Coastal Morphology Research Articles

Carbonate sediment dynamics in the Abu Dhabi lagoon - implications for low-angle inner-to-middle ramp models

Carbonate ramps are prominent features of continental margins and intrashelf basins throughout much of Earth's history. Among the limited number of recent analogues of ancient carbonate ramps, the Persian/Arabian Gulf stands out due to its morphologically complex array of open coastal to sabkha environments. This study presents detailed field and laboratory data on spatial facies variability linked to different hydrodynamic regimes spanning from open coastal to inner lagoon settings in Abu Dhabi. Sediment transport and deposition are determined by waves and tidal currents, with spatially and temporally complex variations in the hydrodynamic regime, resulting in a complex facies mosaic. The open coastal domain is subject to persistent north-westerly trade (Shamal) winds and episodic winter storms, generating waves that affect the deposition of ooids, peloids, lithic clasts and bioclasts. In the outer lagoon, these waves interact with tidal currents and thus become less dominant towards the middle lagoon. Tidal currents are more important in the restricted inner lagoon. The outer lagoonal sediments primarily consist of ooids, bioclasts and lithic clasts and are peloid- and micrite-lean. Bimodal tidal currents, locally with velocities of two or more metres per second, are present in the relatively open regime of the middle lagoon and accumulate bar complexes dominated by skeletal carbonates. Seagrass and biofilms locally stabilise muddy carbonates and limit sediment entrainment even where significant tidal currents exist. In a landward direction, and with decreasing hydrodynamic levels, carbonate mud (micrite) is increasingly abundant, reflecting the lower hydrodynamic conditions in the restricted regime of the mid-and inner lagoon. Data shown here provide a facies distribution model in the shallow coastal portions of what might be one of the few modern analogues of a ‘marginal epeiric’ sea, shedding light on the complex interplay between coastal morphology, wave and tide energy and biological processes. This study discusses how hydrodynamics and seafloor bio-stabilisation influence the spatial carbonate facies of this highly dynamic ramp system by comparing data shown here with data from the Kuwait and Doha coasts, which have different orientations to the prevailing winds. The quantitative and refined composite inner ramp model shown here has wider significance for coastal dynamics and carbonate stratigraphy.

SCShores: a comprehensive shoreline dataset of Spanish sandy beaches from a citizen-science monitoring programme

Abstract. Sandy beaches are ever-changing environments, as they experience constant reshaping due to the external forces of tides, waves, and winds. The shoreline position, which marks the boundary between water and sand, holds great significance in the fields of coastal geomorphology, coastal engineering, and coastal management. It is crucial to understand how beaches evolve over time, but high-resolution shoreline datasets are scarce, and establishing monitoring systems can be costly. To address this, we present a new dataset of the shorelines of five Spanish sandy beaches located in contrasting environments that is derived from the CoastSnap citizen-science shoreline monitoring programme. The use of citizen science within environmental projects is increasing, as it allows both community awareness and the collection of large amounts of data that are otherwise difficult to obtain. This dataset includes a total of 1721 individual shorelines composed of 3 m spaced points alongshore, accompanied by additional attributes, such as elevation value and acquisition date, allowing for easy comparisons. Our dataset offers a unique perspective on how citizen science can provide reliable datasets that are useful for management and geomorphological studies. The shoreline dataset, along with relevant metadata, is available at https://doi.org/10.5281/zenodo.8056415 (González-Villanueva et al., 2023b).

Relative Sea-Level Rise Projections and Flooding Scenarios for 2150 CE for the Island of Ustica (Southern Tyrrhenian Sea, Italy)

The island of Ustica (Italy) is constantly exposed to the effects of sea-level rise, which is threatening its coastal zone. With the aim of assessing the sea levels that are anticipated by 2150 CE under the climatic projections shown in the AR6 report from the IPCC, a detailed evaluation of potential coastal flooding under different climatic scenarios and the ongoing land subsidence has been carried out for three coastal zones. Scenarios are based on the determination of the current coastline position, a high-resolution digital terrain and marine model, and the SSP1-2.6, SSP3-7.0, and SSP5-8.5 climatic projections. Relative sea-level rise projections allowed the mapping of the potential inundated surfaces for 2030, 2050, 2100, and 2150. The results show rising sea levels for 2150, ranging from a minimum of 66 ± 40 cm (IPCC AR6 SSP2.6 scenario) to a maximum of 128 ± 52 cm (IPCC AR6 SSP8.5 scenario). In such conditions, considering the SSP8.5 scenario during storm surges with return times (RTs) of 1 and 100 years, the expected maximum wave run-up along the island may vary from 3 m (RT = 1) to 14 m (RT = 100), according to the coastal morphology. Our results show that adaptation and mitigation actions are required to protect the touristic and harbor installations of the island.

Impact Costs Due to Climate Change along the Coasts of Catalonia

Climate change is an increasingly critical issue impacting coasts and coast structures, leading to erosion, flooding, sea level rise, etc. These significantly impact not only the environment and society, but also the regional infrastructure and economy. This study focused on assessing the costs associated with climate change along the coast of Catalonia. An innovative tool in Python called GCIFS (Georeferenced Impact Forecast System) was developed for the assessment, which is based on LiDAR measurements, cartography, and online databases to predict future coastlines and economic impacts. The proposed methodology considered unique beach-specific scenarios, and multiple direction and altitude vectors to identify difficult-to-erode areas and existing protections were generated. Seven approaches based on forecasted sea-level rise with and without coastal geomorphology were applied to 262 beaches. Local impact factors and potential protection, using detailed data on infrastructure and building typology, were included in the cost evaluation, resulting in estimated costs by the year 2100 of EUR 8846.00 million for the worst-case scenario, EUR 3587.36 million for a conservative prediction including geomorphology, and EUR 822.67 million for a prediction based on local erosion and geomorphology. It was concluded that 170,676 m of protection structures is required. The selected approach, technologies, and detailed information are critical for an adequate assessment.

Efficient representation of transient tidal overheight in a coastal groundwater flow model using a phase-averaged tidal boundary condition

Ocean tides cause water table overheight near the seaward boundary of coastal aquifers which can have a large impact on groundwater flows and saltwater intrusion. Despite this, regional-scale coastal groundwater flow models often neglect the effects of ocean tides or alternatively assume that the influences of ocean tides and sea level are constant over time. These simplifications are often required because simulation of the phase-resolved tidal signal at a coastal boundary is computationally demanding. Our objective was to derive a phase-averaged tidal boundary condition for application along gently sloping coastlines that enables simulation of real, complex tidal signals combined with sea-level changes due to meteorological effects. The boundary condition extends an existing analytical solution of tidal overheight by including an empirical correction function for conditions where the assumptions of the existing solution are violated. The correction function was developed by conducting a parametric study on an idealized two-dimensional cross-sectional coastal aquifer model and considering the effects of parameters including horizontal hydraulic conductivity, vertical anisotropy, specific yield, aquifer thickness, and beach slope. The performance of the new phase-averaged tidal boundary condition was assessed using a three-dimensional groundwater flow model of the island of Spiekeroog, Northwest Germany, which comprises complex coastal morphology with non-planar beach slopes. Simulations applying the new boundary condition were compared to simulations that adopted a phase-resolved tidal boundary condition and to observed groundwater levels. Accounting for time-varying changes in the tidal signal and sea level was found to be critical to simulate observed data and to adequately reproduce the transient tidal overheight simulated by the phase-resolved model. The performance of the new phase-averaged boundary condition in the regional-scale model varied depending on how the coastal morphology was represented in the boundary condition with local morphological features increasingly important for lower intertidal vertical infiltration capacity (low isotropic hydraulic conductivity or high vertical anisotropy) or specific yield. In conclusion, the new boundary condition presented overcomes current limitations in simulating transient tidal overheight in regional-scale groundwater models.

Nearshore ice complex breakup is controlled by a balance between thermal and mechanical processes

AbstractShore ice is an important facet of cold‐climate coastal geomorphology yet is generally understudied in comparison to other aspects such as nearshore hydrodynamics. Climate change is resulting in more dynamic shore ice regimes (i.e., shortened ice season and multiple freeze–thaw cycles); thus, a clear understanding of the role of shore ice in coastal geomorphic evolution is needed. The presence of shore ice is generally thought to provide the coast a protective buffer from storm waves though some studies have indicated enhanced nearshore erosion and sediment transport associated with ice development. This is particularly apparent during the breakup phase of shore ice as sediment can be scoured from the bed, deposited in place, or transported offshore. Given this, understanding the mechanics of shore ice breakup is critical. This study documents the first combined field and laboratory evaluation of the physical conditions leading to shore ice breakup, detailing the complex interplay between thermal and mechanical processes in ice deterioration. Through a wave tank experiment as well as field observations, wave impacts alone are shown to be unlikely to cause breakup of shore ice and thermal weakening is required. This has important implications both for predicting when ice will break up as well as for identifying potential nearshore sediment transport pathways. If ice breaks up entirely from thermal degradation, then sediment is likely to be deposited in place, whereas if ice breaks up from a combination of thermal degradation and wave impact, then sediment can be redistributed across the shoreface. Monitoring of meteorological conditions during ice breakup can likely be used as a first‐order predictor of geomorphic changes resulting from shore ice deterioration.

Optimizing the spatial distribution of Southeast Asia mangrove restoration based on zonation, species and carbon projection schemes

Mangroves contain large amounts of carbon that can reduce the effects of global climate change, which is termed as blue carbon and noted as an important ecosystem service. However, mangrove ecosystems have experienced a huge decline due to human activities and any rehabilitation and restoration efforts should be undertaken with careful planning to optimise their ecosystem service provision and to improve the success of these programs. The main objective of this study was to model a scenario specific to Southeast Asian mangrove distribution based on zonation, species, and coastal morphology, as well as the estimation of future aboveground biomass carbon content resulting from multiple scenarios of successful mangrove growth. This study provides the first assessment of the differences in the distribution of carbon content in a range of native mangrove species, as well as the relationship between the number of propagules, carbon content, mangrove species, and the percentage of living mangroves. The potential location for mangrove planting was dominated by zone 4 inundated by spring high tides, with a suitable area of 4,081,325 ha the next largest area was zone 2, inundated by medium high tides, with a potential area of 2,080,475 ha, followed by zone 3, inundated by normal high tides, with an area of 1,685,800 ha. This study is expected to serve as a reference for mangrove ecosystem conservation and optimisation of carbon storage, especially in Southeast Asia.

Water Masses of the Mediterranean Sea and Black Sea: An Overview

This overview presents the different water masses present in the various primary and secondary marine regions of the Mediterranean Sea and Black Sea, providing information on their main physical characteristics (i.e., temperature, salinity, density), the water depths at which they have been observed and the processes involved in their formation. There is a characteristic difference in the overall hydrology of the Mediterranean Sea compared to the Black Sea, in terms of the number and characteristics of water masses and their formation processes, although they form a single (integrated) marine system. This difference is explained by the limited communication between the two seas through the Sea of Marmara and its straits (the Dardanelles and Bosporus) and by the fact that the Mediterranean Sea is a condensation basin while the Black Sea is a dilution basin; therefore, the deficit of water in the former is compensated by the inflow of Atlantic waters, while the surplus in the latter outflows to the Aegean Sea. In total, 21 different water masses have been identified in the Mediterranean Sea (excluding the Straits of Gibraltar and the Sea of Marmara) compared to the 5 water masses identified in the Black Sea (excluding the Sea of Azov). This large number of water masses is attributed to coastal morphology (i.e., presence of straits) and submarine relief (i.e., deep basin separated by shallow sills) and different formation processes.

ADVANCES ON THE USE OF SATELLITE DERIVED PRODUCTS TO DETECT COASTAL CHANGES: DEMONSTRATION CASE ON THE COAST OF SPAIN

Regular and efficient monitoring of coastal changes is necessary to inform coastal management decisions. In this regard, recent developments based on Google Earth Engine (Gorelick et al., 2017) enable the automatic detection of coastal changes using satellite data (Turner et al., 2021) However, such tools are usually calibrated with limited information and, consequently, they may lead to significant errors when applied to beaches with different conditions than those considered in the calibration data sets. In this work, we evaluate the capability to monitor changes in coastal morphology at various temporal and spatial scales using satellite-derived data obtained from an automatic processing method that includes site-specific information. These method was developed within the framework of the Coastal Erosion from Space Project (https://coastalerosion.argans.co.uk/) that brought together experts from several countries with different backgrounds, such as Earth Observation, Geology, Engineering and Management, to develop satellite products to monitor coastal change based on end-user requirements.

CLIMATE CHANGE IMPACTS ON REEF TOP ISLANDS

It is generally understood that climate change, particularly sea level rise, is a threat to communities and habitats on low lying tropical islands. However, the full nature of this threat is not well understood. These islands have been created by met-ocean forces on the reef platforms and represents the culmination of a dynamic balance between these forces and the supply of sediment over thousands of years. This paper assesses the impact of climate change on the reef top hydrodynamics and coastal morphology of reef top islands.

Assessing the impact factors and corresponding weights affecting the coastal morphology of Hsinchu Coast, Taiwan

This study investigates the long-term morphological pattern of the Hsinchu coast in northwestern Taiwan using three different methods: long-term isobath and shoreline change analysis, bathymetric volume change analysis, and the empirical orthogonal function (EOF) method. Our objectives include analyzing and understanding the effects of anthropogenic structures, natural processes, and their combined impacts on coastal morphological change. The shoreline analysis and bathymetric volume analysis briefly reveal that the morphological pattern of Hsinchu coast. Then, EOF analysis is applied to identify the dominant impact factors affecting the coastal morphology near the harbor, determine the weights of the impact factors, and infer the impact range of anthropogenic structures. Moreover, the EOF analysis is divided into two-time segments—namely, the periods 2005–2010 and 2017–2021—based on different bathymetric surveys and the corresponding values of impact factors. The primary and secondary EOF modes are strongly linked to the “interaction between wave and structure” and “interaction between river discharges and structure”, respectively. The spatial components of the EOF modes demonstrate that the impact range influenced by river discharges was mainly located in the northern part of the harbor, while the minimum impact range of the structures on coastal morphological interaction changes under natural factors was 3.5 km south of Hsinchu Fishing Harbor.

Assessing Typhoon Soulik-induced morphodynamics over the Mokpo coastal region in South Korea based on a geospatial approach

Abstract. The inner shelf and coastal region of the Yellow Sea along the Korean Peninsula are frequently impacted by typhoons. The Mokpo coastal region in South Korea was significantly affected by Typhoon Soulik in 2018, the deadliest typhoon strike to the southwestern coast since Typhoon Maemi in 2003. Typhoon Soulik overran the region, causing extensive damage to the coast, shoreline, vegetation, and coastal geomorphology. Therefore, it is important to investigate its impact on the coastal ecology, landform, erosion/accretion, suspended-sediment concentration (SSC), and associated coastal changes along the Mokpo region. In this study, the net shoreline movement (NSM), normalized difference vegetation index (NDVI), fractional vegetation coverage (FVC), coastal-landform change model, normalized difference suspended-sediment index (NDSSI), and SSC–reflectance relation have been used to analyze the coastal morphodynamics over the typhoon periods. We used pre- and post-typhoon Sentinel-2 MultiSpectral Instrument (MSI) images for mapping and monitoring the typhoon effect and recovery status of the Mokpo coast through short- and medium-term coastal-change analysis. The findings highlighted the significant impacts of typhoons on coastal dynamics, wetland vegetation, and sediment resuspension along the Mokpo coast. It has been observed that typhoon-induced SSC influences shoreline and coastal morphology. The outcome of this research may provide databases to manage coastal environments and a long-term plan to restore valuable coastal habitats. In addition, the findings may be useful for post-typhoon emergency response, coastal planners, and administrators involved in the long-term development of human life.

The Application of CNN-Based Image Segmentation for Tracking Coastal Erosion and Post-Storm Recovery

Coastal erosion due to extreme events can cause significant damage to coastal communities and deplete beaches. Post-storm beach recovery is a crucial natural process that rebuilds coastal morphology and reintroduces eroded sediment to the subaerial beach. However, monitoring the beach recovery, which occurs at various spatiotemporal scales, presents a significant challenge. This is due to, firstly, the complex interplay between factors such as storm-induced erosion, sediment availability, local topography, and wave and wind-driven sand transport; secondly, the complex morphology of coastal areas, where water, sand, debris and vegetation co-exists dynamically; and, finally, the challenging weather conditions affecting the long-term small-scale data acquisition needed to monitor the recovery process. This complexity hinders our understanding and effective management of coastal vulnerability and resilience. In this study, we apply Convolutional Neural Networks (CNN)-based semantic segmentation to high-resolution complex beach imagery. This model efficiently distinguishes between various features indicative of coastal processes, including sand texture, water content, debris, and vegetation with a mean precision of 95.1% and mean Intersection of Union (IOU) of 86.7%. Furthermore, we propose a new method to quantify false positives and negatives that allows a reliable estimation of the model’s uncertainty in the absence of a ground truth to validate the model predictions. This method is particularly effective in scenarios where the boundaries between classes are not clearly defined. We also discuss how to identify blurry beach images in advance of semantic segmentation prediction, as our model is less effective at predicting this type of image. By examining how different beach regions evolve over time through time series analysis, we discovered that rare events of wind-driven (aeolian) sand transport seem to play a crucial role in promoting the vertical growth of beaches and thus driving the beach recovery process.

Influence of the Coriolis Force on Spreading of River Plumes

Wind is the main external force that governs the spreading of river plumes in the sea. Many previous studies demonstrated that the spreading direction of river plumes (especially small plumes) generally coincides with wind direction. At the same time, the majority of river plumes are strongly affected by the Coriolis force, which is also among the baseline knowledge about the plumes. In this study, we focus on the deflection of plumes from wind direction induced by the Coriolis force, which received little attention before. For this purpose, we analyzed an extensive set of Landsat 8 and Sentinel-2 satellite images of multiple small- and medium-sized river plumes at different parts of the World Ocean and synchronous wind reanalysis data. We demonstrated that the deflection angle is stable for individual river plumes for different wind directions, albeit with certain limitations related to wind speed and coastal morphology. Moreover, the deflection angle is similar for river plumes located at similar latitudes and varies from ~0° near the Equator to 15–25° in temperate zones and ~30° in polar zones. Finally, we derived a direct relation between latitude and the deflection angle. The obtained results contribute to our understanding of universal features of river plume dynamics, which is important for monitoring and forecasting of delivery and fate of fluvial water and river-borne matter in different coastal regions of the World Ocean.

Coastal forecast through coupling of Artificial Intelligence and hydro-morphodynamical modelling

ABSTRACT As climate-driven risks for the world’s coastlines increase, understanding and predicting morphological changes as well as developing efficient systems for coastal forecast has become of the foremost importance for adaptation to climate change. Artificial Intelligence is a powerful technology that has been rapidly evolving recently and can offer new means of analysis for the coastal science field. Yet, the potential of these technologies for coastal geomorphology remains relatively unexplored with respect to other scientific fields. This article investigates the use of Artificial Neural Networks and Bayesian Networks in combination with fully coupled hydrodynamics and morphological models (Delft3D) for predicting morphological changes and sediment transport along coastal systems. Two sets of Artificial Intelligence models were tested, one set relying on localized modeling outputs or localized data sources and another set having reduced dependency from modeling outputs and, once trained, solely relying on boundary conditions and coastline geometry. The first set of models provides regression values greater than 0.95 and 0.86 for training and testing, respectively. The second set of reduced dependency models provides regression values greater than 0.84 and 0.76 for training and testing, respectively. Our results highlight the potential of AI and statistical models for coastal applications.

Sedimentary Facies and Morpho-dynamics of Sand Spit and Island Inference as Coastal River Process

Abstract This study aimed to characterize the sedimentary facies and understand the morphodynamics of the study area, and their results were correlated with various analytical methods. Different analyses such as depositional environmental, statistical, shoreline change, and grain size illustrated the temporal and spatial distribution of sediments. It has previously been claimed that current research locations are locii to fluvial landforms and are affected by fluvial processes. However, there are currently no rivers in the study region. This study was done to better understand the presence of fluvial landforms and to evaluate the previous findings. The dynamic behavior of the coast was revealed through shoreline analysis, which was done using satellite images from various years. Oceanographic parameters and longshore sediment transport play a vital role in geomorphological changes in coastal zones. According to the grain size analysis results, mean values showed that the deposits predominantlyare medium grained. The outcome discussed the spatiotemporal variations in geomorphology, sedimentation, and the function of coastal and fluvial processes on the beach of an island and a sand spit. Also highlighted was the role that wave action, fluvial currents, and tidal currents had in the long-term evolution of coastal geomorphological features such as spits, beaches, open coasts, and islands. The standard deviation signifies that the sediments are very well sorted to poorly sorted. Skewness ranges from fine skewed to strongly fine skewed and the kurtosis values show that the sediments are predominately very platykurtic which implies a low-energy environment of deposition. Four sedimentary facies (Facies A, B, C, D) have been found and facies A, B, and C may be wave-influenced deposits, but facies D may be formed by fluvial processes and contain medium to sand-sized particles. The direction of the tip area is also pointing to the south and this result concluded that the tip area is continuously growing. Thus, the results of this study revealed that sediment transport and coastal geomorphology evolution may be governed by two main processes such as the present ocean hydrodynamics and paleo fluvial processes of the study regions.

Unravelling Spatial-temporal Evolution of Shoreline Changes in Pantai Mek Mas – Pantai Cahaya Bulan, Kelantan, Malaysia

Kelantan is a state on Peninsular Malaysia’s East Coast famed for its tropical jungle and seaside areas. Kelantan is a “flood-state” that encounters monsoons and tidal currents. Kelantan was devastated by tsunami-like floods in 2014 where it brought changes on its coastal geomorphology. Using a universal Digital Shoreline Analysis System (DSAS) technique, this study assesses shoreline changes along Kelantan’s coastline between 2013 (before the catastrophic flood) and 2021. A multipronged approach incorporating DSAS via GIS and satellite imagery were used to explore the coastline changes in Kelantan. This study found that Pantai Mek Mas and Pantai Kundur were the most sedimented and the most eroded area were around Pantai Cahaya Bulan, Kota Bharu respectively. The Shoreline Change Envelope (SCE) and Net Shoreline Movement (NSM) analysis concluded that the coastal area has the highest accretion rate of 177.07m/year and the greatest negative distance via NSM of -171.53m/year. The sedimentation along Pantai Mek Mas may happen due to the transportation of sedimentation via river flows from Kelantan River estuary and the degradation of shoreline along Pantai Cahaya Bulan may cause by the concentration of anthropogenic interventions. In conclusion, can be seen that the Kelantan’s coastal area shoreline does progressively proliferate over the past decade and the community vulnerability on the shoreline changes are at risk which comprehensive mitigation is needed to improve its resilience.

Shoreline change dynamics along the Augusta coast, eastern Sicily, South Italy

AbstractThe coastal region of Augusta, eastern Sicily, Italy, is a densely populated zone, where human pressures profoundly shaped the coastal and land dynamics. So far, understanding the interaction between natural and human processes in modelling coastal geomorphology is still quite challenging. However, coastal and environmental monitoring poses the bases for managing coastal areas properly. Therefore, the aim of this research was first to understand the medium‐term shoreline changes along Augusta Bay between 1972 and 2021, and then assess the main local coastal modifications determined by the increasing coastal armouring. To do so, the shorelines dataset was extracted from Landsat and Sentinel‐2 satellite imageries using the NDWI and mNDWI methods and then statistical parameters were computed using Digital Shoreline Analysis System (DSAS). Results show that this coastal fringe experienced significant shoreline recession over the studied time interval. Negative shoreline shifts are higher in correspondence with torrent deltas, as a result of the increasing human and natural forces insisting on the land and coastal environments. Since 1970s, Augusta Bay registered a significant increase in artificial coastal length and a coastal armouring index of Maximal level was reached today.

Modeling and Analysis of Sediment Trapping Efficiency of Large Dams Using Remote Sensing

AbstractQuantifying the role of sediment trapping by dams is important due to its control on fluvial and coastal geomorphology, aquatic ecology, water quality, and human water uses. Sediment trapping behind dams is a major source of bias in large‐scale hydrogeomorphic models, hindering robust analyses of anthropogenic influences on sediment fluxes in freshwater and coastal systems. This study focuses on developing a new reservoir trapping efficiency (Te) parameter to account for the impacts of dams in hydrological models. This goal was achieved by harnessing a novel remote sensing data product which offers high‐resolution and spatially continuous maps of suspended sediment concentration across the Contiguous United States (CONUS). Validation of remote sensing‐derived surface sediment fluxes against USGS depth‐averaged sediment fluxes showed that this remote sensing data set can be used to calculate Te with high accuracy (R2 = 0.98). Te calculated for 222 dams across the CONUS, using incoming and outgoing sediment fluxes from their reservoirs, range from 0.13% to 98.3% with a mean of 45.8%. Contrary to the previous understanding that large reservoirs have larger Te, remote sensing data show that large reservoirs can have a wide range of Te values. A suite of 22 explanatory variables were used to develop an empirical Te model. The strongest model predicts Te using four variables: incoming sediment flux, outgoing water discharge, reservoir length, and reservoir storage. A global model was also developed using explanatory variables obtained from a global dam database.

Vulnerability of sea turtle nesting sites to erosion and inundation: A decision support framework to maximize conservation

AbstractSandy beaches provide essential nesting habitats for sea turtles but are threatened globally by a rapidly changing climate. Identifying which nesting sites are at the greatest risk from erosion and inundation remains an important goal of sea turtle conservation globally. Yet, efforts to identify at‐risk sites have been hindered by the ability to model complex processes and incomplete information on nesting distribution and abundance. To assess the erosion and inundation risk to the reproductive success of a discrete genetic stock of flatback turtles (Natator depressus) across its nesting range in the Pilbara region of Western Australia, we used the Integrated Valuation of Ecosystem Services and Trade‐offs (InVEST) Coastal Vulnerability Model. A relative exposure index was calculated for 402 nesting beaches in terms of six geophysical variables: wind and wave exposure, surge potential, relief, observed sea level rise, and coastal geomorphology, and coupled with published information on the distribution and abundance of turtle tracks in the region. The majority of beaches (74%) had intermediate to high exposure. In particular, 36% of beaches with a high abundance of flatback tracks (the top 25% of the frequency distribution) had a high exposure (the top 25% of the frequency distribution). This suggests that coastal exposure is a key vulnerability to the reproductive success of sea turtles that nest in this region. Promisingly, five beaches with a high abundance of turtle tracks also had a low exposure (bottom 25% of the frequency distribution), and these beaches may be critical for the long‐term resilience of the stock against sea level rise and severe storms. Exposure varied across nesting sites, and the approach presented here allows for a rapid and broadscale assessment of relative erosion and inundation risks at a scale most relevant to management.