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Global environmental factors (e.g., extreme weather, climate action failure, natural disasters, human environmental damage) increasingly threaten coastal communities. Shorelines are often hardened (seawalls, bulkheads) to prevent flooding and erosion and protect coastal communities. However, hardened shorelines lead to environmental degradation and biodiversity loss. Developmental pressures that are growing in scale, scope, and complexity necessitate the development of sustainable solutions to work with, rather than against, nature. Such nature-based solutions (NBS) provide protection and improve environmental quality and enhance biodiversity. To further this pressing need into action, the US Army Corps of Engineers (USACE) began the Engineering With Nature (EWN) initiative to balance economic, environmental, and social benefits through collaboration with partners and stakeholders. This work shows how engineering practice can be advanced through structured decision-making and landscape architecture renderings that include ecological sciences and NBS into an integrated approach for enhancing biodiversity in coastal marine environments. This integrated approach can be applied when designing new infrastructure projects or modifying or repairing existing infrastructure. To help communicate designs incorporating NBS, drawings, and renderings showcasing EWN concepts can aid decision-making. Our experiences with implementing EWN in practice have revealed that involving landscape architects can play a crucial role in successful collaboration and lead to solutions that protect coastal communities while preserving or enhancing biodiversity.

The US Army Corps of Engineers, Galveston District, is executing the Coastal Texas Protection and Restoration Feasibility Study coastal storm risk management (CSRM) project for the region. The project is currently in the feasibility phase. The primary goal is to develop CSRM measures that maximize national net economic development benefits. This report documents the coastal storm water level and wave hazard, including sea level rise, for a variety of flood risk management alternatives. Four beach restoration alternatives for Galveston Island and Bolivar peninsula were evaluated. Suites of synthetic tropical and historical non-tropical storms were developed and modeled. The CSTORM coupled surge-and-wave modeling system was used to accurately characterize storm circulation, water level, and wave hazards using new model meshes developed from high-resolution land and sub-aqueous surveys for with- and without-project scenarios. Beach morphology stochastic response was modeled with a Monte Carlo life-cycle simulation approach using the CSHORE morphological evolution numerical model embedded in the StormSim stochastic modeling system. Morphological and hydrodynamic response were primarily characterized with probability distributions of the number of rehabilitations and overflow.

Sea-level rise impacts on salt marsh for Guana Tolomato Matanzas National Estuarine Research Reserve are investigated using field measurements (six sites within the marsh) and a tide-marsh equilibrium model (Hydro-MEM). The hydrodynamic component of the model enables for prediction of spatially variable tidal data (mean low water and mean high water), which are coupled with a marsh equilibrium model (MEM) for prediction of spatially based biomass productivity of Spartina alterniflora. The field measurements corroborate the model results by way of prediction of relatively productive marsh at four of the six sites (percent coverage of Spartina alterniflora of 30–41%, canopy height of 0.27–0.67 m and simulated biomass density of greater than 750 g m−2 over at least half of the local area within 500-m radii of the measurement sites) and relatively limited marsh at the two other sites (percent coverage of Spartina alterniflora of 3–5%, canopy height of 0.11–0.29 m, and simulated biomass density of greater than 750 g m−2 over less than one-tenth of the local area within 500-m radii of the measurement sites). The model is applied in a coupled fashion for 50 years of time into the future using ten 5-year increments, where each increment of Hydro-MEM accounts for the natural accretion of the marsh, an update of the digital elevation model and bottom-friction parameterization, and the subsequent feedback to the hydroperiod and marsh productivity. Hydro-MEM is shown to exhibit rate-sensitivity with respect to sea-level rise exceeding the marsh accretion rate, whereby a sudden loss of marsh elevation occurs in such instances of marsh destabilization. Demonstrating rate-critical transition, the model proves flexible to account for the non-homogeneous and transient nature of the fast-slow variables, whereby the marsh migrates away from the tidal creeks and further into the upland zones. Practical implication of the model results is illustrated by identifying zones of lands into which marsh will be able to migrate and where existing marsh will not survive under increasing sea level. Post-analysis compares the final model output against land use/cover zonation to correct the 50-year simulation results of marsh productivity for elevation-appropriate regions but that are developed, freshwater, or otherwise inappropriate land type for salt-marsh habitat.