Analysis of Drainage Capacity and Flood Risk Areas for Integrated Urban Planning of Sam Khok District, Pathumthani Province

Abstract

After flood crisis in Thailand in 2011, Department of public works and town planning improved the regulation for urban planning to include flood protection plan in the urban planning. The aim of this paper is to present an analysis of the drainage capacity and flood-risk areas for integrated urban planning of Sam Khok district, Pathum Thani province. The main cause of flooding in this area is overbank from Chao Phraya River. The topography, climate, hydrological and historical flood data of study areas are collected for analysis. Rational method is used to analyze drainage capacity of 12 main canals from total 87 canals by using design rainfall with 5 years return period from Don Muang station. The results show that the drainage capacity of 4 canals (Koi Mai, Bang Pho Neor, Khok Ta Kraw and Khu) are not enough. Flood risk index is calculated to draw flood risk map representing 5 risk levels. The result shows that flood risk in the west of Sam Khok is very high, while flood risk in the southeast of Sam Khok is low. Combined results of flood risk analysis and drainage capacity of main canal are used to define canal plan with 4 sizes: 10, 20, 30 and 40 meter and space area for flood drainage in integrated urban planning of Sam Khok district.