55 research outputs found
Satellite image processing for the coarse-scale investigation of sandy coastal areas
No full textIn recent years, satellite imagery has shown its potential to support the sustainable management of land, water, and natural resources. In particular, it can provide key information about the properties and behavior of sandy beaches and the surrounding vegetation, improving the ecomor-phological understanding and modeling of coastal dynamics. Although satellite image processing usually demands high memory and computational resources, free online platforms such as Google Earth Engine (GEE) have recently enabled their users to leverage cloud-based tools and handle big satellite data. In this technical note, we describe an algorithm to classify the coastal land cover and retrieve relevant information from Sentinel-2 and Landsat image collections at specific times or in a multitemporal way: the extent of the beach and vegetation strips, the statistics of the grass cover, and the position of the shoreline and the vegetation–sand interface. Furthermore, we validate the algorithm through both quantitative and qualitative methods, demonstrating the goodness of the derived classification (accuracy of approximately 90%) and showing some examples about the use of the algorithm’s output to study coastal physical and ecological dynamics. Finally, we discuss the algorithm’s limitations and potentialities in light of its scaling for global analyses.Coastal Engineerin
Uncertainty analysis in integrated catchment modelling
No full textThe adoption of increasingly restrictive water quality standards is directed to maintain natural ecosystems in a good status. Complying with such standards requires significant investments in water infrastructure and operations. Consequently, mathematical simulation is usually applied to assist in the decision-making process for such large-scale actuations. In particular, environmental models are proposed to represent the wastewater cycle in natural water bodies, such that the effect of different pollution mitigation alternatives can be estimated. Integrated catchment models (ICM) aim at simulating water quality dynamics by representing the link between urban drainage networks, wastewater treatment operations, rural hydrology and river physical-biochemical processes. However, these subsystems present dynamics acrossmultiple spatiotemporal scales and many relevant processes are still not fully understood. System observations are scarce and often insufficient to identify most model representations. As a result, ICM studies often produce significant output uncertainties
Propuesta de itinerarios turísticos a partir del análisis de obras literarias góticas en Cuba:
No full textSince the end of the last century, the changes experienced in tourism had led to its diversification to meet the needs and demands of contemporary tourists. Culture, more and more, occupies a preferential place in the consumption of its experiences. It highlights a modality of cultural tourism linked to literature in which the tourist shows his interest in knowing the scenarios where the arguments of his favorite fictions are developed, as well as those spaces related to the author of the literary works. In the form of tourist products, several tourist routes and itineraries have been developed throughout the world that support these practices in the territory. In this context, this research aims to analyze the possibilities of diversification of consolidated Cuban tourism from proposing literary tourist itineraries by reading three works that have their stage in Cuba. For that, own methods of geography and literature will be used, two disciplines that have common points. We will proceed to an analysis of these works to discover which elements are susceptible to tourist use and thus analyze the potential of these literary routes.Desde finales del pasado siglo, los cambios experimentados en la actividad turística han propiciado su diversificación para satisfacer las necesidades y exigencias del turista contemporáneo. La cultura, cada vez más, ocupa un lugar preferente en el consumo de sus experiencias. Destaca una modalidad del turismo cultural vinculada a la literatura en la que el turista muestra su interés en conocer los escenarios donde se desarrollan los argumentos de sus ficciones favoritas, así como aquellos espacios relacionados con el autor de las obras literarias. Bajo la forma de productos turísticos se han desarrollado por todo el mundo una serie de rutas e itinerarios turísticos que tienen en el territorio el soporte de estas prácticas. En este contexto, la presente investigación tiene como objetivo analizar las posibilidades de diversificación del consolidado turismo cubano a partir de proponer itinerarios turísticos literarios mediante la lectura de tres obras que tienen su escenario en Cuba. Para eso, se emplearán métodos propios de la geografía y la literatura, dos disciplinas que tienen puntos comunes. Se procederá a un análisis de estas obras para descubrir qué elementos son susceptibles de uso turístico y así analizar las potencialidades de estas rutas literarias
Parametric emulation and inference in computationally expensive integrated urban water quality simulators
No full textWater quality environmental assessment often requires the joint simulation of several subsystems (e.g. wastewater treatment processes, urban drainage and receiving water bodies). The complexity of these integrated catchment models grows fast, leading to potentially over-parameterised and computationally expensive models. The receiving water body physical and biochemical parameters are often a dominant source of uncertainty when simulating dissolved oxygen depletion processes. Thus, the use of system observations to refine prior knowledge (from experts or literature) is usually required. Unfortunately, simulating real-world scale water quality processes results in a significant computational burden, for which the use of sampling intensive applications (e.g. parametric inference) is severely hampered. Data-driven emulation aims at creating an interpolation map between the parametric and output multidimensional spaces of a dynamic simulator, thus providing a fast approximation of the model response. In this study a large-scale integrated urban water quality model is used to simulate dissolved oxygen depletion processes in a sensitive river. A polynomial expansion emulator was proposed to approximate the link between four and eight river physical and biochemical river parameters and the dynamics of river flow and dissolved oxygen concentration during one year (at hourly frequency). The emulator scheme was used to perform a sensitivity analysis and a formal parametric inference using local system observations. The effect of different likelihood assumptions (e.g. heteroscedasticity, normality and autocorrelation) during the inference of dissolved oxygen processes is also discussed. This study shows how the use of data-driven emulators can facilitate the integration of formal uncertainty analysis schemes in the hydrological and water quality modelling community.Sanitary Engineerin
Impact of spatiotemporal characteristics of rainfall inputs on integrated catchment dissolved oxygen simulations
No full textIntegrated Catchment Modelling aims to simulate jointly urban drainage systems, wastewater treatment plant and rivers. The effect of rainfall input uncertainties in the modelling of individual urban drainage systems has been discussed in several studies already. However, this influence changes when simultaneously simulating several urban drainage subsystems and their impact on receiving water quality. This study investigates the effect of the characteristics of rainfall inputs on a large-scale integrated catchment simulator for dissolved oxygen predictions in the River Dommel (The Netherlands). Rainfall products were generated with varying time-aggregation (10, 30 and 60 min) deriving from different sources of data with increasing spatial information: (1) Homogeneous rainfall from a single rain gauge; (2) block kriging from 13 rain gauges; (3) averaged C-Band radar estimation and (4) kriging with external drift combining radar and rain gauge data with change of spatial support. The influence of the different rainfall inputs was observed at combined sewer overflows (CSO) and dissolved oxygen (DO) dynamics in the river. Comparison of the simulations with river monitoring data showed a low sensitivity to temporal aggregation of rainfall inputs and a relevant impact of the spatial scale with a link to the storm characteristics to CSO and DO concentration in the receiving water.Sanitary Engineerin
“Castles in Connecticut.” Isaac Mitchell and Alonzo and Melissa (1804): Trans-Hemispheric Gothic in Early America
No full textThis Gothic Literature is today understood as crucial in order to comprehend the future evolution of American Literature, from its chronological origins to the present day. During the first phases of its evolution, along with Charles Brockden Brown, the most widely renown author shortly after the political independence of the United States, another name needs to be considered in order to understand the relevance of incipient American Gothic: New Yorker Isaac Mitchell, a collaborator of James Fenimore Coope. However, unlike Brown, Mitchell has remained in oblivion almost to the present day. Mitchell’s professional career mostly developed within the branch of journalism and edition. Beyond this, between 1802 and 1802, Mitchell published three novels that fall under very diverse classifications. The last of them, Alonzo and Melissa, would acquire more recognition, and it is today probably the most relevant to stablish how American Gothic first evolved. In consequence, the aim of this paper is to recover the most prominent features of this nearly forgotten work (under a fake attribution) and locating it within the long-standing American gothic tradition
Uncertainty analysis in a large-scale water quality integrated catchment modelling study
No full textReceiving water quality simulation in highly urbanised areas requires the integration of several processes occurring at different space-time scales. These integrated catchment models deliver results with a significant uncertainty level associated. Still, uncertainty analysis is seldom applied in practice and the relative contribution of the individual model elements is poorly understood. Often the available methods are applied to relatively small systems or individual sub-systems, due to limitations in organisational and computational resources. Consequently this work presents an uncertainty propagation and decomposition scheme of an integrated water quality modelling study for the evaluation of dissolved oxygen dynamics in a large-scale urbanised river catchment in the Netherlands. Forward propagation of the measured and elicited uncertainty input-parametric distributions was proposed and contrasted with monitoring data series. Prior ranges for river water quality-quantity parameters lead to high uncertainty in dissolved oxygen predictions, thus the need for formal calibration to adapt to the local dynamics is highlighted. After inferring the river process parameters with system measurements of flow and dissolved oxygen, combined sewer overflow pollution loads became the dominant uncertainty source along with rainfall variability. As a result, insights gained in this paper can help in planning and directing further monitoring and modelling efforts in the system. When comparing these modelling results to existing national guidelines it is shown that the commonly used concentration-duration-frequency tables should not be the only metric used to select mitigation alternatives and may need to be adapted in order to cope with uncertainties.Sanitary EngineeringIntegral Design & Managemen
Assessment of beach face slope extraction and monitoring with ICESat-2: from local to global level
No full textCoastal areas are appealing for human beings and are the most populated areas of the world. Therefore, coastal processes have large impacts on economy and on millions of people's lives. Not only processes such as erosion, extreme events, and flood events must be understood and monitored, but the uncertainty given by the rapid climate change on these processes and on coastal systems pose a bigger issue on these populated areas. One of the key parameters of coastal processes, which is notably required for modelling coastal floods, is the beach face slope. Unfortunately, there is a lack of a reliable global dataset of the steepness of the beach face, which has been indicated to be key limitation for developing operational coastal inundation forecasting systems, as well as for quantifying the run-up and set-up contribution at the shoreline relative to global sea-level-rise.In this report, a methodology for providing this parameter at a global level by using a LiDAR-based satellite (ICESat-2) is presented. Here, the accuracy of the beach face slope estimation, its dependency on the angle and distance between ICESat-2 measurements (passes) and the transect perpendicular to the coastline they are projected into (transect), a spatial and temporal exploration of ICESat-2 measurements on world's coasts, as well as the limitations and opportunities of this methodology are presented.The findings of this study reveal strong visual agreement between the beach profiles and beach face profiles obtained from the validation datasets and ICESat-2. Moreover, the computed metrics, including the Mean Absolute Error (MAE), Mean Squared Error (MSE), and Root Mean Squared Error (RMSE), present low values, indicating a high level of agreement. The MAE values, ranging from 9 to 34 cm, not only demonstrate good agreement within the beach and beach face profiles but also indicate that the errors fall within the inherent variability of the beach. For assessing the impact of the angle and distance between passes and transect on the beach face slope extraction, synthetic data is generated using Digital Elevation Models (DEMs). The results demonstrate that long and spatially homogeneous beaches withstand larger α, whereas smaller, more variable, and pocket-shaped beaches are more sensitive to large angles due to the rapid decrease of spatial information alongshore. Nevertheless, regardless of the beach type, the closer the synthetic ICESat-2 measurements intersect over the beach face, the more likely the extracted beach face slope is to match the actual one. For both analysed cases, the beach face slope can be extracted with a tolerable level of uncertainty up to 60 degrees, and if the synthetic data is close to the beach face, the angle that it bears can be increased up to 70-80 degrees.The novel methodology for upscaling the beach face slope extraction is validated using the Dutch yearly coastal dataset, JARKUS. The results reaffirm the dependence of the beach face slope on the angle between pass and transect. It is concluded that even though further refinement of the algorithm for demarcating the beach face is necessary, the extraction of beach face slopes can be implemented on a global scale, if some challenges are overcome. Moreover, this methodology yields a valuable byproduct in the form of cross-shore profiles, which can be extracted globally with high accuracy. This additional output enhances the utility and versatility of the methodology. Additionally, a spatial and temporal exploration of ICESat-2 ATL03 data on the world's coasts, by globally sampling boxes of 20 km2, is implemented. Then, by analysing the preliminary results from boxes already processed, it is observed that these boxes can encompass anywhere from 0 to 160 passes over the course of the available 5-year data. On average, approximately 63 passes are recorded within each box. From this analysis, it is concluded that particular coastal stretches, depending on their geometry and cloud coverage, can be effectively monitored for beach face slope changes using ICESat-2. Moreover, from the information extracted from these boxes, a map is being constructed for the purpose of revealing potential areas where the extraction of beach face slopes are possible given the beach geometry and availability of data. In summary, this study provides a novel methodology that sets the basis for a new era of coastal management and monitoring using LiDAR-based satellites at a global level.Geoscience and Remote Sensin
Wave field measurements of regular wave–monopile interaction using Free-Surface Synthetic Schlieren
No full textSpatio-temporal wave patterns due to wave field–structure interaction can be very complex to measure and analyze when using (intrusive) point probes. Free-surface field measurements can offer much needed insight in this domain. Nevertheless, to the best of the authors’ knowledge, these methods are rarely used in experimental offshore engineering and research. In these fields, typical domain sizes are at least in the order of several m2, whereas (optical) free-surface field measurements are often not performed in domains with dimensions larger than roughly 0.5 × 0.5 m2. In the current work, the optical free-surface measurement technique named Free-Surface Synthetic Schlieren (FS-SS) is applied to measure the interaction between an incident wave field and a surface piercing cylinder, or monopile, in a domain of several m2 for the first time. The FS-SS method is validated for wave fields with wavelengths λ ≪ L to λ ≫ L, where L is the domain size in the direction of wave propagation. It is found that the incorporation of an additional water level measurement improves the agreement between intrusive wave height meters and the FS-SS measurement for large wavelengths (λ / L> 0.5) as compared to assuming a zero-mean free-surface. Wave field–monopile interaction is measured for two values of D/ λ: D/ λ= 0.1 and D/ λ= 0.2 , where D is the monopile diameter. For the case D/ λ= 0.2 the interaction wave field is analyzed by subtracting the measured wave field in the absence of a structure, from the measured interaction wave fields. The measured difference wave field reveals many interaction phenomena such as locations of amplification, both near the monopile and further away, a wake that has certain similarities with a Kelvin wake, and a circular small wavelength diffraction pattern. Additionally, the embedding of the measurements in a wave breaking regime map is presented. In this map, the applicability for certain wave conditions can be clearly visualized. It is concluded that the FS-SS method, including the proposed improvement using additional sensor data, is a useful addition to the toolbox of hydraulic engineers and researchers, and that especially the measured locations of wave amplification in the far field will not be easily detected using (arrays of) point probes.</p
Analysis of sand mining in a mega-delta using satellite image processing: Applied to the Vietnamese Mekong Delta
No full textThis study is an analysis of sand mining in the Vietnamese Mekong Delta (VMD) with the use of the optical satellite data set PlanetScope. This is done with a detection and classification model of sand mining vessels in the VMD. The classification model is based on machine-learning and it is trained with three classes: sand mining vessels, other vessels, and background. This study shows that it is possible to distinguish vessel types with a 3 metre spatial resolution and it shows great potential for a vessel classification model based on machine learning.Civil Engineering | Hydraulic Engineerin
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