Monte Carlo simulation of distributed rainfall-runoff conditions for probabilistic short-term flood forecasting

A framework for short-term probabilistic forecasting of watershed flood stage conditions using a distributed rainfall-runoff model is proposed. A stochastic rainfall pattern simulation model capable of generating input for a distributed rainfall-runoff model is developed. Generation of rainfall patterns over a 6-hour period is achieved using a translation vector rainfall forecasting process modified to account for uncertainties in rainfall pattern development. The stochastic rainfall generation model is coupled with a distributed rainfall-runoff model in a Monte-Carlo simulation to provide a short-term ensemble forecast of distributed flood discharge. An adaptive updating procedure for the real-time reduction of forecast error suitable for use with a distributed rainfall-runoff model is developed for the system. An example application of the proposed probabilistic flood stage forecasting system is provided for a typhoon event that occurred in the vicinity of the Nagara River watershed located in Gifu, Japan.