Dogal Afetler ve Cevre Dergisi

216 - 239

Authors: Vedat AVCİ ; Ömer ÜNSAL

This study aims to analyze the flood disaster that occurred in Kastamonu-Bozkurt in 2021 through the morphometric parameters of the basin. In the study, the Basin of Ezine Stream, which is the flood experienced most effectively, was analyzed together with the neighboring basins. Bozkurt flood is one of the most destructive floods in the history of Türkiye. As a result of the floods that occurred in Kastamonu and neighboring provinces on 10th - 12th August 2021, 82 people lost their lives. The Digital Elevation Model (DEM) of the study area was created with a cell size of 10*10 m using topography maps, and the boundaries of the basins to be analyzed with the ArcGIS-Archydro Module were determined. 30 indices were applied to these basins within the scope of shape (geometric), areal and relief morphometric features of the basins. The relationship between morphometric parameters was determined with the Pearson correlation coefficient. When the analysis results are evaluated for the Basin of Ezine Stream, it is the basin with the largest area, and the largest value of basin relief, relative relief and ruggedness. As a result, erosional activities and the risk of flood are high. When all basins are evaluated in general, it has been revealed that the shape of basins are more elongated, and the features of relief morphometry facilitate the formation of floods. Basin relief, relative relief, dissection degree, slope values, and average slope values are high for all basins; and both the amount of water added to the overland flow and the speed of the overland flow increased. This situation also increased the amount of material carried during the flood. Constructions built close to the stream bed increased the effect of the flood. Depending on the global climate change, the study area corresponds to the area where the change in daily maximum precipitation varies between 5-10%. Therefore, floods are likely to continue. For this reason, it is recommended to consider geometric, areal and relief morphometric features of the basins along with the climatic features of the basins while taking the necessary precautions. According to CORINE land cover data, urban areas in the Ezine Stream Basin increased by over 100% between 1990 and 2018, which is also affected by disastrous floods and overflows. Conservation and strengthening of natural vegetation in the study area will reduce the damage level of floods and overflows.

258 - 267

Authors: Can BAŞARAN; Hüseyin MANAP

The water points located in the northwest part of the Afyon Plain are used as mains and irrigation water, by approximately 8000 people approximately 56 km2 of agricultural land. In order to use water resources effectively and efficiently, it is necessary to know the physical, chemical properties and the qualities of the waters very well. For this purpose, 12 groundwater were sampled within the scope of the study, and the hydrgeoochemical processes that gave the current compositions of the waters were determined, the analysis results were compared with the standards, and the irrigation water quality was Electrical conductivity (EC), Schoeller and Wilcox Diagram, Sodium Hazard (%Na and SAR), Residual Sodium Carbonate. (RSC), Magnesium Ratio (MR), Potential Salinity (PS) and Kelley index (KI) were interpreted using parameters. According to the analysis results, it was determined that the major cations of the waters were Ca, Mg and Na, and the major anion was HCO3. The schists and carbonate rocks cropping out in the region affect the current composition of the waters. However, the elements such as nitrate, arsenic, fluorine and boron, detected at some water points and exceeding the limit value may originate from domestic-agricultural wastes and fertilizers. The sampled waters should be used carefully and necessary precautions should be taken in terms of drinkability and irrigation water characteristics.

279 - 294

Authors: Pınar POLAT; İbrahim KOPAR; Fatih YALÇIN

The research area is Günebakan, which represents a large number of parallel drained river basins located in the south-southwest part of the Keşiş (Esence) Mountains (Keşiş Tepe, 3549 m) that border the Erzincan Plain from the north in the northwest (NW)-southeast (SE) direction. The stream includes the Allahmedet Stream and Çadırtepe Stream basins. In this study, the formation and development processes of two flood-overflow events that occurred in Günebakan Stream Basin, the first on 17/07/2011 and the second on 03/07/2020, in the size of a natural disaster and resulted in significant property losses, and their effects on the natural and human environment were examined. In addition, the morphometric characteristics of the Günebakan, Çadırtepe, and Allahmedet stream basins, which are adjacent to each other in the south-southwest catchment area of the Esence Mountains, which surround the Erzincan Plain from the north, were revealed and their flood-overflow potentials were investigated. In this context, with an approach that prioritizes the flood-overflow events occurring in the Günebakan Stream basin, areal, linear, and relief morphometric indices were used to determine the effect levels of the basin morphometry in the flood-overflow events that occur or are likely to occur on the existing running waters. In the analyzes carried out, it was observed that there was a close relationship between the morphometric structure of the relevant basins and the debris-laden floods. In addition, it was concluded that the Günebakan Stream basin in the same catchment area has a higher flood and overflow potential compared to the neighboring basins.

311 - 323

Authors: Mustafa UTLU; Mehmet Fatih AKGÜMÜŞ

This study focuses on the high-resolution 3D cone-based rockfall modeling using Qproto, a QGIS plugin, based on UAV-DSM data in an area near Mazı Village, located north of Derinkuyu and Ürgüp districts in Nevşehir province, where rockfall events occur intensively. The volcanic ignimbrites corresponding to the source zones in the study area have steep and vertical slope profiles, particularly resembling cornices. Therefore, 16 rock blocks with a potential for rockfall were identified within the rock mass structure characterized by cooling cracks (vertical discontinuities) commonly observed in ignimbrites where discontinuities near the vertical occur. Rockfall modeling was performed for these identified blocks. According to the modeling results, rockfalls with a maximum kinetic energy of 142 kJ and a displacement velocity of 16.8 m/s were determined. Based on these results, the maximum values of the rockfall model within the study area were generally reached in areas with high slope values, and it was observed that the energies and velocities of rock blocks attenuated at points with decreased slope, indicating the influence of the existing gravitational condition. Rockfall susceptibility degrees were categorized into five classes, and it was observed that the trajectories of fallen blocks, resulting from rockfalls, corresponded mainly to the moderate-high and high susceptibility classes, where they were scattered and dispersed.

341 - 364

Authors: Mustafa Utku YILMAZ

This study aimed to provide a comprehensive drought analysis for Kırklareli province, whose economy is largely based on agriculture. The trend and temporal variability of drought were examined at 1, 3, 6, 9, and 12-month time scales using the Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI). The monthly precipitation and temperature data from the Kırklareli meteorological station between water years 1960-2021 were used to calculate the SPI and RDI. Mann-Kendall and modified Mann-Kendall tests were used to determine trends of SPI and RDI series for different time scales, Sen’s slope was used to identify the magnitude of trends in the series, and Pettitt's test was used to detect the change point of the series. The results revealed that the SPI and RDI behaved similarly for all time scales and both indices were able to capture almost the same drought events. Besides, it was observed that SPI had a strong linear relationship with RDI over the same time scale (r=0.99). RDI mostly had slightly higher values than SPI and it was concluded that RDI was more sensitive in the detection of extreme and severe drought events. The percentages of occurrence of drought events at different time scales ranged from 46.9% to 51.3% for SPIs and between 47.2% and 50.6% for RDIs. In the 12-month time scale for both indices, 76 months between February 1989 and May 1995 were determined as both the longest and the most severe dry period. As the time scale increased, the number of drought events decreased and the drought duration increased. No statistically significant trend was found for SPI and RDI values at all-time scales (p>0.05). For both indices, there was no change point in the 1-month time scale, but the change point was identified in the 3, 6, 9, and 12-month time scales.

385 - 403

Authors: Ece POLAT; Hülya ÜNVER; Mahmut ALTINBAŞ

Mucilage formation is a very complex phenomenon involving various biological and hydrological interactions. Mucilage is formed as a result of bacterial and phytoplankton-based activities in the environment. Oceanic shifts can provide an environment favorable for mucilage development; however, other factors also play a role in forming mucilage. Mucilage's microbiological structure and morphology, which have been studied in many waters and habitats since the 17th century, are also distinct. This is due to the fact that mucilage development is largely taxon-specific, and mucilage thickness and texture vary depending on environmental conditions. In mucilage studies, phytoplankton is the main component. A high level of organic matter and nutrients in the environment stimulates the formation of phytoplankton and the microenvironment. Furthermore, various water properties, such as temperature, fluidity, and so on, have an increasing effect on mucilage production. The purpose of this review is to describe how aggregates and mucilage are produced by dissolved organic matter (DOM) and microbial populations. Then, living groups discovered in the structure of mucilage during microbial ecology researches are discussed. Several examples of living organisms negatively affected by the development of mucilage were discussed following a detailed description of the dominant species observed in mucilage regions and case information.

16-38

Authors: Melek DALKES; Mehmet Seren KORKMAZ

Landslides are one of the leading natural disasters in the Black Sea Region of Türkiye. Trabzon is the province where the most landslides occurred in the country. Landslide susceptibility maps should be prepared in order to predetermine the areas with high landslide susceptibility in order to minimize the losses due to landslides. In this study, landslide susceptibility analysis is performed, and landslide susceptibility maps are produced to reveal the areas with high landslide susceptibility within the boundaries of Akçaabat and Düzköy districts of Trabzon province using Analytical Hierarchy Process (AHP) and Frequency Ratio (FR) methods. ArcGIS for Desktop, one of the Geographic Information Systems (GIS) platforms, is used for landslide susceptibility analysis. Geographical data are obtained from public institutions and open access online sources. The data are spatially organized according to the study area and purpose by various GIS tools. A total of 13 criteria which are respectively; slope, curvature, lithology, precipitation, aspect, topographic wetness index (TWI), distance to rivers, distance to highways, distance to fault lines, land use, soil type, elevation and normalized difference vegetation index (NDVI) for landslide susceptibility are evaluated as effective to cause landslides as a result of the literature review. Pairwise comparisons are made to determine the importance of the effects of each criterion on landslide formation and the weights between the criteria by using the AHP method. Then a landslide susceptibility map is produced according to the AHP method. In addition, a landslide susceptibility map was produced according to the FR method using the landslide inventory records obtained from responsible institutes of the country. It is noticed that the FR method produced more realistic results than the AHP method in terms of determining the locations of the landslides observed in the study area when the maps produced by both methods are compared.

58-70

Authors: Ahu KÖMEÇ MUTLU; Ülgen MERT TUĞSAL; Musavver CAMBAZ

The earthquake (Mw 6.9) that occurred in the northern part of Samos Island and Doğanbey-İzmir offshore in the Aegean Sea at 14:51 local time on October 30, 2020 was felt in İzmir, Samos Island and many surrounding cities and settlements. Considering the earthquake intensity map, contrary to what is expected, the highest impact occurred in Bayraklı district, which is 70 km away from the epicenter, and caused not only severe structural damage but also fatalities in the region. When the structural damages are evaluated, determining the local soil properties has an important place in the studies to predict the effects of a possible earthquake. The HVSR (Horizontal Vertical Spectral Ratio) method provides an advantage in determining the soil fundamental frequency and the soil amplification factor in the event of an earthquake, in that it can be widely used even in the seismically in-active regions. In this study, it is not only aimed to analyze the earthquake and ambient noise data obtained from the accelerometer and velocity stations but also to compare the results obtained by using HVSR method utilizing different softwares. Furthermore, response spectra were obtained for different local soil classes by using the data of the same stations and they are given in comparison with the design spectra included in the earthquake code. As a result of the study, it has been observed that the results obtained by the HVSR method are in good correlation with the soil effects in the region and the consequential structural damages. These examples illustrate HVSRpy’s commitment to exactly reproduce the results of GEOPSY, wherever the processing parameters and functionality of HVSRpy and GEOPSY overlap. This was done to allow users to check HVSRpy and to encourage standardization in HVSR processing.

81-89

Authors: Şerife Pınar GÜVEL; Mehmet Ali AKGÜL; Mehveş Feyza AKKOYUNLU

The mass movement towards stream beds and their accumulation there may cause flood events as a result of landslide events. In this study, Devrek Landslide, which occurred in 2015, was investigated by using a remote sensing technique. The Çomaklar stream is located at the lower elevations of this landslide region. Çomaklar stream and surrounding settlements are at risk of flooding due to the probability of preventing the water flow in the stream because of the effects of the landslide. Devrek district is located in Zonguldak in the northern part of Turkey. LANDSAT-8 satellite images between the dates 27 January 2015 and 22 July 2015 were used to investigate the location and size of the Devrek district landslide. Satellite-derived remote sensing data have been widely used in recent years to monitor changes on the earth's surface and to provide information. In this study, the Spectral Angle Difference method was used to compare the images before and after the landslide event. A change detection analysis was conducted between pre-landslide and post-landslide images to investigate the area affected by the disaster. As a result, the landslide was determined as 1050 meters in length and 110 meters in width, and the landslide area was calculated as 10.87 ha.

101-111

Authors: Bülent TURGUT

Wetlands are invaluable ecosystems as they provide important services, but these areas are rapidly degrading due to anthropogenic pressures and natural changes/transformations. It is thought that this negative change will increase in the upcoming period due to the climate change and the rising demand for soil and water. Determining the changes in wetlands is very important in terms of management planning of these areas. NDWI (Normalized Difference Water Index) is a widely used method for determining the hydrological characteristics of wetlands. This study was carried out to determine the temporal variability of wetlands in the Batumi Delta and the relationship of this change with basic climate parameters such as average temperature and total precipitation. For this purpose, the average temperature and total precipitation amount of the months of April, May, June, July, August, and September in the period between 2016-2021 of the study area and the NDWI values of these time periods were determined. Green and NIR bands of Sentinel2 satellite images were used to determine NDWI values. QGIS software was used to process satellite images, and ArcGIS software was used to determine and map NDWI values. As a result of the study, it was seen that NDWI values changed by months and years, and the temperature was more effective than precipitation on this change.

125-135

Authors: Betül METE; Sinan NACAR; Adem BAYRAM; Osman Tuğrul BAKİ

In this study considering total suspended solids (TSS) parameter monitored in a stream watershed, the predictability of upstream values from downstream data was investigated using regression analysis, which were applied to linear, power, exponential, and quadratic functions, and artificial neural networks (ANNs) method. The data were obtained within the scope of sampling studies carried out 40 times between June 2019 and March 2020 at eight monitoring stations selected in the Sera Stream Watershed (Trabzon). The monitoring stations were divided into two groups as upstream, the first four, and downstream, the last four, stations. Half of downstream data (two stations) was used for training, a quarter (one station) for validation, and the rest (one station) for testing. Two models with different combinations of independent variables were established. In the first model (M1), only the TSS values, and in the other model (M2), the month and week information of the sampling dates were digitized and used as independent variables, in addition to the TSS values. Root mean square error, mean absolute error, and Nash-Sutcliffe (NS) efficiency coefficient statistics were used to evaluate the model and method performances. Compared to other functions, the power one had the best estimation results in the regression analysis. On the other hand, the ANNs method gave better results than the regression analysis. In both methods, M2 performed better overall. In the ANNs method, the NS efficiency coefficients obtained from M1 and M2 were calculated as 0.980 and 0.997, respectively, for the training, and 0.978 and 0.978, respectively, for the testing data sets. Considering the efficiency values, it has been understood that the use of date information as an independent variable will positively affect the model performance in the stream TSS modeling studies. Within the scope of this study, it has been concluded that upstream TSS values can be successfully estimated from downstream TSS data in stream watersheds.

152-167

Authors: Onur AKSOY; Elif ALTAŞ; Kamil ERKEN

There are many possible impacts of global climate change such as loss of vegetation in urban and rural areas, deterioration in agricultural patterns, heat island effects. One of these effects is floods due to the deterioration of the precipitation regime. Floods threaten ecosystems and human life in urban and rural areas in many ways. In this context, many methods have been developed in the last century to combat flood risk. Landscape architecture discipline with the structural and vegetative measures it has taken also plays an active role in reducing the impact of the floods that will occur. With the ecological landscape design approach that came to the fore in the 20th century, the possible effects of flood can be decreased. This study covers the center of Kemer, which is the district of Antalya, and its nearby neighborhoods. Kemer district was selected as the study area because it faces with flood disasters at different times of the year. The study mainly consisted of 3 stages. In the first stage, literature research was made. In the area determined in line with the data examined in the second stage; the slope, aspect, land use, soil, precipitation and distance to stream maps were graded according to the multi-criteria decision making method on the Geographical Information Systems platform and then flood susceptibility analysis was performed in the ArcGIS environment. According to the results of the analysis, in a possible flood event, it was concluded that 893 ha of agricultural land and 2/3 of the residential areas in the study area will be affected by the flood. As a result of the study, ecological landscape design proposals have been developed in areas with high flood susceptibility. In case of suggestions are implemented, it is expected that besides economic and social benefits, ecological benefits will be gained as well as. The aim of this study is to develop ecological landscape design applications that are less costly and less harmful to the environment than structural engineering-based applications in areas where flood susceptibility is high. With the proposed ecological landscape design approaches, the water flow will be regulated with plant-based applications, while the groundwater will be fed by increasing open green areas and permeable areas.

181-190

Authors: Hakkı Oral ÖZHAN

Geosynthetic clay liner (GCL) can be used as a lining material in freshwater reservoirs due to its very low hydraulic conductivity. The high amount of water that can be collected on top of a GCL might force the bentonite in the GCL to be extruded out of the geotextiles and as a result, the sudden increase in the hydraulic conductivity might cause the GCL to loose its hydraulic capability. This interaction is defined as internal erosion. In this study, triaxial permeability tests were conducted on chitosan and Na carboxymethyl cellulose-added GCLs. These two biopolymers were added to the bentonite component of the GCLs with a content of 0.25, 0.5, 1, 2, 5 and 10% by dry weight respectively. Na and Ca bentonites were used in the GCLs and the GCLs that were placed over a rounded coarse gravel with a grain size of 37.5 mm, were tested at high hydraulic heads in order to observe internal erosion. This condition represents one of the worst-case scenarios. Test results indicated that all of the GCLs experienced internal erosion at a hydraulic head of 10 m. Furthermore, the permittivity values of the GCLs just before internal erosion, were measured and the effects of the biopolymers on the GCL’s hydraulic performance were investigated. According to the test results, 1% chitosan and 2% Na carboxymethyl cellulose addition to the bentonite component of the GCLs resulted in more than 2 orders of magnitude decrease in permittivity. Due to the results of this study, the usage of two different biopolymers that are environmentally friendly organic additives can be encouraged to be used as barriers in geoenvironmental application by decreasing the hydraulic conductivity of the lining material.