Showing papers by "Candan Gokceoglu published in 2018"

Considerations on the use of sentinel-1 data in flood mapping in urban areas: ankara (turkey) 2018 floods

Abstract: . Flood events frequently occur due to -most probably- climate change on our planet in the recent years. Rapid urbanization also causes imperfections in city planning, such as insufficient considerations of the environmental factors and the lack of proper infrastructure development. Mapping of inundation level following a flood event is thus important in evaluation of flood models and flood hazard and risk analyzes. This task can be harder in urban areas, where the effect of the disaster can be more severe and even cause loss of lives. With the increased temporal and spatial availability of SAR (Synthetic Aperture Radar) data, several flood detection applications appear in the literature although their use in urban areas so far relatively limited. In this study, one flood event occurred in Ankara, Turkey, in May 2018 has been mapped using Sentinel-1 SAR data. The preprocessing of Sentinel-1 data and the mapping procedure have been described in detail and the results have been evaluated and discussed accordingly. The results of this study show that SAR sensors provide fast and accurate data during the flooding using appropriate methods, and due to the nature of the flood events, i.e. heavy cloud coverage, it is currently irreplaceable by optical remote sensing techniques.

A review on citizen science (citsci) applications for disaster management

Abstract: . The traditional way of doing science has been changing with the recent movements on open science, open data and the world-wide spread of volunteer activities. With the help of technological advancements, in particular mobile technologies, do-it-yourself kits and free online education sources, ordinary citizens may contribute to scientific processes based on their interest and abilities. Citizen Science (CitSci) is an active research agenda which draws the interest of scientists from different disciplines. It investigates the various contributions that citizens could do to improve scientific process. These contributions are utilized in diverse areas ranging from biology to environmental monitoring to classification of galaxies, all of which have a spatiotemporal dimension. The emerging developments in spatial information science allow the public to understand their environment better and efficiently. In this way society would have the means to deal with complex modern problems including but not limited to water/air pollution monitoring and mapping a region after a natural disaster to aid relief and recovery efforts. In addition, there is a growing public demand for research projects involving CitSci; because such collaborative efforts can be critical to achieve sustainability goals. The aim of this paper is to provide an overview on the state-of-the art methods and applications where CitSci is a crucial component in different phases of disaster management, from environmental protection to risk analysis and aid provision. Use of CitSci methods in disaster situations can be vital for different reasons, such as acquisition of local and most current information, organization of help during emergency, development of instant rescue plans, accurate information dissemination, and monitoring of the post-disaster influences to the society and the environment. Open issues on the use of CitSci methods in disaster management, such as data quality, technical and management-related barriers, open-standards and interoperability, and volunteer engagement, will also be discussed.

Deformation Modulus of Rock Masses: An Assessment of the Existing Empirical Equations

Abstract: Rock mass deformation modulus is an important parameter for all geotechnical applications However, the determination of rock mass deformation modulus with in situ tests are highly expensive and time consuming For this reason, rock engineers and engineering geologists have proposed numerous empirical equations based on various rock mass and intact rock properties to estimate the deformation modulus of rock masses In the present study, an assessment of the existing empirical equations was undertaken For the purpose of the study, the data obtained from four investigation galleries opened during a dam construction (Artvin Dam, Turkey) were used A total of 34 plate loading tests were employed in these galleries The tested rock mass is poor quality tuff Rock mass rating (RMR89), rock tunnelling quality index (Q) and geological strength index of each test levels were determined The empirical deformation modulus values of rock mass were calculated by the 26 most cited empirical equations proposed by various researchers The cross-checks between the measured rock mass deformation modulus and the empirically calculated rock mass modulus values were performed by simple regression analyses The empirical equations with higher prediction capacity were also examined with root mean square error, values account for and prediction error evaluations Among the empirical equations compared in this study, two empirical equation giving best performance and other four empirical equations providing acceptable results were determined

Comment on “Comparative study of the deformation modulus of rock mass” by Panthee et al. (2018) in the Bulletin of Engineering Geology and the Environment

Abstract: Recenly, a paper entitled BComparative study of the deformation modulus of rock mass^ has been published online in the Bulletin of Engineering Geology and the Environment by Panthee et al. (2018). Indirect determination of the deformation modulus of rock masses has been an interesting subject among rock engineers and engineering geologists for the last two decades. A considerable number of empirical equations have been proposed. However, each equation has limited prediction capacity depending on the data used. For this reason, some authors (e.g. Kayabasi et al. 2003; Panthee et al. 2018) have tried to check the performances of the equations proposed. It is evident that such type of studies are highly important for rock engineering practice. The study published by Panthee et al. (2018) is one of the good examples of these type trials. Panthee et al. (2018) presented new data and discussions. However, correct use of equations is crucially important; otherwise, incorrect results are obtained and incorrect conclusions are drawn. Palmstrom (1995) proposed the following empirical equation for the deformation modulus of the rock mass:

Combination of discontinuity characteristics and GIS for regional assessment of natural rock slopes in a mountainous area (NE Turkey).

Abstract: Geographical Information Systems (GIS) have a very large spectrum of users. As in many engineering applications, GIS are frequently used in geotechnical projects, especially in producing various thematic and zoning maps such as various susceptibility and hazard maps. Instability maps for large areas with similar characteristic can be produced in a practical way by evaluating the results obtained by the data collected from field and laboratory studies. In order to introduce a methodology for producing rock slope instability maps for a large area, discontinuity controlled slope failures in the Kose Granitoid Complex (NE Turkey) were selected. To determine the types of failure such as planar, wedge, and toppling, and possible instable slope orientations kinematic analyses were carried out in the limited areas. The relationships between orientations of natural slopes and discontinuities obtained from kinematic analyses were evaluated with GIS software. Finally, discontinuity controlled instability maps were produced for the study area. Resulting maps show that the most common type of failure is wedge type. Additionally, the distributions of unstable areas along road networks were determined. Various land use types such as agriculture, grassland, settlement, and forest were also classified in order to predict the possible effects of slope instabilities. The methodology introduced in this study indicates highly promising results for the assessment of rock slope instability in large areas.

Possible contributions of citizen science for landslide hazard assessment

Abstract: . Landslide is perhaps one of the most complex natural phenomena and is quite common throughout the World. Before the human appearance on the World, it was only an earth surface process, whereas it became one of the most destructive natural hazards with the anthropogenic activities and the increase in human population. Landslides cause serious harmful and destructive effects on roads, railways, buildings, infrastructures, lifelines, quality of surface waters, etc. To reduce the losses caused by landslides, high quality landslide susceptibility and hazard maps are crucial. With the recent technological developments, the quality of regional landslide susceptibility and hazard assessments has been increased. Preparation of a complete landslide inventory map with accurate temporal dimension can be extremely difficult, or even impossible. Inaccurate and incomplete temporal landslide inventory maps result in serious uncertainties on the assessment results of regional landslide hazard. Therefore, lack of timely accurate data is the main source of problem affecting quality of the regional landslide assessments. With the emerging developments in geospatial technologies, as well as the transforming power of information and communication technologies (ICT) on the society, it became possible to use the citizen science methods in scientific processes, which has enormous potential in landslide data collection and thus reduce the losses. The main aim of this review is to discuss the uncertainties lead by missing data and affecting quality of regional landslide assessments, and to describe the potential of citizen science to reduce the uncertainties. For this purpose, a brief review on the landslide susceptibility and hazard studies have been performed and the sources of uncertainties have been described. Finally, the role of citizen science is discussed with specific examples. As a final conclusion drawn from the present study, it is possible to say that citizen science may provide substantial contribution on the quality of regional landslide assessments.

Preliminary investigations on flood susceptibility mapping in ankara (turkey) using modified analytical hierarchy process (m-ahp)

Abstract: . Susceptibility mapping for disasters is very important and provides the necessary means for efficient urban planning, such as site selection and the determination of the regulations, risk assessment and the planning of the post-disaster stage, such as emergency plans and activities. The main purpose of the present study is to introduce the preliminary results of an expert based flood susceptibility mapping approach applied in urban areas in case of Ankara, Turkey. The proposed approach is based on Modified Analytic Hierarchy Process (M-AHP), which is an expert-based algorithm and provides data based modeling. The existing spatial datasets are evaluated in the decision process and the specified number of decision points according to the degree desired can be formed. The parameter priorities can be identified at the beginning of the modeling with this approach by the responsible expert. The spatial datasets used in the modeling and mapping process have been provided by the General Directorate of Mapping (HGM). Additionally, the slope gradient of topography, drainage density, and topographic wetness index of the site being one of the second derivatives of topography have been evaluated to identify the main conditioning factors controlling water accumulation on ground. Considering the uncertainties in flood hazard assessment and limitations in sophisticated analytic solutions, the proposed methodology could be evaluated to be an efficient tool to detect the most influential parameters representing the flood vulnerability and assessing the mitigation applications in urban environment.

On the use of citsci and vgi in natural hazard assessment

Abstract: . The developments in the geospatially-enabled mobile communication technologies have opened new horizons in many fields of geosciences research, especially in those where data collection, processing and interpretation are time consuming and costly. Being one of these research fields, natural hazards also require high spatiotemporal data density and distribution, which is extremely difficult to obtain and also equally essential to secure the main assumptions of these researches and thus yield to proper conclusions. These problems can be solved with the help of citizen science (CitSci) methods and the volunteer geographical information (VGI). These two terms are complementary, or intertwined, and mutually benefit from each other for achieving their goals. This paper investigates the developments in CitSci and VGI with a specific focus of natural hazard researches and gives a brief overview of the literature. The importance of their use in natural hazards, open research areas and future aspects are also analysed. Based on the previous experiences and analyses, the authors foresee that such investigations would help researchers to utilize CitSci and VGI in their studies, and thus benefit the advantages of both approaches and improve the quality of their data. On the other hand, the growing interest of citizen scientists for supporting scientific processes could be steered to the fields where most help is needed. Specifically, detection of ground deformations after earthquakes is explained here and a simple mobile app developed for landslide data collection is briefly depicted as use case.

CitSci as a New Approach for Landslide Researches

Abstract: Landslide is a commonly and frequently observed disaster on the Earth both spatially and temporally. The landslide researches mainly aim at characterizing and understanding this process and the earth dynamics, and predicting their occurrence based on triggering factors, their spatial and temporal dimension, thus assess the hazard potential; and estimating the risks which they cause on the economy, environment, and lives. Due to the great variety and amount of data included in this field, it is crucial to form complete landslide databases both at regional level and worldwide. The main aim of this assessment is to bring new insights to the landslide data acquisition aspect by different users. The need of accurate and reliable geodata collection by ordinary people is inevitable for ensuring sufficient spatiotemporal density and distribution, thus forming extensive landslide databases and simulating and planning the future. With the developments in geoinformation technologies, as well as the transforming power of information and communication technologies (ICT) on the society, it became possible to use the citizen science (CitSci) methods in many scientific fields. It has as well enormous potential in landslide data collection, validation and interpretation, and thus contribute to landslide researches. In this review, the uncertainties lead by missing data and affecting quality of regional landslide assessments are discussed, and the potential of citizen science in landslide researches is described. The role of volunteer data is portrayed with specific examples from the literature. The levels of citizen contribution are depicted accordingly.

A Photogrammetric Surface Comparison for a Dam Reservoir in a Landslide—Prone Area in Eastern Anatolia, Turkey

Abstract: The purpose of the study was to analyze the slope deformations of a dam reservoir by comparing digital elevation models (DEMs) produced before and after data sets. The DEMs were generated automatically from large format aerial images acquired in 2012 and Gokturk-2 satellite images acquired in 2018. Both DEMs were compared and analyzed to obtain slope deformations. The results showed that the reservoir waters affected the slopes and some displacements were seen clearly in northeast slopes of the reservoir. The slope deformations can be monitored accurately with the proposed approach, with a note on the ground resolution of the images, which affected the accuracy and the density of the DEMs directly. The methodology provided promising results for automatic, low-cost and practical monitoring for slope deformations in large mountainous regions.

An Experimental Study to Compare Two Soil Improvement Techniques Performance

Abstract: The main purposes of the present study were to compare in situ performances of two ground improvement techniques, which are jet grout and deep soil mixing techniques. In this study, Manisa State Hospital Project location was selected as the test site, because this location has difficult geological and geotechnical conditions. In the test site, three jet grout colons and three deep soil mix colons having same cement content were constructed. After 28 days of curing time, the core specimens were extracted for the uniaxial compressive testing, and lump specimens were collected for further tests and analyses such as X-ray diffraction, electron microscopy and determination of physical properties. The results of the uniaxial compression tests show that the uniaxial compressive strengths of the specimens extracted from the deep soil mix colons are drastically higher than those of the jet grout colons. Additionally, to understand the causes of this difference, several features of the improved soil were investigated by various mineralogical and petrographic methods. According to the results of these investigations, the fabric and some mineralogical properties were seriously affected by the improvement technique.