PART I : INTRODUCTION Final Report, Volume II Introduction Main Report Chapter 1 CHAPTER 1 INTRODUCTION 1.1 Background of the Study As the urbanized area of the Colombo Metropolitan Region (CMR) expands into the coastal lowland, the difficulty of drainage is causing an increase in the frequency of flood inundation. The inundation results in damage to property and deterioration of infrastructures as well as a worsening hygiene environment for residents. Implementation of remedial measures to reduce inundation is important to secure lands for future development in the CMR (population 5.3 million at 2001). Since the early 1990’s, the Government of Sri Lanka (GOSL) has been implementing the Greater Colombo Flood Control and Environment Improvement Project, being assisted by an Official Development Assistance Loan from the Government of Japan (GOJ). GOSL has also recognized the need for a comprehensive master plan for storm water drainage in the entire CMR and in September 1999 requested GOJ to undertake a study to formulate such a master plan GOJ agreed to conduct the Study on Storm Water Drainage Plan for the Colombo Metropolitan Region in the Democratic Socialist Republic of Sri Lanka (the Study). The Scope of Work was agreed between the Sri Lanka Land Reclamation and Development Corporation (SLLRDC) of the Ministry of Urban Development, Construction & Public Utilities (presently Ministry of Housing & Plantation Infrastructure) and Japan International Cooperation Agency (JICA) on March 7, 2001. 1.2 Objectives of the Study The objectives of the Study are: 1) To formulate a master plan for storm water drainage in the Colombo Metropolitan Region, 2) To conduct feasibility study on a priority project to be identified in the master plan, and 3) To carry out technology transfer to counterpart personnel in the course of the Study. 1.3 Study Area The area for master plan study is shown in the Location Map, and covers part of the Colombo Metropolitan Region. The area is roughly divided into four drainage basins Nippon Koei Co., Ltd. 1 - 1 The Study on Storm Water Drainage Plan for the Colombo Metropolitan Region Final Report, Volume II Introduction Main Report Chapter 1 comprising Ja Ela basin, Kalu Oya basin, Greater Colombo basin and Bolgoda basin. The total catchment area is 830 km2 as shown in Figure 2.1. 1.4 Priority Project for Feasibility Study Based on the master plan study, the storm water drainage project for the sub-catchment of the Bolgoda basin, namely Weras Ganga basin, was selected as a priority project for the feasibility study. The Weras Ganga basin, with a catchment of 55.5 km2 is shown in Figure 2.1. 1.5 Study Schedule and Activity The Study is scheduled to be carried out for 18 months from September 2001 to February 2003 and the entire study period is staged into two phases as follows: Phase 1: Master Plan Study • Preparatory Work in Japan (0.2 months in September 2001) • First Field Work in Sri Lanka (5.8 months from September 2001 to March 2002) • First Home Work in Japan (0.5 months in June 2002) Phase 2: Feasibility Study on Priority Project • Second Field Work in Sri Lanka (3.5 months from July to October 2002) • Second Home Work in Japan (1.5 months from October to November 2002) • Third Field Work in Sri Lanka (0.5 months in December 2002) • Third Home Work in Japan (0.5 months in February 2003) (1) Phase 1 The first field work in Sri Lanka commenced on September 17, 2001. The Inception Report on the Study was agreed by GOSL at the meeting with the Steering Committee established for the Study held on October 10, 2001. The investigation works for the master plan study were carried out till March 9, 2002 in the fields of engineering, environment, social and economy. The results of the first field work were compiled as Progress Report (1). At the end of the first field work, a workshop on the master plan was held on March 4, 2002 inviting personnel of the relevant organizations aiming at transferring technology and exchanging the opinions on the study results between the Study Team and Sri Lanka participants. Based on the results of the first field work, the master plan study was carried out in Japan and the master plan study results were compiled in the Interim Report. In this Nippon Koei Co., Ltd. 1 - 2 The Study on Storm Water Drainage Plan for the Colombo Metropolitan Region Final Report, Volume II Introduction Main Report Chapter 1 Report, the storm water drainage master plan for the Colombo Metropolitan Region and also the priority project for the feasibility study are proposed. (2) Phase 2 The second field work commenced on July 1, 2002. The priority project for the feasibility study was affirmed at the Steering Committee meeting held on July 9, 2002 and the storm water drainage project for the Weras Ganga basin was determined as a priority project. Investigation works for the feasibility study were carried out till October 13, 2002 in areas of engineering, environment, social and economy. The second Progress Report compiled the findings and interim results of the Second Field Work in Sri Lanka carried out for the feasibility study. At the end of the second field work, a workshop on the feasibility study was held (on March 4, 2002) involving personnel of the relevant organizations and aimed at transferring technology and exchanging the opinions on the study results between the Study Team and Sri Lanka side. Based on the results of the second field work, the feasibility study was carried out in the second home work in Japan and the result of feasibility study were compiled together with the master plan study result as the Draft Final Report. The Draft Final Report was presented and discussed at the third field work in Sri Lanka. During this period, a seminar on the Study was held (on December 17, 2002) involving personnel of the relevant organizations and aimed at transferring technology and exchanging the opinions on the study results between the Study Team and Sri Lanka side. The Final Report was prepared at the third home work in Japan in the light of the discussions at the presentation of the Draft Final Report and the comments issued by the Sri Lanka side afterwards. The Final Report was finalized in March 2002. 1.6 Technology Transfer Technology transfer is one of the objectives of the Study. The technology transfer was carried out in the form of on-the-job training through joint work by the team member and the counterpart personnel, occasional discussion with other team members and counterpart personnel, workshop and seminar. Workshops for technology transfer were held twice during the study period as below. The first workshop was held on March 4, 2002 at Lanka Oberoi Hotel, Colombo in the first field work in Sri Lanka for the master plan study having 40 participants after inviting 78 from relevant central government agencies, relevant local authorities, Nippon Koei Co., Ltd. 1 - 3 The Study on Storm Water Drainage Plan for the Colombo Metropolitan Region Final Report, Volume II Introduction Main Report Chapter 1 foreign donors, etc. At the workshop, interim results of the master plan study were presented by the Study Team and discussed among the participants. The second workshop was held on October 4, 2002 at Colombo Hilton, Colombo in the second field work in Sri Lanka for the feasibility study involving 55 participants from 87 invitations to relevant central government agencies, relevant local authorities, foreign donors, etc. At this workshop, interim results of the feasibility study were presented by the Study Team and discussed among the participants. The technology transfer seminar was held on December 17, 2002 at Lanka Oberoi Hotel, Colombo in the second field work in Sri Lanka for the feasibility study involving 48 participants from 110 invitations to relevant central government agencies, relevant local authorities, foreign donors, etc. At this workshop, all the results of the Study and topics on storm water drainage in Japan and Sri Lanka were presented by the Study Team and Sri Lanka side and discussed among the participants. In addition to the workshops, the JICA Team undertook a mini workshop on the master plan study for the counterpart personnel on July 4, 2002 at the meeting room of SLLRDC. The Study Team also held a mini seminar on the MIKE 11 software (for hydrological and hydraulic analyses used in the Study), for about 20 engineering staff of SLLRDC. Nippon Koei Co., Ltd. 1 - 4 The Study on Storm Water Drainage Plan for the Colombo Metropolitan Region PART II : MASTER PLAN Final Report, Volume II Master Plan Main Report Chapter 2 CHAPTER 2 PRESENT CONDITIONS OF THE STUDY AREA 2.1 Natural Conditions 2.1.1 General Topography The study area extends from Katunayake in the north to Kalutara in the south or approximately between lat. 6°36´N and lat. 7°10´N and between long. 79°50´E and long. 80°05´E. It is broadly bounded by Negombo Lagoon and Dandugam Oya to the north, the proposed route of the Outer Circular Highway to the east, and the Bolgoda Lake watershed to the south. There are several drainage basins which are entirely or partly included in the study area. The delimitation of drainage basins in the study area for the purpose of the present study is shown in Figure 2.1 and tabulated below: Relevant River Basins and Study Area Basin Basin Area (km2) Within Study Area (km2) Ja Ela 860 173 Kalu Oya 58 58 Kelani Ganga 2,292 89 Greater Colombo 85 85 Bolgoda 394 394 Other Areas along Coast 31 31 Total - 830 Note: Extent of basin area is estimated from 1:50,000 scale topographic map.