Patent ID: 8747027

Claim:
A drainage control material for filtering silt and debris from water flows, comprising: a flexible, water permeable sheet material having a series of stages defined at selected differing elevations therealong, including: a filtering stage for filtering silt and debris; a first release stage having a first apparent opening size; and a second release stage at a different elevation from the first release stage and having at least a second apparent opening size that is different from the first apparent opening size; and a plurality of reinforcing elements arranged at spaced locations along the sheet material, including at selected intervals so as to define transitions between the filtering, and the first and second release stages, the reinforcing elements providing areas for attachment of fasteners to the sheet material and providing increased horizontal load strength and resistance to tearing of the sheet material; wherein the reinforcing elements comprise at least two linear bands arranged at transitions between the first and second release stages; wherein during periods of excessive water flow, as a water level rises against the sheet material, incrementally varying amounts of overflow water can be permitted to flow through the release stages as needed to help relieve hydrostatic pressure against the sheet material while the reinforcing elements strengthen and provide enhanced horizontal load support to the sheet material as the apparent opening size of the sheet material increases from the first release stage to the second release stage, for retaining and blocking silt from passing therethrough and for resisting collapse of the sheet material, while enabling increased water flows therethrough as the water level rises along the water permeable sheet.