What type of flow is silt fence designed to manage?

The correct choice is that silt fences are specifically designed to manage sheet flow coming to the silt fence evenly at all locations. Silt fences act as a barrier that allows water to flow through while capturing sediment from sheet flow, which is the thin layer of water moving over a broad surface.

When sheet flow occurs, water spreads out over a wide area, and silt fences help to intercept sediment that is carried along by this flow before it can enter streams, rivers, or lakes. Proper installation and positioning of silt fences ensure that they effectively manage this type of flow, preventing large quantities of sediment from being washed away and thereby reducing erosion and pollution in water bodies.

Concentrated flows, which can come either from a single point or different points, typically require different erosion and sediment control measures, such as sediment basins or diversion structures, because they involve water moving with greater velocity and volume than what is typically seen with sheet flow. As such, managing concentrated flow is beyond the primary function of a silt fence.