Casey Dietrich

The overall project is a comparative assessment of total water levels for coastal military facility readiness and resilience using numerical models. NCSU will lead the development of models for storm waves and coastal flooding, both for direct predictions at the military facilities and for use as boundary conditions to nearshore models.

In this project, one-way coupling from a one-way coupling from ADCIRC+SWAN to XBeach following a two-scale approach will be attempted. One-dimensional (1D) transects will be used as the storm is far from landfall, switching to two-dimensional (2D) models for known hot-spots as the storm approaches land. For 1D, we will start with FEMA NFIP transects, because they already exist for the entire U.S. coast and have been well-validated in the development of coastal flood maps.

This project will address the problem of recurrent, shallow flooding in low-lying coastal communities. As local sea-level rise (SLR), land subsidence, and heavy rainfall events increase, so does the frequency of flooding in low-lying coastal areas. The tidal cycle now takes place on higher average sea levels, resulting in ????????????????sunny-day??????????????? flooding of roadways during high tides. Sea water also infiltrates stormwater drainage systems at low tidal levels, such that ordinary rainstorms lead to flooding. While these minor floods draw less attention than catastrophic storms, their high frequency imposes a chronic stress on coastal communities and economies by disrupting critical infrastructure services. The proposed work integrates outreach and research activities over the two-year project period to improve our prediction and communication of chronic flood hazards. First, we will couple an existing high-resolution hydrodynamic model used for prediction of estuarine flooding in the region (SWAN+ADCIRC) with a stormwater management model (SWMM5) to hindcast and identify the drivers of unexpected flood events in Carolina Beach, a community plagued by chronic flooding. In parallel, we will co-develop potential flood-mitigation actions with Carolina Beach??????????????????s Flood Working Group to inform future work using the coupled model framework. Second, we will deploy a real-time flood sensor network (in development by PIs Anarde, Hino, and Gold) in Carolina Beach to fill data gaps on the incidence and causes of chronic flooding. These data will inform an early-warning system, designed with local officials and community members, for real-time communication of flood hazard.

The integrity and reliability of flood-control earthen dams and levees are essential components to homeland safety. The failure of such systems due to natural or man-made hazards may have monumental repercussions, sometimes with dramatic and unanticipated consequences on human life and the country??????????????????s economy. The levees network in the Sacramento-San Joaquin Delta support exceptionally rich agricultural area (over a $500 million annual crop value). Currently, the risk of levee failure in this area from potential flooding or draught threatens the lives of individuals living behind the levees, but also, the water quality in this water-transfer system. Preliminary risk assessment demonstrated a 40% chance that at least 30 islands within the Delta area would be flooded by simultaneous levee failures in a major earthquake in the next 25 years. The teamwork proposed herein will extend the remote sensing monitoring by InSAR and Joint Scatterer interferometry (JSInSAR) to monitor levees deformation with a resolution on the order of a few millimeters. The research team ay NCSU will participate by integrating the use of measurement data and modeling techniques, using the concept of performance limit states, to effectively achieve a performance based health assessment of the delta levees network.

This project will address the problem of beach and dune nourishment in a changing climate. As storms become more powerful and seas continue to rise, major erosion events will occur more frequently. However, coastal communities do not yet understand how to evaluate their increasing vulnerabilities and adapt their long-term planning. We will identify which climate patterns most often trigger the need to nourish, the variability of the time interval between such nourishments, and the economic costs and sediment volumes necessary to maintaining this coastal protection policy into the 21st century. A stochastic climate emulator will first be developed to simulate 1000s of realizations of chronological climate patterns (forced by satellite and GCM products) to create future storm events coupled with sea level rise scenarios. A library of high fidelity, open source, hydrodynamic and morphologic simulations (SWAN+ADCIRC and XBeach) will then be used to develop a surrogate model to predict erosion and flooding for each future realization. Triggers like beach width, dune height, and community preferences will be used to identify how often communities will need to re-nourish, contingent on future climate and sea level rise scenario.

This project will address the problem of storm-driven circulation and flooding in estuaries. The research plan will have two components. First, the existing modeling system will be enhanced for the NC estuaries, and then numerical experiments will explore the sensitivities of estuarine flooding to the main drivers during storms. By varying systematically the atmospheric forcing, bottom friction, incoming river flows, and other parameters, we will improve our understanding of how storm surge is developed in these regions. Second, the modeling system will be extended to consider density-driven circulation and salinity transport, by leveraging earlier work for estuarine circulation in the northern Gulf. It is known that horizontal salinity transport during storms can devastate marine life and vegetation, but there is not currently a modeling system that can predict both transport and overland flooding. This project will combine those processes and explore questions about stratification during storms. This research will produce modeling technologies that will benefit coastal communities in NC, and we will share these technologies and findings with stakeholders.

The goals of this project are to understand the correlations in storm surge properties within coastal regions like a bay or marsh, and then to convert those correlations into subgrid-scale corrections for forecast models. Storm surge models are the primary method for predicting inundation during strong storms. There is presently a divide between the high-resolution surge models used for hindcasts and climate studies, and coarse-resolution models used for real-time forecasts. High-resolution models are known to be more accurate, partly because they can represent the small-scale hydraulic features of the coastal environment, including the inlets and channels that convey surge into coastal areas. But while these high levels of resolution can increase accuracy, they cause the models to be too slow to use operationally for ensemble forecasts. However, nearby locations in surge models are known to have strong correlations in surface elevations and velocities which will be exploited here to increase accuracy and efficiency. The research objectives of this project are to: (1) understand and quantify the correlations between nearby locations, and between different spatial scales in storm surge models; (2) develop techniques for subgrid-scale corrections to increase accuracy in surge models; (3) implement corrections and test against high resolution solutions and existing storm data; and (4) transfer codes and techniques to academic and industry partners. This work will enhance fundamental understanding of surge, in particular how processes in nearby locations are linked, and how the essential degrees of freedom in the system may be extracted. It will improve our capability to model and forecast surge not only for the low-resolution models, where the technique will first be implemented, but also for higher-resolution models which will now be able to make use of the very high resolution lidar data that is now available in many regions. With these corrections, lower-resolution models will approach the accuracy of higher-resolution models with a much lower cost, which will increase accuracy of practical real-time ensemble simulations. This project will be a first step towards more accurate and efficient surge models and is seen as a necessary step towards more complete coastal modeling systems including wave propagation and pollutant transport, both of which may be adapted under this type of framework.

The goals of this project are to better understand the storm-induced erosion of barrier islands, and to develop ways to represent that erosion in predictive models on large domains. The critical objectives will be: (1) Develop a high-resolution hindcast of inlet creation in a barrier island system, (2) Explore the sensitivity of erosion predictions to the quality of input data, and (3) Implement a two-way coupling of small-scale erosion to larger-scale flooding. As a study area, we will consider the erosion of Hatteras Island during Hurricane Isabel (2003) and the creation of the so-called Isabel Inlet. The model will be validated with aerial surveys of island topography, collected immediately before and after the storm. We will quantify the model's ability to predict the inlet creation given coarse inputs, and identify the necessary resolution to include this process in larger-domain models. The evolving ground surface will be used to update topography in a region-scale flooding model, to examine how flow through the Isabel Inlet affected the back side of the island.

Our goal is to improve simulations of coastal flooding in regions where the beach morphology is highly dynamic during a storm event. The feedback between waves, surge and morphology must be better linked, specifically through the extension and coupling of state-of-the-art numerical models. Although most morphology models are limited in their geographic extents, we will extend and apply a process-driven model to represent erosion and breaching at larger scales. And, although most wave, surge and morphology models are coupled with one-way communication, we will develop an automated system to map information in both ways. This research will produce modeling technologies that will benefit coastal communities within North Carolina, and we will share these technologies and findings with stakeholders. Simulations of wave propagation and flooding (and specifically the simulations from our models) are used in North Carolina and elsewhere for building design, the establishment of flood insurance rates, and real-time decision support during storm events. These predictions will be strengthened via the proposed tight coupling with a beach morphology model. The resulting modeling system will better represent the nearshore response to storm impacts.

The Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) fuses into one group investigators with unique scientific and technical knowledge and extensive publications related to oceanic and atmospheric transport, air-sea interactions, tropical cyclones, laboratory experiments, computational modeling and observations. Our primary emphasis will remain on predictive oil transport modeling from a deep water well-head to the beach. Two new, ambitious experiments are proposed because of the potential for large coordinated field studies to discover new phenomena, focus our modeling activities, and provide data sets for their assessment: LASER will be targeted at understanding seasonal and sub-mesoscale variability in the DeSoto Canyon, and SOPYS will focus on transport processes across the continental shelf. These experiments are designed to complete transport pathways and address questions arising from GLAD and SCOPE. Lagrangian experiments are the most accurate way to quantify the net effect of all flow scales on ocean transport. We propose an approach that combines satellite, shipboard, and airborne observations of the upper ocean. A plane will be used for aerial observations with real-time communication of surface maps (high-resolution temperature, convergence zones) to the ocean vessels for detailed measurements. Virtual experiments before the field experiments will identify the phenomena, and a suite of operational models will be run during the experiments; model gaps will be identified after the field data is digested; improvements and parameterizations will follow. Laboratory experiments in the unique SUSTAIN laboratory (University of Miami) and uncertainty quantification will complement field and numerical work. Laboratory experiments at the University of Cambridge will serve to assess plume model developments. The scientific progress made during this project through a better understanding of the air-sea interaction will not only allow us to better respond to deep-ocean oil blowouts, but will also have far-reaching implications for navigation using local currents, potential off-shore green energy production, and the influence of upper-ocean flows on the ocean??????????????????s carbon intake in climate.