Abstract

The observed peak stage of 1998-flood at Luoshan Hydrographic Station of Changjiang Middle River is 1.78m higher than that of 1954-flood. Four causes are firstly analyzed in this paper, they are: (1) Difference of flood features; (2) Effect of 1954-flood retention and diversion; (3) Change of Dongting Lake diversion and confluence flows; and (4) Fluvial processes of Changjiang Main Channel. Then, a 1-D hydrodynamic mathematical model for flood routing is developed. Next, based on 81.7-flood and 1998-flood calibrations, 1954-flood restoring calculation and 1998-flood and 1954-flood routing calculations are implemented by means of the Model. Finally, quantitative contributions of different causes to rise of 1998-flood peak stage at Luoshan are analyzed and summarized as follow: (1) 1954-flood detention and diversion would enable peak stage of 1954-flood at Luoshan to decrease 0.83m (or peak stage of 1998-flood would increase 0.83m); (2) Combinative effects of two causes (change of Dongting Lake diversion and confluence flows and fluvial processes of Changjiang Main Channel) would increase peak stage of 1998-flood by 0.74m～0.84m; and (3) fluvial processes of Changjiang Main Channel would enable peak stage of 1998-flood to increase 0.33～0.36m.

Keywords: Flood Peak Stage; 1-D Hydrodynamic Mathematical Model; Changjiang Main Channel; Dongting Lake; Luoshan Hydrographic Station