Sand Nourishment Research Articles

Numerical evaluation of the impact of sandbars on cross-shore sediment transport and shoreline evolution

Nearshore nourishments are a common intervention used to mitigate sediment deficits in coastal areas experiencing erosion problems. This coastal intervention involves placing nourished sediments in the submerged zone of the beach profile to form an artificial submerged sandbar which are then distributed by natural forces occurring in the coastal zone. Coastal processes that control the morphological evolution of coastal zones operate on several spatial and temporal scales (seconds to years) and can be divided into cross-shore and longshore components. Usually, the numerical models that simulate the evolution of cross-shore profiles due to sediment transport within the profiles, are related with short to medium-term events (days to months), and shoreline evolution models, that allow for long-term analysis (years to decades), are typically only considering longshore sediment transport. Describing all the processes in a single numerical model is complex and computationally demanding, and therefore, the numerical models are typically focused on specific processes, categorized by their temporal and spatial scales. This article presents a numerical study focused on medium to long-term numerical modelling of coastal zone evolution, examining the combined effects of cross-shore and longshore sediment transport processes of sediment transport. The model incorporates two simplified numerical models: LTC - Long Term Configuration, for shoreline evolution and CS-Model, for cross-shore sediment exchanges. Applied to nine different sandbar scenarios, model results revealed that disturbances in sandbar volume tend to return to equilibrium through cross-shore sediment transport processes. In situations that considered a constant sandbar volume alongshore, the longshore effects are null, because the volume entering in the coastal domain is equal to the volume leaving, and the sediment balance is only dependent of the cross-shore processes. Variable sandbar volume alongshore leads to impacts on shoreline position due to longshore sediment transport gradients generated by the sandbar disturbance. The results demonstrate the potential of the proposed combined model for medium to long-term projections, allowing for the interpretation of how physical aspects of nearshore nourishments evolve. These aspects include sandbar volume, shoreline position, berm width, and shoreline displacements induced by cross-shore and longshore sediment transport processes. These parameters aid in understanding sandbar-beach sediment dynamics, which is valuable for supporting coastal management, particularly in the development and design of shoreface sand nourishments, enabling the optimization of sand resources.

Balancing recreation and flood safety for integrated coastal management: Understanding beach visitors' types of attitude and behaviour in sandy anthropogenic shores

In the Netherlands, with its coastal lowlands, coastal management is performed through sand nourishment and dune utilisation. While policy aims for multifunctionality, coastal management studies predominantly emphasise flood safety, neglecting the recreational function and its interplay with flood safety measures. This study aims to investigate beach visitors' views and behaviour at two reinforced sandy shores in the Netherlands, namely Sand Motor and Hondsbossche Dunes. As the magnitude of the sand-based reinforcements completely changed the original beach landscape, we refer to these as sandy anthropogenic shores (SAS). We conducted surveys to assess SAS visitors' profiles, attitudes (visit motivations, landscape attractiveness), and recreational behaviour (facility preferences, activities, visitation patterns, spatial distribution). We examined differences between SAS and non-SAS beach visitors and compared their perspectives with management expectations. In our analysis, we categorised visitors into three types: local, one-day, and overnight visitors. Our analysis identified three distinct visitor motivation clusters: socialising, relaxation while appreciating beach landscapes, and engaging in sports activities. Natural landscape quality and quietness were the top attractions for SAS visitors. Despite significant human intervention in the design and alteration of the SAS landscape, visitors still appreciate its natural dynamics and beauty. Our analysis indicates that users perceive the SAS as either natural or semi-natural beaches, as intended by their designers and managers. We also developed a conceptual framework of the SAS recreation model based on survey data, forming the foundation for a quantitative model of SAS socio-environmental dynamics in the next phase of our research. Moreover, considering the similarities between SAS and natural shores, we anticipate that our findings will have broad applicability well beyond the specific SAS we have studied.

Impact of a coastal protection measure on sandy-beach meiofauna at Ahrenshoop (Baltic Sea, Germany): results from metabarcoding and morphological approaches are similar

Sand nourishment is a common and often applied coastal protection measure along the beaches of the German Baltic Sea coast. At the tourist beach of Ahrenshoop, large-scale sand nourishments are completed every five years along a 4-km stretch. The nourishment in question was executed between the end of October 2021 and mid-February 2022. Meiofaunal communities at the beach-water interface were monitored at six stations before (September 2021) and for one year after the impact (March and September 2022, March 2023). To assess the effects of sand nourishment on meiofauna communities, two complementary approaches were employed: whole community metabarcoding and morphological determination and counting of the animals. Both methods produced consistent results regarding community response to disturbance and subsequent recovery. During the period from autumn 2021 to spring 2023, drastic changes in the composition of communities were observed. Directly after the impact, the taxa Acari and Annelida nearly disappeared, abundances of Copepoda decreased substantially, and Platyhelminthes increased notably. The fact that the studied beach held a low diversity may have facilitated that metabarcoding and morphological determination followed the same trend. After initial studies comprising both methods, efficient assessments using only metabarcoding may be considered for comparable sites and situations.

Examining hydro-morphological modulations in proximity to a drain's estuarine outlet, case study: Kitchener Drain, Northern Coast of Egypt

In recent years, the Kitchener Drain has been affected by littoral erosion and sedimentation at the estuary where its discharge enters the Mediterranean Sea. Several measures have been taken to mitigate the impact of these problems. From 1993 to 2007, four stages of hard protection work were finished, including the construction of groins and detached breakwaters along the drain's eastern and western shores. Work on these projects began in 1992. At the drain outlet, dredging works are still proceeding. Nevertheless, shoreline instability continues even after these efforts. The Coastal Modelling System (CMS) was used to figure out what effect the ongoing hard work had on the erosion and accretion hot spot near the drain's output. The CMS-flow and CMS-wave steering modules are part of the CMS, a two-dimensional model of hydrodynamic circulation. To begin mitigating this effect, we ran the simulation beginning in 2012 and experimented with different calibration settings. After the calibration phase, the research area was subsequently simulated for five years. This study aims to assess the current state of affairs concerning the stabilization of the outflow sedimentation process and the erosion that is taking place on the eastern and western sides. In addition to that, we offered alternate structural modulation scenarios that incorporate both hard and soft structures. We looked at plenty of different possibilities. The scenario with the 600-meter-long jetty and sand nourishment was the most similar to the original coastal characteristics. Regarding a sediment reduction to ‐5706.99 m3 from ‐15321.70 m3 (at benchmark) computed at the outlet zone, this scenario was the most similar to the shoreline's initial appearance. Reducing sediment from ‐133433 m3 (at benchmark) to ‐114512 m3 was also achieved on the western side. Despite this, it was determined that the stability of the coastline would be influenced subtly by this circumstance.

Ecological Impacts of Coastal Protection on the Vegetation of Sandy Coasts at the German Baltic Sea Coast

Sand nourishments and groynes as coastal protection measures (CPM) address similar challenges on sandy coasts but take different approaches: while groynes are intended to reduce alongshore sediment transport and erosion, nourishments add new sediment to the system to compensate for erosion. The aim of this study is to compare the ecological effects of such measures on the vegetation. To this end, nutrient analysis and botanical mappings were carried out on a site with installed groynes, a site where sand nourishments are regularly carried out, and a control site without any CPM. In addition to an increase in nutrient availability after the sand nourishment, significant changes in plant species diversity and composition were also measured. The number of higher plants, mosses, and lichen species was lower at the nourishment site. The opposite impacts were observed at the groyne site: an increase in sediment cover by higher plants and mosses and a distinct increase in lichen species. The results suggest that groynes lead to a stabilization of the coastal system and enable dense vegetation growth. In contrast, sand nourishments lead to nutrient input and unstable habitat conditions, attracting certain plant communities but preventing the establishment of ground-covering vegetation.

Future sediment transport to the Dutch Wadden Sea under severe sea level rise and tidal range change

Future sediment transport from the North Sea coasts to the Dutch Wadden Sea for various future sea level scenarios has been studied because it influences the future sand nourishment demand for the maintenance of the coastline and because it determines bio-geomorphological development of the Wadden Sea. The present study focuses on two questions which have not yet been considered in the previous modelling studies using ASMITA: How will the transport develop around drowning of the intertidal flats in the Wadden Sea? How will tidal range change influence the future sediment exchange? By using SLR scenarios with faster acceleration and running the simulations for longer periods of time some inlets exhibited drowning, i.e., where the tidal flat volume vanishes. When drowning occurs, the sediment import rate approaches a maximum or a minimum, depending on the initial morphological state of the tidal inlet system. This maximum or minimum rate for a certain tidal inlet system depends on the SLR scenario. Theoretical analysis as well as modelling results show that tidal range change will influence the sediment import to the Wadden Sea. A tidal range increase will cause a decrease of the sediment demand in the Wadden Sea resulting into less sediment import to the Wadden Sea. It is thus important to study the tidal range development in the Wadden Sea by considering the interaction between SLR, tidal range change and morphological development in the system. It is further concluded that the empirical relation used in the previous studies is not representative of conditions in a tidal basin with fixed basin area, even though this relation has been derived from field observations in many tidal inlet systems worldwide. The equilibrium channel volume should be proportional to the tidal prism instead of to its 1.5th power.

Shoreline retreat and beach nourishment are projected to increase in Southern California

Sandy beaches in Southern California are experiencing rising coastal erosion due to changes in precipitation patterns and urban growth. As a result, beach nourishment is necessary for mitigation. In our study, we forecast the rates of shoreline retreat and the required volumes of sand nourishment to mitigate it for the coming decades. We employ photogrammetric multi-decadal shoreline positioning and Digital Shoreline Analysis System methods to measure and predict the coastal evolution of the Gulf of Santa Catalina in Southern California. This region is hypothesized to be globally representative of other semi-arid sandy coasts facing similar hydroclimatic and anthropogenic challenges. Our findings indicate that Southern California’s shoreline retreat rates for sandy beaches will increase from the present average value of ~−1.45 to −2.12 meters per year in 2050 and to −3.18 meters per year in 2100. Consequently, the annual volume of sand required for beach nourishment could triple by 2050, increasing from the present-day amount of ~1223 to ~3669 cubic meters per year per kilometer. However, the associated cost for this nourishment will grow five times, exacerbating several coastal communities’ economic and logistical pressures. Similar trends are emerging globally, with semi-arid developing nations already grappling with coastal hazards and may struggle to manage the escalating costs of curbing beach nourishment.

Exploring The Influence Of Artificial Root Systems Modeled After Marram Grass (Ammophila Arenaria) On Dune Erosion

Vegetated dune systems represent a remarkable landform along numerous coastal areas worldwide. They provide a valuable contribution to local ecosystems and coastal protection. The influence of vegetation on the stability of soils potentially counteracts erosion and, on sandy coasts under suitable conditions, leads to the accumulation of sediments driven by aeolian transport, resulting in dune formation (Feagin et al. 2015). The assessment of the coastal protection potential of dunes is far from being a streamlined, mature procedure, and it will demand more parameters than merely the dunes’ height, dimensions or volume, but tentatively also their vegetation coverage. Artificial dunes or dunes regenerated through sand nourishment often lack additional substrate stabilization since no vegetation bound root systems are present (Nordstrom and Jackson 2022). The role of stabilizing root components in the overall dune body matrix is currently not well understood, in particular, when highly dynamic processes such as wave attack is involved. The hypothesis of this novel work hence is that root systems of dune grass (i.e., A. arenaria) can be quantified for the modelling in experimental campaigns and for more reliable erosion results. To investigate this hypothesis novel physical experiments are currently conducted in the wave flume at the Leichtweiß-Institute for Hydraulic Engineering and Water Resources in Braunschweig (Germany), testing different root surrogate materials and quantities for the first time.

Low-Crested Structures In Front Of Rubble Mound Breakwaters

Climate adaptation of coastal structures has become more important due to climate change, resulting in sea level rise and increased wave loading for coastal structures with depth-limited wave conditions. If sea level rise causes wave loading that becomes too severe, one of the options is to reduce the wave loading before the waves reach the existing coastal structure (see for instance Van Gent, 2019, and Van Gent and Teng, 2023). This can be achieved by increasing the foreshore (e.g. sand nourishment) or by constructing a low-crested structure in front of the coastal structure. In this study the climate adaptation measure to add a submerged low-crested structure in front of an existing (emerged) coastal structure has been studied. Between the two structures, structure-induced wave set-up occurs. This structure-induced wave set-up has been studied based on wave flume tests. The effects of structure-induced wave set-up on wave transmission at the low-crested structures and the effects on wave overtopping at the emerged coastal structure were also measured and analyzed. To evaluate the performance of submerged low-crested structures Van Gent et al (2023) performed wave flume tests to examine wave transmission at various types of submerged low-crested structures, without an emerged structure behind the low-crested structures. For a submerged low-crested structure in front of an emerged coastal structure, the transmitted waves can be used as incident waves for estimates of wave overtopping at a rubble mound breakwater, using wave overtopping expressions described in Van Gent et al (2022). However, to verify whether the expressions for wave transmission and wave overtopping can be applied for submerged low-crested structures in front of rubble mound breakwaters, new physical model tests have been performed at Deltares. The new wave flume tests were performed with impermeable and permeable low-crested structures in front of impermeable and permeable emerged structures (see Figure 1 for permeable structure).

Tracking fluorescent tracer to monitor grain size-selective dispersion in subtidal zone: Patos Beach case study (NW Iberian Peninsula)

Sediment tracer studies have become an increasingly used and improved technique. This approach allows to evaluate the sediment dispersion and track their pathways in a real marine environment. This type of study is essential to improve current coastal morphodynamic models since questions such as 'Where does the sand nourishment go?' are complex to answer, but essential for improving coastal management. The goal of this work is to analyze the behavior of fluorescent sediment tracers with heterometric grain size distributions in Patos Beach (Ria de Vigo, NW Spain). A field experiment was performed between 24th of September and 22nd of October 2018 with the injection of 200 kg of fluorescent tracer of native sediment in the subtidal zone. Oceanographic and topobathymetric data were acquired, and daily bed sediment samples were taken in order to observe tracer advection and dispersion. The results obtained on this beach allowed the establishment of selective sediment transport at two spatial scales: tracer transport towards the beach and tracer organization around bedforms. This research contributes to improve the current knowledge of sediment transport in a natural environment and its relationship with wave nonlinearities.

Effectiveness of Dune Reconstruction and Beach Nourishment to Mitigate Coastal Erosion of the Ebro Delta (Spain)

Coastal areas facing increasing erosion are resorting to sand displacement strategies to mitigate the erosive impact, which is exacerbated by climate change. In the face of climate change, coastal managers are more frequently resorting to sand displacement strategies to recover eroding coastlines. These vulnerable coastal zones require innovative approaches to minimize the need for frequent sand replenishment, extend their effectiveness and lower their maintenance expenses. This study undertakes a comparison of four primary nourishment strategies—a conventional uniform nourishment technique and the placement of a single sand dune evaluated at three different positions—in contrast to a scenario where no intervention is carried out. The investigation employs the XBeach numerical model to assess the outcomes of these diverse strategies under both low- and high-energetic storm conditions. The case study is a degraded coastal beach in the Ebro Delta (Spain). The results reveal a significant decrease in erosion when the dune is positioned closest to the shoreline. However, this erosion mitigation effect diminishes as the dune is situated further inland. Conversely, the sand nourishment measure exhibits minimal fluctuations in the volume of eroded sand when compared to the scenario with no intervention.

Changed sediment composition prevents recovery of macrobenthic community four years after a shoreface nourishment at the Holland coast

Sand nourishment is a widespread management strategy to protect sandy coasts against erosion. Nourishments can impact the benthic fauna directly by burial and indirectly by changing environmental conditions such as bottom shear stress and/or sediment composition (grain size distribution). The macrobenthic community in soft-bottom environments is often strongly correlated with sediment composition, however, because of the strong correlation with other environmental conditions, it is difficult to determine the direct effects of sediment composition on the macrobenthic community from field observations. Nourishments can temporarily break this correlation allowing to study the relation between sediment composition and macrobenthic community more or less independent from other environmental factors. In 2017, a shoreface nourishment was constructed at the Holland coast near Callantsoog at a water depth of about 10 m. Because the influence of waves is limited at this depth, the nourishment is not very mobile. Sediment composition and macrobenthos was monitored at the nourished site and two reference locations before (2015 and 2016), and in 2021, four years after nourishment. In 2021, the sediment composition at the nourished site was much coarser (median grain size 330 ± 59 μm) than in the years before nourishment (195 ± 34 μm), while the sediment composition at the reference locations remained comparable over the years. The average number of taxa per sample at the nourishment decreased from 14.1 before nourishment to 3.0 taxa in 2021. Also the average total density at the nourishment location decreased from 12731 ind.m−2 before nourishment to 320 ind.m−2 in 2021. While before nourishment, the composition of the macrobenthic community at the nourished site was comparable to the southern reference location, in 2021 the macrobenthic community was more comparable to the community at the coarser sediments of the northern reference. Clearly, four years after the nourishment, the macrobenthic community has not recovered due to the presence of coarser sediments at the nourished site. Logistic regressions show that most of the dominant species have a negative correlation with median grain size, but some species are more sensitive to changes in sediment composition than others. The sensitivity of the macrobenthos to sediment composition illustrates the importance of using sediments of similar grain size as in the placement area, especially for nourishments in the deeper parts of the shoreface.

CONSTRUCTED OYSTER REEFS AS SEDIMENT STABILISERS AND ECOLOGICAL ENGINEERS: A DUTCH CASE STUDY

Global degradation and the collapse of valuable coastal ecosystems has resulted in major efforts to reestablish ecosystem engineering species that provide valuable services like ecosystem-based coastal defense (EBCD). However, conditional outcomes of ecosystem engineering effects make it hard to predict the services provided by such restored systems. In this study we focused on reefs constructed with Crassostrea gigas shells on a sand nourishment at the Oesterdam, in the Oosterschelde tidal bay in the Netherlands. We investigated how the environmental setting, waves and currents, influence sediment stabilisation, as well as oyster spat recruitment and the development of associated biodiversity.

FUNWAVE MODELLING OF BEACH INUNDATION IN RESPONSE TO MASS SAND NOURISHMENT: A STUDY USING SOME PROFILES FROM STOCKTON BEACH NSW

Mass sand nourishment is recognized as a means of restoring beach amenity and one that possibly offers long-term protection from further shoreline loss and inundation of adjacent urban areas. While large scale beach nourishment has been used elsewhere, examples in NSW are extremely limited. Model inundation results, based on an actual beach profile, suggest that nourishment alone provides little reduction to inundation rates and therefore inundation risks.

STRENGTHENING COASTAL DEFENCE WITH ARTIFICIAL DUNES

The Belgian coast is primarily sandy and is locally subject to erosion (Deronde, 2004). Traditionally, erosion was counteracted using hard engineering structures like groynes, seawalls and sea dikes. Nowadays, the Belgian government uses a different strategy by adopting a more soft and dynamic approach where possible. Many ‘soft’ managing activities at the Belgian coast are carried out in the form of regular and routine sand nourishments to cope for future flooding risks and coastal erosion (Houthuys, 2012). This method gives room to a new approach for coastal management where the natural elements and processes facilitate the development of new engineered dune areas at locations where traditional dike structures currently protect the hinterland. In the context of climate change and strict requirements for water safety, these hard to adapt engineering structures will not resist future flood events and more innovative solutions like dune in front of a dike principles to deal with rising sea level are receiving considerable attention. As a result, concepts are worked out in which traditional sea dikes are reinforced with newly created dune systems, offering a high level of protection of coastal infrastructure and at the same time offering a more natural appearance and higher ecological and socio economical values. In the framework of the SARCC project, one pilot site is realized in Raversijde. Besides the coastal defense function of the artificial dune, a second benefit is achieved: mitigating the nuisance, created by aeolian sand transport and preventing roads and tram tracks at the dike crest to be buried in sand.

SATELLITE-DERIVED SHORELINE DYNAMICS AT THE GERMAN BALTIC SEA

Dunes play a central role in the coastal protection strategy of the German part of the Baltic Sea coastline in the state of Mecklenburg Western Pomerania (MWP). Considering the sea level rise and the limited supply of sand a closer inspection of the sand nourishment strategy and its impact on the regional shoreline of MWP is needed. Data availability on the shoreline development is sparse and only recently have the authorities (StALU) in MWP started to increase the temporal and spatial resolution of measurements (StALU 2009). The Google Earth Engine (Gorelick et al. 2017) has facilitated the possibility to investigate shorelines at the planetary scale with freely available satellite images spanning more than 30 years. Luijendijk et al. (2018) and Bishop-Taylor et al. (2021) have demonstrated the need and feasibility of long-term time series that depict the shoreline development over large spatial scales. We present the results from the remote sensing of the shoreline development at the German Baltic Sea utilizing three decades of satellite images.

Comparison of high turbidity events: Sand nourishments and storm events on sandy beaches at the Baltic Sea, Germany

Coastal zones are permanently under stress by storms, cliff breaks, waves and currents. These events can cause the retreat of the coastline and are currently compensated by beach nourishments. The commonality of these sediment eroding and accumulating processes are turbidity plumes created in coastal waters, increasing the resuspension of particles and possibly nutrient concentrations. To compare sand nourishments and storm events, total suspended solids (TSS) and nutrient measurements were performed during winter season at the German Baltic Sea Coast. A pre-experiment showed that the TSS was homogenous through the water column. There were significant differences between both events, with sand nourishments exceeding the TSS of storms with the factor two. Due to the nourishment mechanism, the relative organic content was lower than during storm events. The nutrient uptake was unsteady. Therefore, sand nourishment can be considered to have more influence on the ecology of sand shores than storm events.

A Study on the Characteristics of Beach Profile Evolution According to the Particle Size Variation of Beach Nourishment

This study investigated the beach nourishment effect and topographical changes when using nourishment sand with relatively large particle diameters to perform beach nourishment on a beach subject to erosion. A physical model test was conducted in a 2D wave flume with an installed wind tunnel. The experiment examined the sediment transport mechanism under conditions with wind and waves. Although applying nourishment sand with large particle diameters attenuated sediment transport, the increase in particle diameter was not always proportional to the reduction in topographical changes. Increasing the particle diameter of the nourishment sand increased the friction force between particles, resulting in large-scale erosion and accretion around the coastline, and this trend increased with winds. Also, with wind, the wave run-up height increased, the undertow became stronger, and large-scale scouring occurred at the boundary between the nourishment sand and the existing beach. Increasing the particle diameter of the nourishment sand played a role in reducing the run-up phenomenon (d50: 1.0 mm with 24–50%, d50: 5.0 mm with 59–83%), and the range of particles moved by winds also decreased (d50: 1.0 mm with 10–38%, d50: 5.0 mm with 5–37%).

Long-term shoreline changes at large spatial scales at the Baltic Sea: remote-sensing based assessment and potential drivers

In this study, we demonstrate how freely available satellite images can be used to understand large-scale coastline developments along the coast of Mecklenburg-Western Pomerania (MWP). By validating the resulting dataset with an independent Light Detection and Ranging (LIDAR) dataset, we achieved a high level of accuracy for the calculation of rates of change (ROC) with a root mean square error (RMSE) of up to 0.91 m, highlighting the reliability of Earth observation data for this purpose. The study assessed the coastal system’s natural evolution from 1984 to 1990, prior to significant human interventions, and examined the period from 1996 to 2022, which was characterized by regular sand nourishments amounting to approximately 16 million m³. The results reveal notable changes in the study area, with a significant decline in erosive trends and an increase in the number of stable and accreting transects. However, it is important to note that the regular sand nourishments may be masking the true ROC along the coastline. Furthermore, the future supply of sand raises concerns about the sustainability of coastal developments, particularly in the context of future sea level rise (SLR). The study provides valuable insights for coastal authorities and policymakers, informing decisions on sand resource allocation and highlighting the need for appropriate adaptation strategies to address future SLR and ensure long-term coastal resilience.

Influence of living shoreline elements on wave run up elevations

Nature-based coastal protection, also known as engineering with nature or living shorelines, is becoming increasingly popular due to its dual benefits of reducing coastal flooding and providing ecological and recreational opportunities. In many coastal areas experiencing chronic erosion, changes in sediment supply, composition, and grain size are significant contributing factors to shoreline recession. One living shoreline strategy to consider includes the application of cobbles over more traditional sand nourishments. On sandy beaches that experience high-energy wave conditions, the introduction (or reintroduction) of cobbles can mitigate backshore erosion. Cobble-backed beaches have been found to mitigate the effect of coastal erosion and flooding in laboratory settings and field observations, and they have recently been piloted in locations such as Cape Lookout State Park in Tillamook County, Oregon, and Surfers Point in the City of Ventura, California. However, there are no formal engineering guidelines stipulating the calculation of wave run-up on cobble-backed beaches. This study applies three different wave run-up equations on a living shoreline design (i.e. mixed sand and cobble berm-backed beach) in Malibu, California, and compares the predicted run-up levels with existing condition flood levels for typical and eroded conditions. The different wave run-up equations were designed for cobbles only, revetments, and composite beaches, respectively, where the composite beach equation was most applicable to project design. For typical beach conditions (higher levels of sediment accretion resulting in shallower beach face and berm slopes), all three equations showed a reduction in wave run-up values. When applied to worst-case conditions (i.e. scoured by a creek channel and steeper fronting beach slopes), the equation most applicable to the design showed the highest reduction of total water levels. A sensitivity analysis found that the cobble-backed beach equation predicted the most consistent values of run-up (run-up values changed the least), even when input parameters (slope and water depth) changed. This study shows that cobblebacked beaches hold promise to mitigate coastal flooding in appropriate areas, in addition to being a natural solution for areas experiencing erosion. This study also points to the need for more studies and field observations to validate the run-up levels determined here.