Flood-control dam system in Shanxi
This picture shows a typical dam system which is provided with a core dam large enough to protect the valley downstream from floods. This system is located in Shanxi, Lishi, Wangjiagou gully. Implemented in the 60's
its main purpose was to trap sediment so as to reduce the sediment load on the Yellow River. Its reservoir was quickly filled to the top, creating highly-prized sediment land. New dams
were then added upstream to improve the valley's flood resisting potential. This picture illustrates the final stage of the check dams, and for you to decide whether or not they
are ecologically sound. Built entirely of local soil, and without concrete spillway
or other extraneous features, this dam blends in with the local landscape readily.
In my opinion however this is not the best way to utilize a large check dam for it fills up too rapidly, and the land it creates is too small in size, which is not making good use of the sediment. Sediment should be considered as valuable resources, and land can be created with just a layer 2 meters deep. I advocate letting the sediment-laden flood water to pass through the dam to fill up the gully downstream from the dam. Already protected from flood by the core dam, the sediment-trappers built downstream may be just 2 to 3 m high, and useful sediment land is created readily in a controlled way.
A view of the reservoir filling process is shown in the picture below. This part of the gully has not been rehabilitated, and cannot be utilized for the next ten years after the dam is built. This site is at Shanxi, Mizhi, Yulingou gully.
Other views of core dams and their development:
Picture source: George Leung 1997