元谋干热河谷冲沟沟头径流水动力学特性及产沙效应初探

Preliminary Study on Hydrodynamic Characteristics of Overland Flow and Sediment Yields of Gully Heads in Yuanmou Hot-dry Valley

采用原位放水冲刷试验研究不同放水流量下元谋干热河谷冲沟沟头径流水动力学参数、径流泥沙含量和沟头土壤侵蚀量的变化特征,进一步探明沟头的产沙效应。结果表明:(1)各试验流量条件下,1号沟头(沟壁无内凹洞)、2号沟头(沟壁有内凹洞)的集水区、沟床径流雷诺数均远大于500,处于紊流状态,弗罗德数均大于1,处于急流状态;2个沟头的集水区、沟床阻力系数(f)随放水流量增加而减小,径流侵蚀力(径流剪切力、水流功率、单位水流功率)随放水流量增加而增大。(2)相同径流条件下,1号沟头(沟壁无内凹洞)径流泥沙含量和土壤侵蚀量都大于2号沟头(沟壁有内凹洞),表明相同条件下,冲沟沟壁内凹洞的形成起始阶段比沟壁内凹洞后续发育阶段更活跃。(3)冲沟沟头土壤侵蚀量与径流能量损耗、雷诺数、弗罗德数、剪切力、水流功率、单位水流功率呈正相关关系,与径流阻力系数(f)呈负相关关系。

Runoff dynamic parameters,sediment contents and soil erosion amounts of gully heads were studied in Yuanmou dry-hot valley by situ scouring tests under different runoff fluxes.The results showed that：（1）Under different runoff flow condition,Reynolds numbers obtained in gully head drainage area and gully bed were both greater than 500,which indicated the state of runoff flow belonged to turbulence flow.Their Froude numbers were greater than 1,which indicated the runoff flow was torrent flow.Resistance coefficient（f） obtained from drainage area and gully bed both in gully 1（without inner cavities in gully wall） and gully 2（with inner cavities in gully wall） decreased with the increase of runoff flow.Runoff erosivity（runoff shear stress,stream power,unit stream power） increased when runoff flux increased.（2）In the same runoff conditions,sediment content and soil erosion amount of gully 1 were greater than those of gully 2,which indicated that in the same conditions,the forming stage of cavities was more active than its successive stage in sediment yielding.（3）A positive correlation was found between soil erosion amount and runoff energy loss,Reynolds numbers,Froude numbers,shear stress,stream power,unit stream power of gully heads,and a negative correlation was also found between soil erosion amount and the runoff resistance coefficient（f）.