长江中游螺山站'98洪水位偏高原因分析计算

 长江中游螺山站1998年洪水实测洪峰水位比1954年洪水实测洪峰水位偏高1.78 m，经综合分析认为主要有洪水特性差异、54洪水分洪影响、洞庭湖分汇流变化影响、长江干流河道变化影响4个方面的原因。为研究各影响因素对螺山站98洪峰水位偏高的影响程度，建立了一套适用于长江中游河道的洪水演进水动力学数学模型，在“81.7”洪水和98洪水复演计算的基础上，进行了54洪水还原、98洪水演进和54洪水演进计算。计算成果分析表明：由于54洪水分洪使得螺山站54洪峰水位降低了0.83 m（即相当于使得98洪峰水位抬高了0.83 m），洞庭湖分汇流和长江干流河道变化联合影响引起的螺山站98洪峰水位抬高值为0.74～0.84 m，而仅长江干流河道变化引起的螺山站98洪峰水位抬高值为0.33～0.36 m。

Analysis and Calculation on Reasons of Increasing 1998-Flood Peak Stage at Luoshan Hydrographic Station of Changjiang River Middle Reach

The observed 1998-flood peak stage is 1.78 m higher than that of 1954-flood at Luoshan hydrographic Station of the Changjiang River middle reach. The 4 main reasons, summarized in this paper, are: ①the difference of flood characteristics；②the effect of 1954-flood detention and diversion；③the changes of the Dongting Lake inflow and outflow； and ④the fluvial processes of the Changjiang River mainstream channels. To quantitatively study the effects of the individual or combinative above-mentioned reasons, a 1-D flood routing hydrodynamic mathematical model has been developed, which can be applied to the Changjiang middle river channels. Based on 81.7-flood and 1998-flood calibrating calculations, 1954-flood restoring calculation and 1998-flood and 1954-flood routing calculations have been implemented by means of the model. The results and analysis show that: ①1954-flood detention and diversion enabled 1954-flood peak stage at Luoshan Hydrographic Station to decrease 0.83 m (i.e. 1998-flood peak stage would increase 0.83 m), ②due to the combinative effects of changes of the Dongting Lake inflow and outflow and fluvial processes of the Changjiang River mainstream channels, 1998-flood peak stage would raise 0.74-0.84 m, and ③because of fluvial processes of the Changjiang River mainstream channels, 1998-flood peak stage at Luoshan Hydrographic Station would increase 0.33-0.36 m.