Abstract In this study, a Level III reliability method for the performance-based design of nature-based solutions (NbS) is developed and applied to mangroves to mitigate wave overtopping. This method was developed incorporating both hydrodynamic and ecological processes and uncertainties. The model was examined with an idealized use case of a coastal embayment, which considered the overtopping of fetch-limited wind waves over a revetment fronted by mangroves. Uncertainties were evaluated using field and laboratory data. The model output was the reliability of the hybrid NbS, determined with the probability of failure, Pf, and encounter probability of failure, PEf, which is the probability of at least one failure occurring over the design life. The model was run for four cases: (1) the baseline case without mangroves, (2) a mangrove forest of moderate (20–100 m) cross-shore width using the drag coefficient parameterized with the Reynolds number, (3) the same mangrove forest as Case 2 using the drag coefficient parameterized with the Keulegan–Carpenter number, and (4) the same as Case 2 with the addition of during-storm mangrove mortality. For the baseline configuration without mangroves, PEf over the 50-year design life was 99.98%. For Case 2, PEf reduced to 37% and 6% for 20 and 100 m of mangroves, respectively, highlighting the role that mangroves can play to improve the reliability of the hybrid system. While Pf was constant for the baseline case, it decreased with time when including mangroves. PEf was approximately 1.5 times larger for Case 3 than for Case 2 for 20 m of mangroves, indicating that the parameterization of the drag coefficient affected the probability of failure. Mangrove mortality also affected the reliability, with PEf increasing from 37% (Case 2) to 66% (Case 4) for the 20 m of mangroves.

We performed a 1:2 scale experiment investigating the performance of green (mangrove), grey (revetment), and hybrid green-grey (mangrove + revetment) systems in mitigating wave overtopping. Six configurations were tested under irregular, regular, and transient (tsunami-like) wave conditions. This paper focuses on the performance of the systems under transient wave conditions, with amplitudes between 0.113 m and 0.228 m and rise times between 4.18 s and 15.40 s. Results indicated that while the conventional (revetment only) configuration reduced total overtopping volumes compared to the baseline (wall-only configuration) by 6

This study examines the hydrodynamic performance of an idealized Rhizophora mangrove forest subjected to various flooding scenarios using a high-resolution computational fluid dynamics model. The numerical model was developed within the OpenFOAM framework and validated against time series of water surface elevation, wave velocity, and pressure obtained from prototype-scale experiments of Kelty et al., 2022). The simulations were further extended to capture wave-vegetation interactions, providing detailed insights into flow dynamics, wave transformation, and energy dissipation mechanisms. The investigation focused on how wave parameters, such as water depth, relative wave height, and wave steepness, and mangrove characteristics, particularly stem density, affect wave attenuation. Results show that attenuation coefficients generally decrease with increasing water depths; however, when the effect of water depth was incorporated through the submerged mangrove volume fraction, the attenuation exhibited a unified dependence on relative wave height and wave steepness. The fractional increase in mangrove density is nearly proportional to the fractional increase in wave attenuation coefficients. Empirical equations with strong correlations (R-2 > 0.95) were proposed to investigate the influence of key dimensionless parameters derived from wave characteristics and vegetation properties on the attenuation coefficient. Furthermore, an artificial neural network (ANN) model was employed to identify dominant parameters driven wave attenuation, revealing relative wave height, relative forest width, and mangrove densities as primary factors, attributing to 70% of wave attenuation. The findings contribute to advancing nature-based coastal protection strategies and provide engineering guidance for incorporating mangrove forests into resilient shoreline design.

Traditional storm surge models represent urban areas using parameterized surface roughness, which captures bulk resistance effects but does not resolve building-scale flow-structure interactions or their influence on neighborhood-scale hydrodynamics. Laboratory and field evidence shows that structures redirect currents, accelerate flow through gaps, and create sheltered wake zones-affecting hazard intensity at neighborhood scales. Here, we present a building-aware surge model with dynamic collapse capability, applied to Estero Island, Florida, during Hurricane Ian. Using Delft3D-FM with real-time control, we simulate how building presence and failure reshape local hydrodynamics. While surge heights remain similar across scenarios, building inclusion alters flow velocity and shear patterns, producing local velocity increases up to 1.0 m/s near corridors and amplifying shear near corners and constrictions. The collapse of structures triggers nonlinear feedbacks, rerouting flow and exposing sheltered areas, and increasing local velocities by 40-60% within 25-50 m of the collapse location, transitioning from 1.0 m/s to 1.4-1.6 m/s. This result underscores the nonlinear amplification of flow in response to structural failure.

Supplying potable water and other services to critical facilities such as hospitals and evacuation shelters is crucial following disasters. Identifying areas at high risk for service loss and optimal shelter locations is challenging due to complex infrastructure networks, uncertain damage, and dynamic populations. This study presents a framework for analyzing the resilience of water infrastructure networks while considering the interdependencies between human behavior, evacuation shelter location, and infrastructure service availability. The framework provides opportunities to determine the likelihood of water service availability at shelter sites, how shelter location impacts services at other critical locations, and how evacuation patterns change which infrastructure components are most critical. The value of the framework is demonstrated with an analysis of probabilistic damage scenarios from a 250-year seismic event on a water distribution network for a small coastal town. Hydraulic performance is measured over 72 hours assuming 10 different possible shelter sites. Results show that water availability varied widely among evacuation sites, where average availability differed by as much as a factor of 2.6 between sites. Sites not reliant on pumps, along larger diameter pipes in looped sections, and closer to water sources had more consistent water availability. Evacuation location can influence water availability at other critical locations, particularly when evacuation-driven demand is concentrated upstream of critical facilities in capacity- or redundancy-limited portions of the network. This research highlights the advantages of evacuation scenario analysis as a decision-support tool and offers valuable insights into enhancing infrastructure network resilience through both network design and evacuation strategy.

A quantitative method is proposed for predicting the engineering performance of a hybrid green-gray system comprised of a mangrove forest seaward of a conventional engineered structure to mitigate wave action. The method coupled existing empirical equations to (1) predict the wave height attenuation of random waves transmitted through the mangrove forest and (2) use the resulting significant wave height as input to existing equations to estimate wave overtopping on a vertical wall or rubble-mound revetment or wave force on a vertical wall. The predicted wave height attenuation was parameterized by a drag coefficient obtained from an empirical relation developed from previous laboratory results. The method was validated with data from two large-scale wave flume studies of wave overtopping and wave force, which used similar model mangroves at 1:2 and 1:1 scale, respectively. The method conservatively predicted the overtopping of a vertical wall or rubble-mound revetment within a factor of 1.7 for discharge rates greater than 1 x 10- 3 m3/s/m and a factor of 3.5 for discharge rates greater than 1 x 10-4 m3/s/m. The predictions of wave forces were also conservative and were within a factor of 1.3 compared to the measurements. The overprediction of the wave force increased slightly with mangrove forest density, indicating a possible interaction between the waves and the green and gray features that reduced the wave forces more than expected from the wave attenuation alone. The apparent interaction was small, and the results of the proposed method were reasonable compared to the observations. The present results show promise for a design approach which assumes independent performance of the components to motivate a calculation coupling empirical equations to estimate the performance of hybrid green-gray systems for coastal defenses. Future study is necessary to parameterize wave attenuation by natural mangrove forests and to account for nonlinear processes such as wave breaking and wave-induced setup.

Coastal vegetation is of great importance in attenuating coastal flooding and enhancing coastal disaster prevention. While numerous studies have examined wave attenuation by mangroves simplified using rigid cylinder models, limited research has focused on the interactions between extreme waves and mangroves with complex root systems, such as those of Rhizophora species. Prototype-scale experimental and CFD numerical models were conducted to investigate the protective performance of the Rhizophora mangrove forest under tsunami-like wave conditions. The influence of wave and mangrove characteristics on wave attenuation coefficients was systematically analyzed. Results indicate that higher incident wave heights and water depths generally reduce wave attenuation coefficients, while high-density mangrove forests (HDM) significantly enhance wave attenuation coefficients compared to low-density configurations (LDM). To predict the wave attenuation coefficient, five dimensionless parameters, derived from mangrove and wave characteristics, were evaluated using Artificial Neural Networks (ANN). The ANN model shows excellent predictive performance (R2 = 0.98) for wave attenuation coefficients, identifying mangrove density and cross-shore width as the most dominant factors, contributing 47

This study presents a methodology for a fully virtual damage assessment (VDA) and first-floor elevation (FFE) estimation for buildings impacted by hurricanes. The methodology integrates publicly available street-level and aerial imagery, the National Structures Inventory (NSI) data, municipal property appraiser records, structured assessor training, and a unified VDA–FFE estimation process implemented simultaneously across two university campuses. The methodology is applied to Horseshoe Beach and Cedar Key, Florida, following the impact of Hurricane Helene (2024). A total of 1,085 buildings were assessed for component-level damage, overall damage state, building characteristics, and FFE. VDA validation against field reconnaissance data ( N = 28) yielded good agreement, with root mean square error of ± 0.76 damage state. FFE estimates validated against flood elevation certificates ( N = 29) demonstrated a mean absolute difference of 1.2 ft (0.4 m). Assessor inter-comparison for a 30-building sample showed standard error in overall damage state below 1, supporting methodological repeatability, scalability and limited subjectivity in assessments. Geospatial visualization revealed that building damage severity was strongly affected by topography and FFE, with Cedar Key exhibiting less damage with increasing landward elevation, while Horseshoe Beach experienced widespread damage due to lower overall elevation and greater storm surge inundation above ground level. Buildings with pile and column foundation types consistently exhibited greater resistance to damage relative to lower-elevation foundation types. The resulting open-access dataset provides high-resolution, property-level damage and FFE information to support post-event reconnaissance, hazard model validation, fragility development, and future training efforts using machine learning (ML).

This study investigates the effectiveness of green and gray mitigation measures in protecting coastal communities from tsunami-driven flooding using Computational Fluid Dynamics (CFD) simulations in OpenFOAM, validated against 1/16 scaled physical experiments. Strong agreement was observed between measured and simulated free surface displacement and horizontal forces. The analysis highlights that increasing the cross-shore width of mangrove forests enhances velocity dissipation, though its effect on maximum wave height reduction is limited. While gray structures-seawalls (SW), submerged breakwaters (SB), and their combination (SWSB)-were more effective in reducing inundation depths, mangroves significantly attenuated flow velocity. Buildings with full mangrove protection experienced reduced wave runup heights and pressures, whereas partial protection led to increased runup due to edge effects. Notably, an eight-row mangrove forest achieved similar load reductions over the first five building rows as the SWSB configuration. Additionally, an empirical equation was developed to quantify the relationship between force reduction and mangrove width. These findings provide critical insights for coastal resilience planning, demonstrating that while gray structures excel at reducing inundation, mangrove forests offer substantial velocity mitigation, emphasizing their role in sustainable coastal defense strategies.

This paper presents a methodology for virtual damage assessment (VDA) of building structures using primarily pre- and post-storm street-level and aerial imagery data. The methodology includes component-based damage assessment on a damage state (DS) scale from no damage (DS0) to complete damage (DS6) for roof, walls, elevated floors, windows and doors, attachments, and foundations, and to estimate the overall damage to the structure. The methodology was applied to assess exterior damage of the 3,408 structures impacted by Hurricane Ian (2022) in Fort Myers Beach, Florida, situated on a barrier island that was completely inundated during the event. The methodology was implemented using engineering students and was validated through a cross-comparison between the assessments performed by the students and a group of ten experts. The cross-validation showed that results obtained by students and experts were within +/- one damage state classification, indicating that the VDA can be conducted by trained engineering students as reliably as experts returning from the field. A second methodology is presented based on previous studies to assess the foundation type and first-floor elevation (FFE) of each building using street-level and aerial imagery. When the foundation type was correctly identified, the FFE estimates had a mean absolute error (MAE) of 1.0 ft (0.31 m), which were significantly more accurate than the FFE estimates from the National Structures Inventory with MAE of 4.27 ft (1.30 m). The resulting data set indicated that distance from the shoreline, building elevation, and year built were strong indicators of overall damage. This data set can be utilized to improve understanding of hurricane damage to buildings and identify important variables, which can lead to the development of reliable models to predict damage in coastal communities.

Debris damming forces of 1:20-scale shipping containers freely accumulated against elevated coastal structure columns were experimentally determined to evaluate ASCE 7-22 tsunami-resilient design standards. Three inundation conditions were generated to represent Froude regimes estimated in posttsunami field studies. Three different column array densities and two different shipping container sizes were evaluated. A photogrammetric method was employed to estimate the submerged projected area of in situ transient debris dams from two synchronized camera perspectives. Relative to this experimental data, it was found that the ASCE 7-22 equation for simplified equivalent uniform lateral static pressure is conservative by a mean factor of safety of 14.6 and performs as intended given the prescribed scope. Similarly, the ASCE 7-22 equation for detailed hydrodynamic lateral forces yielded a lower mean factor of safety of 2.4 but maintained design conservatism across all tested experimental conditions, also performing as intended. Minimum closure ratios and overall structure drag coefficients serve as input values for these detailed hydrodynamic lateral design loads. The proportion of closure coefficients prescribed by ASCE 7-22 tend to be reasonably conservative in general, and any instances of experimental exceedance of these design values did not appear to affect the design conservatism of Eq. (3). Finally, drag coefficients for rectilinear structures prescribed by ASCE 7-22 appear unrepresentative of coastal structures, which tend to generate column-flow interactions and unbalanced hydrostatic conditions. It is therefore suggested that the flow resistance of such structures be quantified via a bulk resistance coefficient, indicated by recent literature as a more appropriate measure applicable to surface-piercing flow obstructions.

Natural and Nature-Based Features (NNBF) are increasingly growing in popularity as flood risk reduction measures. However, the implementation of these systems is hampered by barriers, including the lack of engineering design methodologies. Existing engineering design methodologies for traditional coastal infrastructure cannot be directly applied to NNBF systems, because NNBF systems contain additional uncertainties. For example, vegetation experiences natural growth and mortality, affecting the engineering parameters associated with its flood protection capabilities. Performance-based design (PBD) describes a type of engineering design methodology that relies on designing a system to meet a set of performance objectives. The focus on performance, rather than known failure thresholds, makes PBD an appropriate methodology for new technologies (Atkan et al. 2007). Furthermore, PBD allows for the direct incorporation of uncertainties due to vegetation. PBD methodologies already exist in coastal engineering design. For example, Goda (2010) outlined the development of PBD for the design of caisson breakwaters. To develop an engineering design methodology for emergent vegetation systems, Ostrow (2023) expanded the existing method in Goda (2010), adding extra steps to quantify the engineering characteristics of vegetation. This paper describes the model in Ostrow (2023), improvements made to the model, and the application of the model to climate change.

Tsunami events have major impact on coastal communities including loss of life and high economic damage. Tsunamis have led to greater interest in, and awareness of, the risks posed by tsunamis to coastal communities. Tsunamis can damage coastal structures in a variety of different ways. In many cases, waterborne debris has been found to be a significant factor in structural failure (Shekhar et al., 2020). However, only recently emphasis was placed on evaluating debris transport, impact, and damming forces (Shekhar et al., 2020; Stolle et al., 2018; ASCE 2022). This study describes an extensive series of large-scale experiments to create a comprehensive dataset of horizontal hydrodynamic, impact and damming forces of tsunami-like and waterborne debris on slender columns as those found in elevated coastal structures. The experimental work presented herein is part of a multi-year experimental campaign to better understand the mechanisms that lead to debris damming and increased structural loading (Doyle, et al., 2024). This study will include a detailed description of the experimental procedures, model layout, instrumentation, and dataset characteristics. The work also includes the description of the different wave and water level conditions tested, and the uncertainty analysis of the results via model characterization and repeatability tests.

This study presents experimental findings on debris damming loads on columns of an elevated coastal structure under tsunami-like wave conditions. A total of 183 cases (140 with and 43 without debris) were tested at a 1:20 scale to understand the impact of various factors on debris-driven damming loads, including wave characteristics, structure configurations, and debris shapes. The debris impact and damming processes were observed and quantified from optical measurements, and corresponding loads were measured on the entire structure using a force balance plate and on an individual column in the front row using a multi-axial load cell. The experimental results indicated the horizontal debris damming load on the entire column structure increased by up to 3.2 times compared to conditions without debris, while the load on the individual column increased by up to 11.0 times. The total damming loads for the whole structure increased, but the load for the individual column decreased at a reduced opening ratio. The smaller debris sizes relative to column spacing showed significantly lower chances of debris damming across different column configurations. Overall, the load on the whole structure showed stronger correlations between debris damming loads and hydro-kinematic variables such as flow depth, velocity, momentum flux, and Froude number compared to the loads on the individual column. Among these variables, momentum flux emerged as the most consistently influential across all categories.

On the U.S. Pacific Northwest (PNW) outer coast, there are both naturally occurring dune backed beaches and cliff backed cobble beaches that have inspired nature- based engineering strategies for erosion control (i.e., sandy and vegetated dunes and dynamic revetments). Coastal communities want to mitigate and/or manage sand movement now, so policy and regulatory-based agencies are seeking the best available knowledge regarding the ecosystem services and dynamics associated with coastal foredune and cobble berms. Management needs and gaps in scientific knowledge and engineering practice often go hand in hand. Therefore we are working to develop guidance documents that combine management needs with the best available engineering and scientific knowledge to identify, synthesize, and address community-driven priorities for coastal dunes and dynamic cobble revetments in the PNW.

Low-lying regions are vulnerable to extreme waves and surges triggered by hurricanes and tsunamis. Anticipated sea-level rise is expected to cause shorelines to encroach further onto coastal land, potentially exacerbating the risk of flood-induced damage to coastal areas. Consequently, the implementation of countermeasure structures is imperative in mitigating wave-induced overland flows. Recently, Natural and Nature-Based Features (green structures), such as mangroves, have garnered significant attention for their potential to mitigate flood hazards. Mangrove forests are acknowledged as ecological buffer zones that effectively attenuate wave energy, protect shorelines, and enhance ecological functions. Dang et al. (2023) conducted a series of 1:16 scaled physical experiments to evaluate the efficacy of mangrove forests in mitigating inundating tsunami-like waves. However, this experiment only quantitatively analyzed flow dynamics at specific positions, and a comprehensive study of tsunami-induced flow patterns in coastal communities, characterized by a series of building arrays shielded by mangrove forests, has yet to be thoroughly investigated. Therefore, this study conducted a numerical investigation to further examine the influences of mangroves on dynamic flooding patterns and force mitigation on a series of building rows.