Storm Surge Disasters on the Yellow River Delta and Countermeasures

Based on statistics from historical and modern records,the occurrence period of storm surges averaged 11.3 a on the old Yellow River delta,and 6.4 a on the modern Yellow River delta,which shorten nearly 5 a.For storm surges of the modern Yellow River delta,the occurrence frequency decreased from once in 5.5～6.5 a before 1949 to once in 7.9 a after 1949,but the frequency of large storm surge disasters increased.It indicated that existing dykes shown their efficacy to withstand general storm surges,currently it is needed to build higher standard dykes.Analyses suggest that the storm surge disasters on the Yellow River delta came into being due to combined effects of weather,topography and hydrological factors.Storm surge disasters have the characteristic seasonally occurred in initial winter,April and typhoon period due to weather conditions;they easily occurred when southeasterly winds turned to northeasterly winds under topographic condition restrict;and they occurred in different times between west and south side of the delta bounded as the amphidromic point under the control of hydrological factors.Taking the three characteristics as a breakthrough,to forecast storm surge disaster and construct dykes may defense storm disasters and alleviate damages.