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Title: Sabine-Neches Waterway, Sabine Pass jetty system: past and future performance
Authors: Seabergh, William C.
Smith, Ernest R.
Rosati, Julie Dean
Keywords: Consolidation
Jetty rehabilitation
Jetty stability
Numerical modeling
Sabine-Neches Waterway (Tex. and La.)
Coastal Inlets Research Program (U.S.)
Publisher: Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (Engineer Research and Development Center (U.S.)); no.ERDC/CHL TR-10-2
Abstract: This study evaluated the present and future functionality of the Sabine Pass jetties considering planned deepening of the Sabine-Neches Waterway Navigation Channel from 42 to 48 ft mean low water (MLW) and possible rehabilitation of the jetty system. The Sabine Pass jetties were constructed to their full length (East jetty, 25,270 ft; West jetty, 21,860 ft) between 1880 and 1930 and, during the 130 years since construction began, have incurred loss of elevation and damage because of regional subsidence, scour at the base of the structures, storms, disintegration of the original fascine (willow) mats used as foundation for the structures, and consolidation of the underlying substrate. This study evaluated the 2003 condition of the jetties and anticipated functionality in 50 years given change in relative sea level at the site, future consolidation of the underlying substrate, and possible storm damage. Three integrated tasks evaluated 1) the stability of the jetties to storm waves, 2) the decrease in structure elevation through time relative to the mean water level caused by consolidation of the underlying substrate and relative sea level rise, and 3) waves, currents, and potential sediment transport pathways in the vicinity of the jetties and navigation channel. Each task assessed the 2003 “existing” condition, a hypothetical jetty condition in 50 years without rehabilitation, and two repair scenarios that were assumed to occur in 2010 and were assessed after 50 years. The repair scenarios were rehabilitation of the entire length of both jetties vs. rehabilitation of the seaward 4,000 ft. Both alternatives would be constructed to elevations of +9.2 ft MLW (East) and +9.3 ft MLW (West). Shear stresses from numerical calculations of waves, currents, and water levels were applied to indicate the potential for cohesive sediment transport and channel shoaling magnitudes. Recommendations from these analyses were that the jetties should be rehabilitated to +9.2 ft/+9.3 ft MLW to ensure safe navigation and reduce channel shoaling, and that stone size should be increased to approximately 17-18 tons for stability during storms and higher water levels. Repair of the seaward 4,000 ft of both jetties provided similar navigation benefits (reduction in waves and currents, no change in total shoaling) as restoration of the full length of both jetties. Physical model studies are recommended to optimize stone size for rehabilitation. Numerical modeling is recommended to assess the potential for scour of the seabed in the vicinity of the jetties, and to determine magnitudes of channel shoaling for cohesive sediment. Numerical shoreline modeling with anticipated water levels over the project lifetime is recommended to assess the likelihood for structure flanking and minimize adjacent beach erosion.
Description: Technical Report
Gov't Doc #: ERDC/CHL TR-10-2
Rights: Approved for public release; distribution is unlimited
Appears in Collections:Technical Report
Technical Report

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