Responsibilities are as follows:
1. Study, analyze and prepare a master plan, work Plans and Projects regarding Bangkok Flood Prevention and Drainage System
2. Study and analyze national water management strategic plans and prepare policy proposals for Bangkok water management.
3. Planning, preparing, monitoring, analyzing and evaluating the implementation achievement of both Operation plan of the Department of Drainage and Sewerage and Strategic Plan for Bangkok Water Management
4. Construction of flood protection line along the Chao Phraya River, Bangkok Noi Canal And Maha Sawat Canal.
5. Construction of flood prevention system, drainage system of enclosed areas (Polder) and construction of large drainage tunnels, including procurement and development of the monkey Cheek (Kaem Ling) Water Reservoir or Water Bank with appropriate conditions in Bangkok
6. Determine the size and bottom level of the drainage pipes in the Bangkok area.
7. Monitoring, surveillance, prevention and solving of coastal erosion problems and manage the center for the exploration and coastal surveillance at Bang Khun Tien
8. Consider allowing, form and specification for construction of intrusive structure along Chao Phraya River, Bangkok Noi Canal And the Maha Sawat Canal and also to improve the drainage system in the Bangkok area for both government and private agencies.
9. Centric collaboration for research studies, technological innovation, as well as promote knowledge, advice and support academic information on urban water management, flood response and coastal erosion caused by terrain and climate change.
10. Perform other related duties or assigned

The office consists of
1. General administration Section
 1. Correspondence and general administration
 2. Administration and coordination work
 3. Procurement
 4. Staff and discipline work
 5. Finance and budget
 6. Public relations
 7. Office premises and vehicles maintenance
 8. Perform other related duties or assigned

2. The subjects and plans Sub-office has the following responsibilities:
 1. Study, analyze and prepare a master plan, work plans and projects for department of drainage and sewerage
 2. Prepare, supervise and evaluate the achievement of implementation according to water management strategic plan and action plan of the Department Drainage and Sewerage
 3. Planning for procurement and development of innovative construction of water receptacles or monkey cheeks or water banks in suitable formats with the area conditions of Bangkok.
 4. Prevent and solve the problem of erosion of the sea coast of Bang Khun Thian and to operate the Bang Khun Thian Coastal Survey and Surveillance Center.
 5. Study and develop innovation in flood prevention and coastal erosion for Bangkok.
 6. Perform other related duties or assigned.

The sub-office consists of:
2.1. Planning and Project Division
 1. Prepare Master Plan for the Flood Prevention and Drainage System of Bangkok
 2. Study and analyze the National Water Management Strategic Plan and establish policy proposals and water strategic plans of Bangkok
 3. Preparation of plans and projects of the Department of Drainage in terms of emergency, short term, medium and long term
 4. Prepare working plans to prevent and mitigate flooding of Bangkok
 5. Consulting. Provide advice, support information and cooperate in planning and water management projects to the relevant departments.
 6. To be a center for cooperation and exchange of knowledge and experience in urban water management to the departments both domestic and abroad
 7. To prepare annually action plan for the Department of Drainage and Sewerage
 8. Monitor and evaluate the achievement of the policies implementation formulated by the government and the endorsement to government's annual Action Plan
 9. Perform other related duties or assigned.

2.2. Academic and Water Management Innovation Division
 1. Study, survey, analyze flood response strategies and coastal erosion to support topographic and climate change
 2. The preparation of flood risk maps, evaluate and improve according to the changing terrain
 3. Survey, design and development of innovative water reservation basins (Monkey cheeks) or water banks in forms those are suitable to conditions of Bangkok
 4. Study, analyze the flood problem and find solutions to prevent and solve
 5. Study, analyze, prepare, supervise, monitor and evaluate the project performance in the Bangkok Resilient City plan and Master Plan on Climate Master Plan on Climate Change Adaptation and Response
 6. Support education of the development of flood adaptation in the Bangkok area in collaboration with local and international agencies.
 7. Study, survey, design, construct, inspect and repair the coastal erosion protection lines
 8. Management of Bang Khun Thian Coastal Surveillance Center to be data center the coastal erosion learning center
 9. Monitoring, analyze and finding method of prevention and mitigate coastal erosion from changing topographic and climate. Also develop an exchange center of knowledge and technological innovations as well as integrating coastal management with the Department of Marine and Coastal Resources.
 10. Study, analyze and arrange training courses to improve personal capacity in flood prevention
 11. Perform other related duties or assignments.

3. Drainage system engineering sub-office
Responsibilities are as follows:
 1. Survey, design, construction and repair of the flood protection line along the Chao Phraya River, Bangkok Noi Canal and Maha Sawat Canal
 2. Survey, design and construction of flood protection system and the drainage system of enclosed area (Polder) and large drainage tunnel
 3. Determine the dimension of sewer and the lowest pipe invert elevation
 4. Consider allowing intrusive construction of waterway infrastructure and the construction of various departments, affecting the development of the Chao Phraya River and Bangkok's main drainage system
 5. Consider and improve standards in the technical aspects in construction regarding flood protection and drainage
 6. Perform other related duties or assigned.

The sub-office consists of:
3.1. Drainage Engineering Group 1
 1. Construction of flood protection line along the Chao Phraya River
 2. Construction of flood protection system and the drainage system of the enclosed area( Polder).
 3. Construction of large drainage tunnels.
 4. Determine the dimension of sewer and the lowest pipe invert elevation in Bangkok area.
 5. Consider setting the size, level and construction requirements for improving the drainage system for agencies under the Bangkok Metropolitan Administration.
 6. Consider requesting for permission to construct intrusive waterways and infrastructure that affect the development of the Chao Phraya River and the main drainage system of Bangkok.
 7. Consider and improve the standards of technical aspects in construction regarding flood prevention and drainage
 8. Prepare operation control and inspection manuals for drainage system construction
 9. Provide drainage information in the area to accompany the EIA report (Environmental Impact Assessment)
 10. Perform other related duties or assigned. Which is responsible for the area of 15 districts : Phra Nakhon, Pom Prap Sattru Phai, Samphanthawong, Pathumwan, Bang Rak, Phra Khanong Yannawa, Ladkrabang, Prawet, Khlong Toei, Wattana, Sathorn, Bang Kho Laem, Suan Luang and Bangna

3.2. Drainage Engineering2 Work Group :has the same authority as Drainage Engineering Group 1 , responsible for 20 areas: Dusit Phayathai, Huay Kwang, Bang Khen, Sai Mai, Bangkapi, Saphan Sung, Wang Thonglang, Minburi, Khlong Sam Wa, Nong Chok, Bang Sue, Ratchathewi, Don Mueang, Laksi,Chatuchak, Lat Phrao, Bueng Kum Khanna Yao and Din Daeng

3.3. Drainage Engineering3 Work Group
 1. Construction of flood protection lines for Bangkok Noi Canal and Maha Sawat Canal
 2. Has the same authority as Drainage Engineering Group 1, responsible for 15 areas, including Bangplat, Bangkok Noi, Bangkok Yai, Thonburi, Khlong San, Rat Burana. Talingchan, Thawi Watthana, Phasi Charoen, Bang Khae, Nong Khaem, Bang Khun Thian, Bang Bon, Jomthong and Thung Khru