Coastal Engineering Archives

Simulating Compound Flooding During Hurricane Harvey with AdH

Simulating Compound Flooding During Hurricane Harvey with AdH Harris County, Texas DCCM was tasked by the USACE ERDC Coastal Hydraulics Laboratory to utilize and test an in-development version of the Adaptive Hydraulics Model (AdH) software to complete a monolithic simulation of Hurricane Harvey compound flooding that occurred in August 2017. Many efforts investigating the effects of compound flooding have relied on discrete models that simulate each flooding process separately. Consequently, they fail to mechanistically account for the complex interaction of multiple flood processes and the resulting impact on hazard estimates. Novel capabilities of AdH enable economical simulations of very large model domains while providing a high-resolution description of flood hazards in two dimensions. AdH provides the capability to simultaneously implement spherical coordinates and solve the shallow water equations and diffusive wave equations within a simulation. The combination of these capabilities makes AdH an effective model to simulate rainfall, overland flow, and storm surge to produce estimates that account for the interacting effects of pluvial, fluvial, and coastal flooding. Model terrain derived from LiDAR provided a high-resolution description of topography and large river channel bathymetry was resolved. Spatially and temporally variable rain rates and wind fields within the model resolved heterogenic storm characteristics. Model results were compared to stage and discharge time series observations at over 30 locations throughout Harris County and Galveston Bay. Modeled peak stages are within 1 m of observed peaks at more than 80% percent of the stations. The methods presented here can serve as a template for estimating flood hazards that result from compound flood events, and the results have documented the ability to mechanistically account for the interacting effects of multiple flood processes with a 2-D hydrodynamic model. At a Glance $168,500 Project Cost Markets Water Government Services Water & Wastewater

Artesian Slough Hydraulic Model and Closure Structure Conceptual Design

Artesian Slough Hydraulic Model and Closure Structure Conceptual Design Santa Clara County, California DCCM was contracted by the USACE San Francisco District to complete a hydraulic analysis and conceptual design for a water control structure on Artesian Slough. The San Jose – Santa Clara Regional Wastewater Facility (SJRWF) discharges effluent to the upper end of Artesian Slough, which terminates in South San Francisco Bay. An engineered levee is proposed to cross Artesian Slough and a gated outfall structure is required at the levee crossing to allow SJRWF effluent discharges to pass while protecting areas behind (south) the levee during extreme high tide events. A 2D HEC-RAS model was constructed representing the existing site conditions and calibrated to observed water level data above and below the SJRWF weir. A 1D model was also developed and calibrated for rapid simulations of various closure culvert designs. With-project conditions (WPC) 2D and 1D models were developed. The 1D WPC model was utilized to perform the closure design analysis. Sea-level rise (SLR) estimates were computed for the area based on the Coyote Creek tide gage and the USACE high SLR curve. The models were run for current and year-50 tidal signals, adjusted by the SLR curve. A total opening area of 210 square feet was selected to minimize the increase in water surface elevations upstream of the structure while considering cost-efficiency. The conceptual design was informed by the hydraulic analysis and looking ahead to maximize cost efficiency, be readily constructable, and minimize maintenance procedures and costs. It consists of six 72-inch by 70-inch culverts for a total opening of 210 square feet. The conceptual design has two sets of 3 culverts spaced closely together near each wing of the closure, with staggered outlets turned 90-degrees inward, which improves construction and maintenance efficiency. The conceptual design was translated to the 2D HEC-RAS model and run for six cases of varied tidal conditions, SJRWF outflow, and sea level. The water level results from the 2D HEC-RAS model were modified for areas above closure structure to account for the 90-degree bends recommended in the conceptual design. The water level, velocity, and shear stress results from the cases tested in the 2D model of the conceptual design were used to make conclusions regarding closure operations and erosion potential. At a Glance $170,000 Project Cost Markets Water Government Services Water & Wastewater

Design Services for Turpentine Run

Design Services for Turpentine Run U.S. Virgin Islands Turpentine Run, the only perennial stream on St. Thomas, experiences significant flooding due to intense rainfall, steep topography, and shallow soils. The Nadir neighborhood and surrounding area have endured flooding from Hurricane Maria, tropical storms, and other major rainfall events over the past 50 years. DCCM provided hydraulic modeling, analysis, and design support for improvements intended to protect the community from a 25-year storm event. The team conducted field investigations and gathered local flood-history information, including observed high-water marks. HEC-HMS was used to model watershed runoff for 25- and 100-year storm events, while a two-dimensional HEC-RAS model evaluated existing and proposed hydraulic conditions. The design focused on safely routing approximately 8,000 cubic feet per second through a constrained corridor between a roadway and the neighborhood, beneath a bridge, through dense vegetation, and ultimately to the sea. The analysis also informed streambed and bank protection, riprap sizing, and the evaluation of sea-level rise impacts. DCCM performed flood-frequency and hydrologic-hazard analyses to evaluate water-surface elevations, uncertainty, and residual risk under existing and proposed conditions. Multiple design alternatives were modeled and compared with computational fluid dynamics results to optimize performance. The findings supported USACE’s risk analysis and development of a Risk-Informed Design for the project. At a Glance 8,000 CFS Design Flow $93 million Estimated Construction Cost Markets Water Government Environmental Services Water & Wastewater

Charlie’s Pasture North & South Trails

Charlie’s Pasture North & South Trails Port Arkansas, Texas North Trail: DCCM provided the civil engineering and construction management services for the installation of the Phase II Charlie’s Pasture North Trail. During the preliminary phase of the project, DCCM worked with environmentalists to determine boundaries of existing wetlands and uplands. During construction, DCCM provided the construction staking for the location of the trail on the uplands and the locations of the main post supports for the boardwalk. This project consisted of 1,100 linear feet of concrete sidewalk, 2,000 linear feet of crushed granite upland trail, and 3,700 linear feet of boardwalk with flow through decking. Other improvements that were installed as part of this project included a wetland observation area adjacent to the trail and a picnic area. This project is located on the west side of Port Aransas and starts at The Nature Preserve at Charlie’s Pasture North and meanders over wetlands connecting to a crushed granite trail on Salt Island. Salt Island is totally surrounded by wetland areas and this trail provides the public with access to the island to view the existing coastal bird habitat. South Trail: DCCM provided the civil engineering and construction management services for the installation of the Phase I Charlie’s Pasture South Trail. During the preliminary phase of the project, DCCM worked with environmentalists to determine locations where the trail would transition from crushed granite trail to boardwalk. During construction, DCCM completed construction staking for the location of the trail on the uplands and the locations of the main post supports for the boardwalk. This project consisted of 2,900 linear feet of crushed granite upland trail and 4,400 linear feet of boardwalk with flowthrough decking. Other improvements that were installed as part of this project include three observation decks and a 17’x17’ observation tower. This project is located on the southwest side of Port Aransas, and starts at the Nature Preserve at Charlie’s Pasture South and meanders over wetlands and uplands and connects to a nature trail on the south end of the Leonabelle Turnbull Birding Center. The boardwalk and upland trails provide the public with viewing access to natural areas that are habitat to a number of different species of birds. At a Glance 3,700 Linear Feet Boardwalk North Trail 4,400 Linear Feet Boardwalk South Trail Markets Water Services Water & Wastewater

Vilano Pier Floating Dock

Vilano Beach Floating Pier Vilano Beach, Florida DCCM provided engineering design services for a 100-foot floating dock installed perpendicular to the Vilano Pier in St. Johns County, Florida, enhancing boater access to the Vilano Town Center. The project required careful evaluation of challenging site conditions, including heavy boat traffic, wind-driven wave action, and strong tidal currents. Our team conducted a comprehensive review of existing conditions and anticipated loading requirements to inform the development of performance-based design specifications for the floating dock system and associated gangways, ensuring long-term functionality and durability. In collaboration with subconsultants, DCCM supported the project through bathymetric surveying and water quality analysis to assess water circulation and flushing characteristics critical to the dock’s performance and environmental compliance. The team also coordinated permitting efforts with regulatory agencies, including the Florida Department of Environmental Protection (FDEP) and the U.S. Army Corps of Engineers (USACE). During construction, DCCM provided ongoing support through contractor submittal reviews and coordination, helping to ensure the project was delivered in accordance with design intent and regulatory requirements. At a Glance 100 Foot Floating Dock Markets Water Municipal Services Service

Vilano Beachfront Park

Vilano Beachfront Park Vilano Beach, Florida DCCM provided comprehensive concept planning, master planning, engineering, and landscape architectural services for Vilano Beachfront Park on Vilano Road in St. Johns County, Florida. The project aimed to seamlessly integrate the preservation of the natural coastal environment with the historic character of the area, creating a unique space for civic engagement and social recreation. Key features of Vilano Beachfront Park include a 1,300-square-foot pavilion that seats up to 190 people, designed to host concerts, educational events, and community gatherings. The pavilion incorporates rotating panels, which can be opened to provide ocean views or closed for events, and is equipped with performance lighting that is directed away from the Vilano Town Center, also considering turtle nesting season regulations. Additional upgrades to Vilano Beachfront Park focus on enhancing accessibility and visitor experience. These include new changing stations, a recreational area featuring a climbing play structure, new outdoor showers, renovated restrooms, and improved parking with restriping for ADA compliance. A mobimat provides accessible beach entry along the northern boundary, while updated dune walkovers, including an ADA-compliant viewing turnaround, allow easy access for all. Vilano Beachfront Park provides the only disability-accessible beach in St. Johns County, with a wheelchair-accessible path to the sandy beach and a wooden ocean-viewing ramp. These enhancements ensure an inclusive coastal experience for all visitors. At a Glance 1.7 Acres $109,000 Project Cost Inclusive Design Award, Florida Planning and Zoning Association Project Award Markets Land Development Buildings Water Services Land & Site Development Buildings & Places Program Management Water & Wastewater