The study team developed a comprehensive set of Coastal Storm Risk Management (CSRM) alternatives based on the problems facing the coastal region and the opportunities to restore and protect the Galveston Bay area. The CSRM alternatives screened for the upper coast are listed below. Alternative A was determined to be the lowest cost comprehensive plan and included in the Tentatively Selected Plan identified in the draft report.
Five alternatives were evaluated around the bay to provide risk reduction. Alternatives A, B and C were scoped for a gulfward alignment, which differed in the location that the system crossed the bay. Alternatives D1 and D2 were proposed along the bayside perimeter, rather than along the gulf. The evaluation and comparison assessed the risk reduction performance and economic benefits of the entire system.
The Draft Report published in October 2018 reviews the original alternative evaluation for CSRM and concluded by recommending Alternative A as the Tentatively Selected Plan. Following publication, the Team refined the plan to combine the ecosystem restoration and risk reduction features to reduce costs and impacts, and to address public, technical and policy comments received on the Draft Report.
The Fact Sheets accessible through the Information Tools page provide interim updates on the plan refinements to project features and alignments that have been made since the Draft Report was published.
This alternative was developed to address storm surge flooding at the Gulf interface, but also tried to avoid some of the high and intense surges on a large navigation gate that may be present at the pass to Bolivar Roads. The strategy includes preventing storm surge from entering Galveston Bay, but the large navigation gate would be placed in an area that would avoid direct wave action from the open Gulf. The system would still include a barrier across Bolivar Peninsula, but the barrier would be set back north of the GIWW and would utilize existing dredge disposal sites that are located within the area to minimize impacts to the habitat along Bolivar Peninsula. The closure at the pass at Bolivar Roads would be north of the existing ferry landing and would tie into the existing Texas City Dike. The Texas City Dike would require significant improvements to be able to address coastal storm surge. The system would then tie into the existing Texas City Hurricane Flood Protection Levee system, with improvements to that system, and would include new levee construction further west into the communities of Hitchcock and Santa Fe. Due to the uncertainties associated with Gulf and bay driven storm surges on the City of Galveston, this Alternative includes a ring levee around the city. To address wind-driven surges in the bay’s upper reaches, nonstructural measures, ring levees, and closures on key waterways were also investigated on the west side of Galveston Bay. The study team investigated the nexuses between ER and CSRM features by reviewing the beach and dune restoration features along Bolivar Peninsula and Galveston Island. The ER features would also increase the resiliency of the CSRM features.
This alternative was developed to address storm surge flooding at the Gulf interface, but also tried to avoid some of the high and intense surges on a large navigation gate that may be present at the pass to Bolivar Roads. The strategy includes preventing storm surge from entering Galveston Bay, but the large navigation gate would be placed in an area that would avoid direct wave action from the open Gulf. The system would still include a barrier across Bolivar Peninsula, but the barrier would be set back north of the GIWW and would utilize existing dredge disposal sites that are located within the area to minimize impacts to the habitat along Bolivar Peninsula. The closure at the pass at Bolivar Roads would be north of the existing ferry landing and would tie into the existing Texas City Dike. The Texas City Dike would require significant improvements to be able to address coastal storm surge. The system would then tie into the existing Texas City Hurricane Flood Protection Levee system, with improvements to that system, and would include new levee construction further west into the communities of Hitchcock and Santa Fe. Due to the uncertainties associated with Gulf and bay driven storm surges on the City of Galveston, this Alternative includes a ring levee around the city. To address wind-driven surges in the bay’s upper reaches, nonstructural measures, ring levees, and closures on key waterways were also investigated on the west side of Galveston Bay. The study team investigated the nexuses between ER and CSRM features by reviewing the beach and dune restoration features along Bolivar Peninsula and Galveston Island. The ER features would also increase the resiliency of the CSRM features.
This alternative was developed to avoid possible navigation impacts at Bolivar Roads, by placing a surge barrier near the middle of Galveston Bay. The system would start on the east side of Galveston Bay near Smith Point, and would continue across the bay, crossing the Houston ship channel, and tying into the existing Texas City Hurricane Flood Protection Levee system. Improvements to this existing levee system would be included as well as new levee construction further west into the communities of Hitchcock and Santa Fe. The plan also addresses flooding on Galveston Island with a levee system. Due to the limited open water area north of the barrier system, wind-driven surges in the bay’s upper reaches would not be a concern, which is why the nonstructural measures, ring levees and closures on key waterways, were dropped from consideration. The study team investigated the nexuses between ER features and CSRM features by reviewing the beach and dune restoration features along Bolivar Peninsula and Galveston Island. The ER features would also increase the resiliency of the CSRM features.
This alternative was developed to potentially reduce possible navigation impacts, by focusing on a levee system on the west side of Galveston Bay along State Highway 146 from Texas City to the Hartman Bridge. The levee system would be located such that there would be structures east of the levee and outside of the system. Nonstructural measures were formulated to address existing surges and any surges induced into the area by the levee system. With the second option, called D2, the alternative would be modified to include the levee system between State Highway 146 and the bay rim. This option would include a levee or floodwall system along the bay rim or would be designed like the New Orleans Lakefront, where the system is built out into the bay.
This alternative is similar to Alternative D1; however, it would include a levee or floodwall system along the bay rim or would be designed similar to the New Orleans Lakefront, where the system is built out into the bay. With either option the alternative would eventually tie into the existing Texas City Hurricane Flood Protection Levee system and would include improvements to that system. The plan would also include additional levee construction further west into the communities of Hitchcock and Santa Fe. The alternative includes a Surge Gate and Barrier at the Hartman Bridge; however, this is likely a separable element that will be evaluated for navigation impacts and benefits to the upper ship channel. The alternative also addresses flooding on Galveston Island with a levee system that rings the island. As with the other alternatives, the study team investigated the nexuses between ER features and CSRM features by reviewing the beach and dune restoration features along Bolivar Peninsula and Galveston Island. The ER features would increase the resiliency of the CSRM features.
The CSRM alternatives screened for the mid and lower coast are identified below. Both alternatives were determined to be the lowest cost comprehensive plan and included in the Tentatively Selected Plan identified in the draft report.
Improvements to the existing Matagorda levee system were investigated. It has been determined that improvements are needed for interior drainage and not for storm surge risk; therefore, it has been recommended for investigation under another study with that authority.
The CSRM measure proposed for South Padre Island consists of a beachfill template with an equilibrium dune height of 12.5 feet NAVD88, dune width of 20 feet, berm width of 100 feet, and berm height of 4 feet NAVD88 along a portion of the island with a renourishment interval of 10 years. The exact extent of the beach and dune restoration that meets the USACE CSRM criteria is being investigated.
Ecosystem restoration measures (ER measures) ,,were specifically developed to address ecosystem degradation throughout the coastal Texas area. The measures were identified from the NEPA public scoping process; consideration of the existing and future without project conditions, the conceptual ecological model (CEM) process; coordination with other resource management agencies, private, local governmental, or landowner groups, information and scientific data from prior studies and the professional judgment of the interagency team.
The ER measures were designed to achieve two primary goals:
Ecosystem restoration projects in the Coastal Texas Study will provide ecological benefits along the entire Texas coast. They also maintain natural landforms that and are the first line of defense for coastal communities during storms and hurricanes. They reduce the effects of wind, waves and storm surge by absorbing storm energy; provide essential and critical habitats for terrestrial and aquatic species and maintain an important boundary between the more saline conditions of the marine ecosystem and the fresher estuarine ecosystem.
Eight individual measures remained after multiple screening criteria to ensure the features meet area-specific goals to restore the coastal habitat and provide resiliency from coastal storms. Following publication of the October 2018 Draft Report, one of the 9 ecosystem restoration measures (G-5) was refined to provide greater risk reduction and redefined as a coastal storm risk reduction measure in the Tentatively Selected Plan.
Project Description: Install breakwaters and restore marsh habitat to protect 25 miles of the shoreline along the GIWW on Bolivar Peninsula and 9 miles of shoreline along the north shore of West Bay. The project will use sediment to restore an island adjacent to the GIWW to protect 5 miles along the GIWW and the mainland in West Bay. Oyster cultch will also be added to protect the island and create additional habitat. Subsequently in the future, based on relative sea level rise, the project will re-nourish approximately 6,900 acres of marsh identified as “unconsolidated shore” using the 2017 NOAA marsh migration viewer.
Project Benefits: This marsh is an important nursery for both commercially and recreationally important species, acts as a feeding and nesting area for many species of birds and provides many other ecologically important functions. The shoreline and marshes in these areas will be restored and protected from storm surge and erosion, and from the effects of sea level rise. Breakwaters are a proven method to greatly reduce, and sometimes reverse, the loss of marsh habitat from erosion along the GIWW due to barge wakes. This project also will reduce maintenance dredging of the GIWW and may reduce risk from waves for the vessels in the GIWW.
Future Without Project: If the shoreline is not protected, approximately 18,000 acres of existing intertidal to high marsh along the south shore of the GIWW through Bolivar Peninsula and the north shore of West Bay will be inundated at a sea level rise of 3 feet. Loss of a marsh buffer will expose infrastructure to increased risk of storm impacts. In addition, the sediment that the lost marsh would have captured, is expected to accumulate in the GIWW and increase shoaling and maintenance dredging frequency. The increased width of open water in the GIWW due to the loss of marsh and the erosion of the islands adjacent to the GIWW can change the waves and currents and accelerate erosion. These factors can also negatively impact navigation.
Another important outcome of not protecting the shoreline, specifically Bolivar Peninsula, is an increased likelihood that Bolivar Peninsula will breach to the Gulf. At 3 feet of sea level rise, portions of the peninsula may narrow to less than 2,000 feet wide.
Project Description: Restore, protect, and/or enhance beach and dune complex on approximately 10 miles of Gulf shoreline on Follets Island in Brazoria County.
Project Benefits: A restored shoreline on Follets Island will guard against beach and dune breaches caused by erosion, storm surge and sea level rise. This will protect inland wetlands, seagrass meadows and other habitats. The beach, dune, wetland and seagrass meadow ecosystems along Follets Island are the first line of defense for Bastrop, Christmas, and Drum bays, as well as the Brazoria National Wildlife Refuge and various residential developments on the mainland. Christmas Bay is a designated Gulf Ecological Management Site because of its relatively undeveloped shorelines, high water quality, and unique mix of seagrass meadows, oyster reefs, and smooth cordgrass marsh. It is also a Texas Parks and Wildlife Department Coastal Preserve. These habitats shield State Highway 257 from the effects of storm surge. State Highway 257 is the only road accessing and providing evacuation capability to the east towards Galveston Island and to the west towards Freeport.
Future Without Project: The Gulf shoreline in this area is eroding at a rate of 13 feet/year. Over the next 50 years, more than 200 acres of existing beaches and dunes that provide habitat to multiple organisms (including threatened and endangered species), protect habitat, homes, and infrastructure may be washed away due to erosion and severe storms. A Gulf-water breach of Follets Island into Christmas Bay would substantially impact its unique ecological features. In addition, the critical evacuation route of State Highway 257 will be threatened because of its proximity to the shoreline. Currently, some sections of the highway are within 180 feet of the shoreline.
Project Description: Restore, create, and/or enhance critical areas of shoreline in the bay complex of Bastrop Bay, Oyster Lake, Cowtrap Lakes and the western side of West Bay. This will be accomplished through several methods - using breakwaters along approximately 43 miles of the GIWW and along the land that separates Oyster Lake from West Bay - and restoring approximately 550 acres of marsh behind the constructed breakwaters. In Oyster Lake, add 0.7 miles of oyster reef balls near the shoreline that is expected to breach into West Bay. To maintain and protect the GIWW shoreline that is identified as an “unconsolidated shore” using the 2017 NOAA marsh migration layer at 3-foot sea level rise, a one-time marsh nourishment of approximately 19,800 acres would occur.
Project Benefits: This habitat is an important nursery for both commercially and recreationally important species, acts as a feeding and nesting area for many species of birds and provides many other ecologically important functions. This restoration will protect this complex from being breached by West Bay. This will safeguard the critical shoreline in this bay complex from erosion, and the effects of storm events, vessel wakes and sea level rise. This also will preserve the marsh, oysters, colonial waterbird rookeries and other habitats in this bay complex.
Future Without Project: If this project does not occur, 10 miles of shoreline in this bay complex and more than 6,000 acres of intertidal marsh and freshwater wetland along the north side of the GIWW will be inundated with 3 feet of sea level rise. The Brazoria National Wildlife Refuge will lose valuable wetland habitat. Patterns of sedimentation flow will change, which will negatively affect the oyster reefs in Bastrop Bay and Oyster Lake. The conversion of large expanses of wetlands to open water will also adversely affect navigation in the GIWW.
Project Description: Use breakwaters and/or living shorelines to restore, protect, create, and/or enhance approximately 5 miles of shore along Matagorda Bay between Matagorda Bay and Keller Bay. Add oyster reef balls to protect and enhance about 2.3 miles of western shoreline along Sand Point, which separates the two bays. In the future, nourish approximately 620 acres of marsh along the back side of the initial restoration to maintain and protect areas identified by NOAA as “unconsolidated shore” with a 2.5-foot sea level rise. This measure was was transitioned from ER to a CSRM feature.
Project Benefits: This project will prevent the breaching of the Matagorda Bay and Keller Bay shoreline into Keller Bay. This will reduce erosion to preserve and enhance the intertidal marsh, seagrasses, and oysters in Keller Bay. This habitat is an important nursery for both commercially and recreationally important species, acts as a feeding and nesting area for many species of birds and provides many other ecologically important functions.
Future Without Project: If a breach into Keller Bay occurs, erosion will accelerate, and currents will be modified. This will lead to the degradation and loss of 330 acres of seagrasses, 7 acres of oysters, and more than 250 acres of intertidal marsh in Keller Bay along the Matagorda Bay and Keller Bay shoreline.
Project Description: Restore, protect, create, and/or enhance approximately 7 miles of Matagorda Bay shoreline with breakwaters and/or living shorelines, and marsh restoration. This will enhance the Powderhorn Lake estuary and Texas Parks and Wildlife’s Powderhorn Ranch by restoring marsh at three areas protecting estuarine bays and bayous between Powderhorn Lake and Port O’Connor. This area fronts portions of the community of Indianola and will provide added resiliency.
Project Benefits: This habitat is an important nursery for both commercially and recreationally important species, acts as a feeding and nesting area for many species of birds and provides many other ecologically important functions. The restoration will enhance the economic value of this area and protect the intertidal marsh and ecological integrity of Powderhorn Lake estuary.
Future Without Project: Some areas of intertidal marsh/open water complex may be eroded and submerged at a 2.5-foot relative sea level rise combined with higher potential for breaches along the shoreline (NOAA, 2017). The mouths of Powderhorn Lake and Huckleberry, Bid Dam, Broad and Big Boggy Bayous will widen significantly with subsequent changes in salinity regime, wave generated erosion combined with possible losses of oysters and marsh. The ecological nature of Powderhorn Lake and the other estuarine bayous would be changed substantially. Potential navigation improvements within Matagorda Bay would also exacerbate erosion and estuarine resource loss.
Project Description: This project will use living shorelines and/or breakwaters to restore, protect, create, and/or enhance approximately 12 miles of shoreline and associated marsh along the Big Boggy National Wildlife Refuge shoreline and eastward to the end of East Matagorda Bay. About 3.5 miles of shoreline directly in front of Big Boggy National Wildlife Refuge will also be enhanced by restoring an island on the south side of the GIWW. The island will be created with marsh and oysters on the backside to provide additional habitat. Subsequently, in the future, a one-time marsh nourishment of approximately 6,000 acres will occur along the north shore of East Matagorda Bay in areas designated by NOAA as “unconsolidated shore” at 2.5-foot sea level rise.
Project Benefits: This habitat is an important nursery for both commercially and recreationally important species. It also acts as a feeding and nesting area for many species of birds and provides many other ecologically important functions. This project will reduce the effects of breaches, erosion, sea level rise, storm events, and vessel wakes to protect the GIWW shoreline, islands, and marshes in this area.
Future Without Project: If this project does not occur, the following areas will convert to open water at 2.5-foot sea level rise: 1.) More than 2,000 acres of intertidal marsh and wetlands around the Pelton, Kilbride and Boggy lakes complex in the Big Boggy National Wildlife Refuge along the north shore of the GIWW and west of the Chinquapin community; and 2.) Over 7,000 acres of intertidal marsh and wetlands to the east of Big Boggy National Wildlife Refuge towards Bay City at the east end of Matagorda Bay. This will increase wave erosion along the north shore and on marsh, reefs, and islands in East Matagorda Bay and south of the GIWW.
Project Description: Use breakwaters and/or living shorelines, beneficial use material, and oyster reef balls to restore, create, and/or enhance the island complex of Dagger, Ransom, and Stedman islands in Redfish Bay. The project also will protect about 7 miles of GIWW shoreline from erosion along the backside of this island complex.
Project Benefits: This project will prevent loss of islands that protect extensive seagrass meadows and support coastal waterbirds and fisheries. The project will also increase oyster population and diversity as well as provide additional habitat for submerged aquatic vegetation between the breakwaters and the islands.
Future Without Project: Not restoring this island complex will result in continued erosion and will expose the area to greater wave action from the deep draft navigation in the Corpus Christi Ship Channel. This will threaten approximately 2,000 acres of seagrass meadows and damage the habitat for coastal waterbirds and fisheries.
Project Description: This project will restore the Port Mansfield Channel area by implementing the following: 1.) Restore and maintain the hydrologic connection between the Laguna Madre and the Gulf of Mexico with dedicated dredging of a portion of the Port Mansfield ship channel. 2) Protect and restore Mansfield Island with 3,500 feet of rock breakwater and barrier island restoration using the dredge material beneficially; and 3) Beneficial use of beach quality dredge material and sediment management of the sand along the jetty for beach and dune restoration to improve and maintain the geomorphic function of the Gulf shoreline north of the Port Mansfield Channel through the barrier island.
Project Benefits: Although the Laguna Madre is one of 6 natural hyper-saline bays in the world, the reduced connectivity and circulation with the Gulf has degraded it. The dredging of the Mansfield channel will increase the connectivity and circulation, allowing the hyper-salinity in the Laguna Madre to be reduced, improving the habitat. In addition, jetties block the prevailing south to north longshore current. This project will restore sediment transport north of the Port Mansfield Channel jetties. This will prevent the eminent breach of the barrier island and maintain access to visitors and National Park Service staff. Restoration of sediment transport will support dune development and help control erosion along the Gulf shore. This will help protect the critical habitat for wintering piping plovers and the primary U.S. nesting beach for the endangered Kemp’s ridley sea turtles. Restoring Mansfield Island will increase the size and elevation of the island to mitigate erosion due to sea level rise, storms, and vessel wakes.
Future Without Project: If this project does not occur, erosion on the north side of the pass will continue at a rate of 14 feet per year. The beach and dune system will erode toward washovers, which can increase the likelihood of system breaches. Increased water exchange with the Gulf will result in salinity, circulation, and turbidity changes resulting in habitat changes or losses in the Laguna Madre.
Without the project, the area will not be protected from the effects of sea level rise. With an expected 2-foot relative sea level rise by 2085, dune areas can transition to brackish intertidal wetlands on the back side of South Padre Island and increase the possibility of breaches in the barrier island. Based on the NOAA Sea Level Rise Viewer and current erosion rates, relative sea level rise of 2 feet combined with ongoing erosion will completely convert the 3-acre Mansfield island, used by colonial waterbirds, to unconsolidated tidal flats.
The following individual measures were combined to create alternatives that restore the various natural lines of defense against coastal storms. The individual measures are described above, and the combination of measures for each alternative are presented in maps and summaries. ER alternatives screened are listed below. Alternative 1 was determined to be the lowest cost comprehensive plan and included in the Tentatively Selected Plan and identified in the draft report.
This alternative provides a baseline for comparison of with and without project conditions and supports the identification of specific benefits to be achieved as a result of each alternative.
This alternative proposes all 9 of the measures. This is the largest alternative which would restore natural features which provide habitat along the Texas coast and support natural conditions to withstand coastal storm conditions that cause land and habitat loss.
Measures included in Alternative 2 were combined because they would restore or protect critical landscape features of the coastal ecosystem, such as barrier islands, barrier and bay shorelines, etc. The features prevent land loss over time to sustain a natural line of defense against coastal storms.
Measures included in Alternative 3 were combined because they would prevent coastal barrier system degradation, fragmentation or loss, which would expose interior bay shorelines and marshes to high energy gulf forces. The barrier features prevent interior land loss over time.
The combination of features in Alternative 4 protects bay shorelines, inlets and estuarine marshes, which preserve habitat, as well as slow down waves and sediments.
Alternative 5 includes the restoration features that will defend the natural line of defense around existing infrastructure, such as navigation routes, industrial centers, or community resources.
Alternative 6 includes the combination of measures that meet the goals to be included in at least 4 of the other alternatives and scored highest in preliminary screening against project goals.
To develop the Tentatively Selected Plan (TSP) a combination of an Upper Coast CSRM, South Padre CSRM, and an Ecosystem Restoration alternatives were combined.
