Experimental analysis of breakwater stability with antifer concrete block

Armor is a pavement made of erosion-resistant materials like a stone or concrete that is constructed to protect breakwater, coasts, and other coastal line features against erosion. These armors are a kind of protective layer made of stone or concrete, used in breakwater constructions or coastal lines, arrayed with specific regular or irregular pattern on the breakwater or the coast. The antifer concrete blocks have almost cubic form, often changed into frustum by adding inclined plates to their sides. One of the most important advantages of these armors is their diversified regular and irregular placement patterns. In this study, using the physical modeling and different tests, the stability level of antifer concrete blocks was evaluated considering the decrease of the armor weight. Results of this study show that by a 10% decrease in the block weight, the failure graph slope is increased and the damage is intensified.     

Flood hazard mapping in western Iran: assessment of deep learning vis-à-vis machine learning models

Natural Hazards - On March 25, 2019, widespread flood events occurred across Iran’s provinces and set a new record for socioeconomic losses and casualties. In hindsight, it opened an...     

Earthquake risk–sensitive model for urban land use planning

Natural Hazards - Analysis of the run-out of landslides is essential and vital for disaster mitigation. However, accurate run-out analysis is difficult because of the uncertainty of earthquake...     

Experimental Investigation on Spray Cooling Using Saline Water

Mathematical Geosciences - Natural draft dry cooling towers (NDDCTs) are a type of cooling technology used in thermal power plants, including geothermal power plants. Interest from industry in this...     

Multi-scale assessment of invasive plant species diversity using Pléiades 1A,RapidEye and Landsat-8 data

We used a full remote sensing-based approach to assess plant species diversity in large and inaccessible areas affected by Lantana camara L., a common invasive species within the deciduous forests of Western Himalayan region of India, using spectral heterogeneity information extracted from optical data. The spread of L. camara was precisely mapped by Pléiades 1A data, followed by comparing Pléiades 1A, RapidEye and Landsat-8 OLI – assessed plant species diversities in invaded areas. The single plant species analysis was improved by Pléiades 1A-based diversity analysis, and higher species diversity values were observed for mixed vegetation cover. Furthermore, lower Coefficient of Variation and Renyi diversity values were observed where L. camara was the only species, while higher variations were observed in areas with a mixed spectral reflectance. This study was concluded to add a crucial baseline to the previous studies on remote sensing-based solutions for rapid estimation of biodiversity attributes.     

The influence of environmental variables on distribution patterns of Irano-Turanian forests in Alborz Mountains,Iran

Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot (1000 m2) and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J. excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA (Canonical Correspondence Analysis) results indicated that the altitude, precipitation, pH, EC, SP, clay and CaCO₃ are the most important factors determine the distribution of trees and shrub in central Alborz     

Numerical modeling of sediment scouring phenomenon around the offshore wind turbine pile in marine environment

In recent years, with daily progress in technology, application of wind turbines for energy generation has become common all around the world. Installation of these turbines at sea encountered a great deal of challenge. One of the most important challenges is scouring around the piles of these turbines due to sea waves and current interaction. Many studies have been conducted in this respect; however, the results are insufficient, and the phenomenon remains poorly understood in tripod wind turbines. In this work, an attempt is made by combining the waves and currents, and changing the substructure of the turbine and the type of the bed materials, to extend the investigation of this phenomenon. The current research is focused on presenting the trend of changes in the amount of scouring. By changing the conditions (including variation in the wave height, variation of the current velocity, variation of the pile diameter, and variation in the size of bed particles), one can arrive at an appropriate estimate and prediction of the shape and the depth of the scour pit.     

Synthetic RapidEye data used for the detection of area-based spruce tree mortality induced by bark beetles

Tree mortality caused by outbreaks of the bark beetle Ips typographus (L.) plays an important role in the natural dynamics of Norway spruce (Picea abies L.) stands, which could cause far-reaching changes in the occurrence and duration of vegetation phenology. Field-based early detection of tree disturbances is hampered by logistic, terrain, and technical shortcomings, and by the inability to continuously monitor disturbances over large areas. Despite achievements in remote mapping of bark-beetle-induced tree mortalities, early warning has been mostly unsuccessful mainly because of the lack of spectral sensitivity and discrepancies in definitions of field- and image-based disturbance classes. Here we applied a method based on inter-annual phenology of Norway spruce stands derived from synthetic multispectral data to part of the Bavarian Forest National Park in Germany. We fused temporally continuous Moderate Resolution Imaging Spectroradiometer and discrete RapidEye data using a flexible spatiotemporal data fusion method to achieve validated 8-day RapidEye-like composites of normalized difference vegetation index for 2011. We assumed that the dead trees delineated on 2012 aerial photographs were those in which bark beetle infestations were initiated in 2011. Samples were drawn with variable-sized buffering to represent the areas prone to infestations and their surroundings. We applied a conditional inference random forest to select the best image date among the entire 46 synthetic datasets to best discriminate between the core infestation patches and their surroundings from the subsequent year. Of the discrete time points identified, day 281 of the year represented the highest discrepancy between aerial image-based dead trees and their surroundings. Classification results were significantly correlated with beetle count data obtained using pheromone traps. Our method provided valuable information for management purposes and enabled wall-to-wall mapping of stands prone to infestation and its uncertainty. The results offer potential implications for rapid and cost-effective monitoring of bark beetle outbreaks using satellite data, which would be of great benefit for both management and research tasks.     

Wave run-up and rundown on ACB Mats under granular and geotextile filters’ condition

Articulated concrete block mattress revetment (ACB Mats) is an appropriate revetment for shore protection and breakwater. ACB Mats act as an integrated and flexible revetment against waves. There is a necessary need of investigation due to the lack of exact ACB Mat design relations in the estimation of hydrodynamic processes including wave run-up and run-down parameters. In the present study, using proper laboratory equipment, run-up and run-down processes were investigated under irregular waves and also granular and geotextile filters’ conditions. In this study, wave run-up and run-down estimation relations in ACB Mat revetment with the open area were explored for the first time. As the obtained results showed, relative maximum wave run-up and rundown are desirable for all conditions. Using a geotextile layer under ABC Mat caused a 14% increase in relative wave run-up values compared to granular filter. Further, in the run-down process, geotextile filter caused a 40% decrease in relative wave run-down values. The intensive decrease in run-down value occurred due to the outflow rate of the water from inside the filter with delay during water attack toward downward, which can be effective on structure stability significantly and should be considered in designs.     

Calibration of weather radar using region probability matching method (RPMM)

In this paper, spatiotemporal variability of drought in Xilingol grassland during pasture growing season (from April to September) was investigated, using 52 years (1961–2012) of precipitation data recorded at 14 rain gauge stations in the study area. The Standardized Precipitation Index was used to compute the severity of drought. The Mann-Kendall test, the linear trend, and the sequential Mann-Kendall test were applied to standardized precipitation index (SPI) time series. The results indicate that drought has become increasingly serious on the region scale during pasture growing season, and the rate of SPI decreases ranged from ?0.112 to ?0.013 per decade. As for the MK test, most of the stations, the Z value range is from ?1.081 to ?0.005 and Kendall’s τ varies from ?0.104 to ?0.024. Meanwhile, drought is increased obviously from the northwest to the southeast region. Meanwhile, the occurrence probability of each severity class, times for reaching different drought class from any drought severity state, and residence times in each drought class have been obtained with Markov chain. Furthermore, the drought severities during pasture growing season in 2013–2016 are predicted depending on the weighted Markov chain. The results may provide a scientific basis for preventing and mitigating drought disaster.