What was the traditional method of construction in ancient times?

In China's ancient times, the traditional construction method is, generally longer bridges tend to use porous form, so that the span of each hole is small, gentle slope, easy to build.

But the porous bridge also has shortcomings, such as piers, not only is not conducive to navigation, but also impede the discharge of floodwaters; piers for a long time by the impact of the water, erosion, long days easy to collapse.