FORMING THE MAP OF LANDSLIDE SENSITIVITY OF KARLIOVA BASIN AND ITS SURROUNDING
Journal Name:
- Turkish Studies
Keywords (Original Language):
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Abstract (2. Language):
Karlıova Basin is a fault wedge basin which is begun to open in Quaternary between the North Anatolia (NAF) and East Anatolia Faultlines (EAF). The Basin is located among the high plateaus and surrounded by faultlines all around. Shaped by the NAF, EAF, and Varto Faultlines it gained important characteristics. The most important of these characteristics is the settlement of important tributaries, which drain the streams of basin, into the faultlines. The existence of vertical component in the faultlines that limits the basin provides the high values of slope. This state is clear on the hillsides of Göynük, Peri, and Hasanova Stream valleys that settles the faultlines. The lithology formed from tuff leads up to landslides on the hillsides of valleys in which the angle of slope is high. The important tectonic faultlines has intersected in the basin, the seismic activity is high in the area, and the basin and its surrounding comes first in our country in terms of the number of the earthquakes occurred. The main reasons for the prevalence of landslides is the highness of slope values depending on the tectonism and the admittance of lithology. The highness of precipitation and the frequent earthquakes plays an important role in generating the landslides. Landslides are seen clearly from the east, southeast, and southwest of the basin (along the linear faultline).
Affecting the settlements, transportation, agriculture and pasture lands, landslides lead to significant economic losses. The earthquakes, which occur frequently in tectonically active area, have enabled landslides to be seen continuously. We aim to determine the landslide sensitive areas in Karlıova Basin and its surrounding that is limited with important tectonic lines. In this study, by superposing the factors that causes landslides in terms of their degree of effect landslide sensitivity has been mapped for the Karlıova Basin and its surrounding and the factors that causes landslides have been determined.
In the preparation of landslide susceptibility maps, geological and topographical features, and environmental and climatic conditions are used. In this study slope, aspect, elevation, Normalized Difference Vegetation Index (NDVI), lithology, the distance parameters to the fault lines and river network have been used as the landslide susceptibility map being formed. With digitization of topographic maps of the study area, Digital Elevation Model (DEM) has been obtained, and from DEM slope, aspect, elevatıon map and from geological map, the distance maps to the lithology and fault lines, and from topographic maps the distance maps to river network have been obtained. The NDVI values have been obtained from an image taken by Landsat TM in September 2011. Susceptibility map has been formed by applying the weighted overlay method. This method has been applied using Spatial Analysis Module in ArcGIS 10.1 program. Utilizing field observations and landslide inventory map, landslide areas have been digitized and overlaying with other maps prepared for the landslide susceptibility, weights of the parameters have been determined. Combining the parameters whose weights have been specified, the susceptibility map has been formed. Susceptibility map has been classified as very low, low, medium, high and very high susceptibility.
According to the map created for Karlıova Basin and its environment the rate of high landslide sensitive areas is 41 % in the basin and its surrounding, the rate of most sensitive areas is 14 %, and more than the 50 % of an area within the study area the landslide sensitivity is high. Another remarkable point is the existence of high rate of population and settlements and the passing of main roads from these areas. According to the results of analysis, while the lithology and slope factors are determinants in the occurrence of landslides, earthquakes and rainfall play a triggering role. Depending on tectonic, the landslide susceptibility increases on the sides of valleys and plateaus where slope values are high and the lithology is formed with tuff and basalt. It is seen that the landslide susceptibility is high in the southwest and southeast of the basin. In these areas high susceptibility depends on high slope values and favorable lithology conditions. These high susceptibility areas also correspond to the sides of the fault valleys. It is seen that landslide susceptibility decreases in the north and south of the basin. Despite the high slope values in the north, lithology is not suitable for the formation of landslides. For this reason landslide susceptibility is low in the north. In the south of basin plateaus cover a wide area. In this area where lithology is formed with tuff, landslide is low in accordance with low slope values. When evaluated generally, the bases of plain and basin correspond to areas where susceptibility is very low and low, and the sides of valley and plateau to areas where susceptibility is very high and high. Göynük Valley, through which East Anatolian Fault passes and Kargapazarı Basin, on which North Anatolian Fault is effective correspond to the area with highest density of population in Karlıova Basin. This area has favorable conditions for landslide events which may occur after an earthquake. There are rocks with clay and marl on the sides with steep slopes in a large part of Göynük Valley. The material on these sides has the feature to be able to create landslide by exceeding the limits of plasticity and liquidity along with the shake occured during earthquake. Thus, landslides triggered by earthquakes could lead to serious problems. Because of landslides there were a great deal of economic losses. More important, owing to the tectonic activity the lanslides go on to occur every year.
In Karlıova Basin and surrounding areas it is seen that the landslide susceptibility is high and these areas are relatively densely populated. Landslides causing the relocation of settlements and highway are seen in the basin and its surroundings. Landslides cause damage to drinking water supply network, agricultural and pasture lands. To reduce the economic losses because of the landslides in the basin the landslide sensitive zones should not be populated, and the existing settlements should be evacuated.
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Abstract (Original Language):
Bu çalışmada önemli tektonik hatlarla sınırlandırılan Karlıova Havzası ve çevresinde heyelana duyarlı alanların belirlenmesi amaçlanmıştır. Çalışmada heyelana neden olan faktörler etki derecelerine göre çakıştırılarak havza ve çevresi için heyelan duyarlılık haritası oluşturulmuş, heyelana neden olan faktörler belirlenmiştir. Karlıova Havzası, Kuzey Anadolu Fayı (KAF) ile Doğu Anadolu Fayı (DAF) arasında Kuvaterner’de açılmaya başlamış fay kaması (fault-wedge basin) havzasıdır. Havza yüksek düzlükler arasında yer almakta olup, dört yandan faylarla çevrilidir. Havzanın KAF, DAF ve Varto Fayı tarafından şekillenmesi önemli özellikler kazanmasını sağlamıştır. Bu özelliklerinin başında havzanın sularını drene eden önemli akarsuların fay hatlarına yerleşmiş olması gelmektedir. Havzayı sınırlandıran fayların düşey bileşeninin de olması eğim değerlerinin yüksek olmasını sağlamıştır. Bu durum fay hatlarına yerleşen Göynük Çayı, Peri Suyu ve Hasanova Çayı Vadileri’nin yamaçlarında belirgindir. Eğim değeri yüksek olan vadi yamaçlarında litolojinin tüflerden oluşması heyelanlara zemin hazırlamaktadır. Önemli tektonik hatlarının kesiştiği havzada sismik etkinlik yüksek olup, meydana gelen deprem sayısında havza ve çevresi ülkemizde ilk sırada yer almaktadır. Havzada heyelanların yaygın olarak görülmesinin ana nedenleri tektonizmaya bağlı olarak eğim değerlerinin yüksek olması ve litolojinin elverişli olmasıdır. Yörenin yağış miktarının fazla olması ve sık yaşanan depremler heyelanları tetikleyici bir rol oynamaktadır. Heyelanlar havzanın doğu ve güneydoğusu (çizgisel uzanımlı fay hattı boyunca) ile güneybatısında belirgin olarak görülmektedir. Havza ve çevresinde heyelana yüksek duyarlı sahaların oranı % 41, en yüksek derecede duyarlı olan sahaların oranı % 14 olup, çalışma alanının % 50’sinden fazla bir alanda heyelan duyarlılığı yüksektir. Dikkat çeken başka bir durum da heyelan duyarlılığı yüksek olan sahalarda aynı zamanda nüfus yoğunluğunun ve yerleşmelerin fazla oluşu, ana ulaşım hatlarının bu sahalardan geçirilmesidir. Heyelanlar nedeniyle önemli ekonomik kayıplar yaşanmaktadır. Daha önemlisi tektonik aktivite nedeniyle heyelan olaylarının her yıl devam etmesidir. Havzada heyelanlar nedeniyle doğabilecek ekonomik kayıpları azaltmak amacıyla heyelan duyarlılığı yüksek olan sahalar nüfuslanmamalı, var olan yerleşmeler tahliye edilmelidir.
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