MATTERS TO BE ATTENDED TO FLOOD CONTROL PLAN THROUGH EXTREME ANALYSIS WITH PEAK DISCHARGE AND CATCHMENT AVERAGE RAINFALL

Abstract

 Hydrological frequency analysis generally deals with annual maximum series of flood peak discharges or catchment average rainfalls during rainfall duration of the flood control plan. The shape parameter of the generalized extreme value distribution is closely related with the thickness of the upper tail of the probability density function. Because the peak flood discharge at a flood control reference point is closely connected with basin averaged rainfall in the basin upper than the reference point during adequate duration, it is expected to get similar results between peak discharge direct frequency analysis and runoff analysis after rainfall depth frequency analysis, however, they are often different. This paper shows the reasons of the difference and matters to be attended to flood control planning.