Flood-hazard assessment and risk-based zoning of a tropical flood plain: case study of the Yom River, Thailand
Flood-hazard risk of the Yom River, Thailand
Tawatchai Tingsanchali1 & Fazlul Karim2
1Programme of Civil and Environmental Engineering, Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000 Thailand
(formerly at: Asian Institute of Technology, Thailand)
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2CSIRO Land and Water, University Drive, Douglas, Queensland 4814, Australia
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Received 20 July 2008; accepted 7 August 2009; open for discussion until 1 September 2010
Abstract
This study contributes to the comprehensive assessment of flood hazard and risk for the Phrae flood plain of the Yom River basin in northern Thailand. The study was carried out using a hydrologic–hydrodynamic model in conjunction with a geographic information system (GIS). The model was calibrated and verified using the observed rainfall and river flood data during flood seasons in 1994 and 2001, respectively. Flooding scenarios were evaluated in terms of flooding depth for events of 25-, 50-, 100- and 200-year return periods. An impact-based hazard estimation technique was applied to assess the degree of hazard across the flood plain. The results showed that 78% of the Phrae flood-plain area of 476 km2 in the upper Yom River basin lies in the hazard zone of the 100-year returnperiod flood. Risk analyses were performed by incorporating flood hazard and the vulnerability of elements at risk. Based on relative magnitude of risk, flood-prone areas were divided into low-, moderate-, high- and severe-risk zones. For the 100-year return-period flood, the risk-free area was found to be 22% of the total flood plain, while areas under low, medium, high and severe risk were 33, 11, 28 and 6%, respectively. The outcomes are consistent with overall property damage recorded in the past. The study identifies risk areas for priority-based flood management, which is crucial when there is a limited budget to protect the entire risk zone simultaneously.
Key words flood hazard; vulnerability; land use; flood risk; Yom River Basin; return period
Hydrological Sciences Journal – Journal des Sciences Hydrologiques, 55(2) 2010
