黄河乌兰布和沙漠段越冬期下垫面变化对沿岸风沙运移机理影响的研究

Because of the particularity of environment, blown-sand activity along Yellow River is different from the one in desert area or coastal area. The blown-sand movement in Ulanbuh Desert Section of Yellow River causes serious silting-up of watercourse, influence the running of hydraulic engineering directly, and pose threat to the lives and property of people along the river. During the ice flood season, rise of Yellow River in Inner Mongolia arouse confluence of river and the sand dune along the river. It is still the active season of blown-sand movement after frozen in winter. At this time, the ice surface to sand flow and dune migration "land" channel.On the ice - the the the dune system sandstorm migration studies have not been reported. Aiming to this special phenomenon, we study the dynamics mechanism of effect of changing process of underlying surface on blown-sand movement during wintering period; observe the underlying surface change of sand dune along Yellow River, structure of wind-sand flow, movement law of sand dune, sediment discharge and wind erosion amount. Then we will reveal the effect of changing process of underlying surface during wintering period on movement characteristics and space-time distribution of blown-sand and movement law of sand dune. The research content is important for coastal wind-drift sand controland promotion of blown sand physics underlying surface sand migration.

由于环境的特殊性，黄河沿岸的风沙活动过程既不同于沙漠（沙地）地区，也有别于海岸地区。黄河乌兰布和沙漠段的风沙活动对河道造成严重淤积，直接影响下游水利工程的平稳运行，威胁两岸居民的生命财产安全。黄河内蒙古段在凌汛期水位上涨，沿黄沙丘与黄河握手。冬季封河后，沿岸风沙活动的进入活跃期。此时，冰面为风沙流和沙丘运移提供了"陆路"通道，关于冰面-沙丘系统风沙运移的研究尚未见报道。针对这一特殊现象，展开越冬期下垫面变化对风沙运移影响的动力学机理研究。以沿岸沙丘-冰面为研究对象，通过野外调查、定点观测、动力学理论分析，对越冬期黄河沿岸沙丘下垫面风沙流结构、沙丘移动、输沙量、风蚀量等进行长期系统、动态、定量观测研究，揭示越冬期下垫面变化对沿岸风沙流的运移特征、时空分布、沙丘移动规律的影响。越冬期流沙-冰面风沙运移研究，为沿黄风沙治理提供理论依据，对推动风沙物理学不同下垫面风沙运移过程的研究，有重要意义。

由于黄河越冬期的封河，导致河水上涨并向河岸扩张，沿岸风沙活动活跃。风沙淤积河道，影响下游水利工程的运行和两岸居民的生存。以黄河乌兰布和段为研究区，从风沙运移机理方面围绕着不同下垫面下的风沙流结构、风速廓线、粗糙度以及输沙量展开；从风沙运移宏观表现形式上围绕沙丘迎风侧的风蚀堆积、背风侧降尘以及沙丘的移动规律开展观测研究。结果表明：.（1）不同下垫面与流沙相比，近地表处风速有显著降低，地表粗糙度显著增加。输沙量及输沙率均较流沙显著减小，仅为流沙的1.07%～38.27%。近地表0～1和1～10m内的输沙通量垂直变化符合对数分布；1～10m内，水平风沙通量大于垂直通量，冬季大于夏秋季节；冰面-沙丘复合系统，冰面起沙风为4.25m/s，沙丘4.9m/s，风速廓线呈对数分布，随风速增大，冰面0～0.2m范围风速受到下垫面的影响增加，沙丘0～0.5m内影响增加。.（2）沙丘的迎风侧坡脚、坡中和坡顶平均净风蚀量分别为1.07cm/d、1.31cm/d和0.837cm/d，背风侧平均沉积量2.19cm/d，沙丘低地平均净风蚀量为0.019。沙丘低地与背风坡风蚀量、背风坡与迎风侧风蚀量、冬春季净风与夏秋季蚀量均存在显著差异。与迎风侧差异不显著；沙丘移动速度与高度成反比关系：D=-0.52H+6.11，多年平均移动速度为2.92m/a。.（3）沙丘下风向降尘量总体上符合对数分布规律；50cm高度和200cm高度的降尘量：下层降尘量大于上层，且二者存在显著差异。降尘粒径主要在50～250μm之间，以极细砂和细砂为主，二者合计为65.5%～94.5%。降尘中以跃移颗粒（＞70μm）为主，占94.65%～99.37%；近距离输送的悬移颗粒（20～70μm）占0.63%～5.03%，远距离输送的悬移颗粒（＜20μm）占0～0.32%。.沿岸风沙运移机理研究结果，为黄河沿岸风沙治理提供理论依据，具有重要意义。