What is required between the two stone types in a stone check dam?

In the construction of a stone check dam, the primary purpose is to slow down water runoff, reduce soil erosion, and promote sediment deposition. The design of these structures generally relies on the properties of the stone material used to ensure adequate filtration and structural integrity.

Typically, no geotextile fabric is required between the two types of stone—such as coarse and fine aggregate—that might be used in a check dam. The stones should be placed in a manner that allows for effective interlocking, which helps maintain the stability and functionality of the dam. The infiltration capacity and drainage are influenced more by the arrangement and size of the stones than by the addition of a geotextile layer. This is why the correct answer indicates that there is no geotextile requirement in this scenario.

Utilizing materials like woven or nonwoven geotextiles is common in other applications, such as reinforcing soil or separating different soil layers, but those functions do not apply to the intended use and design of stone check dams. Therefore, the absence of a necessary material between stone types makes the first three options inappropriate for this specific practice.