河道泥沙淤积对洪灾风险评估的影响

建立了考虑泥沙淤积的洪灾风险估计的一般模式,并以螺山站为例,定量分析了泥沙淤积对洪水频率和洪灾风险的影响.结果表明,考虑泥沙淤积对水位频率会产生影响,在相同水位下,泥沙淤积会缩短洪水的重现期,水位越低,频率变化越大.对于相同频率的洪水,泥沙的淤积使水位抬升,且频率越小,水位变化越小.另外,泥沙淤积使洪灾风险增加,加重了洪灾的损失.螺山下游的洪灾风险率从6%增加到22.5%,水位超高期望值从0.114 m增加到0.233 m.

AN ASSESSMENT OF THE INFLUENCE OF THE WATERWAY SILT-UP ON THE FLOOD-DISCHARGE

Taking Luoshan Station as an example for the flood risk assessment, the present paper makes a quantitative analysis on the effect of the waterway silt up on the flood discharge with the author's self established general assessment mode. In recent decades, serious flood and high level water passing through a waterway with small discharge capacity has become more and more frequent happenings in China. Such discharge difficulty has been mainly caused by the sledge silt up in the waterway. So how to assess the effect of the sledge silt up and increase the discharge capacity has become an urgent need. Since the factor of waterway silt up is often ignored in the traditional flood research, a general risk assessment mode has to be established, which involves two parts. One is to analyze the effect of the silt up situation on the flood frequency. For this purpose, a water level frequency curves before and after the silt up formation has to be drawn up and the flood frequency change has also to be measured in a statistical manner so that the effect of the silt up on the flood can be analyzed. Then, a general mode is used to observe the data collected in Luoshan to show how to operate the mode. To this end, the authors are engaged in continuous measuring and calculating the water level of Luoshan from 1954 to 1985 before the silt up deposition with an empirical formula by means of a multivariate linear regression, and the effect of the silt up deposition on the flood frequency to analyze the flood risk. Two conclusions are finally obtained as follows. First, the water level frequency increases because of silt up deposition. Second, according to the change of the two indexes before and after the deposition, the silt up deposition has made it possible for the lower reach to commit more flood risk. Furthermore, with the rising of water level of Luoshan, the water level in Dongting Lake is likely to rise too. Hence, more flood risk with Dongting.