What primarily causes the development of a clogging layer in a leaching trench?

The development of a clogging layer in a leaching trench is primarily attributed to biological growth. This occurs when microorganisms, such as bacteria and fungi, proliferate within the trench environment, leading to the accumulation of organic matter. As these organisms break down materials and multiply, they can create a mass that partially obstructs the flow of water through the trench. This biological activity can result in a sticky biofilm or sludge that adheres to surfaces and impedes drainage.

While other factors such as physical obstruction could contribute to clogging, it is the biological growth that tends to be the most significant cause in the context of leaching trenches. Excessive water flow can lead to erosion or displacement but does not directly create a clogging layer in the same manner as biological processes. Chemical reactions may alter the properties of the materials involved but are not the main cause of a clogging layer formation.