N Legend Retention Area Retention Areas in Highly Urbanized Area Development Plan incorporated (Nugegoda-Rattanapitiya Sub-basin) with Future Land Use Total 36 ha Projection Identified Location of Outstanding Land Filling
Location of Previous Plan with Land Filling
Location of Envisaged Development Vicinity of Retention Area
Police Academy Garbage Dumping Site Compound Belanwilla-Attidiya Marsh Retention Area 108 ha
Boralesgamuwa Theme Park Project Area
Weras Ganga Swamp Expansion Area for Retention Area Ratmalana Airport 65 ha
Maha Ela Marsh and Lowland Retention Area Retention Area in 132 ha Highly Urbanized Area (Ratmalana-Moratuwa Sub-basin) 23 ha Retention Area in Highly Urbanized Area (Thumbowila Sub-basin) 8 ha
Scale 0 400 800 1200 1600 2000 m
The Study on Storm Water Drainage Plan Figure 4.6.1 for the Colombo Metropolitan Region Retention Areas and in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY Surrounding Development Envisaged
A7 - F76 N Legend Retention Area Retention Areas in Highly Urbanized Area Development Plan incorporated (Nugegoda-Rattanapitiya Sub-basin) with Future Land Use Total 36 ha Projection
Assumed Loss of Retention Area
Police Academy Compound Belanwilla-Attidiya Marsh Retention Area 108 ha
Boralesgamuwa Theme Park Project Area
Weras Ganga Swamp Expansion Area for Retention Area Ratmalana Airport 65 ha
Maha Ela Marsh and Lowland Retention Area Retention Area in 132 ha Highly Urbanized Area (Ratmalana-Moratuwa Sub-basin) 0 ha Retention Area in Highly Urbanized Area (Thumbowila Sub-basin) 0 ha
Scale 0 400 800 1200 1600 2000 m
The Study on Storm Water Drainage Plan Figure 4.6.2 for the Colombo Metropolitan Region Assumed Loss of Retention Area (1/3) in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY Case-2
A7 - F77 Legend N Retention Area Retention Areas in Highly Urbanized Area Development Plan incorporated (Nugegoda-Rattanapitiya Sub-basin) with Future Land Use Total 36 ha Projection
Assumed Loss of Retention Area
Police Academy Compound Belanwilla-Attidiya Marsh Retention Area 68 ha
Water Park Project Area
Weras Ganga Swamp Expansion Area for Retention Area Ratmalana Airport 65 ha
Maha Ela Marsh and Lowland Retention Area Retention Area in 132 ha Highly Urbanized Area (Ratmalana-Moratuwa Sub-basin) 0 ha Retention Area in Highly Urbanized Area (Thumbowila Sub-basin) 0 ha
Scale 0 400 800 1200 1600 2000 m
The Study on Storm Water Drainage Plan Figure 4.6.2 for the Colombo Metropolitan Region Assumed Loss of Retention Area (2/3) in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY Case-3
A7 - F78 Legend N Retention Area Retention Areas in Highly Urbanized Area Development Plan incorporated (Nugegoda-Rattanapitiya Sub-basin) with Future Land Use Projection
Assumed Loss of Retention Area
Police Academy Compound Belanwilla-Attidiya Marsh Retention Area 68 ha
Boralesgamuwa Theme Park Project Area
Weras Ganga Swamp Expansion Area for Retention Area Colombo Airport 65 ha
Maha Ela Marsh and Lowland Retention Area Retention Area in 106 ha Highly Urbanized Area (Ratmalana-Moratuwa Sub-basin) 0 ha Retention Area in Highly Urbanized Area (Thumbowila Sub-basin) 0 ha
Scale 0 400 800 1200 1600 2000 m
The Study on Storm Water Drainage Plan Figure 4.6.2 for the Colombo Metropolitan Region Assumed Loss of Retention Area (3/3) in the Democratic Socialist Republic of Sri Lanka Case-4 JAPAN INTERNATIONAL COOPERATION AGENCY
A7 - F79 1.8 Rattanapitiya Ela Case 1 1.7 Case 2 Weras Ganga Swamp
1.6 Case 3
Case 4 Borupana Bridge 1.5
Maha Ela 1.4
1.3
1.2
Kospalana Bridge 1.1
1.0 Elevation (above MSL) (above Elevation
0.9
0.8
0.7
Bolgoda 0.6 Weras Ganga Canal
0.5
0.4 0 1000 2000 3000 4000 5000 6000 Distance (m)
The Study on Storm Water Drainage Plan Figure 4.6.3 for the Colombo Metropolitan Region Water Surface Profiles of Weras Ganga in the Democratic Socialist Republic of Sri Lanka JAPAN INTERNATIONAL COOPERATION AGENCY
A7 - F80 1.300 Line-A Maha Ela Bellanwila- 1.250 Marsh Attidiya Marsh Small Retention Areas 26 ha 40 ha 31 ha 1.200 Water Level 1.150 under Without Measures
1.100
1.050 312 ha
1.000 200 250 300 350 400
1.300 Line-B Maha Ela Bellanwila- Small Retention Areas Marsh Attidiya Marsh 1.250 31 ha 26 ha 40 ha
1.200 Water Level under Without Measures 1.150
1.100
1.050 340 ha
1.000 200 250 300 350 400
1.300 Line-C Bellanwila- Maha Ela Attidiya Marsh Marsh Small Retention Areas 1.250 40 ha 26 ha 67 ha
1.200 Water Level under Without Measures 1.150
1.100
1.050 295 ha
1.000 200 250 300 350 400
The Study on Storm Water Drainage Plan Figure 4.6.4 for the Colombo Metropolitan Region Relationship between Retention Area in the Democratic Socialist Republic of Sri Lanka and Average Water Level in Weras Ganga JAPAN INTERNATIONAL COOPERATION AGENCY
A7 - F81