近70a来椒江河口河床冲淤调整机理

利用近70a来19个不同年份的水深地形资料,基于GIS技术进行数字化冲淤分析,结合实测水文泥沙资料和人类活动,探讨椒江山溪性强潮河口河床冲淤调整过程。研究表明,近70a来无论是在河床纵横剖面还是在平面上,冲淤调整经历了较明显的四个阶段,可是平面上比纵横剖面上的平均冲淤速率更趋于整体性:(1)以自然作用为主,处于缓慢冲刷状态,冲刷区占65.4%,全区年均冲刷速率为2.3cm/a,年均冲刷量为53.7×104m3;(2)受支流永宁江上游建库蓄水影响,从缓慢冲刷转为较明显的淤积状态,淤积区占66.2%,全区年均淤积速率为2.2cm/a,年均淤积量为50.4×104m3;(3)受航道整治完成的部分工程作用,由淤积又转为轻微冲刷状态,冲刷区占62.6%,全区年均冲刷速率为1.8cm/a,年均冲刷量为41.4×104m3;(4)受航道和支流永宁江的综合整治作用,从轻微冲刷朝加速冲刷方向发展,冲刷区占71.5%,全区年均冲刷速率为5.6cm/a,年均冲刷量为130.8×104m3。这在某种程度上意味着椒江山溪性强潮河口河床冲淤调整受人为影响比受自然影响大。

Adjustment mechanism on the erosion and accretion of riverbed in the Jiaojiang Estuary in Zhejiang Province, China

An adjustment process in erosion and accretion was discussed on the riverbed sediment in the Jiaojiang mountain-seream macrotidal estuary with the data of the observed tidal current,suspended sediment and anthropogenic activity,based on the GIS digitized and calculated sediment erosion and accretion on the riverbed using 19 bathyorographies in different years in the recent 70 a.It was shown that the adjust ment between erosion and accretion on the riverbed underwent the more remarkable four stages either on the transverse and longitudinal profiles or on the riverbed planes in this estuary,the average erosion-accretion rate on the riverbed planes,however,was more approachable to ward the whole area than that on the transverse and longit udinal profiles % (1) it was in slowly scoured state and the erosion region made up 65.4% in the study area where the average annual scouring rate was 2.3 cm/a or 537 000 m³ by the dominant natural action between 1933 and 1962;(2) it was transformed from the slow erosion into the clearer accretion and its region taken up 66.2% in the entire area where the average annual depositing rate was 2.2 cm/a or 504000 m³ by the influence that the reservoir was built up on the upper reaches of the tributary Yongning River between 1962 and 1984;(3) it was changed from the accretion into the slight erosion and its region accounted for 62.6% on the whole area where the average annual scouring rate was 1.8cm/a or 414 000 m³ by the action that the partial work construction was completed for the navigable channel regulation between 1984 and 1990;(4) it was developed to wards the direction of the accelerating erosion from the slight one and its region occupied 71.5% in the study area where the average annual scouring rate was 5.6 cm/a or 1 308 000 m³ between 1990 and 2003.This implies to a certain extent that the adjustment between erosion and accretion on the riverbed sediment is subjected to human impact stronger than nature in the Jiaojiang Estuary.