An emergency response‐type rainfall‐runoff‐inundation simulation for 2011 Thailand floods

<jats:title>Abstract</jats:title><jats:p>A devastating flood disaster occurred in Thailand in 2011. In case of such large‐scale flooding, it is important to predict the dynamics of inundation on a near real‐time basis for safe evacuation. To predict widespread inundation, where both rainfall‐runoff from surrounding mountains and rainfall on floodplains contribute to the event, this paper applied a rainfall‐runoff‐inundation (<jats:styled-content style="fixed-case">RRI</jats:styled-content>) model to the entire Chao Phraya River basin (160 000 km<jats:sup>2</jats:sup>). Near real‐time simulation was conducted for emergency responses with globally available dataset including satellite‐based topography (<jats:styled-content style="fixed-case">HydroSHEDS</jats:styled-content> derived from <jats:styled-content style="fixed-case">SRTM</jats:styled-content>) and rainfall (<jats:styled-content style="fixed-case">TRMM</jats:styled-content> 3<jats:styled-content style="fixed-case">B42RT</jats:styled-content>) during the disaster. Post‐flood simulation was also carried out with more local information. The <jats:styled-content style="fixed-case">RRI</jats:styled-content> model was found capable of representing the peak inundation extent with an acceptable accuracy and correctly predicting a 1‐month lasting inundation in the lower part of the basin. On the other hand, the prediction overestimated the river discharge by 40% and the inundation water level by 2 m mainly due to the neglect of the evapotranspiration effect. The post‐flood simulation improved its accuracy by up to 10% for river discharges and 1 m for peak inundation water levels, but it did not lead to better agreement of flood extents with those based on the remote sensing. Further study is recommended to improve accuracy for modelling of spatial extent of flooding. Furthermore, sensitivity analysis with different input suggested what information should be prioritised for emergency response‐type flood simulations.</jats:p>