Hasil untuk "Harbors and coast protective works. Coastal engineering. Lighthouses"

Masoumeh Lari, Aliakbar Nazari Samani, Aqil Tariq et al.

Owing to the overuse of wild land, the mountainous watersheds in Iran have experienced severe land degradation and consequent downstream flooding. To design effective soil and water conservation strategies, it is crucial to understand how sediment yield and flow fluctuations respond to conservation practices. The purpose of this study was to evaluate the GeoWEPP model for runoff and sediment yield predictions via multiple endemic inputs, namely, climate, soil characteristics, topography, and LULC. Through the calculation of four parameters related to soil properties, namely, the effective hydraulic conductivity (ke), baseline critical shear stress (τc), baseline rill erodibility (kr), and baseline interrill erodibility (ki), the assessment of the initial run illustrates that calibration is inevitable. Given the geographical context and summer snowmelt dynamics, the model was unable to estimate summer runoff accurately. To address this problem, additional modeling for meltwater runoff was incorporated. The NSE and R2 values for discharge are 0.74 and 0.84, respectively, while those for sediment yield are 0.64 and 0.51, respectively. The results indicated that good predictions of runoff and sediment yield were obtained with the calibrated GeoWEPP model at the watershed scale. The key contribution of this research is the assessment of how eight biological conservation scenarios influence watershed behavior. Eight biological conservation scenarios were considered, representing incremental increases in canopy cover in poor, medium, and good pastures, both individually and in combination, as well as an additional scenario including expanded channel cover. The results showed that enhancing canopy cover could lower runoff and sediment yield by up to 44 % and 47 %, respectively, while the channel-cover scenario could lead to increases of up to 54 % and 67 %, respectively. These findings demonstrate the model's effectiveness in accurately replicating the hydrological and erosional responses resulting from soil and water conservation strategies.

Ludmila Kuksina, Pelagiya Belyakova, Valentin Golosov et al.

Flash floods are one of the most dangerous hydrometeorological events in the world. The current study investigates flash floods on the northern Black Sea Coast. The data about stochastic and relatively stable factors of flash flood formation (such as hydrological, meteorological, lithological, geomorphological, and anthropogenic parameters) were collected for 22 events. The main trigger of flash floods is heavy rainfall of high intensity in the region but in some cases flash flood occurrence is connected with combinations of several “non-critical” factors. The small watershed area (≤351 km2) of river basins experiencing flash floods promotes very rapid flow concentration. Analysis of extreme precipitation demonstrates significant increasing trends in river basins on the Crimean Peninsula and decreasing a maximum precipitation amount in 5 days (r5d) and 1 day (r1d) in river basins in the Caucasus Black Sea Coast in the 21st century as determined by processing of Integrated Multi-satellite Retrievals for Global precipitation measurement (IMEGR) satellite data. At the same time land network data indicates increasing r5d at the Anapa and r1d at the Tuapse meteorological stations in 1961–2020. More frequent occurrence of flash floods has been suggested in the area due to statistical analysis of the longest precipitation ranges. The main reason for significant social and economic damage is uncontrolled human activity in flooded areas on the northern Black Sea Coast.

Xinghua He, Zihan Zhao, Yanqin Zhang et al.

The Yangtze River Delta, renowned for its intricate waterway system and fertile soil, is a crucial ecological zone in China. However, anthropogenic activities have led to significant changes in sediment nitrogen (N) forms and associated ecological risks in this region. This study aims to comprehensively investigate the occurrence of various N forms in the sediment of the Yangtze River Delta plain-river network through field sampling and laboratory analysis and to assess their ecological implications. The results revealed that the concentration of total N in river water (TNw) ranged from 1.24 to 5.96 mg/L, decreasing from northwest to southeast. The nitrate in river water (NO3−–Nw) was the major species of TNw, accounting for 67.97% of the total. The average values of TN, total carbon (TC), and total sulfur (TS) in the sediment were 1.97, 18.36, and 1.35 mg/g, respectively. The predominant N fractions in the sediment were residual nitrogen (RN) (72.42%) and hydrolyzable nitrogen (HN) (22.44%). The ammonia in river water (NH4+–Nw) was significantly affected by the sediment N (p < 0.05). Residential density (RD) and industrial density (ID) were significantly positively correlated with the concentration of TNw (p < 0.01), and ID was significantly positively correlated with increased RN (p < 0.05), which suggests that industrial wastewater may be a source of RN. The risk assessment revealed that 36% of the sediment samples were above the moderate TN pollution level. Furthermore, 94% of the sediment was contaminated with organic matter, with 66.7% specifically affected by organic N contamination. High riverine RN and NO3−–Nw contents indicate serious ecological pollution risks in the complex river network area in the Yangtze River Delta. This study provides valuable insight into N cycling and associated ecological risks in the Yangtze River Delta plain-river network, which is crucial for developing effective management strategies to safeguard the ecological health of this vital region.

Cheikh Omar Tidjani Cisse

Today, coastal storms represent one of the most formidable environmental challenges, causing significant impacts on coastal communities. This situation underscores both the importance and urgency of studying storms and their characterization. This study proposes an innovative approach combining Principal Component Analysis (PCA) and machine learning (Classification and Regression Trees, CART) to characterize and distinguish damaging storms from non-damaging ones along the coast of Dakar, Senegal. The analysis revealed that among several hydrometeorological variables studied (wave height, period, direction, runup, wave energy, sea level anomaly, tide, etc.), the variables SLA and tide play a central role in the occurrence of damage, although they are weakly correlated with the others. By cross-analyzing these variables, critical thresholds were established, such as Tide > 0.53 m combined with SLA ≥ 0.061 m, Tide > 0.53 m and ECWL ≥ 1.3 m, as well as Runup ≤ 0.64 m associated with a high wave period (Tp), allowing accurate differentiation of potentially damaging storms. The CART method validated these results and identified three key combinations: (1) Tide–SLA, where no damage is observed if Tide < 0.53 m, and damage occurs beyond this threshold when SLA ≥ 0.061 m; (2) Tide–ECWL, where storms are damaging if Tide > 0.53 m and ECWL ≥ 1.3 m; (3) Runup–Tp, where storms are damaging if Runup ≤ 0.64 m or if Runup > 0.82 m with Tp ≥ 16 s. These results constitute the first application of machine learning for storm classification on the Senegalese coast, providing a novel quantitative foundation for better understanding the hydrodynamic conditions associated with damaging storms. The findings of this study could be valuable for risk management and the development of early warning systems

Houda Lamane, Latifa Mouhir, Rachid Moussadek et al.

Machine learning (ML) has become a powerful tool for predicting suspended sediment concentration (SSC). Nonetheless, the ability to interpret the physical process is considered the main issue in applying most of ML approaches. In this regard, the current study presents a novel framework involving four standalone ML models (extra trees (ET), random forest (RF), categorical boosting (CatBoost), and extreme gradient boosting (XGBoost)) and their combination with genetic programming (GP). Three metrics (coefficient of correlation (r), root mean square error (RMSE), and Nash–Sutcliffe model-fit efficiency (NSE)) and a more advanced interpretation system SHapley Additive exPlanations (SHAP) are used to assess the performance of these models applied to hydro-climatic datasets for prediction of SSC. The calibration process was based on data from 2016 to 2020, and the validation was done for 2021 data. Further description and application of the framework are provided based on a case study of the Bouregreg watershed. The results revealed that all implemented models are efficient in SSC prediction with NSE, RMSE, and r varying from 0.53 to 0.86, 1.20–2.55 g/L, and 0.83–0.91 g/L respectively. Box plot diagrams confirm the enhanced performance of these combined models, and the best-performing ones for the four hydrological stations being the combined RF + GP model at the Aguibat Ziar station, the combined XGBoost + GP model at the Ain Loudah station, the CatBoost model at the Ras Fathia station, and the RF model at the Sidi Med Cherif station. The interpretability results showed that flow (Q) and seasonality (S) are the features most impacting SSC. These outcomes indicate that the applied models can extract accurate and detailed information from the interactions between the hydroclimatic factors and the generation of sediment by erosion (output). ML approaches illustrated the good reliability and transparency of the models developed for predicting SSC in a semi-arid setting, offered new perspectives for reducing ML models' “black box” character, and provided a useful source of information for assessing the consequences of SSC on water quality. The SHAP system and exploring other interpretable techniques are recommended to provide further information in future research. In addition, incorporating additional input data could enhance SSC predictions and deepen understanding of sediment transport dynamics.

Torbjörn E. Törnqvist, Michael D. Blum

Major technological advances have made measurements of coastal subsidence more sophisticated, but these advances have not always been matched by a thorough examination of what is actually being measured. Here we draw attention to the widespread confusion about key concepts in the coastal subsidence literature, much of which revolves around the interplay between sediment accretion, vertical land motion and surface-elevation change. We attempt to reconcile this by drawing on well-established concepts from the tectonics community. A consensus on these issues by means of a common language can help bridge the gap between disparate disciplines (ranging from geophysics to ecology) that are critical in the quest for meaningful projections of future relative sea-level rise.

Daniela Glueck, Ulf Schiefelbein, Hendrik Schubert

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

Anushka Egoda Gamage, Andrew M. Fischer, David S. Nichols et al.

The spatiotemporal distribution of phytoplankton in estuaries is indicative of processes and transport across the land–ocean aquatic continuum (LOAC). Estuaries, as biogeochemically and physically active systems, process large amounts of nutrients and organic matter influencing the transformation of ecological functions. The transformation of the water column drives variation in phytoplankton composition, biomass, and their spatial distribution. Understanding the dynamics of nutrients and organic matter is challenging, yet it provides a comprehensive insight into phytoplankton spatiotemporal distribution across estuaries. Multiple studies have been conducted to understand the spatiotemporal distribution of phytoplankton. Recently, phytoplankton photosynthetic pigments, fatty acids and stable isotopes have been widely used to identify and quantify phytoplankton distribution. This review highlights the use of biogeochemical markers to identify phytoplankton functional groups. It also assesses the current understanding of patterns in the spatiotemporal distribution of phytoplankton and the impact of physical and environmental factors on their distribution in estuaries and coastal oceans. The review will also gather information from in situ sampling studies to evaluate the current state of knowledge and identify gaps.

Rafael Schroeder, Luís G. Cardoso, Luciano G. Fischer et al.

Endangered sharks and rays usually often lack basic information specific to conservation, such as population size. Previous studies have reconstructed shark and ray catch statistics between 1950 and 2019 for the southeast = south of Brazil, but lacking detail at the species level, because the catches were grouped by family, genus or even common name (e.g., skates and rays, Dasyatidae, <i>Rhinobatos</i>, Sphyrnidae, Squatinidae). In this study, we used proportions between species from scientific observer fishing trips and Dirichlet regression modelling to reclassify these categories. This model is a multivariate extension of beta regression and enables the modeling of asymmetric and heteroscedastic compositional data, allowing multinomial data to be obtained in a more informative way. The reconstruction of catches for unclassified data showed a massive dominance of the Squatinidae family until the late 1970s, when catches showed signs of decline. At the same time, the rays of the “emplastro” family showed a progressive increase from 2006 onwards. However, this scenario changed after the reclassification. The category Squatinidae was maintained almost exclusively by <i>S. guggenheim</i>, while 16 categories of species were observed within “emplastro” rays, many of which fall into “endangered”, “vulnerable” and “critically endangered” criteria. These reconstructed series provide a more reliable scenario of the catches of thirty elasmobranch species in the southeast and south of Brazil and serve as baseline information for understanding the conservation status of these species.

Hengameh Motamedi, Maryam Rahbani, Abbas Harifi et al.

Possessing precise water level data in any coastal area is crucial, for any coastal engineering or managements. One of the main processes responsible for a regular water level changes is tide. Due to its nature, tidal prediction is relatively easily accessible. However, the precision of the results depends on the number of constituents have been considered for the prediction. The aim of this paper is to identify the most relevant tidal constituents and their relevant amplitudes for tidal prediction in the Beris port, south of Iran, using artificial neural network (ANN). The main constituents in the area is obtained as M_2, K_1, S_2, N_2 and O_1. To regenerate the tidal condition considering these constituents two ANN methods has been applied including Feed Forward, and Radial Basis Functions (RBF). For the training and network test tidal data of the year 2017 has been considered. For the training a variety of months and constructions has been applied. For the Feed-Forward the Levenberg-Marquardt learning method has been considered. After executing different structures in terms of the number of neurons in the hidden layer and taking into account the minimum error and run time, the network with 5 neurons in the hidden layer and two months training was qualified. For the RBF, the radius of 2.5 has been qualified. The evaluated network of both Feed-Forward and RBF has been employed to reproduce tidal water level of the whole year 2018, and the results were compared with both field data and those derived from harmonic analysis. It was found that the three layers Feed-Forward network shows the best performance in tidal prediction with the correlation coefficient of 0.85, which is followed by RBF, with the correlation coefficient of 0.81.

Maryam Kaveh, Majid Fattahi, Rahman Ghaffari

This study aims to identify an appropriate model for developing the transit capacity, known as an instrument that countries use in relation to their geographical locations to diversify their income sources. In international aspects, developing transit capacity can also provide a country with other advantages in foreign affairs. Moreover, it is necessary to develop transit by Iran because of reducing economic vulnerability and increasing deterrence against hostile activities of Iran’s enemies. Therefore, transit opportunities and bottlenecks were identified in addition to reviewing previous studies and interviewing the experts. Considering the semi-structured and in-depth interviews given to 13 informed transit experts, this is a qualitative study in which the grounded theory was employed. Finally, the proper transit capacity development model was proposed by extracting causal, main category, intervening, and contextual conditions and outcomes.

Sirous Yasseri

The ISO requires a two-level seismic qualification, namely Extreme Level Earthquake (ELE) and Accidental Level Earthquake (ALE) where damages that do not lead to leak is acceptable. ISO accepts both the response spectrum method and the time history approach.  Since the spool-soil system behaves non-linearly, the time domain analyses must be performed for both levels. ISO requires 7 real earthquakes scaled for the site to be used for each seismic level and the system must pass at least 50% of the cases.  Best estimate soil models were developed to represent soil conditions at the manifolds locations in Part I. A set of 10 real earthquake time histories were propagated through the soil column for each location. The resulting ground motion at the surface was computed using a nonlinear model. The frequency-dependent ratio of spectra acceleration at the mudline to the stiff soil outcrop spectral acceleration (Spectral Amplification Ratio or SAR) was computed for each time history. The mean SAR was then used to modify the stiff soil hazard results from the PSHA to obtain design response spectra at the mudline. This is the second part of three interlinked papers summarises the state of art for the benefit of practitioners of subsea engineering.

Akbar Rashidi Ebrahim Hesari, Sajad Andi, Hosein Farjami

In this research, density, temperature and salinity fields were investigated in different seasons using observational data of ROPME Marine Cruise in the Persian Gulf (PG). Based on in-situ measurements, areas with density stratification were identified. Having analyzed Landsat and SAR satellite images, internal waves (IW) were detected in different regions of the Persian Gulf and more frequently in the eastern part of the PG related to seawater stratification. Based on analysis of satellite images, it is shown that the length of internal waves crest detected in the north-eastern part of Al-Zhahirah (Qatar) was more than 120 km; while it’s in range of 5 to 20 km in the south and east of Larak Island, 15 to 40 km in the north-east of Abu Musa Island, and 3 to 65 km in the south-east and south of Hondurabi Island. Moreover, IWs with shorter crest’s wide were recognized near Lavan, Siri, Farur, Halul, Khark Islands and Bandar Lengeh, as well. In addition, studying satellite images in the above mentioned areas for a longer time period from 2000 to 2017 showed that IWs mostly occur in the eastern part of the PG in summer and disappear in other seasons.

Maryam Rahbani

Hadish watercourse located in the in south of Iran, is a seasonal channel of water which crosses through Bandar Abbas to reach to the Persian Gulf. This watercourse is faced with numerous environmental problems in regard with the pollution entrance. Huge amount of the urban and industrial sewages of the city are discharged into this watercourse. In this investigation, considering the discharge of 1.36 m3/s into this watercourse, according to the literatures, the procedure of emission of pollution in the area was modeled. For this purpose Delft3D software has been employed. The model has been calibrated and evaluated considering water level data from Rajaee Port. It was found that, the pollution mainly remains inside the watercourse which is due to the ebb dominance nature of the channel. The results of this research show that the discharging the sewage into this channel endangers not only the western coast of Bandar Abbas, but the health of the citizens.

Omid Shabankareh, Mohammad Javad Ketabdari, Mohammad Ali Shabankareh

Coastal erosion has always been a serious problem in shorelines, which causes heavy damage to coastlines and public properties around the world. Rapid and uncontrolled coastal developments were started to prevent the exacerbation of erosion hazards. However in turn they have had a damaging impact on coastal ecosystems. The current study presents a comparative environmental impact assessment of two protective alternatives in coastal and shoreline structures, including traditional rubble system and a more novel one called geotube system. A case study of two breakwater structures in Bushehr and Qeshm in the south of Iran was performed and beneficial aspects of geotube system were identified.Coastal erosion has always been a serious problem in shorelines, which causes heavy damage to coastlines and public properties around the world. Rapid and uncontrolled coastal developments were started to prevent the exacerbation of erosion hazards. However in turn they have had a damaging impact on coastal ecosystems. The current study presents a comparative environmental impact assessment of two protective alternatives in coastal and shoreline structures, including traditional rubble system and a more novel one called geotube system. A case study of two breakwater structures in Bushehr and Qeshm in the south of Iran was performed and beneficial aspects of geotube system were identified.

Bahram Mehrafrooz, Pedram Edalat, Mojtaba Dyanati

Construction quality plays an important role in the integrity of submarine oil and gas pipelines during their lifetime. Quality of material and quality of construction contractors are two major contributors to the durability of the pipelines. The risk regarding quality material and contractors creates major concerns in durability of pipelines and has a significant impact on the optimized balance between CAPEX and OPEX in Risk-based integrity management of pipeline. In this study, the impacts of construction quality and corresponding uncertainties on the probability of failure of submarine pipelines are investigated in a reliability analysis using Monte Carlo Simulation. A sensitivity analysis is also conducted to show the important parameters within the study. The results show that the 33 percent reduction in uncertainty of construction quality has led to a reduction of more than 99 percent of the probability of failure. This indicates a high sensitivity of the probability of failure to structural uncertainty.

Ali Sheikhbahaei, Said Mazaheri, Syrus Ershadi

For the purpose of having a safety navigation, the transportation path, deployment of carrier, physical specifications, locations and … have high level of importance. In this research, along with the above mentioned factors, we have compared the result with technical standard and commentaries for port and harbor facilities in Japan, and to analysis both advantage and disadvantages of them. The IRAN LNG project (ILC), will product the overall amount of 10/80 million tons of LNG per annum. Based  on the type and capacity of LNG ship (Membrane Type,150000 m3 ), 13 vessels and 6 tug boat are estimated, mostly considered as high capacity LNG carriers. Since the IRAN LNG ships enter to terminal on ballast and after loading departure and also with considering number and marine traffic on  South pars, one way channel with 0.5 L (L is length of ship) considered. On this base, we need Maximum width of 157.5 m and minimum 122m (for LNG Ships), and Maximum width 120m and minimum 89m (for LPG Ships). Area, circumference and diameter of basin with anchorage & buoys on general jetty that in collusive general Cargo, Sulphar & Ro-Ro berth respectively are 154610 m2, 1830m and 320m that covered Japanese’s standard completely but about turning circle, we have area, circumference and diameter respectively 5896 m2, 250m and 708m which doesn’t coordinate with Japan’s standard except only one subject (Sulphar berth with aids tug boat).

Ali Zinati, Mohammad Javad Ketabdari

Oscillating hydrofoils in presence of waves under the free surface as new systems for energy extraction is a hybrid renewable marine energy sources. In this system energy extraction is associated with oscillating hydrofoils operating as biomimetic systems in harmonic waves and currents in coastal regions using active pitch control. Another way of energy exploiting is used by installation of foils under the hull of the ships. Flapping foils located beneath the hull of the ship are investigated as unsteady thrusters, augmenting ship propulsion in rough seas and offering dynamic stabilization. In this system the foil undergoes a combined oscillatory motion in the presence of waves. For the system in the horizontal arrangement, the vertical heaving motion of the hydrofoil is induced by the motion of the ship in waves. The survey shows that exploiting of energy from sea using these techniques can be proposed for Iranian hybrid ships for their propulsion as secondary source of energy. Particularly North part of Persian Gulf has a proper situation for installation and operation as marine energy device in coastal regions.