What is the main purpose of the geotextile fabric used over gravel in drainfields?

The main purpose of geotextile fabric used in drainfields is to prevent backfill from entering the porous media. This use is essential to maintain the functionality and longevity of the drainage system. By acting as a barrier, the geotextile fabric keeps the gravel and soil separate from the backfill materials that could clog the drainage system. This ensures that the drainage remains effective, allowing water to flow freely through the gravel while protecting it from finer particles that could impede drainage.

The other options, while related to drainage systems, do not capture the primary role of the geotextile fabric. Stabilizing the ground and enhancing drainage may occur as a secondary benefit, but these are not its main functions. Similarly, while the fabric does contribute to some filtration, its primary purpose is to prevent unwanted materials from entering and blocking the gravel layer, ensuring a proper drainage system is maintained.