The office adopts the self-developed REFOR mode (Real time flash flood FORecasting model), which are further divided into five online Sub-models and one off-line model of REFOR
◆Rainfall Prediction Model:
It adopts the inertia law to estimate the average rainfall of the storage area in 1 to 6 hours. Two methods, the arithmetic method of average and Wufenshan radar observation, are used for calculating the average rainfall.
◆Tide Prediction Model (includeing astronomic and atomospheric tides)
◆Rainfall Runoff Simulation Model (Tank Model):
It uses bucket model to divide the Danshuei River into 16 buckets. The results, based on different areas, can be coordinated with the Muskingum method and used as the intake capacity of the next Tank, or the intake capacity of the reservoir, or the intake of the boundaries of the one dimensional unsteady flow model.
◆One dimensional Unsteady Flow Simulation Model:
It simulates the flood-control-period operation model of Shih-Men Reservoir and Fei-Tsui Reservoir, under the premise of reservoir safety, using reservoir stage and the forecasted reservoir intake (provided by the Bucket Model) then following the reservoir operational regulations for simulation. Moreover, it suggests proper flood discharge capacity of the reservoir, hoping to ensure reservoir safety during floods and downstream flood control.
◆River Flood Forecast Model:
It is based on one dimensional unsteady flow(Dynamic wavetheory) and uses Preissmann four-point Preissmann finite difference method to calculate the stages and flow rates of each river’s cross-section at various time. To simulate the tide level effects, the estimated values of the astronomic tide levels and meteorological tide levels of the Danshuei River outlet tide levels station are utilized for downstream border conditions. In the future, the instant water levels of the station will be obtained to improve its accuracy. The upstream border conditions are the forecasted results of the Rainfall Runoff Forecast model. This model can forecast the river stages from 1 to 6 hours. The river stage values are then used to conduct parameter feedback calculation and modify the model parameter to avoid the increasing errors between forecast values and measured values.
◆Yuansantz Diversion Simulation Model
◆Simulation of Reservoir Operation(off-line simulation)
◆Integration, Display and Decision Model
The aforementioned models are module programs, and integrated master formula should be set up to control the operation of each program. Moreover, it can derive the forecast results and automatically produce diagrams, flood announcement and warning lists as references for decision makers; such information is uploaded on the Web site and available to the media and general public.