What is a recommended material to place under riprap installations for outlet protection?

Utilizing non-woven geotextile filter fabric beneath riprap installations is advantageous for several reasons related to sediment control and outlet protection. This type of material serves as a barrier that prevents fine particles from washing away while allowing water to flow through. By placing geotextile fabric under riprap, it helps maintain the structural integrity of the installation by reducing the potential for erosion of the underlying soil.

Additionally, this fabric functions to filter water, reducing turbidity and maintaining water quality as it allows for adequate drainage without loss of sediment. The geotextile filter fabric can adapt to various environmental conditions and is effective in stabilizing soils under new or existing erosion control measures, providing significant long-term benefits in various applications for sediment control.

In contrast, other materials such as heavy gravel or sandbags do not offer the same filtration and stabilization benefits as non-woven geotextiles. While riprap can be effective on its own, the inclusion of filter fabric strengthens the protection it provides at outlets, making it a recommended practice in effective erosion and sediment control strategies.