It is an erosion-resistant, permeable concrete lining formed with a double-layer woven fabric, joined together by interwoven filter points (drains). Once pumped, the cobbled surface and relatively high coefficient of friction act to reduce velocity and wave run-up. The filter points provide for the relief of hydrostatic uplift pressure, increasing the system’s stability.

Filter Point Mats (FPM) form a lining of average thickness and specified weight to provide strength and erosion protection to resist the calculated tractive forces. The design criterion for the selection of lining thickness is the same as that used to determine the thickness of conventional concrete slope paving. FPM is custom fabricated into multiple mill-width panels, designed to fit actual site dimensions and topography.