Figure 4.4 Runoff Hydrograph in Ja Ela Basin
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Ja Ela at Negombo Road 150 10-year Return Period Basic Flood Probable Flood 100 /sec) 3 65 m3/sec 50 m3/sec 50 Runoff (m Runoff 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 Runoff 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 Runoff 50 0 0 6 12 18 24 30 36 42 48 54 60 Time (Hours) The Study on Storm Water Drainage Plan Figure 4.4 for the Colombo Metropolitan Region Runoff Hydrograph in Ja Ela Basin in the Democratic Socialist Republic of Sri Lanka (Ja Ela at Negombo Road) JAPAN INTERNATIONAL COOPERATION AGENCY F - 42 Dandugam Oya at Negombo Road 400 10-year Return Period 350 Basic Flood 300 Probable Flood 250 /sec) 3 205 m3/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 195 m3/sec 200 150 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 4.5 for the Colombo Metropolitan Region Runoff Hydrograph in Ja Ela Basin in the Democratic Socialist Republic of Sri Lanka (Dandugam Oya at Negombo Road) JAPAN INTERNATIONAL COOPERATION AGENCY F - 43 N Dandugam Oya Channel Improvement Katunayake Mapalam Oya Negombo Lagoon Kotugoda-Seeduwa Diversion Channel Storm Water Retention Area Attanagalu Oya Gampaha Ja Ela Uruwal 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 Wattala Kelani Ganga Scale Colombo-Katunayake Colombo Expressway The Study on Storm Water Drainage Plan Figure 4.6 for the Colombo Metropolitan Region Conceivable Structural Measures for in the Democratic Socialist Republic of Sri Lanka Ja Ela Basin JAPAN INTERNATIONAL COOPERATION AGENCY F - 44 Lower Retention Area (Return Period 50-years) 3.90 Lower Retention Area 1,357 ha 3.80 3.70 3.60 Allowable Water Level + 3.50m J0 3.50 J1 3.40 Average Water Level in Retention Area (m) J2 J3 3.30 J5 3.20 J6 J4 3.10 0 200 400 600 800 1000 1200 1400 1600 Retention Area (ha) The Study on Storm Water Drainage Plan Figure 4.7 for the Colombo Metropolitan Region Relationship between Retention Area and in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY Water Level in Ja Ela Basin (1/3) F - 45 Ja Ela at Negombo Road (50-year Return Period) 2.00 Lower Retention Area 1,357 ha 1.90 1.80 1.70 Allowable Water Level + 1.65 m J0 1.60 1.50 J4 J1 1.40 J2 Water Level in Ja Ela at Negombo Road (m) Road at Negombo in Ja Ela Level Water 1.30 J3 J5 1.20 J6 1.10 1.00 0 200 400 600 800 1000 1200 1400 1600 Retention Area (ha) The Study on Storm Water Drainage Plan Figure 4.7 for the Colombo Metropolitan Region Relationship between Retention Area and in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY Water Level in Ja Ela Basin (2/3) F - 46 Dandugam Oya at Negombo Road (50-year Return Period) 2.00 Lower Retention Area 1,357 ha 1.90 1.80 ) 1.70 Allowable Water Level + 1.58 m Oya at Negombo Road (m 1.60 J0 J4 1.50 J1 J2 Water Level in Dandugam J3 J5 1.40 J6 1.30 1.20 0 200 400 600 800 1000 1200 1400 1600 Retention Area (ha) The Study on Storm Water Drainage Plan Figure 4.7 for the Colombo Metropolitan Region Relationship between Retention Area and in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY Water Level in Ja Ela Basin (3/3) F - 47 N Katunayake Bridge DO-4 L=72m B=10m t n e Mapalam ya m O e m v 0 o 7 r = p B m a Negombo y m l I 0 e O 0 Lagoon n n ,9 m a 5 a h = g C u L nd a D Bridge DO-3 L=72m B=10m nt Lower Retention Area (500 ha) oveme l Impr hanne =80m C 00m B L=4,0 Bridge DO-2 L=80m B=15m Upper Retention Area (376 ha) A ttan Bridge DO-1 a Conservation Zone L=80m B=20m galu of Mathurajawela O Marsh y (Retention Area) a Bridge JE-2 L=60m B=20m Gampaha Bridge JE-3 Bridge JE-1 L=60m B=15m L=60m B=10m Ja Ela Legend Ja Ela t River/Canal men rove Channel Improvement Imp 0m nel B=6 han m Town C ,000 Canservation L=7 Storm Water Zone of Retention Area Mathurajawela Marsh Conservation (Retention Area) Zone of Marsh Proposed Bridge Expressway/Highway Canservation Scale The Study on Storm Water Drainage Plan Figure 4.8 Zone of Mathurajawela 0 1 2 3 km for the Colombo Metropolitan Region Proposed Storm Water Drainage Plan Marsh Colombo-Katunayake in the Democratic Socialist Republic of Sri Lanka (Retention Area) Expressway for Ja Ela Basin JAPAN INTERNATIONAL COOPERATION AGENCY F - 48.