14

13 Mapalam Oya N 16 15 12

11

17

10 1 18 9

25 19 8 21

27 4 3 23 26 5 7 6 22 20 2

24

Scale 024 6 8 10 km

14

I Lagoon 16 15 13 12 Mapalam Oya

J 11

25 H Legend 17

L No. Base Point 21 19 18 10 Stretch and Positive Flow K ID 26 Direction in the Hydraulic Model 9 G 23 8

D A 4 3 1 M 5 Ja Ela C 22 20 7 27 6 2 F E B

Muthurajawela 24 Marsh

Old Negombo Canal

The Study on Storm Water Drainage Plan Figure 3.6 for the Metropolitan Region in the Democratic Socialist Republic of Base Points in the Ja Ela Drainage System JAPAN INTERNATIONAL COOPERATION AGENCY

F - 27 0 0 20 Total Rainfall : 203 mm 20 Total Rainfall : 203 mm 40 40 8.0 40 7.5 30 7.0

20 6.5

Present Land Use Condition Present Land Use Condition 10 6.0 Future Land Use Condition Future Land Use Condition 0 5.5 0 6 12 18 24 30 36 42 48 54 60 0 6 12 18 24 30 36 42 48 54 60 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 2 (BP-2)

0 0 20 Total Rainfall : 203 mm 20 Total Rainfall : 203 mm 40 40 9 160

8 120

80 7

40 Present Land Use Condition 6 Present Land Use Condition Future Land Use Condition Future Land Use Condition 0 5 0 6 12 18 24 30 36 42 48 54 60 0 6 12 18 24 30 36 42 48 54 60 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 3 (BP-3)

0 0 Total Rainfall : 203 mm 20 Total Rainfall : 203 mm 20 40 40 250 1.6

200 1.2 150

100 0.8 Present Land Use Condition Present Land Use Condition 50 Future Land Use Condition Future Land Use Condition

0 0.4 0 6 12 18 24 30 36 42 48 54 60 0 6 12 18 24 30 36 42 48 54 60 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 19 (BP-19)

0 0 20 Total Rainfall : 203 mm 20 Total Rainfall : 203 mm 40 40 80

1.6 60

1.2 40

0.8 20 Present Land Use Condition Present Land Use Condition Future Land Use Condition Future Land Use Condition 0 0.4 0 6 12 18 24 30 36 42 48 54 60 0 6 12 18 24 30 36 42 48 54 60 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 20 (BP-20)

The Study on Storm Water Drainage Plan Figure 3.7 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Calculated 50-yr Probable Flood Hydrographs JAPAN INTERNATIONAL COOPERATION AGENCY for the Ja Ela Basin

F - 28 N

Legend Present Condition Simulated Flood Inundation Area : 2-yr Probable

: 10-yr Probable

: 50-yr Probable

Scale Future Condition 0 2 4 6 8 10 km

The Study on Storm Water Drainage Plan Figure 3.8 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Simulated Flood Inundation Area in the Ja Ela JAPAN INTERNATIONAL COOPERATION AGENCY Basin

F - 29 N

6

7

8 5

14 9 4 11 10 13 15 12 3

17 1 16 2

Scale 012345 km Old Negombo Canal

6

D

7 Muthurajawela C A Marsh 5 4 3 1 Kalu Oya 8 2 B E

9

Isolation Bund F (Culvert Crossing) 10 14 J 11 G I 13 Legend 12 15 K H No. Base Point L Stretch and Positive Flow ID Direction in the Hydraulic Model 17 16 M

Kelani Ganga

The Study on Storm Water Drainage Plan Figure 3.9 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Base Points in the Kalu Oya Drainage System JAPAN INTERNATIONAL COOPERATION AGENCY

F - 30 0 0 20 20 40 Total Rainfall : 300 mm 40 Total Rainfall : 300 mm 60 60 25 4

20 3 15

10 2 5 Present Land Use Condition Present Land Use Condition Future Land Use Condition Future Land Use Condition 0 1 0 6 12 18 24 30 36 42 48 0 6 12 18 24 30 36 42 48 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 1 (BP-1)

0 0 20 20 40 Total Rainfall : 300 mm 40 Total Rainfall : 300 mm 60 60 8 4

6 3 4

2 2 Present Land Use Condition 0 Present Land Use Condition Future Land Use Condition Future Land Use Condition -2 1 0 6 12 18 24 30 36 42 48 0 6 12 18 24 30 36 42 48 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 2 (BP-2)

0 0 20 20 40 Total Rainfall : 300 mm 40 Total Rainfall : 300 mm 60 60

30 2

20

1 10

Present Land Use Condition Present Land Use Condition 0 Future Land Use Condition Future Land Use Condition 0 0 6 12 18 24 30 36 42 48 0 6 12 18 24 30 36 42 48 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 8 (BP-8)

0 0 20 20 40 Total Rainfall : 300 mm 40 Total Rainfall : 300 mm 60 60 40 2.0

30 1.6 20 1.2 10

Present Land Use Condition 0.8 Present Land Use Condition 0 Future Land Use Condition Future Land Use Condition -10 0.4 0 6 12 18 24 30 36 42 48 0 6 12 18 24 30 36 42 48 Time (hour) Time (hour) Discharge and Water Level Hydrographs at Base Point 13 (BP-13) The Study on Storm Water Drainage Plan Figure 3.10 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Calculated 50-yr Probable Flood Hydrographs JAPAN INTERNATIONAL COOPERATION AGENCY for the Kalu Oya Basin

F - 31 N Present Condition

Legend Simulated Flood Inundation Area

: 2-yr Probable

Future Condition : 10-yr Probable : 50-yr Probable

Scale 012345 km

The Study on Storm Water Drainage Plan Figure 3.11 for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka Simulated Flood Inundation Area in the Kalu JAPAN INTERNATIONAL COOPERATION AGENCY Oya Basin

F - 32 N Kelani Ganga North Lock 1

B A 3 1 Main Drain 2 3 C 4 15 D 2 St. Sebastian Lock 5 4 Gotatuwa Bund Madiwela East Diversion Canal E Ela 㪈㪌 6 7 F 5 Kolonnawa 㪢 Ela 㪡 8 㪈㪍 㪈㪋 25 7 17 11 H 㪣 12 9 㪈㪎 Parliament 6 Lake G 16 Heen Ela 8 㪤 13 㪉㪋 14 㪥 㪉㪊 18 㪉㪌 㪉㪉 10 Torrington Canal 㪈㪈 㪠 Kirillapone 9 23 㪈㪉 19 24 㪧 㪨 Kotte Ela 㪈㪊 22 㪈㪇 㪪 㪩 㪈㪐 㪈㪏 20 21 Welawatta Kirillapone 㪦 Outfall 㪫 Canal 㪭 㪉㪇 Legend Outfall 㪉㪈 㪬 㪥㫆㪅 Base Point

Bolgoda Canal Stretch and Positive Flow 㪠㪛 Scale Direction in the Hydraulic Model 012345 km