Field study on mechanism of topography variation of bottom surface of tidal flat in which benthos are living in lagoon

1.影响加莫泻湖主潮滩底部地形的地形因素有：分隔泻湖与河流的合闸杆、合闸杆上的开口、混凝土护岸、部分泻湖宽度的收缩或增大。主潮滩底表面的外观有两种情况：一是不凹凸不平，二是凹凸不平。2 .一年中大部分时间，主潮滩有一半的底高较高且不均匀，其余部分底高较低且不均匀。主潮滩附近测点日最大入流速度为0.6m/s，日最大出流速度为0.5m/s。主潮滩底面高度一年内变化幅度在5 ~ 10cm之间。接近冬季时，底面高度有一年上升，另一年下降。每年从春天到七月都是如此。在春潮涨潮时，它似乎主要发生变化。主潮滩底部沉积物为砂质。中径0.3mm。根据Hjulstrom图，侵蚀速度为0.12m/s。有许多瞬间超过侵蚀速度，但没有发生底面高度的变化。它似乎发生在洪水低潮高的时候。底栖动物对底面高度变化的影响不明显。

1.Topographical factors having effects on bottom topography of main tidal flat in Gamo lagoon are closing lever which separate lagoon and river, opening in closing lever, concrete-made revetment, and part of contraction or enlargement of width in lagoon.2.The appearance of bottom surface of main tidal flat are two cases : first is not uneven and smooth, second is uneven. Most days in a year, bottom height of a half in main tidal flat is high and a little uneven, and bottom height of the rest is lower and more uneven.3.Maximum inflow velocity and Maximum outflow velocity in a day at a measuring point near main tidal flat is respectively 0.6m/s and 0.5m/s.4.Variation of height of bottom surface in main tidal flat in a year is 5 to 10cm. Toward winter, height of bottom surface rises in one year, and drops in other year.It rises from spring to July all of the three years. and it seems mostly to change at flood in spring tide.5.Bottom sediments in main tidal flat is sandy. Medium diameter is 0.3mm. Following Hjulstrom's diagram erosion velocity is 0.12m/s.6.There are many moments exceeding erosion velocity, but variation of height of bottom surface do not occur. It seems to occur at flood when low water is high.7.Effect of benthos on variation of height of bottom surface is not evident.