Desktop Study for La Quinta Project; Shoaling Prediction in La Quinta Navigation Channel and Effect of a Barrier on Siltation in Extended La Quinta Channel

摘要

The U.S. Army Engineer District, Galveston, proposed two modifications of the La Quinta navigation channel: (1) extension of the navigation channel and providing a new turning basin at the end of the extension, both having the same depth as that of the present navigation channel, namely 13.7 m (45 ft), and (2) constructing a barrier on the south side of the extended channel. The District requested the Coastal and Hydraulics Laboratory (CHL) of the U.S. Army Engineer Research and Development Center (ERDC), Vicksburg, MS, conduct a desktop study for estimation of future shoaling in the navigation channel with these two modifications. The results of a desktop study are given in this report in two parts for the above two problems. Shoaling Prediction in La Quinta Navigation Channel The approach consisted of the following steps. Field data already available as well as those collected by CHL were analyzed and the results of analysis used. Assumptions were made on the spatial and temporal variation in the values of relevant parameters. Runs were conducted on the existing numerical hydrodynamic model for a few selected conditions to determine the effect of channel extension on the currents in the area of interest. A quantitative estimate was provided on future shoaling in the navigation channel based on the field and model data analysis. The following conclusions were drawn. a. Proposed extension of La Quinta navigation channel and provision of a new turning basin will cause an increase in the present tidal currents. This is expected to increase the inflow of sediment in the channel, which would result in increased shoaling. b. Bed sediment in the La Quinta channel consists of mostly fine sediment in the category of silt and clay. This suggests that the major process of shoaling consists of deposition of suspended sediment.