Impact of shoreline change on proposed Texas Highway 87 reconstruction

Abstract

Over seventeen miles of Texas State Highway 87, located in Jefferson County on the Upper Texas Coast, have repeatedly been destroyed by shoreline recession throughout its history. Jefferson County is currently seeking a long term solution in their efforts to once again rebuild the highway. Due to a lack of sound engineering data, Texas A&M University has undertaken a project responsible for collecting a comprehensive set of baseline data in the Highway 87 study area. The first phase of data collection requires an estimation of storm surge and wave setup associated with hurricane landfall in the Gulf of Mexico. Estimates of wave setup include the effects of landfall location and are presented in terms of any given return period. Over one-hundred and twenty sediment samples have been collected from the beach and analyzed using the rapid sand analyzer at the University of Florida. Samples from the beach berm, beach face and offshore were taken each half-mile along the beach and indicate that the beach is made up of very fine sands and silts. Quarterly surveys will be taken consisting of both along-shore position of the beach and cross-shore profiles extending to the depth of closure. The surveys will be performed using real time kinematic differential global position equipment mounted to a jetski and all terrain vehicle. Planned survey lines, equipment used and data processing techniques are discussed in this thesis. The shoreline evolution model GENESIS has been calibrated and used to predict the 2015 high water line position from Sabine Pass to Rollover Pass. Results of the model study lend credit to the idea that oval-wash due to storm surge penetration is the major mechanism of erosion in the area. All data collected has been stored in a geographic information system creating an easily shared and accessible database.