Radiation Sandbar Inside Edge Of The Tidal Creek Development In Response To Human Activities

The study area locates in the landward part of the Radiate Sand Ridges and is the most important region of coastal resource exploitation in Jiangsu in the near future. The area is a macro-tidal region with great tide range and strong tide current. There are some large-scale tidal creek systems which frequently migrate. They have been impacted by artificial forces.17 pieces of satellite images collected from 1979 to 2003 were analyzed, combined with measured data from the tidal flat in the area from 1999 to 2003. The paper discussed the manners and mechanisms of the response of tidal creek systems to artificial activities by case research. This study focused on the responses of tidal creek evolution to reclamation, spartina alterniflora and runoff of water from tidegate. The conclusions is follows:(I) Response of tidal creek evolution to reclamationReclamation cut off upper parts of tidal creek systems and brought the decrease of the tidal water which went back to tidal creeks in ebb phase. Tidal creeks on the upper intertidal accreted quickly in the beginning years after reclamation, with deposition capacity increasing by six to eleven times than one in unreclamation. The tidal creek section on the lower intertidal was indirectedly influenced by it. Branches of tidal creek systems added 1-2 grades. The lateral movement of tidal creeks near sea wall became slower.(2)Response of tidal creek evolution to new-formed spartina alterniflora salt marshesWith expansion of spartina alterniflora and formation of salt marshes, there were more ebb runoff of returning to tidal creeks in the salt marshes. In the new-formed spartina alterniflora salt marshes, tidal creeks increased its amount and density; ridges developed along both sides of tidal creeks with higher height; ratio of width with depth of tidal creeks decreased; mud cliff, which became the wash along the boundary between the salt marshes and the mud flat to lead the direction of tidal creeks, came into being ; branches of tidal creek systems increased to 6-7 grades.(3) Response of tidal creek evolution to runoff of tidegateRunoff of tidegate adds the drainage of ebb tide, which promotes the formation point in its vertical section of the creek. It is advantageous to maintain the stability of the upper portion of tidal creek and restricts movement of the middle and lower portions, and promotes creation of meander the middle portion of tidal creek.