Factors controlling navigation-channel shoaling in Laguna Madre, Texas

Shoaling in the Gulf Intracoastal Waterway of Laguna Madre, Tex., is caused primarily by recycling of dredged sediments. Sediment recycling, which is controlled by water depth and location with respect to the predominant wind -driven currents, is minimal where dredged material is placed on tidal flat s that are either flooded infrequently or where the water is extremely shal low. In contrast, nearly all of the dredged material placed in open water > 1.5 m deep is reworked and either transported back into the channel or disp ersed into the surrounding lagoon. A sediment flux analysis incorporating g eotechnical properties demonstrated that erosion and not postemplacement co mpaction caused most sediment losses from the placement areas. Comparing se diment properties in the placement areas and natural lagoon indicated that the remaining dredged material is mostly a residual of initial channel cons truction. Experimental containment designs (shallow subaqueous mound, subme rged levee, and emergent levee) constructed in high-maintenance areas to re duce reworking did not retain large volumes of dredged material. The emerge nt levee provided the greatest retention potential approximately 2 years af ter construction.