Thin Thin creator Shrestha, Sangam Chairperson Vojinovic, Zoran Co-Chairperson Mohana Sundaram Shanmugam Examination committee Xue, Wenchao Examination committee Torres, Arlex Sanchez Examination committee Orange Knowledge Programme (OKP) Ministry of Foreign Affairs, The Netherlands/NUFFIC/IHE Delft Scholarship Donor Asian Institute of Technology Scholarship Donor text series technical report th Pathum Thani, Thailand Asian Institute of Technology 2021 continuing eng 92 leaves : ill. Climate change and urbanization have been supporting to happen more the flooding problem though flooding itself is one of the unavoidable natural disaster which can adversely affect social, economic, and environmental of the affected area. As a result of that flood mitigation measures have been implementing over the decade all over the world. Traditional flood mitigation measures also known as grey infrastructures based on the concept of conveying the storm water from one place to another as fast as they can. However, it is likely that transferring the problem from one place to other. Moreover, these grey infrastructures are not flexible measures that can respond the uncertain conditions like urbanization and climate change. Nature Based-Solutions (NBSs) has been come out to fill the gaps of flexibility and sustainability. Part of large scale NBS, room for river is giving more space to rivers and came out from the Dutch concept. It is not deniable that more research will be needed as a recently came out idea. Next, though a significant amount of research for small scale NBSs have been doing, it is only implemented in developed countries, and it is still needed to accept in developing world. Combining large and small scale NBSs could be a good question to answer and could be a measure that can give more benefits than only large and small scale NBSs. In this research, the benefits of combined large and small scale NBSs were assessed, and the study area is World Heritage Site, Ayutthaya, which is in the middle of Chao Phraya River basin and is a flood prone area. Large scale NBS was implemented upstream part of study area and small scale NBSs was assigned within the study area. As a result of large scale NBS, water level of 6.2 cm was reduced at gauge station C35, and the reduced water level influence the flood mitigation system of the downstream study area of Ayutthaya Island. As a result of small scale NBSs. 0.12 Mm3 of runoff reduction was received within Ayutthaya Island. Consequently, the reduction in pumping hour of 1.18 hour that is needed to drain out the flood water was obtained. The result of combining large and small scale NBSs have a benefit of reduction of flooding in the study area, an economic benefit in term of reduction in pumping hours, moreover ecological benefit along Chao Phraya River creating floodplain area and giving aesthetic view for human being. A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Urban Water Engineering and Management Jointly offered by Asian Institute of Technology, Thailand and IHE Delft Institute for Water Education, The Netherlands Thesis (M. Sc.) - Asian Institute of Technology - IHE, 2021 Flood damage prevention Thailand Ayutthaya Flood control Thailand Ayutthaya Water use Management Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B14877 http://203.159.5.9/ait-thesis/detail.php?q=B14877 211005 20260817163529.0