黄河什四份子弯道河冰生消及冰塞形成过程分析

什四份子弯道因其特殊的河道形态及地理位置而成为黄河内蒙古段易发生冰塞断面。通过对2014—2015年冬季该段野外冰情监测及水文、气象资料分析,结合Landsat8遥感影像数据解译,研究了什四份子弯道河冰生消及冰塞形成过程。结果表明,野外观测结合遥感影像解译能够准确地反映河冰的时空特性。该河段弯道凹岸处冲积岸冰及凸岸静态岸冰的生长,极大地束窄了河面宽度,降低了水流的输冰能力,而使其成为初始卡冰位置;冰盖至此向上游发展,弯道下游因来冰量减少和上下游水力坡度增大而形成清沟;受弯道径向水流方向改变及弯道螺旋流的影响,导致冰花在冰盖下主槽与滩地的交界处堆积;稳封期受气温升降变化使得冰盖表面冻融交替,冲积冰反射率增大,后期解译的遥感影像中平滑岸冰面积较初始封河期增加。

Processes of river ice and ice-jam formation in Shensifenzi Bend of the Yellow River

Because of the special channel morphology and geographical location,the initial ice jam is easily formed in the Shensifenzi bend of the Yellow River in Inner Mongolia. According to the field observation and hydrological, meteorological data collection during the winter of 2014-2015, and combining Landsat8 remote sensing image data, the processes of river ice evolution and ice jam formation in Shensifenzi Bend were analyzed. The results show that field observation combined with remote sensing image interpretation can accurately describe the spatio-temporal characteristics of river ice. The growth of dynamic border ice in concave bank and static border ice in convex bank decreased the river width obviously, and reduced the ice transport capacity, which caused ice jamming firstly formed in this bend. Further, ice cover developed upstream from this site. Due to the reduction of ice discharge and increase of the hydraulic slope,the lead form at the downstream of river bend. Under the effect of spiral flow, the frazil ice accumulated under ice cover around the junction of main channel and shoals;during the freeze-up period,changes of air temperature lead ice cover surface solidification and melting, decreasing the roughness and increasing area of smooth ice cover.