Abstract
A combined hydrological and hydraulic model is presented for flood prediction in Vietnam. This model is applied to the Huong river basin as a test case study. Observed flood flows and water surface levels of the 2002–2005 flood seasons are used for model calibration, and those of the 2006–2007 flood seasons are used for validation of the model. The physically based distributed hydrologic model WetSpa is used for predicting the generation and propagation of flood flows in the mountainous upper sub-basins, and proves to predict flood flows accurately. The Hydrologic Engineering Center River Analysis System (HEC-RAS) hydraulic model is applied to simulate flood flows and inundation levels in the downstream floodplain, and also proves to predict water levels accurately. The predicted water profiles are used for mapping of inundations in the floodplain. The model may be useful in developing flood forecasting and early warning systems to mitigate losses due to flooding in Vietnam.
Highlights
As a result of human intervention in the natural environment and the effects of global climate change, floods are occurring more frequently
Flood generation and flow routing in the three upper reaches of the Huong River basin are simulated with the WetSpa model with a spatial resolution of 50 m and a 6-h time step
2003–2005 flood seasons observed at Binh Dien station on Ta Trach River are used for calibration of the WetSpa model, while observed discharge time series for the 2006 and 2007 flood seasons are used for model validation
Summary
As a result of human intervention in the natural environment and the effects of global climate change, floods are occurring more frequently. Of all natural disasters in Vietnam, flooding ranks first in terms of affected area, severity, frequency, and financial losses [1]. Red River in August 1971 (which may have caused as many as 100,000 deaths), and the severe flooding of the central coastal provinces of Vietnam in early November 1999, caused by a huge storm with a peak rainfall intensity of 120 mm/h, killing hundreds of people and causing huge economic losses [2,3]. There were devastating floods in Northern and Central Vietnam in November 2007, killing dozens of people and causing severe damage to crops, housing, and infrastructure [4]. Efforts to set up real-time flood forecasting in Vietnam began in the 1970s through a combination of telemetry rainfall data acquisition and flood prediction by runoff modeling. Accurate flood forecasting remains problematic due to a lack of expertise and up-to-date flood forecasting models
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