潮沟疏通对滩涂水动力的影响分析

Analysis of the Influence of Tidal Creek Dredging on Tidal Flat Hydrodynamics

为分析潮沟疏通对滩涂水动力的影响,基于非结构数值模型开展了滩涂区域水动力及水质点输移模拟分析。数值结果显示:疏通后涨潮时潮沟内流速显著增大,滩涂北侧的流速略有减小,变化范围在50%左右;涨潮时潮沟内潮位变化较快,涨潮流速大于落潮流速;落潮时受滩涂归槽水体影响,退水时间较长,落潮历时是涨潮的2倍以上;涨潮时潮沟内流速呈单峰分布,落潮时的流速呈双峰分布,第一个峰值为滩涂整体潮位下降引起,第二个由滩涂归槽水引起。潮沟是滩涂水体输运的主通道;潮沟疏通有利于增加滩涂纳潮量,降低外海的直接漫滩流速,减少滩面滞留水体,提高了落潮末期的归槽水流速;疏通后进入滩涂内的水质点数量增加了1倍,部分水质点贯穿整个滩涂,提高了滩涂与外海的水交换过程。

In order to analyze the influence of tidal creek dredging on tidal flat hydrodynamics,a simulation analysis of hydrodynamics and water quality point transport in tidal flat area is carried out based on unstructured numerical model.The results show that after dredging the flow velocity in the tidal creek increases significantly during the high tide,whereas at the north side of the tidal flat the flow velocity decreases slightly,with a variation range being about 50%.The water level in the tidal creek changes rapidly during the high tide and the flow speed of the rising tide is greater than that of the falling tide.Affected by the water body returning from the tidal flat to the creek,the water returning time becomes longer during the falling tide.As a result,the ebb duration is over two times longer than the high tide duration.During the high tide the flow velocity in the tidal creek shows a unimodal distribution.In the period of falling tide,however,the flow velocity in the tidal creek shows a bimodal distribution,of which the first peak is caused by the dropping of water level in the whole tidal flat and the second one is induced by the water body returning from the tidal flat to the creek.The tidal creek is the main channel of water-body transportation.Tidal creek dredging is beneficial to increasing the tidal-holding capacity,reducing the direct floodplain velocity from the open sea,decreasing the retained water on the surface of the tidal flat and enhancing the flow speed of the water returning from the flat to the creek at the end of the falling tide.After the tidal creek dredging the number of the water quality point entering the tidal flat has increased by one times,of which parts of the water quality points run through the whole tidal flat,thus improving the water exchange process between the tidal flat and the open sea.