CAJ | 학술논문

根据兰州市黄河高漫滩沉积剖面的观察和81个样品的颗粒分析,研究了兰州市黄河高漫滩剖面沉积特征和洪水事件.结果表明:黄河兰州段高漫滩洪水沉积分层明显,对洪水的发生和短期降水量变化反映清楚,分辨率高,能够作为指示洪水和降水量变化的指标.LC剖面可分为10个沉积层,颗粒组成以粗粉砂、极细砂、细砂为主,胶粒、粘粒、细粉砂、中砂、粗砂含量都较小,这10个沉积层指示了10次大小不同的洪水事件.在充分考虑沉积厚度引起的地形增高对粒度成分的影响之后,可以确定LC剖面10个阶段河漫滩洪水深度和规模由大到小的变化顺序为第10阶段>8阶段>9阶段>1阶段>2阶段>3阶段>7阶段>5阶段>4阶段>6阶段.LC剖面第1、8、9、10层形成时漫滩上的洪水深度大于2.2 m,第2、3、4、5、6、7洪水阶段漫滩上的洪水深度小于2.2 m.根据兰州市及其以上黄河流域降水量少推断,LC剖面中的10个大洪水阶段的发生是由年降水量明显增多造成的.
근거란주시황하고만탄침적부면적관찰화81개양품적과립분석,연구료란주시황하고만탄부면침적특정화홍수사건.결과표명:황하란주단고만탄홍수침적분층명현,대홍수적발생화단기강수량변화반영청초,분변솔고,능구작위지시홍수화강수량변화적지표.LC부면가분위10개침적층,과립조성이조분사、겁세사、세사위주,효립、점립、세분사、중사、조사함량도교소,저10개침적층지시료10차대소불동적홍수사건.재충분고필침적후도인기적지형증고대립도성분적영향지후,가이학정LC부면10개계단하만탄홍수심도화규모유대도소적변화순서위제10계단>8계단>9계단>1계단>2계단>3계단>7계단>5계단>4계단>6계단.LC부면제1、8、9、10층형성시만탄상적홍수심도대우2.2 m,제2、3、4、5、6、7홍수계단만탄상적홍수심도소우2.2 m.근거란주시급기이상황하류역강수량소추단,LC부면중적10개대홍수계단적발생시유년강수량명현증다조성적.
According to the field investigation and grain composition analysis of 81 samples of the section on high floodplain of the Yellow River in Lanzhou city, the sediment characteristic of the section and the paleo-flood changes were studied. Results indicated that the flood sediment layers of the Yellow River are obvious in Lanzhou area, which reflects clearly the variation of the flood and short-term precipitation with a high resolution, and is a good index indicating the changes of the flood and precipitation. The crude grain of the sediment indicates the bigger scale flood and the more precipitation at that time, and the thin grain indicates the smaller scale flood and the less precipitation. The LC section is divided into 10 sediment layers, which indicating 10 bigger-scale flood stages, and the sand grain are composed mainly of the coarse silt, the very fine sand and the fine sand, the colloidal particle, the cosmid, the fine silt, the medium sand and the coarse sand are all less. The 10 sediment layers indicate 10 floods with different scales. The grain composition of the whole section has obvious change rule from above to bottom. Sufficiently considering the effect of landform heightened by the aggradation on grain composition, the order of the depths and scales of floods on the high floodplain of LC section from big to small is the 10th, 8th, 9th, 1st, 2nd, 7th, 3rd, 5th, 4th and 6th stage. The flood depths on the high floodplain are above 2.2 m when the 1st, 8th, 9th and 10th layers formed, and are lower than 2. 2 m when the 2nd, 3rd, 4th, 5th, 6th and 7th layers formed. The flood sediment is not continuous, each of 10 floods generally indicates transitory rainy season of one year, and in the interval of every two adjacent floods there are no floods or small scales floods, indicating there are normal or less precipitation. According to a little precipitation in Lanzhou city and its upper area in the Yellow River drainage basin, it is concluded that the 10 flood stages are caused by obvious increasing of the annual precipitation.