Shoreline Evolution Research Articles

Traditional vs. Machine-Learning Methods for Forecasting Sandy Shoreline Evolution Using Historic Satellite-Derived Shorelines

Forecasting shoreline evolution for sandy coasts is important for sustainable coastal management, given the present-day increasing anthropogenic pressures and a changing future climate. Here, we evaluate eight different time-series forecasting methods for predicting future shorelines derived from historic satellite-derived shorelines. Analyzing more than 37,000 transects around the globe, we find that traditional forecast methods altogether with some of the evaluated probabilistic Machine Learning (ML) time-series forecast algorithms, outperform Ordinary Least Squares (OLS) predictions for the majority of the sites. When forecasting seven years ahead, we find that these algorithms generate better predictions than OLS for 54% of the transect sites, producing forecasts with, on average, 29% smaller Mean Squared Error (MSE). Importantly, this advantage is shown to exist over all considered forecast horizons, i.e., from 1 up to 11 years. Although the ML algorithms do not produce significantly better predictions than traditional time-series forecast methods, some proved to be significantly more efficient in terms of computation time. We further provide insight in how these ML algorithms can be improved so that they can be expected to outperform not only OLS regression, but also the traditional time-series forecast methods. These forecasting algorithms can be used by coastal engineers, managers, and scientists to generate future shoreline prediction at a global level and derive conclusions thereof.

Study of shoreline evolution under the influence of jetty construction: A case study of Karangsong Beach, Indramayu, Indonesia

Karangsong Beach, Indramayu located on the north coast of Java Island of Indonesia has been an important traditional small downstream river port for the fishermen who live in the Indramayu District area. This traditional port has been rehabilitated by construction of jetty in the period 2005 to 2007. The jetty construction affected coastal process, which was previously dominated by erosion turned into dominated by accretion. This study examines the process of shoreline evolution by calculating the sediment transport rate and analyzing the shoreline changes. The analysis began by extracting shoreline data from Google Earth images to provide a historical database of shoreline. The coastal process was then simulated using the coastline model Uniform Beach Sediment Transport Coastline (UNIBEST-CL) with waves and the longshore component of tidal currents as input and also calibrated using the shoreline database. The calibrated model was employed to simulate the annual conditions over a nine-year period, 2008-2017. The results show the sediment transport rate is dominated by the southeast direction. There is a significant difference in coastal processes between northern and southern regions, which is due to the presence of jetty. In the northern region, the sediment transport rate was blocked by the jetty so that this region is accreted. In the southern region, the supply of sediment from the north replaced by sediment supply from the river causes accretion yet smaller than the northern region.

Artificial Nourishments Effects on Longshore Sediments Transport

Serious erosion problems related to significant negative sediments budgets in the coastal systems are referred worldwide. Artificial nourishments are a coastal erosion mitigation strategy that allow for a decrease in those negative budgets by adding sediment to the coastal system. Thus, it is essential to understand and adequately model the shoreline response after a nourishment operation, in order to support the definition of the best intervention scenarios. The main goal of this work was to study the artificial nourishment effects on the longshore sediment transport and consequently on the morphological evolution at the intervention site and nearby areas, in a time horizon of 5 years. The longshore transport of the nourished sediments was evaluated, aiming to contribute to the evaluation of the sediment’s permanence at the deposition site and the frequency required for new nourishments. The shoreline evolution numerical long-term configuration (LTC) model was applied in order to evaluate the spatial and temporal distribution of the nourished sediments along the coast, considering different types of beaches and incident wave climates. The adopted approach is generic and supported by simple numerical models, which can be useful for preliminary site-specific evaluations. The results show that the nourishment impact is mainly observed nearby the intervention site. It is highlighted that higher longshore sediment transport rates are associated with more energetic wave climates, but not necessarily with incident waves more oblique to the shoreline.

On a new statistical wave generator based on atmospheric circulation patterns and its applications to coastal shoreline evolution

Stochastic models have a long history in the simulation of synthetic data sequences for application to risk assessment e.g. in stochastic hydrology. Their use in coastal engineering has recently grown. In this study we illustrate some typical coastal vulnerability applications of a recently developed stochastic wave climate model that has links to synoptic scale atmospheric circulation patterns (CPs). Wave data are explicitly used to delineate the links to CPs. This modelling approach allows for simulating long continuous time series of waves that are linked to their associated CPs. The time series can be used for various types of coastal vulnerability assessments as a new management tool. The east coast of South Africa is used as a case study. The results demonstrate the robustness of the modelling technique and the potential applications in coastal vulnerability assessments. The link to CPs facilitates the application of these methods to the assessment of future climate changes on coastal vulnerability.

Development of a Multi-Dimensional Coastal Vulnerability Index: Assessing vulnerability to inundation scenarios in the Italian coast

Understanding how natural and human-induced drivers will contribute to rising vulnerability and risks in coastal areas requires a broader use of future projections capturing the spatio-temporal dynamics which drive changes in the different vulnerability dimensions, including the socio-demographic and economic spheres.To go beyond the traditional approaches for coastal vulnerability appraisal, a Multi-dimensional Coastal Vulnerability Index (MDim-CVI) - integrating a composite set of physical, environmental and socio-economic indicators - is proposed to rank Italian coastal provinces according to their relative vulnerability to extreme sea level scenarios, in 2050. Specifically, information on hazard-prone areas, potentially inundated by sea level rise and extreme water levels (under the RCP8.5 climate scenario) is combined with indicators of geomorphic vulnerability (e.g. elevation, distance from coastline, shoreline evolution trend) exposure, and adaptive capacity (e.g. sensible segments of the population, GDP, land use patterns). The methodology is applied to a reference timeframe, representing current climate and land use condition, and a future scenario for the year 2050, integrating both climate projections and data simulating potential evolution of the environmental and socio-economic systems.Results show that most vulnerable provinces are located in the North Adriatic, the Gargano area and other Southern parts of Italy, mostly due to the very high vulnerability scores reported by climate-related indicators (e.g. extreme sea level). The number of vulnerable provinces as well as the magnitude of vulnerability is expected to increase in the future due to the worsening of climate, environmental, and socio-economic conditions (e.g. land use variations and increase of the elderly population). These outcomes can timely inform integrated coastal zone management and support climate adaptation planning.

Observations on decadal sandbar behaviour along a large‐scale curved shoreline

AbstractNearshore sandbars are characteristic features of sandy surf zones and have been observed with a variety of geometries in cross‐shore (e.g. location) and longshore direction (e.g. planform). Although the behaviour of sandbars has been studied extensively on spatial scales up to kilometres and timescales up to years, it remains challenging to observe and explain their behaviour on larger spatial and temporal scales, especially in locations where coastline curvature can be prominent. In this paper, we study a data set with 38 years of coastal profiles, collected with alongshore intervals of 50 m, along the 34 km‐long curved sandy shoreline of Sylt island, Germany. Sylt's shoreline has an orientation difference of ~20° between the northern and southern half of the island. We found that the decadal coastal profiles on the southern half show features of a low‐tide terrace and a sandbar located further from the shoreline (~441 m). On the nothern half, the sandbar was located closer to the shoreline (~267 m) and was less pronounced, while the profiles show transverse bar and rip features. The alongshore planform also differed systematically and significantly along the two island sides. The sandbar on the southern island half, with alongshore periodicity on a larger length scale (~2240 m), was coupled out‐of‐phase to the shoreline, while no phase coupling was observed for the sandbar with periodicity on a shorter length scale (~670 m) on the northern half. We related the observed geometric differences of the sandbars to the difference in the local wave climate along Sylt, imposed by the shoreline shape. Our observations imply that small alongshore variations in wave climate, due to the increasing shoreline curvature on larger spatial scales, can lead to significant alongshore differences in the decadal evolution of coastal profiles, sandbars and shorelines. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

A Multiscale Approach to Shoreline Prediction

AbstractShorelines respond to a number of “drivers” operating on a variety of time‐scales. For some time‐scales (e.g., seasonal), the driver‐shoreline relationship is often evident; however, at longer time‐scales (e.g., multiannual), the shoreline changes may be superimposed on changes at shorter time‐scales and thus are difficult to identify. Here, we predict shoreline evolution from storm events to decadal time‐scales, using a novel approach based on the Complete Ensemble Empirical Mode Decomposition. This approach identifies and links the primary time‐scales in the model drivers (large‐scale sea level pressure [SLP] and/or waves) with the same time‐scales in the shoreline position. The multiscale approach reproduced shoreline changes at two beaches more skillfully than a common shoreline model when SLP and wave information were used in combination. In addition, the analysis can be applied to climate indices, providing the opportunity to link longer time‐scales with climate patterns (e.g., El Niño Southern Oscillation).

Coronary artery lumen complexity as a new marker for refractory symptoms in patients with vasospastic angina

Refractory angina is an independent predictor of adverse events in patients with vasospastic angina (VSA). The aim of this study was to investigate the relationship between coronary lumen complexity and refractory symptoms in patients with VSA. Seventeen patients with VSA underwent optical coherence tomography. The patients were divided into the refractory VSA group (n = 9) and the stable VSA group (n = 8). A shoreline development index was used to assess the coronary artery lumen complexity. Shear stress was estimated using a computational fluid dynamics model. No difference was observed in the baseline characteristics between the two groups. The refractory VSA group showed the higher shoreline development index (refractory VSA 1.042 [1.017–1.188] vs stable VSA 1.003 [1.006–1.025], p = 0.036), and higher maximum medial thickness (refractory VSA 184 ± 17 μm vs stable VSA 148 ± 31 μm, p = 0.017), and higher maximum shear stress (refractory VSA 14.5 [12.1–18.8] Pa vs stable VSA 5.6 [3.0–10.5] Pa, p = 0.003). The shoreline development index positively correlates with shear stress (R2 = 0.46, P = 0.004). Increased medial thickness of the coronary arteries provokes lumen complexity and high shear stress, which might cause refractory symptoms in patients with VSA. The shoreline index could serve as a marker for irritability of the medial layer of coronary arteries and symptoms.

Empirical shoreline evolution modeling for Nha Trang beach

Empirical data-driven models are increasingly being used to simulate shoreline evolution over time scales ranging from days to decades. For the empirical shoreline evolution modeling, the combined longshore and cross-shore modeling demonstrate the ability to improve the prediction skills for shoreline changes. This study focuses on the feasibility of the combined model with a case study of the embayed beach shoreline of Nha Trang, Vietnam. Nha Trang’s climate is dominated by the tropical monsoon climate, so the beach changes here are strongly affected by this typical climate. The combined model applied in this study is a coupling of the cross-shore model and a longshore model. The combined model can provide the seasonal shoreline position fluctuations induced by the longshore contribution. Besides, it is realized that the very mild waves in summer induce strong accretion which the model cannot simulate. Therefore, a small modification of the equilibrium Dean number (Ω0) in the ShoreFor cross-shore model is suggested to improve the accretion simulation.

A DSAS-based study of central shoreline change in Jiangsu over 45 years

A large-scale sand ridge group is distributed in the central Jiangsu coastal area, and a deposition muddy sea bank was developed in the nearshore area. Quantitative monitoring of coastline changes is of great significance for tidal beach development and protection. The shorelines of the central coast of Jiangsu within six periods (1973–2018) were extracted in this study, and their length changes over the years were analyzed. The Digital Shoreline Analysis System (DSAS) was employed to generate a cross section perpendicular to the baseline and calculate the linear regression rate (LRR) of the shoreline, changes in end point rate (EPR), and net shoreline movement (NSM), based on which the shoreline change features were analyzed. The DSAS results indicated that the shorelines in the study area maintained fluctuating growth and presented a continuous advancing trend towards the sea. From the changes in shoreline evolution distance during 1973–2018, the advancing shorelines in the study area accounted for over 50% of the total shorelines and presented first rising and then declining trends with the period of 2003–2013 taken as the time boundary. The average shoreline change rate was 207 m/year, and the periods with the highest change degrees were 1983–1993 and 1993–2013. The shoreline change tended to be stable during 2013–2018, and only a few estuaries and ports underwent obvious erosion and sedimentation.

Using quantitative dynamic adaptive policy pathways to manage climate change-induced coastal erosion

Adaptation requires planning strategies that consider the combined effect of climatic and non-climatic drivers, which are deeply uncertain. This uncertainty arises from many sources, cascades and accumulates in risk estimates. A prominent trend to incorporate this uncertainty in adaptation planning is through adaptive approaches such as the dynamic adaptive policy pathways (DAPP). We present a quantitative DAPP application for coastal erosion management to increase its utilisation in this field. We adopt an approach in which adaptation objectives and actions have continuous quantitative metrics that evolve over time as conditions change. The approach hinges on an adaptation information system that comprises hazard and impact modelling and systematic monitoring to assess changing risks and adaptation signals in the light of adaptation pathway choices. Using an elaborated case study, we force a shoreline evolution model with waves and storm surges generated by means of stochastic modelling from 2010 to 2100, considering uncertainty in extreme weather events, climate variability and mean sea-level rise. We produce a new type of adaptation pathways map showing a set of 90-year probabilistic trajectories that link changing objectives (e.g., no adaptation, limit risk increase, avoid risk increase) and nourishment placement over time. This DAPP approach could be applied to other domains of climate change adaptation bringing a new perspective in adaptive planning under deep uncertainty.

ОСНОВНІ СТАДІЇ ТА ЗАКОНОМІРНОСТІ ФОРМУВАННЯ БЕРЕГІВ ВЕЛИКИХ РІВНИННИХ ВОДОСХОВИЩ

The main stages of the reservoir coast formation and their typological characteristics are considered on the base of the analysis of long-term monitoring studies of the Dnieper reservoirs coast dynamics, as well as generalization of published materials on other large plain reservoirs. It is shown that the common scheme of periodization of the shoreline development manifested itself only in the two stages: abrasion and abrasion-accumulative leveling, and therefore it is premature to claim the general stabilization of the coast formation process. The conventionality of the dynamic equilibrium stage for the coast of reservoirs and the growing role of coastal currents and associated sediment flows and dynamic coast systems are noted. The current state of the coasts of large plain reservoirs is estimated as the beginning of the stabilization phase on the coasts with sufficient sand materials. On the coasts composed of loess, clay or loams the processes of intensive transformation are continued. The analysis of the direction of development of the coastal zone showed three stages of change of shore profile and plan: intensive formation, stabilization and the final stage of attenuation according to the leading factors. Active accumulation means the transition to the stage of abrasion-accumulative leveling, and the emergence of dynamic coast systems and activation of coastal sediment flows means the transition to the dismemberment of the shoreline by accumulative forms. The main regularities of development of coast formation processes – heredity, direction, inertia and variability are analyzed. The heredity means that the geographical and geological conditions which developed before the filling of the reservoir are played the leading role in these processes. The direction of development is associated with an increase of the erosion base and its consequence – the leveling of the coastal zone relief. The orientation of the general process of coast formation to achieve a state of dynamic equilibrium includes stages of inertia and variability. Inertial states are the certain periods when a certain set of factors and conditions and corresponding to them type of coast prevails. Variability is a change in factors and conditions, as a result of which new types of shores or fluctuations in the characteristics of the coastal zone (movement of shoals and dynamic coastal systems, seasonal changes in shore profiles) are formed.

Water surface monitoring and water quality parameters inversion of Lijiang River based on multi-temporal active and passive remote sensing, 2016-2020

以漓江流域为研究区域，以2016—2020年Landsat 8 OLI、GF-1、Sentinel-2A及Sentinel-1A逐月影像为数据源，选用归一化水指数（NDWI）、改进型归一化水指数（MNDWI）、增强型水体指数（EWI）、归一化差值池指数（NDPI）、后向散射系数（S）与主被动遥感加权指数（JQ）提取漓江水体信息，采用二类水体区域性近岸海域水色算法（C2RCC）、最大叶绿素指数（MCI）、双波段比值法（Double R）及叶绿素反射峰强度（ρ_chl）4种方式，反演漓江水体叶绿素a（Chl.a）与总悬浮物质（TSM）浓度.将漓江划分为278个基本评价单元，利用水面变化区域差异值（WDr）、河岸线发育系数（SDI）与水体信息变化动态度（K）等指标定量分析漓江上、中、下游枯水期和汛期的水文和水质信息的年内时空动态变化，得出以下结论：（1）主被动遥感加权指数JQ与NDPI指数的提取效果优于NDWI、MNDWI、EWI指数与后向散射系数，但与JQ指数相比，NDPI指数提取精度更高、可信度更强.（2）基于C2RCC算法反演的Chl.a浓度的均方根误差（RMSE）处于0.18~7.88 mg/m³之间，TSM浓度的RMSE为0.17~12.55 g/m³，可较好地反映漓江水质参数变化情况.（3）基本评价单元的划分可清楚地分析出上、中、下游地区水域水面宽度、水域面积、Chl.a与TSM浓度的连续变化情况，实测数据则依靠站点监测，所得结果较分散，无法进行连续性分析.（4）漓江5—10月降水较多、水体流动性强，大部分地区平均水面宽度在100~250 m范围内，水体富营养化程度低，水质较好，但2月水质最差，水体富营养化程度较高地区主要集中于上、中游的兴安县、灵川县等城镇居民区以及下游旅游开发区较多的兴坪镇.;Lijiang River Basin is used as the research area, and Landsat 8 OLI, GF-1, Sentinel-2A, and Sentinel-1A monthly images of 2016-2020 are used as data sources. The normalized water index (NDWI), modified normalized water index (MNDWI), enhanced water index (EWI), normalized difference pond index (NDPI), backscatter coefficient (S) and weighted index of active and passive remote sensing (JQ) are used to extract the water information of the Lijiang River. The case 2 regional coast color (C2RCC), maximum chlorophyll index (MCI), two band ratio method (Double R) and chlorophyll reflection peak intensity (ρ_chl) are used to retrieve the concentration of chlorophyll-a (Chl.a) and total suspended matter (TSM) concentrations in Lijiang River. The Lijiang River is divided into 278 basic evaluation units, and the spatial-temporal dynamic changes of hydrological and water quality information in the upper, middle, and lower reaches in dry and flood seasons of Lijiang River are quantitatively analyzed by difference value of water surface variation (WDr), shoreline development index (SDI) and dynamic degree of water information change (K). The following conclusions are drawn: (1) Compared with NDWI, MNDWI, EWI, and backscatter coefficient, the extraction effect of JQ and NDPI are better. Compared with JQ, NDPI has higher precision and credibility. (2) RMSE of Chl.a based on the inversion of C2RCC algorithm is 0.18-7.88 mg/m³, RMSE of TSM is 0.17-12.55 g/m³, and it can better reflect the changing trend of Chl.a. (3) The division of the basic evaluation unit can clearly analyze the continuous changes of the width, area, Chl.a and TSM of the upstream, middle and downstream areas. The measured data rely on the monitoring of the stations, and the results are scattered and can't be used for continuity analysis. (4) The Lijiang River has more precipitation and strong water mobility from May to October. The average water surface width of most areas is within 100-250 m. However, the water nutrient is low and the water quality is good. The water quality is the worst in February. The areas with high eutrophication are mainly concentrated in Xing'an County, Lingchuan County and other urban residential areas in the upper and middle reaches, and Xingping town with more tourism development zones downstream.

A One-Dimensional Mathematical Model of Long-Term Shoreline Evolution with Groin System Using an Unconditionally Stable Explicit Finite Difference Method

A One-Dimensional Mathematical Model of Long-Term Shoreline Evolution with Groin System Using an Unconditionally Stable Explicit Finite Difference Method

SIMULATION OF LONG-TERM SHORELINE CHANGE DRIVEN BY LONGSHORE AND CROSS-SHORE SEDIMENT TRANSPORT

Driven by wave and current, sediment transport alongshore and cross-shore induces shoreline changes in coasts. Estimated by breaking wave energy flux, longshore sediment transport in littoral zone has been studied for decades. Cross-shore sediment transport can be significant in a gentle-slope beach and a barred coast due to bar migration. Short-term beach profile evolution (typically for a few days or weeks) has been successfully simulated by reconstructing nonlinear wave shape in nearshore zone (e.g. Hsu et al 2006, Fernandez-Mora et al. 2015). However, it is still lack of knowledge on the relationship between cross-shore sediment transport and long-term shoreline evolution. Based on the methodology of beach profile evolution modeling, a semi-empirical closure model is developed for estimating phase-average net cross-shore sediment transport rate induced by waves, currents, and gravity. This model has been implemented into GenCade, the USACE shoreline evolution model.

EQUILIBRIUM MODELING OF CURRENT AND FUTURE BEACH EVOLUTION: VOUGOT BEACH, FRANCE

The impacts of climate change, including sea level and wave climate changes, may increase future erosion risks. Thus, it is important to improve knowledge of the dominant physical processes controlling medium- to long-term shoreline evolution, as well as the performance of beach evolution models reproducing past observations and predicting future changes. Empirical equilibrium beach change models may be an optimal choice at these spatial and temporal scales. Here, morphological changes at Vougot Beach (Brittany, France) are analyzed by evaluating the cross-shore evolution of contour elevations (-1 to 6m) along six intertidal beach profiles using observations and an equilibrium beach change model, and then three methods for estimating the impacts of climate change are applied and compared.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/p70KuzjR1kU

IMPACT OF UNCERTAINTIES IN MODEL FREE PARAMETERS AND SEA LEVEL RISE ON SHORELINE CHANGES: A 20-YEAR HINDCAST AT TRUC VERT BEACH, SW FRANCE

Chronic erosion of sandy coasts is a continuous potential threat for the growing coastal communities worldwide. The prediction of shoreline evolution is therefore key issue for robust decision making worldwide, especially in the context of climate change. Shorelines respond to various complex processes interacting at several temporal and spatial scales, making shoreline reconstructions and predictions challenging and uncertain, especially on long time scales (e.g. decades or century). Despite the increasing progresses in addressing uncertainties related to the physics of Sea Level Rise, very little effort is made towards understanding and reducing the uncertainties related to wave driven coastal response. To fill this gap, we analyse the uncertainties associated with long-term (2 decades) modelling of the cross-shore transport dominated high-energy sandy coast around Truc Vert beach, SW France, which has been surveyed semi-monthly over the last 12 years.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/_NBJ2v-koMs

CROSS-SHORE SEDIMENT TRANSPORT IN THE SWASH ZONE: LARGE-SCALE LABORATORY EXPERIMENTS

The swash zone is a highly dynamic boundary between the beach and the surf zone. Swash processes determine whether sediment is either stored on the upper beach or is transported offshore, and thus strongly affect shoreline evolution. The present research focuses on the hydrodynamics, sand transport processes and net sediment transport in the swash zone through a series of large-scale wave flume experiments. This research aims to improve the understanding of swash zone sand transport processes, in particular the role of cross-shore sand advection and wave-swash interactions, and bring new detailed insights into the relation between intra-swash processes and net sand transport rates.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/tYvJ0pML-kU

ASSESSMENT OF COASTAL VULNERABILITY BASED ON THE USE OF INTEGRATED LOW-COST MONITORING APPROACH AND BEACH MODELLING: TWO ITALIAN STUDY

The use of video-monitoring techniques is significantly increased due to the diffusion of high-resolution cameras at relatively low-costs and they are largely used to estimate the shoreline evolution and wave run-up, as important coastal state indicators to be monitored and predicted for the assessment of flooding and erosion risks. In this work, we present an integrated approach based on the results from the low-cost video monitoring systems and the numerical modeling chain by means of SWAN and XBeach to accurately simulate and predict the swash zone processes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/nLGNneJzmIU

A SHORELINE EVOLUTION MODEL BASED ON EQUILIBRIUM FORMULATIONS

Traditionally, the shoreline hindcast under the influence of changing marine conditions has been considered by means of existing robust shoreline evolution models, such as one-line, multi-line, combined or 3D models. All of them require long data series, many calibration parameters and are computationally intensive. This study presents a new shoreline evolution model considering the integration of cross-shore, planform and rotation equilibrium-based models, applicable over time-scales spanning days, months or several years. The new model successfully reaches the general erosion-accretion trend at a qualitative and quantitative level. As the main conclusion, this is a simple equilibrium-based shoreline evolution model that requires few calibration parameters and is computationally efficient and versatile.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/zkQ7AoAWmEE