Space-time Evolution Analysis Of Coastal Wetland In Modern Yellow River Delta

According to TM images and depth data for many years, using Technology such as GIS and Surfer, in accordance with the research object, information of Coastal Wetland in the Yellow River delta can be obtained, including area changes of coastal wetland, coastlines and vicissitudes of fathom line etc. And using the method of dynamic geomorphology, the evolution characteristics of coastal wetlands and sediment were discussed taking the Yellow River delta for example. Based on the evolution of regional coastal wetland and the influence of its mechanism, basic reference can be provided for environment construction and sustainable development of the region. The results are shown as follows:(1) Delta coastline trends are:Coastline is obviously siltation in the estuary, shoreline of north abandoned areas is obviously erosion, southern lay Zhou bay sediment is not too obvious after 1976.(2) in 1976 Yellow River changed to Qingshuigou Lobe, the coast silt quickly to the sea, the beaches area grew rapidly,1976～1987 year tidal flat area was distributed the ring-like; Along with human activity's and so on tidal flat cultivation as well as oil field construction advances, Qingshuigou Lobe growth is simultaneously mature, the river mouth epeiro genesis speed slows down, tidal flat area slightly reduced during 1981～1987 year; in 1996 Yellow River changed course once more, the new river mouth silted up rapidly, therefore sand spit washout's deposit of the river mouth moved to south, in 1998 the beaches area grew slightly; Hereafter the new river mouth siltation at the same time the old estuary corroded; in addition the artificial activity's unceasing influence, the tidal flat area assumes potential of the reduced.(3) in 1976 the delta northern 6m isobaths is bigger than the low-water mark to the land backlash scope, the wetland area has the reduction slightly, the Shenxiangou lobe wetland area is quite stable, wetland area of the new estuary migrated wholly to the sea, but the area did not have the change basically. Before 1996 the Qingshuigou Lobe south side 6m isobaths and the low-water mark flush and silt by turns, as to the river mouth unceasingly the sediment deposition, the wetland area has the growth slightly. Up to 2004, the coastal section coastline of the abandoned delta north retrocede continually, the submarine 6m isobaths flushes and silt alternately, the entire wetland scope expanded to the land, the area had increases slightly. The new estuary coastline silt enters the boundary to be bigger than the old estuary to the land backlash scope, the 6m isobaths change scope is not obvious, and the entire estuary area wetland area changes slightly. Delta south Lai Zhou sea area seacoast backlash to land, although the 6m isobaths silt less to the sea; this Littoral region wetland area increases.(4) The relevance between beaches and the sediment is small, its change is mainly influenced by the human activity, but the relevance of wetland area between the low-water mark to the 2m and the sediment come to 0.82. So it is dominated by the fluvial dynamics. After in October,1996 the corroded center appeared in the sandpits forehead of old estuary area, the erosion intensity increases gradually by the sea to the shore, and has formed a corroded trench in its sandpits north side; The siltation center also appeared in the sandpits leading edge of the new estuary, and a siltation body separately was formed in its north and south, the accumulation rate has reached above 1m; characteristic of Sediment evolution between the low-water mark and the 6m isobaths was remarkable, which is in nearby basically the siltation center in the new estuary regions; on the contrary,in the old estuary area, it basically lay in the corroded scope, the difference lies in the silt eclipse scope and the intensity.(5) Coastal wetlands tidal flat are influenced by coastal erosion, rising sea levels, ground subsidence and consolidation compaction sinking and other natural factors, sediment of low water line area are mainly influenced by the amount of water of Yellow River and Marine dynamic factors; In addition, human activity has been an important factor that cannot be ignored.