈㫂㫄 㪈㪅㪌㫂㫄 㪇 㪇㪅㪌㫂㫄

Main Drain

4

3

2

1 Elevation (m) 0 Bed Left Bank -1 Right Bank 25-year Flood Level 10-year Flood Level -2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (13/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Main Drain)

A8 - F35 㪊㫂㫄

㪉㫂㫄 㪈㫂㫄

㪇

Kotte Ela

6

Bed Left Bank Right Bank 4 25-year Flood Level 10-year Flood Level

2 Elevation (m)

0

-2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (14/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Kotte Ela)

A8 - F36 0 1km 0.5km

Connection Kotte Ela North - Heen Ela

4

3

2

1

Elevation (m) Bed 0 Left Bank Right Bank -1 25-year Flood Level 10-year Flood Level -2 0.0 0.5 1.0 1.5 2.0 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (15/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Connection Kotte Ela North - Heen Ela )

A8 - F37 㪉㫂㫄

㪈㫂㫄

㪇

Kolonnawa Ela

4 Bed Left Bank 3 Right Bank 25-year Flood Level 10-year Flood Level 2

1 Elevation (m) 0

-1

-2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (16/18) JAPAN INTERNATIONAL COOPERATION AGENCY ( Ela)

A8 - F38 㪈㪅㪇㩷㫂㫄 㪇 㪈㪅㪌㩷㫂㫄 㪇㪅㪌㩷㫂㫄

Kolonnawa Ela North

4 Bed Left Bank 3 Right Bank 25-year Flood Level 10-year Flood Level

2

1 Elevation (m) 0

-1

-2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (17/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Kolonnawa Ela North)

A8 - F39 㪇

㪉㫂㫄

㪋㫂㫄

㪍㫂㫄

㪏㫂㫄

Madiwela East Diversion Canal

14 Bed 12 Left Bank Right Bank 10 25-year Flood Level 10-year Flood Level 8

6

Elevation (m) 4

2

0

-2 012345678 Distance (km)

The Study on Storm Water Drainage Plan Figure 3.3.3 for the Colombo Metropolitan Region Longitudinal Profile of Main Canal in Greater in the Democratic Socialist Republic of Sri Lanka Colombo Basin (18/18) JAPAN INTERNATIONAL COOPERATION AGENCY (Madiwela East Diversion Canal)

A8 - F40 Distance (km) Bolgoda Canal - Weras Ganga Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level 0123456789101112

6 4 2 0 -2 -4 Elevation (m) Elevation 0 2km 4km 6km 8km 10km

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in JAPAN INTERNATIONAL COOPERATION AGENCY Bolgoda Basin (Weras Ganga) (1/7)

A8 - F41 Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level Distance (km) Maha Oya 0 5 10 15 20

8 6 4 2 0

-2 -4 -6 -8 14 12 10 Elevation (m) Elevation 16km 12km 8km 4km 0

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in JAPAN INTERNATIONAL COOPERATION AGENCY Bolgoda Basin (Maha Oya) (2/7)

A8 - F42 Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level Distance (km) Bolgoda Ganga 0123456789101112

4 2 0

-2 -4 -6 Elevation (m) Elevation 10km 8km 6km 4km 2km 0

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in JAPAN INTERNATIONAL COOPERATION AGENCY Bolgoda Basin (Bolgoda Ganga) (3/7)

A8 - F43 Distance (km) Panape Ela Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level 02468101214

8 6 4 2 0

-2 -4 -6 10 Elevation (m) Elevation 12km 10km 6km 8km 4km 2km 0

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in JAPAN INTERNATIONAL COOPERATION AGENCY Bolgoda Basin (Panape Ela) (4/7)

A8 - F44 Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level Distance (km) Keppu Ela 012345678910

6 4 2 0 -2 -4 -6 Elevation (m) Elevation 8km 6km 4km 2km 0

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in JAPAN INTERNATIONAL COOPERATION AGENCY Bolgoda Basin (Keppu Ela) (5/7)

A8 - F45 Distance (km) Alut Ela Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level 024681012

6 4 2 0 -2 -4 Elevation (m) Elevation 0 2km 10km 8km 4km 6km

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in Bolgoda Basin (Alut Ela) (6/7) JAPAN INTERNATIONAL COOPERATION AGENCY

A8 - F46 Distance (km) Ganga Bed Left Bank Right Bank 10-year Flood Level 2-year Flood Level 0123456

4 2 0 -2 -4 -6 Elevation (m) Elevation 2km 4km 0 6km

The Study on Storm Water Drainage Plan Figure 3.3.4 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Longitudinal Profile of Major Stream in JAPAN INTERNATIONAL COOPERATION AGENCY Bolgoda Basin (Panadura Ganga) (7/7)

A8 - F47 JAPAN INTERNATIONAL COOPERATION AGENCY COOPERATION INTERNATIONAL JAPAN in the Democratic Socialist Re Socialist Democratic the in Kimbulapitiya Oya The Study onStorm Water Drainage Plan for the Colombo Metropolitan Region

35 BP-14

Mapalam Oya Dandugam Oya Dandugam 30 Lagoon (2.53) BP-13 p ublic o ublic Legend 205 BP-17 f Sri Lanka (1.85) 65 Runoff at Max. Water Level (m3/sec) 140 BP-11 (2.56) (1.45) Max. Water Level (m)

A8 - F48 A8 - Flow Direction at Max. Water Level

in the Ja Ela Basin (10-year Return Period) Return Basinin theJa Ela (10-year Basic of Diagram Distribution FloodRunoff 5.2.1 Figure Channel (Runoff Confined)

75 205 205 Channel (Present Condition) BP-26 (1.02) (1.47) (1.67) BP-21 BP-19 Attanagalu Oya BP-8 BP-4 130 130 125 (4.31) (5.80) BP-3

BP-22 Ja Ela Urwal Oya 65 (1.45) 65 40 35 25 (1.64) (3.34) (6.00) BP-20 BP-27 BP-6 BP-2

Colombo Negombo Expressway Road JAPAN INTERNATIONAL COOPERATION AGENCY COOPERATION INTERNATIONAL JAPAN in the Democratic Socialist Re Socialist Democratic the in Kimbulapitiya Oya The Study onStorm Water Drainage Plan for the Colombo Metropolitan Region

50 BP-14

Mapalam Oya Dandugam Oya Dandugam 40 Negombo Lagoon (3.36) BP-13 p ublic o ublic Legend 290 BP-17 f Sri Lanka (2.46) 90 Runoff at Max. Water Level (m3/sec) 195 BP-11 (3.41) (1.84) Max. Water Level (m)

A8 - F49 A8 - Flow Direction at Max. Water Level

in the Ja Ela Basin (25-year Return Period) Basinin theJa Ela (25-year Basic of Diagram Distribution FloodRunoff 5.2.2 Figure Channel (Runoff Confined)

105 295 290 Channel (Present Condition) BP-26 (1.32) (1.89) (2.20) BP-21 BP-19 Attanagalu Oya BP-8 BP-4 190 185 175 (5.35) (6.78) BP-3

BP-22 Ja Ela Urwal Oya 90 (1.84) 85 55 50 35 (2.06) (3.88) (6.00) BP-20 BP-27 BP-6 BP-2

Colombo Negombo Katunayake Road Expressway JAPAN INTERNATIONAL COOPERATION AGENCY COOPERATION INTERNATIONAL JAPAN in the Democratic Socialist Re Socialist Democratic the in Kimbulapitiya Oya The Study onStorm Water Drainage Plan for the Colombo Metropolitan Region

60 BP-14

Mapalam Oya Dandugam Oya Dandugam 50 Negombo Lagoon (3.98) BP-13 p ublic o ublic Legend 360 BP-17 f Sri Lanka (2.92) 110 Runoff at Max. Water Level (m3/sec) 245 BP-11 (4.03) (2.14) Max. Water Level (m)

A8 - F50 A8 - Flow Direction at Max. Water Level

in the Ja Ela Basin (50-year Return Period) Basinin theJa Ela (50-year Basic of Diagram Distribution FloodRunoff 5.2.3 Figure Channel (Runoff Confined)

130 365 365 Channel (Present Condition) BP-26 (1.56) (2.21) (2.59) BP-21 BP-19 Attanagalu Oya BP-8 BP-4 235 230 220 (6.09) (7.50) BP-3

BP-22 Ja Ela Urwal Oya 110 (2.14) 110 70 65 45 (2.38) (4.28) (6.00) BP-20 BP-27 BP-6 BP-2

Colombo Katunayake Negombo Expressway Road JAPAN INTERNATIONAL COOPERATION AGENCY COOPERATION INTERNATIONAL JAPAN in the Democratic Socialist Re Socialist Democratic the in Kimbulapitiya Oya The Study onStorm Water Drainage Plan for the Colombo Metropolitan Region

35 BP-14

Mapalam Oya Dandugam Oya Dandugam 20 Negombo Lagoon (1.82) BP-13 p ublic o ublic Legend 140 BP-17 f Sri Lanka (1.34) 50 Runoff at Max. Water Level (m3/sec) 100 BP-11 (1.86) (1.08) Max. Water Level (m)

A8 - F51 A8 - Flow Direction at Max. Water Level

in the Ela Ja Basin (10-year Return Period) Diagram ofProbable Flood RunoffDistribution Figure 5.2.4 Channel (Runoff Confined)

55 145 140 Channel (Present Condition) BP-26 (0.75) (1.09) (1.22) BP-21 BP-19 Attanagalu Oya BP-8 BP-4 100 110 110 (3.55) (5.22) BP-3

5 BP-5 BP-22 Ja Ela Urwal Oya 50 (1.08) 50 40 35 25 (1.25) (3.21) (6.00) BP-20 BP-27 BP-6 BP-2

Colombo Negombo Katunayake Road Expressway JAPAN INTERNATIONAL COOPERATION AGENCY COOPERATION INTERNATIONAL JAPAN in the Democratic Socialist Re Socialist Democratic the in Kimbulapitiya Oya The Study onStorm Water Drainage Plan for the Colombo Metropolitan Region

50 BP-14

Mapalam Oya Dandugam Oya Dandugam 25 Negombo Lagoon (2.16) BP-13 p ublic o ublic Legend 170 BP-17 f Sri Lanka (1.58) 60 Runoff at Max. Water Level (m3/sec) 125 BP-11 (2.21) (1.26) Max. Water Level (m)

A8 - F52 A8 - Flow Direction at Max. Water Level

in the Ela Ja Basin (25-year Return Period) Diagram ofProbable Flood RunoffDistribution Figure 5.2.5 Channel (Runoff Confined)

65 175 170 Channel (Present Condition) BP-26 (0.85) (1.26) (1.43) BP-21 BP-19 Attanagalu Oya BP-8 BP-4 125 145 140 (4.02) (5.68) BP-3

10 BP-5 BP-22 Ja Ela Urwal Oya 60 (1.26) 60 50 45 35 (1.47) (3.63) (6.00) BP-20 BP-27 BP-6 BP-2

Colombo Negombo Katunayake Road Expressway JAPAN INTERNATIONAL COOPERATION AGENCY COOPERATION INTERNATIONAL JAPAN in the Democratic Socialist Re Socialist Democratic the in Kimbulapitiya Oya The Study onStorm Water Drainage Plan for the Colombo Metropolitan Region

60 BP-14

Mapalam Oya Dandugam Oya Dandugam 30 Negombo Lagoon (2.40) BP-13 p ublic o ublic Legend 190 BP-17 f Sri Lanka (1.75) 70 Runoff at Max. Water Level (m3/sec) 140 BP-11 (2.44) (1.41) Max. Water Level (m)

A8 - F53 A8 - Flow Direction at Max. Water Level

in the Ela Ja Basin (50-year Return Period) Diagram ofProbable Flood RunoffDistribution Figure 5.2.6 Channel (Runoff Confined)

70 195 195 Channel (Present Condition) BP-26 (0.94) (1.38) (1.58) BP-21 BP-19 Attanagalu Oya BP-8 BP-4 140 165 165 (4.32) (5.99) BP-3

15 BP-5 BP-22 Ja Ela Urwal Oya 70 (1.41) 70 60 50 40 (1.65) (3.91) (6.00) BP-20 BP-27 BP-6 BP-2

Colombo Negombo Katunayake Road Expressway Ja Ela at Negombo Road

150 10-year Return Period Basic Flood Probable Flood 100 /sec) 3

65 m3/sec 3 50 50 m /sec Runoff (m Volume 0.86 MCM

0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours)

Ja Ela at Negombo Road

150 25-year Return Period Basic Flood Probable Flood 100 3

/sec) 90 m /sec 3

Volume 1.44 MCM 60 m3/sec 50 Runoff (m

0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours)

Ja Ela at Negombo Road

150 50-year Return Period Basic Flood 110 m3/sec Probable Flood 100 /sec) 3 Volume 1.95 MCM 70 m3/sec

Runoff (m 50

0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours)

The Study on Storm Water Drainage Plan Figure 5.2.7 for the Colombo Metropolitan Region Runoff Hydrograph in Ja Ela Basin (1/2) in the Democratic Socialist Republic of Sri Lanka (Ja Ela at Negombo Road) JAPAN INTERNATIONAL COOPERATION AGENCY

A8 - F54 Dandugam Oya at Negombo Road

400 10-year Return Period 350 Basic Flood 300 Probable Flood

250 /sec) 3 3 205 m /sec 200 3 150 145 m /sec

Runoff (m Volume 4.44 MCM 100

50

0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours)

Dandugam Oya at Negombo Road

400 25-year Return Period 350 Basic Flood 295 m3/sec 300 Probable Flood

250 /sec) 3 200 175 m3/sec Volume 7.57MCM 150 Runoff (m 100

50

0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours)

Dandugam Oya at Negombo Road

400 50-year Return Period 365 m3/sec 350 Basic Flood 300 Probable Flood

250 /sec) 3 Volume 10.21 MCM 3 200 195 m /sec

150 Runoff (m 100

50

0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours)

The Study on Storm Water Drainage Plan Figure 5.2.7 for the Colombo Metropolitan Region Runoff Hydrograph in Ja Ela Basin (2/2) in the Democratic Socialist Republic of Sri Lanka (Dandugam Oya at Negombo Road) JAPAN INTERNATIONAL COOPERATION AGENCY

A8 - F55 0 Dandugam Oya Channel Improvement

Katunayake

Mapalam Oya Negombo Lagoon Kotugoda- Diversion Channel

Storm Water Retention Area

Attanagalu Oya

Ja Ela Urwal Oya

Ja Ela Storm Water Retention Area Channel Improvement

Conservation Zone of Muthurajawela Marsh Buffer Zone (Retention Area)

Outer Circular Highway Old Negombo Canal

Hamilton Canal Kalu Oya

Kelani Ganga

Scale Colombo-Katunayake Colombo Expressway

The Study on Storm Water Drainage Plan Figure 5.3.1 for the Colombo Metropolitan Region Conceivable Structural Measures for in the Democratic Socialist Republic of Sri Lanka Ja Ela Basin JAPAN INTERNATIONAL COOPERATION AGENCY

A8 - F56