Coastal Stability Research Articles

Experimental and Numerical Investigation of Solitary Wave Run-up Reduction

Rehman, K.; Park, K.-Y., and Cho, Y.-S., 2018. Experimental and Numerical Investigation of Solitary Wave Run-up Reduction. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1111–1115. Coconut Creek (Florida), ISSN 0749-0208.Rising sea-levels and extreme wave events threaten coastal communities and stability of coastal regions. Accurate prediction of wave over-topping over coastal protection structures is challenging, but vital for effective hazard mitigation. Non-hydrostatic numerical modelling and laboratory experiments are used to assess magnitude of run-up over coastal protection structures under varying relative wave heights and structural features. The primary focus is the investigation of solitary wave impact with breakwaters, the consequent run-up and measures for its reduction. The experiments consisted of generating solitary waves in a 1.1 m high and 32.5 m long flume and observing its run-up for different heights of incident waves. A slope adjuster was used to vary the slope of a plywood plank for reproducing coastal features. Experimental observations were verified by proposing a numerical model based on non-linear shallow water equations (NLSWE) and solution is obtained by Godunov-type finite volume method. The NLSWE provide good approximation of shoaling, wave breaking, and wave reflection which arise due to wave overtopping in the swash and surf zones. The novel feature of the numerical model is the introduction of bed slope discretization technique – applicable on both structure and unstructured meshes- which offers well-balanced solution even for steep slopes encountered in case of breakwaters. Shock-capturing capabilities of Harten, Lax, and van Leer with contact wave restoration (HLLC) solver are utilized for accurate estimation of shocks and bore waves features during flow transitions. The proposed model gives excellentn agreement with experimental observations. The findings will further enhance the understanding of extreme wave propagation events over submerged coastal structures and related mitigation techniques.

Review of Fundamental Properties of Gas Hydrates: Breakout Sessions of the International Workshop on Methane Hydrate Research and Development

The International Workshop on Methane Hydrate (MH) Research and Development (the Fiery Ice Workshop) began in 2001 with the goal of promoting laboratory and field research collaborations and providing a forum to share new knowledge on MH pertaining to coastal stability, climate change, and energy. Ten workshops have been held over the past 15 years in different countries. Each workshop has included presentations on national programs and policy areas, and new research, along with breakout sessions that focused on current key topics. Two or three concurrent breakout sessions were conducted twice during each workshop. In this paper, we review the breakout sessions on hydrate fundamental properties with the goal of identifying the major accomplishments and changes in hydrate science and engineering related to determining fundamental MH properties over the past 15 years.

Extracting the intertidal extent and topography of the Australian coastline from a 28 year time series of Landsat observations

The physical environment of the intertidal zone presents a number of challenges which make traditional surveying methods difficult to implement; whilst the acquisition cost of airborne elevation data can be prohibitive beyond localised applications. Remote sensing data from earth observation satellites has been well established as a method for mapping the extent and elevation profile of the intertidal zone; however the majority of these applications are local in nature, and based on analysis of a limited number of individual image observations.In this paper we outline an automated methodology to model the intertidal extent and topography of the Australian coastline, that leverages a full time series of Landsat observations from 1987 to 2015 managed in the Australian Geoscience Data Cube (AGDC). Our approach reframes the analysis from time of acquisition into the tidal domain through the use of a continental scale tidal model, combined with a median pixel compositing of Normalised Difference Water Index (NDWI) stacks, to robustly estimate the tidal extent and elevation profile across the observed tidal range. We demonstrate the ability of a median-based compositing approach to deal effectively with data quality, modelling outliers and other issues that commonly affect single scene methodologies. Our new framework enables us to produce a continental-scale intertidal model, detailing intertidal zone topography at a 25m spatial scale.We then demonstrate the potential of the modelling framework to derive digital elevation data based on tidal model attribution, validating our models against in-situ GPS observations, before discussing issues that must be addressed to move this capability to a continental scale. The ability of the model to examine coastal stability is introduced, in the context of the conceptual reframing of the data into the tidal domain, with a view to furthering this application in future versions of the model.

Coastal Erosion in Yasawa Islands, Fiji

Coastal erosion may have many different causes. Wherever we came across erosion problems on the Yasawa Islands in Fiji, they had causes other than sea level rise. We present two case studies. At one site, the beach erosion was caused by the construction of a stonewall diverting the currents in a gyre that hit the shore causing local beach erosion. At another site, extensive erosion caused removal and lateral re-deposition of huge quantities of sand. From the Google Earth images we can infer a date between 2005 and 2009 for this change in shore conditions. We suggest that the shallow-water sand was destabilized by the commercial harvesting of thousands of sea cucumbers (Holothuria scabra). These animals, by their sheer numbers and ecological behavior, were exerting a stabilizing influence on the shallow-water sandy deposits off the beach at Yageta Village. In both cases, the erosion was caused by human action. The coasts all along the Yasawa Islands are characterized by coastal stability. The presence of extensive rock-cut platforms and notches, as well as the occurrence of corals grown into “mini-atolls” are indicative of a stable sea level throughout the islands.

Shoreline Changes Dynamics at Bangkalan Regency

Coastal dynamics and stability becomes the distinctive characteristics in northern coastal at Bangkalan. Coastal morphology are dominated by beach sloping, substrate, and hydrooceanographics factors. One of the indicators was suspended sediment fluctuations. This study aims to know the shoreline changes use indicator suspended sediment and image overlay analysis. The research was conducted in April 2015 in the northern and western coastal region of Bangkalan. The main material in this study was suspended sediment samples and the substrates were taken at 28 points, and the image data of Landsat TM 1994 and 2014. Analysis of sediment suspension is using gravimetric method and substrate analysis using ASTM method. Data analyzed at the Laboratory of Marine Science, Trunojoyo University. The result shows in the northern and western coast at Bangkalan regency is dominated by sand and mud as well as a mixture both of them, the coastal waters are dynamic. The distribution of suspended sediment are relatively diverse in all locations with a range of 25-190 mg/L and can be used as an early indication of shoreline changes as a result of erosion and sedimentation. Landsat TM image analysis using 1994-2014 showed almost all areas in the northern and western coastal at Bangkalan regency are both abrasion and sedimentation.

Environmentally- Friendly Proposals for Coastal Stability at Rosetta Promontory, Nile Delta

The Nile Delta Coast is a dynamic system which was in equilibrium or experienced huge amounts of sediment transported with the water discharges from Nile River to the Mediterranean Sea through the Nile branches. A remarkable decrease in the sediment discharges arises with the construction of barrages, low Aswan dam, and Aswan High Dam along the river since the beginning of the 20th century which trapped almost all the flood sediments in its storage basin. Consequently, the Nile Delta coastal zone has suffered from erosion, especially around the three main headlands, Rosetta, El Burullus, and Damietta. Erosion is not the only challenge facing the Delta coast, but also, siltation inside the inlets discharge to the sea. A calibrated depth-averaged model has been used to morphological changes around the nourishment area at Rosetta promontory, and testing the validity of some alternatives proposed to mitigate the outlet problems. Among these alternatives: diversion of side channel from the sea to the Nile River, and finally, the sand motor technique. The aim of this paper is to test different proposed alternatives and analyze it in terms of morph-dynamic processes to reach an applicable solution for the instability of the promontory.

Pleistocene uplift, climate and morphological segmentation of the Northern Chile coasts (24°S–32°S): Insights from cosmogenic 10Be dating of paleoshorelines

We present new cosmogenic (10Be) exposure ages obtained on Pleistocene marine abrasion shore terraces of Northern Chile between 24°S and 32°S in order to evaluate the temporal and spatial variability of uplift rates along the coastal forearc. Both the dispersion of cosmogenic concentrations in samples from the same terrace and data obtained in vertical profiles show that onshore erosion rates, following emergence of paleoshorelines, approached 1m/Myr. Therefore, minimum ages calculated without considering onshore erosion may be largely underestimated for Middle Pleistocene terraces. The elevation of the last interglacial (MIS-5) paleoshoreline is generally between 25 and 45m amsl, suggesting that the entire coast of the study area has been uplifting during the Upper Pleistocene at rates approaching 0.3mm/yr. Available ages for Middle Pleistocene terraces suggest similar uplift rates, except in the Altos de Talinay area where uplift may have been accelerated by the activity of the Puerto Aldea Fault. The maximum elevation of Pleistocene paleoshorelines is generally close to 250m and there is no higher older Neogene marine sediment, which implies that uplift accelerated during the Pleistocene following a period of coastal stability or subsidence. We observe that the coastal morphology largely depends on the latitudinal climatic variability. North of 26.75°S, the coast is characterized by the presence of a high scarp associated with small and poorly preserved paleoshorelines at its foot. The existence of the coastal scarp in the northern part of the study area is permitted by the hyper-arid climate of the Atacama Desert. This particular morphology may explain why paleoshorelines evidencing coastal uplift are poorly preserved between 26.75°S and 24°S despite Upper Pleistocene uplift rates being comparable with those prevailing in the southern part of the study area.

The Sediment Source and Transport Trends around the Abandoned Yellow River Delta, China

Sediment source and transport trends are influenced by various hydrodynamic factors, and thus play important roles in sedimentary evolution and coastal stability. To examine sediment transport trends around the abandoned Yellow River delta promontory and its erosion mechanism, we employ empirical orthogonal function (EOF) analysis to study sedimentary characteristics and transport trends of the abandoned Yellow River delta in northern Jiangsu Province, China. The results showed that: (1) the main sediment source in the abandoned Yellow River delta is the submarine coastal slope and both sides of the abandoned Yellow River Delta; (2) the main hydrodynamics controlling sediment transport is the current that runs along the shore, coupled with waves, especially southward currents; (3) the sediment of the study area was redistributed under hydrodynamics; coarse sediments were eroded and broadly transported to the south. Therefore, it is concluded that the sediment sources and transport have important influence on coastal evolution: the sediment source area shows mass loss of deposits and erosion; deposits in the submarine coastal slope provide the source and were continuously eroded to provide materials to other places as a sediment source.

Estimation of Coastal Stability Due to Coastal Structures

The coastal structures are unavoidable for various industrial operations. These are changing hydrodynamics of the marine and its adjacent areas; and are directly influencing environmental conditions of the marine environment. The sedimentation on shorelines is strongly under influence of the new structures. The methodology, which is introduced in the paper, is a comparative study of situation of sediments before and after constructing the coastal installations. It is a guiding tool for planners to find the influences of the new structures in the marine area.

Coastal impact ranking of small islands for conservation, restoration and tourism development: A case study of The Bahamas

An 11-year project to characterize, then assess, the health of coastal environments of The Bahamas ranked a total of 238 sites on ten different islands. Satellite images and aerial photography were used to characterize coastal types (e.g. substrate, geomorphology and wave energy to describe beaches, mangroves, or rocky shores), and then field assessments ranked four types of anthropogenic impacts that influence ecosystem function and coastal system services. The ranking of coastal health was based on physical alterations, destructive use of the coastal zone, coastal development and occurrence of Invasive Alien Species (IAS). The characterization and assessment methods were developed to serve as a rapid survey of coastal stability, biological diversity and quality of wildlife habitats. A system of coastal ranking is presented using numerical scores for four impact criteria along with terrestrial plant surveys to examine the intactness of the coastal environment. Some locations (Exuma and Great Guana Cay) were repeatedly monitored over time. Scores ranged from “0” for no human impacts or invasive coastal plants to “20” for highly altered with dredging, coastal development and loss of native vegetation. The mean impact rank for all sites across all islands was 5.7 ± 4.3, which indicates “Medium” ranks for at least two of the four human impact criteria. Only one uninhabited island (Cay Sal) had all coastal impacts scores of “None”. Over 77% of all the sites surveyed had abundant occurrences of Invasive Alien Species (IAS) coastal plants. The Australian Pine (Casuarina equisetifolia) was the more pervasive and the most wide-spread IAS in the coastal environment, and its abundance increased in all sites that were re-surveyed over time. Degradation of coastal function can signal greater risks to coastal property, flooding events or loss of wildlife populations. The coastal impact ranking protocol presented here helps identify target areas for conservation as well as identify areas with the greatest feasibility for coastal restoration.

ANALISIS PERUBAHAN LUAS MANGROVE BERDASARKAN CITRA SATELIT IKONOS TAHUN 2004 DAN 2010 DI KECAMATAN MLONGGO, TAHUNAN DAN KEDUNG KABUPATEN JEPARA JAWA TENGAH

Mangrove as one of coastal ecosystem has plenty of role on coastal stability, but the current condition even though of mangroves ecosystem is Java, including Jepara destructed by many reasons mostly human activities such as. Conversion of mangrove forests to ponds, settlements and illegal logging. Rehabilitation was conducted in some places. therefore, there is a need of review the changes. The purpose of this study to determine the mangrove area changes based on IKONOS satellite imagery of 2004 and 2010 in the District Mlonggo, Tahunan and Kedung, Jepara. Descriptive method is used to describe the state of research areas by comparing the field data and interpretation process. Satellite images have been digitized in overlay to know the changes at mangrove area. Ground check was conducted the field using the quadratic sampling plots of 10m x 10m to for tree, 5m x 5m for sapling and 1m x 1m for seedling. The results were increate that the between period of 2004 to 2010. However, the mangrove area increased 5,959 ha and reduced 5,294 ha and so there was in general 0.665 ha increased. The total area at mangrove in 2004 38,098 ha and in 2010 was variously 37,444. There were at least 20 species in the research area and Rhizophora sp was the most dominant species.

A predictive outlook of coastal erosion on a log-spiral bay (trinidad) by wave and sediment transport modelling

ABSTRACT Ganesh, R. and Gopaul, N., 2013. A Predictive Outlook of Coastal Erosion on a Log-Spiral Bay (Trinidad) by Wave and Sediment Transport Modelling Coastal erosion is increasingly becoming a significant concern (economic and recreational) on considerable stretches of Trinidad's coastlines. Modelling investigations were undertaken into the impacts of time varying wave climates on coastal stability issues on Guayaguayare Bay, SE Trinidad. Erosion is currently occurring at an approximate rate of 0.6m per year (8-yr average). By utilising a wave dataset of approximately 5 years collected at both offshore and nearshore locations, a good appreciation into incoming wave energy was gained. Wave transformation modelling was carried out using DHI's MIKE21 SW. Increases in wave energy were found to be directly influenced by the North Atlantic winter storm period. Therefore, some variance in erosion rates, at different times of the year exists. Sediment transport across the bay was investigated using MIKE21 ST ...

Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana

Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies. It also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget. The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work was hindered by insufficient direct measured data. However, the problem was overcome by the application of a regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from gauged rivers with similar characteristics. The regression approach was effective because a regional coherence in behaviour was determined between those rivers, where direct measured data were available. The results of the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons. These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam on the Volta River, has reduced the total fluvial sediment input to the coast from about 71 × 10 6 m 3/a before 1964 (pre-Akosombo dam) to about 7 × 10 6 m 3/a at present (post-Akosombo dam). This sharp reduction threatened the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast. There is the need, therefore, to ensure that catchment management plans and coastal management plans are integrated or interconnected.

In Memoriam: Nicholas C. Kraus

Dr. Nicholas C. Kraus was a Senior Scientist at the Army Engineer Research and Development Center (ERDC) of the Corps of Engineers in Vicksburg, Mississippi. He passed away on February 3, 2011. His research interests included nearshore and coastal inlet processes, including hydrodynamics, sediment transport, morphology change, and inlet stability. He performed research on the interactions of beaches and coastal structures and beach nourishment. Nick developed groundbreaking mathematical models of shoreline change, beach-profile change, coastal inlet morphology, barrier island breaching, and channel infilling. He also performed extensive research relating to navigation channel maintenance and dredged material movement. Nick received a Bachelor’s degree in physics from the State University of New York at Stony Brook in 1967. He did theoretical low-temperature physics research at the University of Minnesota and was awarded a Ph.D. in physics in 1972. His Ph.D. dissertation was on “The Beliaev-Zelivinsky Boson and Particle-Vibration Coupling Approximations Applied to the Exactly Soluble Pairing Plus Monopole Models.” Nick was a “renaissance man”with many interests. After receiving his Ph.D. and spending a year as a postdoc at the University of Minnesota, he left science to pursue martial arts studies in Japan, an avocation that he would have his whole life. After studying martial arts for four years in Japan, his life took a turn toward coastal science and engineering. Through an unusual circumstance, he was introduced to the coastal engineering pioneer, Professor Kiyoshi Horikawa of the University of Tokyo. Professor Horikawa took Nick under his wing, and from 1975 to 1984, Nick worked as a senior engineer at the multiorganizational research consortium, the Nearshore Environment Research Center (NERC) in Japan. At NERC, Nick’s training in coastal science and engineering was hands-on. He learned mainly by reading and field work, which included deploying instruments in the surf zone because he was an exceptional swimmer. Nick began work as a Senior Scientist at the Coastal Engineering Research Center (CERC) of what is now ERDC from 1984 until 1993. During this time at CERC, Nick developed the GENESIS-shoreline-change, SBEACH-beach-response-to-storms, NMLONG-longshore-current, and DYNLET-tidal-dynamics mathematical models that are used throughout the world. He also performed extensive research on measurement of sediment transport in both the surf zone and offshore locations in major experiments such as Duck 85 and SandyDuck. In 1991, he led the multiinstitutional SUPERTANK laboratory experiment on cross-shore sediment transport. The findings from the SUPERTANK experiments contributed to the development of numerical models of cross-shore transport processes and storm-induced beach changes. From 1993 until 1996, he was Director, Conrad Blucher Institute for Surveying and Science, Texas AM Coastal Dynamics 94, 05, 09; and Coastal Sediments 03. He was co-chair of the Organizing Committee of the 25th International Conference on Coastal Engineering and Coastal Sediments 07 of the American Society of Civil Engineers. He was serving as a board member for Coastal Sediments 11. He served from 1988 to 2003 as editor of Shore and Beach, the journal of the American Shore and Beach Preservation Association. He had been an associate editor for the Journal of Coastal Research since 1987. Nick received much recognition for his contributions to coastal science and engineering. He received the Florida Shore and Beach Preservation Association Distinguished Service Award in 1993; an Honorary Doctorate Degree from the University of Lund, Sweden in 2001; the Morrough P. O’Brien Award from the American Shore and Beach Preservation Association in 2004; and several awards from the ERDC. He was honored at Coastal Sediments 07 for his vision that led to development of the first prototype acoustic Doppler velocimeter. He was a member of the American Shore and Beach Preservation Association, the American Society of Civil Engineers, and the Western Dredging Association. Nick Kraus standing on beach west of Shinnecock, NY, 2000

Short-Term Beach and Shoreface Evolution on a Cuspate Foreland Observed with Airborne Topographic and Bathymetric LIDAR

Abstract This paper examines the short-term evolution of a cuspate foreland with diminished sediment supply in the western Gulf of St. Lawrence. Topographic light detection and ranging and airborne light detection and ranging bathymetry are used to provide an overall analysis of the foreland system at Paspebiac, Quebec, including high-resolution digital morphology of combined subaerial and subaqueous components, between 2003 and 2006. Results indicate large differences in coastal stability around the foreland. The western barrier exhibits a stable shoreline (net change = +0.3 m·y−1), a moderate beach slope (0.12–0.18), and no subtidal bar system. The morphodynamic response in this sector is influenced by jetties and alongshore variability and is related to beach planform readjustments to varying wave conditions. The eastern barrier has higher wave exposure, high erosion rates (<6.7 m·y−1), wave washover, and an intermediate barred-beach profile, with higher beach slopes (β = 0.16–0.24). The alongshore...

Variation of genetic and behavioural traits in the sandhopper Talitrus saltator (Crustacea Amphipoda) along a dynamic sand beach

In an attempt to unravel the possible relationships among coastal stability, genetic variability and orientation behaviour in the sandhopper Talitrus saltator, we have screened four subpopulations of this species. Sandhoppers along 3 km of a dynamic sand beach were studied for orientation performance (i.e. adherence to the seaward theoretical escape direction (TED)) and sequence variation for a fragment of the mitochondrial (mt) gene encoding for the cytochrome oxidase subunit I (COI). The sampling sites differed in the stability of the shoreline (from severely eroded to accreting). Analysis of molecular variance (AMOVA) revealed significant subdivisions among the four locations. The subpopulation sampled at the most eroded point showed no haplotype diversity and had the highest scatter in orientation. Genetic diversity increased with decreasing erosion. Orientation performances were best where the beach is in dynamic equilibrium, and were progressively more scattered at the accreting points. Multiple linear regression analyses demonstrated that the variables and factors that affected orientation significantly were daytime, global solar radiation, sex of individuals and haplotype diversity. Environmental factors are likely to influence sandhopper behaviour on a short and medium time scale (i.e. from single individual life span to a few generations). The data also suggest that temporal stability of the shoreline has a positive effect on the genetic variability of the resident sandhopper populations.

Seismic studies of frozen ground in Arctic areas

Seismiv surveys have been applied to investigate the structure of frozen ground, to identify and contour natural and man-caused unfrozen layers in permafrost (taliks), to constrain the position of the permafrost table in the Arctic inner shelf, and to study the related coastal stability. They are the classic methods common in shallow seismic exploration and new techniques specially designed at the Institute of Earth’s Cryosphere (Tyumen’) for different wave components. The joint use of compressional and shear waves provides a higher-quality interpretation of seismic data in permafrost applications. In the case of a single wave component, shear waves are advantageous over P waves.

Implications of Climate Change for Northern Canada: The Physical Environment

The physical environment of the Canadian North is particularly sensitive to changes in climate because of a large concentration of cryospheric elements including both seasonal and multiyear forms of freshwater and sea ice, permafrost, snow, glaciers, and small ice caps. Because the cryosphere responds directly to changes in air temperature and precipitation, it is a primary indicator of the effects of climate variability and change. This article reviews the major changes that have occurred in the recent historical record of these cryospheric components at high latitudes in Canada. Some changes have been less pronounced in the Canadian North than elsewhere, such as changes in sea-ice coverage, whereas others have been potentially more significant, such as ablation of the extensive alpine and high-Arctic small glaciers and ice caps. Projections of future changes are also reviewed for each cryospheric component. Discussion about two other physical components of the North intrinsically linked to the cryosphere is also included, specifically: i) freshwater discharge to the Arctic Ocean via major river networks that are fed primarily by various forms of snow and ice, and ii) the related rise in sea level, which is strongly influenced by ablation of the cryosphere, and coastal stability, which also depends on the thermal integrity of coastal permafrost.

Quantifying the Evolution of a Beach Protected by Low Crested Structures Using Video Monitoring

Abstract The purpose of this study is to analyse the shoreline response of a beach protected by a system of low crested structures (LCS) and to apply the results to the management of coastal stability problems. This contribution aims to provide heretofore scarce detailed data and observations of the shoreline variability of coasts protected by LCS. These aims are acheived by selecting and monitoring the appropriate Coastal State Indicator (CSI) to describe the state of the beach. The CSI used is the Mean Intertidal Position (MIP), which has been detected by the ARGUS system installed in Lido di Dante, Italy. The error in the shoreline estimation from video was assessed by comparing shorelines detected with global positioning system (GPS) and image analysis over a large number of cases. The horizontal error in the shoreline detection is estimated to be on the order of 0.90 ± 0.74 m, which is acceptable because it is on the same order of magnitude as the swash width. The MIP, which has been monitored over a...

Abundance and orientation responses of the sandhopper Talitrus saltator to beach nourishment and groynes building at San Rossore natural park, Tuscany, Italy

Beach nourishment and groynes building were implemented to counteract erosion in sandy beaches located at San Rossore natural park (Tuscany, Italy), near the mouth of Arno river. From 2000 to 2003, nine groynes were built along 3.6 km of coastline at intervals of ca. 400 m, and two of the eight beach segments were filled with marble gravel. Here, we analysed the effects of these beach changes on the abundance and behaviour of the amphipod Talitrus saltator, using field and laboratory observations. Sampling with pitfall traps in order to use the capture frequency as a proxy of abundance was performed bimonthly from September 2004 to January 2006, and orientation experiments were carried out in autumn (2004 and 2005), and spring and summer 2005. Physical variables (beach width, swash width, beach slope, sand penetrability, mean grain size and salinity) were also recorded. The abundance of T. saltator increased with the distance from the river mouth, towards sites with: negligible amounts of marble locally used for nourishment; higher beach width and salinity; lower slope and penetrability values; medium grain sizes, and during the spring/summer seasons. A Generalized Linear Model with a predictive power of 64.5% considered three main descriptors in the model as significant: distance from the river mouth, sand penetrability and a seasonal factor. Orientation experiments showed a highly variable behaviour among sites, depending on coastal stability: at the site stabilized by the concurrent actions of nourishment and groynes protection measures, sandhoppers were oriented to the shoreline direction by using a sun compass; alternatively, at a site situated only 2 km from the nourished sites, they showed scattered orientation. These between-site differences in orientation, described through Spherically Projected Linear Models, were consistent throughout the study period. Different responses obtained at the individual (orientation) and population (captures) levels stress the need to account for several bioindicators to characterize biotic responses to both natural and anthropogenic changes in sandy beaches.