The first picture below shows the scale and function of a rural check dam, also called warping dam, or silt-trapper. It is built across a minor branch gully to trap the eroded silt brought down by a flood during a heavy downpour in its watershed. Its main purpose is to create arable land for the farmers who otherwise would have to work with steep gully slopes by terracing, but as you can see from the picture, the slopes are often so steep that terracing is very difficult if not impossible. More often than not, cultivating on steep slopes without proper terracing creates more severe erosion than before. By building silt trappers, farmers will develop the gully floor instead of struggling with the slopes.
The (left) picture is taken on top of one such silt-trapper to show you its scale (compare it to the size of cattle on the lower right hand corner). This one was built across a wide valley floor 10-15 years ago, and had created an extensive level field for cultivation, as shown in the picture on the right.
This site is located in the Fenxi
county, Shanxi,
which is famous for its silt-trapping system, and a show piece.
For reasons unknown to me, this line of development was
not seriously pursued.