Floods are one of the most frequently occurring weather related disasters, which affected more than 2.3 billion people worldwide and caused the highest amount of financial losses ($662 billion) over the last two decades (CRED and UNISDR, 2015). Flash floods have rapid onset which provides only few hours between rainfall and flooding and hence short time for warning which leads to the majority of flood casualties around the world. Flash floods are usually very localized in time and space, they occur suddenly and are difficult to forecast with accuracy which can leave people without warning.