Disastrous flood,in the light of systems analysis of disaster,is one of the most active and sensetive factors for natural disasters.The analysis for the highest water level,flow quantity of peak flood and flooding disaster\|caused area at Chenlingji Hydrometric Station of Dongting Lake in the years of 1950 to 1999 has shown that disastrous flood of Dongting Lake concurred in high frequency and with huge energy dissemination and strong capacity of sand transportation and that the floods are direct and/or ind...