A Satellite Observations and Numerical Modelling Based Integrated Flash Flood Forecasting System for North-East Region of Bangladesh

North-east region of Bangladesh is comprised of hilly transboundary rivers in the upstream and complex river network along with floodplain in the downstream. In this study, a satellite observation and numerical modeling based near real-time flash flood forecasting framework is developed for the north-east part of Bangladesh. For nowcast information, Global Precipitation Measurement Mission (GPM) developed latest near real-time IMERG precipitation product is chosen. To produce improved quality precipitation forecasts, Global Forecasting System (GFS) based precipitation predictions are corrected by applying climatology based bias adjustment technique. Flow from upstream river channels into the complex river network are calculated by using the nowcast and forecast precipitation products forced into Soil and Water Assessment Tool hydrological Model. The inflow discharges from the hydrological model then used in HecRAS hydrodynamic model to produce forecasted water height/discharge, flood depth and inundation in prominent locations in the study region. Both of the hydrological and hydrodynamic models are simulated sequentially in sub-daily scale to produce 120 hours lead time forecasts. SWAT Model was calibrated and validated in six inflow stations using rated discharge. HecRAS Model was calibrated and validated using measured water level at different locations.