Rainfall-Runoff Models and Flood Mapping in a Catchment of the Upper Nan Basin,Thailand

Sombat Chuenchooklin; Saharat Taweepong; Udomporn Pangnakorn
The Pua Watershed is one of many small catchments in the Upper Nan River Basin, located in the upper portion of the Great Chao Phraya River Basin in Nan Province, Thailand. It was previously considered as an ungauged catchment due to the lack of observed hydrological data. It usually faces flood problems, affecting primarily farmland and residential areas. Two models from the Hydrologic Engineering Center (HEC) were applied: the Hydrologic Modeling System (HMS), and the River Analysis System model (RAS). HMS was used to synthesize daily flood hydrographs from existing daily rainfall data over its catchment, while RAS presents flood behaviors in the river reaches including existing cross-sectional profiles. The HMS model was calibrated in 2008 and validated in 2011 with observed daily rainfall and streamflow data collected at a gauge station in the catchment. Flood mapping on the topographic map in 2011 was delineated from the products by RAS. The simulated results from both the HMS and RAS models fit the observed data well, which can be applied to further efficient flood relief plans and management for any river basin.
Rainfall-runoff Models; HMS; RAS; Ungauged Catchment; Flood Mapping
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