求翻译：单位降雨量对悬浮物沉积影响微小，但是对砂粒沉积影响较大。且随着单位降雨量的减少，管涵内达到自清流速时管底的沉积物逐渐增加。是什么意思？

Units rainfall deposition on suspension of small, but a greater impact on sand deposition.

Rainfall in the suspended solids sediment impact small, but the sand deposition. And as the Organization of the annual rainfall, managed to achieve the flow rate at the end of the sediment gradually increased.

The unit rainfall amount is small to the suspension deposition influence, but is big to the sand grains deposition influence.In also along with the unit rainfall amount reduction, the tube contains achieved purifies oneself when the speed of flow the base deposit increases gradually.

Effect of rainfall on suspended sediment of tiny, but great influence on the sand deposits. And with a reduction in rainfall, culvert reached upon clearance flow in bottom sediments gradually increased.

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