51 research outputs found
Pleistocene and Holocene fluvial development of the Ecemis Valley (Central Anatolia, Turkey)
No full textMeeting on Quaternary Studies in the Italian Southern Alps -- SEP 11-15, 2006 -- Milan, ITALYThe Ecemis River developed during the Pleistocene and Holocene in the Ecemis basin. The basin developed because of tectonic movement on the Ecemis Fault, which is west of the Aladag Mountains. In the Pleistocene, glacial-interglacial climate changes directly affected the regimes and discharges of rivers, causing changes in river levels along the Ecemis channel. Fluvial formations became extremely complicated when active tectonic movements accompanied the changes resulting from the climatic conditions. The rivers embedded in their beds according to new local base levels in interglacials. Terraces formed due to interruptions in the cycle of morphological development along the Ecemis River. From the morphologic structure of these terraces and their positions in the Ecemis Valley two groups and five levels of terraces were defined. In the Ecemis Valley, modern terraces (1-5 m) formed in the Holocene, while low terrace systems (5-10 m and 15-20 m) and high terrace systems (30-40 and 70-80 m) formed in the Pleistocene. (C) 2008 Elsevier Ltd and INQUA. All rights reserved
Evaluation of Drainage in the Upper Catchment of the Yesilirmak River Basin Along the Alm us Fault, Northern Turkey
No full textThe Yesilirmak River Basin is located in the North Anatolian Fault Zone (NAFZ) which is one of the fault zones with intense seismic activity in Turkey. The Almus Fault is a segment of the North Anatolian Fault (NAF). This study aims to reveal the effect of the Almus Fault on the drainage development and morphotectonic evolution of the upper catchment of the Yesilirmak River Basin and the relative tectonic activity of the fault. Morphometric indices such as, stream length gradient index (SL), mountain front sinuosity (Smf) and fan entrenchment (E) indicate that the downward of the sub-basins is tectonically more active than the upward which is ascribed to the tectonic activities along the Almus Fault. The Smf value is 1.4 at the west and decreases to 1.1 at the mouth of the sub-basins on the east. This indicates that the tectonic activity along the Almus fault in the study area increases from west to east and the uplift rate in the northern part is higher than the southern part of the study area. Development of the drainage network started during Pliocene due to differential uplift and a humid climate then developed under tectonic forcing during Quaternary.[SOB 2013/01-BAGEP]This study forms part of the project SOB 2013/01-BAGEP
Response of hydrological drought to meteorological drought in the eastern Mediterranean Basin of Turkey
No full textThe hydrographic eastern Mediterranean Basin of Turkey is a drought sensitive area. The basin is an important agricultural area and it is necessary to determine the extent of extreme regional climatic changes as they occur in this basin. Pearson's correlation coefficient was used to show the correlation between standardized precipitation index (SPI) and standardized streamflow index (SSI) values on different time scales. Data from five meteorological stations and seven stream gauging stations in four sub-basins of the eastern Mediterranean Basin were analyzed over the period from 1967 to 2017. The correlation between SSI and SPI indicated that in response to meteorological drought, hydrological drought experiences a one-year delay then occurs in the following year. This is more evident at all stations from the mid-1990s. The main factor causing hydrological drought is prolonged low precipitation or the presence of a particularly dry year. Results showed that over a long period (12 months), hydrological drought is longer and more severe in the upper part than the lower part of the sub-basins. According to SPI-12 values, an uninterrupted drought period is observed from 2002-2003 to 2008-2009. Results indicated that among the drought events, moderate drought is the most common on all timescales in all sub-basins during the past 51 years. Long-term dry periods with moderate and severe droughts are observed for up to 10 years or more since the late 1990s, especially in the upper part of the sub-basins. As precipitation increases in late autumn and early winter, the stream flow also increases and thus the highest and most positive correlation values (0.26-0.54) are found in January. Correlation values (ranging between -0.11 and -0.01) are weaker and negative in summer and autumn due to low rainfall. This is more evident at all stations in September. The relation between hydrological and meteorological droughts is more evident, with the correlation values above 0.50 on longer timescales (12- and 24-months). The results presented in this study allow an understanding of the characteristics of drought events and are instructive for overcoming drought. This will facilitate the development of strategies for the appropriate management of water resources in the eastern Mediterranean Basin, which has a high agricultural potential
Trends and changes in tropical and summer days at the Adana Sub-Region of the Mediterranean Region, Southern Turkey
No full textIn this study, the long-term variability and trends of the annual and seasonal numbers of summer and tropical days of the Adana Sub-region were investigated using nonlinear and linear trend detection tests for the period 1960-2014 at 14 meteorological stations. The results suggest that the annual number of summer and tropical days was generally below the long-term average through to the end of the 1980s. In particular, positive anomaly values could be observed at all stations between the years 1993-2014. With respect to the Kruskal-Wallis homogeneity test, the significant breaking date was 1993. The rapid rise of the annual number of summer (tropical) days after this year led to the inversion of the negative trends observed from 1987 to 1992 into positive ones. The increasing trend is statistically significance at 0.01 level in Yumurtalik, Mersin and Antalya for the annual number of summer and tropical days. Dortyol, Iskenderun and Elbistan were significance at 0.01 level for tropical days. The largest positive anomalies of the summer of 2010 are observed in coastal vicinity (Mersin, Yumurtalik and Iskenderun). This indicates that these settlements underwent a long-term warm period and thermal conditions due to increasing temperatures in the spring and summer months. The same conditions are found in high inner areas (Goksun and Elbistan) for tropical days. It is noticed that a tendency for greater warming occurred at stations located above 1000 m in the sub-region. The average number of warm days will increase 2-days per 100-years in southern part of the sub-region. The increasing trend in summer temperatures can be considered a potential risk, notably for human health and for economic and crop losses in the Adana Sub-region, including cukurova, one of the most important agriculture areas of Turkey
Changes and trends in total yearly precipitation of the Antalya district, Turkey
No full textIn this study, long term changes and trends in the annual rainfall of the Antalya Part, which is the region located in the western Mediterranean coast of Turkey containing many agricultural areas in its surrounding, were analysed. The aim of this study was to analyse the long term changes and trends in rainfall totals and present spatial distributions of annual and seasonal rainfall variability over the part. Rainfall data from 7 meteorological stations (Antalya, Alanya, Manavgat, Gazipasa, Finike, Korkuteli and Elmali) covering the years 1970-2011 were used in this study. Prepared rainfall variation maps clearly show that the highest annual variation is Antalya, while the lowest variation is Manavgat. According to the results obtained in trend analysis, in general, while a decreasing trend in winter rainfall is apparent, there is an apparent increasing trend in autumn rainfall. These results show a shift in seasons causing long-term droughts and potential infertile land to emerge. At some stations in the vicinity, there has been a prominent change from humid conditions to semi-arid conditions from beginning of 2000s. This study is expected to contribute to better understanding the effects of global climate change over precipitation in Antalya vicinity. (C) 2013 The Authors. Published by Elsevier Ltd
The Flood Risk of the Yeşilırmak Basin (upper course), Turkey
No full textAbstractThis paper presents the flood potential of the sub-basins, which are located in upper course of the Yeşilırmak River, Tokat Province. This potential was determined by analysing shape indices which have been used for several decades to describe the characteristics and hydrological properties of drainage basins. These indices are Form Factor, Basin Elongation, compactness, circularity Ratio, Lemniscate ratio and shape index. Drainage networks for sub-basins were prepared with a topographic map scaled 1/25000 and 10-m resolution DEM using GIS. The study area was divided into six sub-basins. The shape indices show that six sub-basins have an elongated shape causing low-magnitude peak flood. In spite of a moderate amount of rainfall and elongated shapes, the main problem of this area is that it has been subjected to flood since 1950. The results indicate that the steep slopes, impermeable lithology and thick vegetation accelerate the flow of rainfall. In other words, flood events are also formed in an elongated basin. This result will help in better understanding relationships between the flood events and basin shape for basin area planning and management
Geomorphic Signatures of Active Tectonic in Drainage Basins in the Southern Bolkar Mountain, Turkey
No full textBolkar Mountain forms the northeast extent of the Central Taurus Mountains, which are located north of the eastern Mediterranean Sea and consist of 3000 m or higher summits. The study area southern part of Bolkar Mt, has been investigated for geomorphic signatures of active tectonics using Geographical information system (GIS). The lower valley floor-to-width to height and elongation ratios, higher convexity, stream length-gradient (SL) indices, hypsometric integral and convex nature of the hypsometric curves and topographic asymmetry show that relative tectonic activity is greater in the eastern sector affected by Ecemis fault. Spatial variations of tectonic activity along rivers studied point to a general trend of decreasing activity towards the west as well as tectonic activity again increase in the west. Westward migration of basin and range extension is consistent with the place of uplift in the southern Bolkar Mt. Topography of the southern sector is the result of Late Miocene-Early Pliocene extension related uplift. Drainage systems in the upper part of the central and western sectors are under the lithological control and karstic denudation; whereas the development of the drainage systems in the middle and outlet parts of all sectors depend on sea level changes and Late Quaternary tectonism. The development of drainage systems of the eastern sector depends mostly on fault tectonism and climatic changes in the Late Quaternary
Characteristics and age of an uplift signal in the Biga Peninsula (NW Turkey) from a mix of geomorphic indices
No full textSituated in the area where the western end of the North Anatolian Fault Zone meets the extensional domain of
the North Aegean Sea, the Kazdag Mountain range (Biga Peninsula, NW Turkey) is known to have undergone
Plio-Quaternary uplift. However, no detailed chronology of this presumably ongoing uplift phase was so far
available. In order to obtain a first-order estimate of the time of the last tectonic perturbation (uplift rate change) in
the region, we performed a morphometric study of the fluvial landscape at the scale of the Biga Peninsula, coupling
the recently developed R/SR analysis of the drainage network with concavity and steepness measures of a set of
29 rivers of all sizes. Defined as the ratio of two-by-two differences between hypsometric integrals describing
respectively a catchment’s topography, its drainage network "composite profile" and the trunk stream profile, the
R metric is a measure of the catchment’s incision response to a relative base level lowering. The SR index is then
simply the slope of the regional relation R = f(ln A), a feature characteristic of the time elapsed since uplift caused
an erosion wave to propagate in the drainage system. We obtained a SR value of 0.324±0.035 that, according to
the t = f(SR) relation established by Demoulin (2012), yields an age range of 0.54-1.29 Ma and a most probable
value of 0.82 Ma for the time of the last uplift signal in the Biga Peninsula. We also carried out an analysis of
knickpoint migration in a subset of rivers, modelling their propagation by the stream power law under different
assumed ages so as to compare the obtained values of the K coefficient with values mentioned in the literature. The
positive results of this analysis, yielding realistic K values for ages around 0.8 Ma, lend independent support to
our morphometric estimate of the uplift time, moreover corroborated by published observations suggesting basin
inversion of the Bayramiç and Çanakkale depressions at the same epoch. We relate this episode of increased uplift
rate to the early-to-mid Pleistocene tectonic transition identified in the Eastern Mediterranean realm by Schattner
(2010) and marked by a brief compressional episode. Finally, while the dependence of river profile concavity on
basin size confirms that the landscape of the peninsula is still in a transient state, the spatial distribution of profile
steepness values characterized by higher values for streams flowing down from the Kazdag massif shows that the
latter undergoes higher uplift rates than the rest of the peninsula. This indicates that, after the regional Middle
Pleistocene episode of accelerated uplift had come to an end, a local component of uplift persisted associated with
either transpressive conditions along SW-trending segments of the North Anatolian Shear Zone or normal faulting
along the southern border of the massif.
References
Demoulin A., 2012. Morphometric dating of the fluvial landscape response to a tectonic perturbation. Geoph. Res.
Lett. 39, L15402, doi:10.1029/2012GL052201.
Schattner U., 2010. What triggered the early-to-mid Pleistocene tectonic transition across the entire eastern
Mediterranean? Earth Planet. Sci. Lett. 289, 539-548
Determination of drought intensity in Seyhan and Ceyhan River Basins, Turkey, by hydrological drought analysis
No full textThis paper studied hydrological drought identified by the Streamflow Drought Index (SDI) at eight river-gauging stations in the Eastern Mediterranean part of Turkey for a roughly 43-year period covering from 1972 to 2014 (4 stations), from 1973 to 2015 (2 stations), and from 1969 to 2011 (2 stations). Results of SDI analyses indicate that the number of drought years was highest during the 3-month October-December period. A considerable part of the drought years was determined to be mild drought. Although moderate drought conditions were observed in all stations, moderate drought conditions were determined especially at Goksu-H in the Seyhan River Basin and Sogutlu and Savrun in the Ceyhan River Basin. Short-term fluctuations of dry and wet conditions are the dominant pattern for most of the stations; however, long-term persistent drought conditions are also prominent, especially at Tacin and Korkun in Seyhan Basin and Goksun in Ceyhan Basin. The starting point for the negative trend in the 12-month series was the years 1996, 1999, and 2000
CLIMATIC AND TECTONIC EFFECTS ON TERRACE FORMATION DURING THE LATE QUATERNARY IN THE UPPER YESILIRMAK VALLEY, NORTHERN TURKEY
No full textThis study was carried out in the upper course of the Yesilirmak River, which is one of the biggest rivers reaching the Black Sea, northern Turkey. We distinguished two fluvial terraces and dated them using OSL technique. T2 is the young terrace and situated at similar to 11 m above the actual river (at 620 m asl). T1 is the youngest and situated at similar to 5-6 m above the actual river (at 605 m asl). From the lower dated terrace (T1) was dated 6735 ka, 5277 ka and 4226 ka, respectively. From the higher dated terrace (T2) was dated 24,139 ka, 22,008 ka, 12,694 ka and 11,307 ka, respectively. While the higher terrace aggraded during three important cold periods (Heinrich 2 event (H2), the Last Glacial Maximum (LGM) and the Younger Dries (YD), the lower terrace (the present floodplain) aggraded during the Holocene Climatic Optimum (HCO). The river incised during transition from the LGM to Holocene transition and after the HCO. the Yesilirmak has incised its valley similar to 11 m during the last 24 ka. These results indicate an average incision rate of 1.25 mm/yr (1.25 m/ka).Omer Halisdemir University Scientific Research Project [SOB2013/01]This work is part of a project called the Relationship between Morphological Evolution of the Drainage System and Regional Tectonism in Yesilirmak Basin (Upper Course), which is supported by the Omer Halisdemir University Scientific Research Project (SOB2013/01). David Bridgland, Mustafa Karabiyikoglu and Anne E. Mather kindly read and commented on first instance (draft) of this paper. Therefore, we are also grateful them for their suggestions and help during revision of this paper
- …
