Impermeable curtains are best in calmer conditions, where floats aren’t at risk of being submerged under strong waves. While silt curtains aren't meant to stop the flow of water, slower streams can move underneath the curtain without much interruption. Rough conditions and high tides are better handled by the flexibility of a porous, permeable curtain. This allows some water to pass through, reducing the pressure on the fabric, while still filtering out sediment and other particles. If an impermeable curtain is placed in waters too fast or waves too high, the floaters may become submerged, or the fabric may tear from excessive pressure.
You’ll want to consider your particular site when deciding the permeability of your curtain. The depth of the water, the strength of the waves, and how you expect to anchor the curtain will all affect what’s best for your project. An installation expert or engineer may be able to help you with an initial inspection and deciding what’s best for you.
