Tidal Inlet Research Articles

Assessing stability of tidal inlet in a tropical coastal lagoon

Assessing stability of tidal inlet in a tropical coastal lagoon

Field measurements of the carbon to chlorophyll-a ratio using Imaging FlowCytobot: Implications for dissolved oxygen modeling

In subtropical coastal waters around Hong Kong, dissolved oxygen (DO) can undergo significant diurnal changes (up to 40%–50% saturation) during algal blooms. The carbon to chlorophyll-a ratio (CCHL) – a key parameter in water quality models – is variable and depends on factors that include light intensity and temperature. Despite numerous laboratory and field investigations, the prediction of CCHL and DO during high productivity conditions remains a difficult problem; the CCHL during algal blooms has also not been measured.The phytoplankton and DO dynamics are studied in a semi-enclosed tidal inlet using a submerged Imaging FlowCytobot (IFCB) together with a real-time water quality monitoring system. A diurnal pattern of algal abundance is observed with peaks around 4pm. Based on carbon estimates from the bio-volumes of the algal images and direct measurements of chlorophyll-a, the CCHL ratio is monitored continuously during an algal bloom event. The CCHL is found to vary significantly over a bloom cycle—in the range of 10 to several hundred and generally much greater than the constant values (in the order of 10) assumed in industry standard water quality models. A first order theoretical estimate of the CCHL as a function of algal growth rate and light saturation intensity is supported by field data. Using a simple oxygen budget model, the diurnal DO changes during an algal bloom can be satisfactorily predicted by integrating IFCB data with water quality data. The findings help to improve environmental and ecosystem modeling and mariculture management.

Long-term sea level rise modeling of a basin and tidal inlet system reveals sediment sinks

Long-term sea level rise modeling of a basin and tidal inlet system reveals sediment sinks

Numerical Study on the Influence of Tidal Inlet Restoration on Water Exchange in Wanning Lagoon

Wanning Xiaohai is the largest lagoon in Hainan Province. In recent years, the body of water in Xiaohai has been polluted due to the untreated discharge of domestic sewage and aquaculture tailwater directly into Xiaohai. In order to improve the water quality of Xiaohai and relieve the pressure on the water environment, it was decided to restore the tidal inlet of Xiaohai. In this study, the water quality module of the finite volume ocean model was applied to simulate the change of pollution concentration using the Eulerian advection diffusion equation to analyze the half life time and tidal prism before and after the restoration project of the Wanning Xiaohai tidal inlet. The research results showed that after the restoration of the tidal inlet, the half life time of Xiaohai water body changed from 64 d to 58 d, shortened by 6 d, and the tidal prism increased from 8.8×106 m3 to 9.6×106 m3, which can well enhance the exchange between Xiaohai and external water bodies, improve the water quality of Xiaohai and relieve the pressure of water environment.

The tidal prism as a dynamic response of a nonlinear harmonic system

As known, the empirical relationship between the equilibrium cross-sectional area of a lagoon inlet and the tidal prism was intuited for the first time by LeConte [“Discussion on the paper, “Notes on the improvement of river and harbor outlets in the United States” by D. A. Watt,” Trans. ASCE 55, 306–308 (1905).] and then formalized by O'Brien [“Estuary tidal prism related to entrance areas,” Civ. Eng. 1(8), 738–739 (1931)]. This relationship requires knowledge of the tidal prism, which can be estimated either using the cubature method or the current data method [Jarrett, Tidal Prism-Inlet Area Relationships (Coastal Engineering Research Center, US Army Corps of Engineers, Fort Belvoir, VA, 1976)], both of which involve the execution of a number of experimental measurements. However, these methods, besides being very expensive, can only provide the prism value in the present condition and do not allow for predictions in the case of significant morphological changes, of both natural and anthropic origin, to the tidal inlet. On the other hand, the hydrodynamic relationship, which links the tidal prism to the product of the tidal range and the basin extension, can only give a coarse estimate of the prism, especially when the value of the tide outside the lagoon is considered. In this work, we propose a simple hydrodynamic relationship based on the dynamic response of a nonlinear harmonic system. This is a relationship that requires the calibration of a single physically based parameter. Through this relationship, knowing the geometric characteristics, the bottom friction of the inlet channel, the surface of the basin, and the tide amplitude in the open sea, it is possible to estimate the tidal prism. The application of this relationship to real cases shows a good agreement with the experimental data.

Sediments and bedforms of the Harle tidal inlet (Wadden Sea, Germany)

ABSTRACT The paper presents a map of sediment surface distribution and bedforms in the Harle tidal inlet, German Wadden Sea. Data collection, processing, and map editing were realized within the sublittoral mapping program of Lower Saxony national waters carried out by the NLWKN – Coastal Research Station. The map is the result of the combined use of multibeam echosounder, sub-bottom profiler, and ground-truth data. The sediment characterization is achieved by an unsupervised approach using an Object-Based Image Analysis (OBIA) on a normalized backscatter mosaic, verified by nineteen sediment samples. Morphometrical parameters and sub-bottom data provided important information to identify hard substrates and bedforms.

Imminent reversal of the residual flow through the Marsdiep tidal inlet into the Dutch Wadden Sea based on multiyear ferry-borne acoustic Doppler current profiler (ADCP) observations

Abstract. The Dutch Wadden Sea is a UN World Heritage Site connected to the North Sea by multiple tidal inlets. Although there are strong tidal currents flowing through these inlets, the magnitude and direction of the residual circulation in the western Dutch Wadden Sea is important for sediment, salinity and nutrient balances. We found that the direction of this residual flow is reversing. This residual circulation has been the subject of various studies since the 1970s, in which substantially different net volume fluxes were presented. Differences in tidal conditions in the main inlets, tidal rectification and meteorology were identified as driving mechanisms. Here we analysed almost 13 years of acoustic Doppler current profiler (ADCP) observations collected on the ferry crossing the Marsdiep tidal inlet in the Dutch Wadden Sea since 2009. The results are combined with earlier investigations covering the period 1998–2009. We find a significant trend in the magnitude of the residual volume flux, with decreasing export to the North Sea and with occasional imports observed in recent years. We hypothesise that this trend is related predominantly to changes in tides in the North Sea, which are caused by increased strength and duration of stratification in response to global warming. With warming projected to continue, we expect the residual flow in the Marsdiep to continue to reverse to full inflow within the current decade, with potential knock-on effects for the sediment budget and ecosystem of the western Wadden Sea.

Modeling the hydrodynamics of a tidal inlet during bay-side storms

Bay-side storms, defined here as storms with tracks on the landward side of barrier islands, may disturb the hydrodynamics of inner bays to a larger extent than on the ocean side. These storms are common in large-scale O(>100,000 m) estuarine systems and have the potential to modify the circulation in bays and within tidal inlets. Here, we provide an overview of the hydrodynamic response of a tidal inlet under forcings caused by bay-side storms and explore the role of waves in modulating the release of storm surge from the back-barrier regions into the ocean. A two-dimensional horizontal numerical model including wave-current interactions is calibrated and validated against field observations of water levels and depth-averaged velocities at Oregon Inlet, NC. The model is then used to investigate the effect of synthetic bay-side storms with varying wave conditions and water levels based on those generated by Hurricane Irene (2011), which is the strongest bay-side storm to hit the Outer Banks of North Carolina in the last two decades. Effect of timing of the peak storm surge during the ebb and flood phases of the tide is also explored.Results from synthetic storms indicate that, during bay-side storms, the water level gradient along the inlet favors ebbing flows regardless of the timing of the storms relative to tidal phase. These results suggest that waves might be responsible for any influx of volume to the bay during high bay-side surge events. Wave blocking effects were found to be stronger along the ebb shoal and only reached the flood delta when bay water levels were nearly the same as the ocean water levels. Reduction of currents by waves in the inlet have the potential to extend the duration of the inundation period in the back barrier region. Bay-side storms also caused flux enhancement over inlet shoals and channels in the flood delta, which could have implications for circulation patterns as well as the morphodynamics of the system.

Nearshore environments before the evolution of land plants

The long-term evolution of the biosphere has caused fundamental shifts in environmental conditions and sedimentation at Earth’s surface. While effects of the evolution of terrestrial vegetation on river systems have been explored in detail, facies models and possible shifts in sedimentation in pre-vegetation nearshore marine settings have not been sufficiently explored. The circa 800-million-year-old Burra Group, exposed in the Adelaide Fold Belt of South Australia, is a terrestrial to nearshore transgressive sedimentary succession associated with rifting. The Burra Group provides a record of marginal and shallow marine environments before the evolution of land plants. Environments are interpreted to record deposition in low energy fine-grained tidal flat, lagoon, tidal inlet, and beach-barrier environments (a beach-barrier system). The thick mudflats (up to 30 m) of the studied units indicate that vegetation is not essential for mudflat accumulation, contrary to some models. The fluvial–marine transition and the back-barrier–tidal inlet–beach-barrier transition is highly regular and there is little interbedding of units. The Tonian beach-barriers of the Burra Group do not backstep into the back-barrier region and aggrade much like stable modern systems backed by peat. These observations are suggestive of a stable barrier system in the absence of land plants. The high mud percentage and/or early carbonate cementation (including microbialite and stromatolite deposition during transgression) may have contributed to the stability of this beach-barrier system.

Spatial Variation of Soil Organic Carbon from Bamen Bay Mangrove in Southern China

Mangrove forests are large pools of soil organic carbon (SOC) found across the world, and play a vital role in global carbon (C) cycling. In this study, to investigate the effects of spatial factors on SOC in mangrove forests, soil samples at different depth layers from upper estuary (UE), lower estuary (LE), and tidal inlet (TI) in the Qinglangang mangrove forest in Southern China were collected and the differences in SOC among the layers and geomorphological settings were compared. The mean SOC content showed a pattern of LE (4.63 ± 1.28%) > UE (2.94 ± 0.73%) > TI (1.44 ± 0.33%). SOC content and storage decreased with soil depth in TI, but increased in UE. The total SOC storages (0–80 cm) of sites TU, UE, and LE, were 104.41 ± 16.63, 207.14 ± 44.83, and 228.78 ± 19.37 Mg/ha, respectively. The results suggested that top- and subsoil organic C content and storage were largely dependent on their specific location, which underwent different river-sea interactions and human activities. The SOC of the soil profile varied at different sites, implying that the current C storage of mangrove ecosystems can be accurately estimated by quantifying the C of sediments at sites.

A study on the riprap movement based on marine hydrodynamic model and field observation

ABSTRACT The study of mechanisms and the accurate simulation of riprap movement caused by complex hydrodynamics are significant for harbor, channel and coastal engineering. Field measurement of current and riprap drift distance was conducted for a dike project in the port of Lianyungang, Jiangsu Province, China. Meanwhile, a well-validated three-dimensional hydrodynamic model was developed to study and analyze the riprap movement process and the influence of project position combined with the theoretical movement equation of riprap. At the moment of maximum flood, the riprap drift distance is greater than at the moment of maximum ebb. The riprap drift distance increase as the tidal inlet width decreases, which follows a second-order exponential distribution. The riprap mass reduces the riprap drift distance, and the magnitude of the reduction diminishes gradually as the riprap mass increases. Therefore, heavy riprap can reduce the horizontal drift distance in a construction.

Hydrodynamics of a tidal inlet under gray to green coastal protection interventions

Structural coastal protection interventions have been implemented worldwide to stabilize channels and shorelines in tidal inlets. Although these conventional “gray” interventions typically attain their goals, there is an increasing interest and need to consider nature-based or “green” interventions that also address system resilience and environmental impacts. For a better implementation of gray to green interventions in tidal inlets, their effectiveness and their effects on the velocity of these dynamic coastal systems need to be understood. The effects on flow velocity of gray to green coastal protection interventions for tidal inlets are assessed here by exploring six interventions intended to protect against erosion on the estuarine-side shoreline near the inlet. A field-calibrated numerical model with Willmott Skill scores rated as excellent for Oregon Inlet located in North Carolina, United States, is used to simulate tidal currents under present conditions and after implementing a seawall, a set of bendway weirs, a terminal groin extension, a dual-jetty system, a flood channel relocation, and an island restoration project. Comparisons of time series of flow velocities in the flood channel along an eroding, estuarine shoreline are used to identify the effectiveness of each coastal protection alternative at reducing erosive velocities. Geospatial difference maps are used to determine velocity changes caused by each alternative throughout the inlet system. With no coastal protection interventions, the velocities along the eroding shoreline exceeded an erosive threshold velocity (defined as 0.2 m/s) during 50% of the simulated period. Alternatives closer to the green side of the coastal protection intervention spectrum, such as channel relocation and island restoration, tend to display the most effectiveness at reducing flow velocities at the eroding shoreline while resulting in minimal inlet-wide hydrodynamic changes. On the other hand, gray alternatives either cause minimal (seawall and bendway weirs) or extreme (jetties) changes in velocities throughout the inlet system. This comparison of gray and green coastal protection interventions in tidal inlets serves as an example to contrast the effectiveness of different coastal protection alternatives at reducing erosive flow velocities and to inform alternative selection at other inlet systems.

Dispersion Processes in Weakly Dissipative Tidal Channels

AbstractWe report the results of an extensive experimental campaign dedicated to the analysis of turbulent dispersion owing to the circulations in tidal environments, characterized by a tidal inlet and a channel with lateral tidal flats. We focus on weakly‐convergent and weakly‐dissipative estuaries or tidal embankments, where the internal waters communicate with the open sea through an inlet mouth. Tides are reproduced as single or multiple harmonics waves. Particle Image Velocimetry is employed to measure two‐dimensional surface velocity fields. Large‐scale macro‐vortices, generated by vortex shedding during the flood phase from the inlet barrier, tend to occupy the entire tidal flats width and are completely flushed out during the ebb phase. In all experiments, an intense residual current, with shape influenced by the large‐scale flood vortices, is observed. The presence of large‐scale vortices and of a residual current strongly influences the Lagrangian auto‐correlation functions and the corresponding absolute dispersion time evolution. Looping auto‐correlations are the signature of both periodic forcing and vortices, ultimately, leading to super diffusive regimes. An asymptotic Brownian regime is always found for the investigated range of parameters allowing for an estimate of the horizontal dispersion coefficients which turn out to decrease with the friction parameter and tend to be enhanced when the semi‐diurnal constituents prevail. Finally, multiple particle statistics show multiple regimes depending on particle separations, compared to a typical injection length scale that seems to coincide with the inlet mouth dimension.

Wave Enhanced Overtides in an Idealized Tidal Inlet System

AbstractTidal water levels and currents in the shallow water environments of the inner shelf are subject to nonlinear interactions that produce higher frequency harmonics known as overtides, which contribute to the residual transport of scalars. The primary hydrodynamic overtide generating mechanisms (advection, nonlinear continuity and bottom friction) are well known. Yet, other mechanisms may exist in coupled systems characterized by wind waves and barotropic tides. This work uses process‐oriented coupled tides‐waves numerical simulations of an idealized barrier beach domain to study the effect of varying tidal range and wave conditions (height, period, direction) to investigate new mechanisms of overtide generation. Harmonic analysis of results from 92 simulations indicates that an increase in wave height amplifies overtide current velocities in both the alongshore and cross‐shore directions, while changes in wave period and wave direction have a lesser effect. A maximum increase of ∼140% in overtide current velocity magnitudes was observed in domain‐wide averages from a tides only to a coupled tides‐waves simulation. Decomposition of the depth‐averaged momentum balance of the tides only and tides‐waves simulations identify bottom stress, pressure gradient, and bottom wave streaming enhancing overtide generation. Accelerations from wave‐enhanced pressure gradients and bottom wave streaming produce a shoreward bottom current and an offshore directed return flow that persist throughout a semidiurnal tidal cycle, interacting with tidal currents to enhance asymmetries between flood and ebb.

The lower shoreface of the Dutch coast – An overview

The lower shoreface, defined here as between about 8 and 20 m water depth, forms the transition between the inner shelf and upper shoreface. Knowledge of lower shoreface hydro- and morphodynamics is essential for coastal management and maintenance.The shoreface of the Dutch coast is a complex area. It is partly determined by its evolution in the past, whereas present-day processes are influencing or even changing it. The present situation and large-scale anthropogenic supply of sediment will determine its future development.The shoreface morphology varies along the Dutch coast, depending on the coastal slope and superposition of ridges (central Holland coast) and ebb-tidal deltas (Delta area, Wadden Sea). The architecture of the shoreface-connected ridges off the central Holland coast indicates that they are still active today. The development of most ebb-tidal deltas along the Dutch coast is largely influenced by interventions in the tidal inlets and tidal basins.The Kustgenese 2.0 Lower Shoreface project comprised both field data collection in 2017 and 2018 and numerical modelling. Field data was collected in study areas at Ameland Inlet, Terschelling and Noordwijk. Sediment cores and multibeam sonar surveys provided information on the Holocene deposits, geomorphology and sediments. Instrumented frames placed at the seabed collected a wealth of process data.The variation in shoreface composition and morphology is larger than anticipated previously. In general, the lower part of the shoreface consists of older Holocene deposits overlain by an active sand layer that responds to variations in tidal, wave and wind conditions. The deposits at the lower shoreface of Terschelling were comparable to the ebb-delta channel deposits at the ebb-delta front at Ameland Inlet. At Noordwijk, deposits of the Late-Holocene prograded barrier shoreface overlie those of back-barrier tidal channels and river channels. The large-scale morphology of the lower shoreface seems rather stable. Decadal time series show an erosional trend. Small-scale bedforms can change over an interval of days to weeks.The multibeam surveys revealed unexpected details such as geology-based shoreface irregularities between −12m and −18m that probably act as conduits for downslope currents and sand transport. After a high-energy wave event, more erosional features were discovered that suggest seaward sand transport.Measured orbital velocities at the seabed at 14–16 m depth reached 1.5 m per second under high-wave events. This caused high sediment mobility under sheet-flow conditions with abundant sediment suspension. It is not clear what this means for the net sand transport at the lower shoreface.The modelled alongshore-directed sand transport is much larger than the cross-shore transport. The largest transports at the 20m depth contour occurs along the northern part of the Holland coast. Here, transport is parallel to the coast or directed to deeper water. Transports at 20 m depth along the other parts of the coast are directed to shallower water.The modelled total landward sand transport over the −20m contour is c. 4 million m3 per year and c. 7 million m3 per year over the −16m contour. This suggests a yearly erosion of c. 4 million m3 in-between, in case of no alongshore transport gradients.The results of the sand transport calculations imply a net landward sediment transfer that needs to be further tested against the morphological changes in the shoreface.

Modelling study on the sediment dynamics and the formation of the flood-tide delta near Cullendulla Beach in the Batemans Bay, Australia

The first 3-D current-wave-sediment coupled model of the semi-exposed estuary Batemans Bay, New South Wales, Australia, was developed in our study based on the Finite Volume Coastal Ocean Model (FVCOM). Our study explored the hydrodynamics, sediment dynamics and morphology change inside the Batemans Bay under large wave events. The modeled monthly-averaged residual flow, sediment flux and suspended sediment concentration with a combined tidal and wave forcing in the inner bay were significantly different to those only with tidal forcing, this is because the storm wave events can generate wave-induced currents and large bottom stresses, influencing the sediment transport. In addition, the morphology change of the flood-tide delta (FTD) inside the Batemans Bay under wave effects was also investigated in this study. According to previous studies, the FTD is a sediment deposit located on the landward side of tidal inlets, formed by the incoming tidal currents and ocean waves, which is an important morphology coastal feature influencing the sediment exchange with adjacent beach systems. Yet, the dynamic processes of FTDs have not been fully understood and explored quantitatively in sheltered estuaries. Based on our model results, the FTD near Cullendulla Beach is controlled by wave effects and was in an equilibrium status: when the FTD was eroded deeper to a critical value (about 2 m) by waves, sedimentation occurred. The rocky headland adjacent to the FTD contributed to the formation of the FTD due to sheltering effects, and the FTD actually developed at the ‘wave shadow areas’ behind the headland in Batemans Bay, which were dominantly controlled by sheltering effects. Despite being termed a ‘Flood-Tide Delta’, ‘Tide’ here is misleading, and a new name of ‘Wave Shadow Shoal’ should be given to describe such wave-dominated coastal features. In conclusion, this study demonstrated that waves played the dominant role in the hydrodynamic processes, sediment transport and morphology change in Batemans Bay.

Bottom‐up as well as top‐down processes govern zoobenthic secondary production in a tidal‐flat ecosystem

AbstractFor decades, we monitored numbers and weights of the macrozoobenthos in a vast tidal‐flat area in the Dutch Wadden Sea. We used data collected since 1992 to estimate annual secondary production. Data on chlorophyll concentrations and primary production were available for a nearby tidal inlet, showing rapid increases in the late 1970s and gradual declines since the late 1980s. The benthos responded with a doubling of biomass around 1980 and gradual declines of summer biomass, annual production as well as seasonal biomass gain for the 1992–2019 de‐eutrophication period. In nearly all years, production of bivalves (on average 25.5 gAFDM m−2 yr−1) accounted for more than half of the total zoobenthic production (averaging 42.7 gAFDM m−2 yr−1). Production values for individual years were not correlated with chlorophyll concentrations or primary production of that year, but did show a significantly positive relationship with bivalve recruitment success in the preceding year. As recruitment was governed by predation pressure on early bivalve bottom stages, it is a top‐down process. Bottom‐up processes were expressed in the gradually declining long‐term trend of bivalve growth rates and secondary production during the de‐eutrophication period and also in a few years when bivalve numbers were so high that growth rates were reduced by food competition. In by far most years, numbers of bottom animals were too low to fully exploit the carrying capacity of the system and production increased linearly with preceding recruitment.

Numerical Prediction of Siltation Patterns at a Tidal Inlet in Karaikal, India

Tidal inlets are an ecologically sensitive and significant constituent of the coastal environment, where an opening along the shoreline permits the free exchange of fresh and seawater. Predominant longshore currents along the shore result in the formation of sandbars, spits and shoals. Frequent occurrence of such sediment depositions acts as barriers, preventing the ingress of tidal flow. Conventionally training walls are constructed at the inlet to prevent sandbar and spit formations. The volume of water exchanged at the inlet mouth and ebb tidal currents primarily govern the inlet dimensions and the rate of littoral transport, respectively. The case study of a trained micro-tidal inlet at Karaikal (10[Formula: see text]52[Formula: see text]N; 79[Formula: see text]E), India is discussed in this paper. A numerical model using the finite volume method is applied to estimate the siltation rate and distribution within the study domain, driven by tide-induced currents and riverine discharge. A revetment structure is proposed to combat siltation within the inlet to facilitate smooth navigation. The study highlights the notable changes in the presence and absence of the proposed revetment.

Spaceborne InSAR mapping of landslides and subsidence in rapidly deglaciating terrain, Glacier Bay National Park and Preserve and vicinity, Alaska and British Columbia

The Glacier Bay area in southeastern Alaska and British Columbia, encompassing Glacier Bay National Park and Preserve, has experienced rapid glacier retreat since the end of the Little Ice Age in the mid-1800s. The impact that rapid deglaciation has had on the slope stability of valley walls and on the sedimentation of fans and deltas adjacent to fjords and inlets is an ongoing research topic. Using 3-year (2018–2020) Sentinel-1 datasets, and an automated time-series persistent scatterer interferometric synthetic aperture radar (PSInSAR) processing method, we detected landslides or delta subsidence at 27 sites within a vast 180 × 180 km remote region encompassing Glacier Bay proper. Most of the sites that we identified had not been previously identified. We categorized the hazard source areas that we identified into three general types:1) slow-moving landslides on steep rocky slopes not near (> 2 km away from) present-day glacier termini (e.g., Tidal Inlet landslide), 2) slow-moving landslides directly adjacent to (< 2 km away from), and associated with glacier thinning and retreat, and 3) subsidence of glacial outwash fan deltas. In categories 1 and 2, we observed 22 landslides moving at velocities ranging from 0.5 to 4 cm/yr. In category 3, we detected five fan deltas subsiding at velocities ranging from 0.5 to 6 cm/yr. Within our measurement error, these velocities were consistent during the monitoring period. Because acceleration was not observed, the issuance of warnings of imminent rapid failure is not warranted, however, continued remote monitoring is warranted. Our interferometric synthetic aperture radar (InSAR) results could be combined with other data sets including field observations, subaerial and submarine landslide inventories, bedrock fabric mapping from newly available light detection and ranging (lidar) data, and geologic maps to produce an inherent susceptibility map for landslides in bedrock and fan deltas. This map could be used to forecast susceptibility for both earthquake and climatically induced landslides.

Natural and nature based features for environmental enhancement and coastal storm risk management: a case study on Marco Island, Florida, United States

Natural and Nature-Based systems provide an opportunity for adaptive response to Coastal Storm Risk Management and Sea Level Rise. The Tigertail Lagoon/Sand Dollar Island Restoration on Marco Island, Florida, presents a case study designed to maintain and enhance an existing coastal barrier system consisting of a 3-km-long sand spit and tidal lagoon ecosystem that is otherwise evolving toward closure. The case study is part of a nature-based adaptive management plan to restore and stabilize the sandspit and tidal lagoon through cyclic use of sediment within the system. This approach seeks to preserve existing protective habitats and landforms that also serve as natural coastal barriers to protect upland development. Design of the restoration plan considers the functions of a wildlife nature preserve and evolution of complex tidal inlet morphologic features bordered by a heavily developed barrier Island. The design aims to restore and enhance a sandspit degraded by a sequence of storms since Major Hurricane Irma impacted Southwest Florida in 2017 and improve the existing deteriorated habitat by enhancing tidal exchange through restoration of the lagoon flow channel. Total wetland area will be increased by relocating the sand spit seaward of its present location to where it was located in approximately 2017. The reconstructed beach berm will provide enhanced resiliency to high frequency weather events. Sediment will be sourced from the existing sand spit and an innovative sand trap that will maintain the lagoon entrance open while providing beneficial re-use for excess sediment that continues to accumulate at the end of the spit. Components of the project were analyzed using existing engineering models and methods such as the Coastal Modeling System (CMS) and XBeach. Enhancing and preserving this barrier island feature and productive ecosystem provides an example of the enhanced coastal resiliency provided by natural and nature-based systems that are adaptable and responsive to sea level rise and ongoing coastal processes.