雅鲁藏布江中游江心洲、河漫滩面积及其指示的沙源特征

Sand supplement characteristics indicated by the area of river inland,flood plain in the riverbed of the Yarlung Zangbo River

雅鲁藏布江流域中游(贡嘎县至乃东区)江心洲和河漫滩等河流地貌发育,同时也发育了不同类型的风沙地貌,是雅鲁藏布江流域风沙灾害最为严重的地区。冬春季大范围裸露的江心洲和河漫滩,为沙尘暴的发生提供沙源,也可能是北岸沙丘的物源。目前对江心洲和河漫滩面积动态变化过程及其与沙源之间的关系几乎没有研究。为此,本文通过对2019年11月至2020年8月遥感影像解译和风动力条件综合分析,探讨河床动态变化过程与沙源之间的关系。结果表明:江心洲和河漫滩面积具有明显的时空变化特征,主要受径流量的影响。江心洲面积3月最大(222.95 km^(2)),8月最小(80.61 km^(2))。沙源比(河道内江心洲面积与水域面积的比值)具有明显时空变化规律,3月最大(2.00),8月最小(0.28)。河漫滩面积也具有相似的变化规律,3月78.99 km^(2),8月仅45.45 km^(2)。起沙风频率冬春季大,意味着3月风沙活动强度最大,8月最小。由此可知,江心洲和河漫滩能够为研究区的风沙灾害提供物源,而强风提供动力条件。

Fluvial geomorphology is widely distributed in the middle region of the Yarlung Zangbo River,meanly,these regions has experienced the most serious aeolian disaster.River inland and flood plain can provide sand for aeolian disaster.However,the relationships between river inland and flood plain area and aeolian disaster almost not be studied in these regions.For this reason,the remote sensing images and weather station data were used to analyze the area of the riverbed,flood plain and river inland,and the aeolian activities.The results indicated that there are obvious spatial and temporal differences for the area of the riverbed,flood plain,river inland,and the sediment supplement.The area of river inland and flood plain is controlled by monthly river runoff,and the monthly river runoff ranges from 0.93×109 to 8.35×109 m3,which is related to monthly rainfall.The area of river inland is maxinmum in March and minimum in August,with the value of 222.95 km^(2),80.61 km^(2) respectively.Sediment supplement index is maximum in the March(2.00)and minimum in the August(0.28),means that river inland area is largest in March and smallest in August.Similarly,flood plain area is largest in March(78.99 km^(2))and smallest in August(45.45 km^(2)).Sand activities are serious in March and less in August.All results explains that river inland and flood plain can provide sediment for aeolian disaster formation and development.