Evaluation of The Geographical Factors in the Formation of Flashflood and Flood in Erzin Ilicalar (Hatay) On September 25, 2014
Ergin Canpolat, Yücel Dinç, Çetin Furkan Usun, Reşat GeçenThis study investigates the flood disaster that occurred on September 25, 2014 in Ilıcalar, located in the borders of Başlamış, a neighborhood of Erzin district. This study aims to reveal the geomorphological, climatological-hydrographic, and anthropological factors that are effective in the Ilıcalar flood occurrence. It also aims to illustrate the adverse effects of inefficient land use and develop solutions for potential flood disasters. Thus, the relationship between lithological units and flood disaster has been investigated. A hypsometric curve graph has been created using the field’s elevation values, and the Hysplit model of NOAA has been used to explain weather events. Schreiber’s monthly precipitation calculation formula has been used, and precipitation interpolation has been created to evaluate the situation of precipitation throughout the basin. Within the scope of hydrological analysis, stream densities have been calculated, and Normalized Difference Vegetation Index analysis has been applied to evaluate the relationship between vegetation and flood disaster changes. Besides, semi-structured interviews have been applied to the disaster victims, and the effects of the flood disaster have been revealed. In addition to the heavy rain that lasted for 4–5 hours in Erzin on September 25, 2014, the field’s high slope values caused the water to divert to the valley in a short time. The valley, which is very narrow at the point close to Erzin, is filled with rubble, tree trunk, and branches created a natural embankment there, creating a pond. The pressure of the accumulated water destroyed this embankment. Thus, the structures built on the streambed were submerged, five people lost their lives, 14 residences, and 42 workplaces were adversely affected by the disaster. These negative results of the flood showed that the geographical conditions should be analyzed well to select the settlements’ establishment places.
25.09.2014 Tarihinde Erzin Ilıcalarda (Hatay) Meydana Gelen Sel ve Taşkının Oluşumunda Coğrafi Faktörlerin Değerlendirilmesi
Ergin Canpolat, Yücel Dinç, Çetin Furkan Usun, Reşat GeçenBu çalışmada, Erzin İlçesi Başlamış Mahallesi sınırları içerisindeki Ilıcalar mevkiinde 25.09.2014 tarihinde meydana gelen sel felaketi incelenmiştir. Çalışmanın amacı; Ilıcalar selinin meydana gelmesinde etkili olan jeomorfolojik, klimatolojik-hidrografik, antropojenik faktörleri ortaya koymak, yanlış arazi kullanımının neden olduğu olumsuz etkileri açıklamak ve yaşanabilecek sel felaketlerine karşı çözüm önerileri geliştirmektir. Bu amaca yönelik olarak, litolojik birimler ile sel felaketi arasındaki ilişki incelenmiş, sahanın yükselti değerlerinden hareketle hipsometrik eğri grafiği oluşturulmuş, hava olaylarını açıklayabilmek için meteorolojik veriler ile NOAA’nın Hysplit modeli kullanılmıştır. Yağışın havza genelindeki durumunu değerlendirebilmek için Schreiber’in aylık yağış hesaplama formülünden yararlanılmış, yağış enterpolasyonu oluşturulmuştur. Hidrolojik analizler kapsamında akarsu yoğunluğu hesaplanmış, bitki örtüsündeki değişimlerin sel felaketi ile olan ilişkilerini değerlendirmek için NDVI analizi uygulanmıştır. Ayrıca, afetzedelere yarı yapılandırılmış görüşmeler uygulanarak sel felaketinin etkileri ortaya konulmuştur. 25.09.2014 tarihinde Erzin’de 4-5 saat süren şiddetli yağışa ek olarak, sahadaki eğimin fazla olması, suyun kısa sürede vadiye yönelmesine neden olmuştur. Ilıcalara yakın noktada oldukça daralan vadinin, moloz, ağaç gövde ve dalları ile dolması, burada doğal bir set oluşturarak göllenme meydana getirmiştir. Biriken suyun basıncı ile bu set yıkılmış, dere yatağında inşa edilmiş yapılar su altında kalmış, 5 kişi hayatını kaybetmiş, 14 konut ve 42 işyeri afetten olumsuz etkilenmiştir. Su baskınının bu olumsuz sonuçları, yerleşmelerin kuruluş yeri seçimlerinde coğrafi şartların iyi bir şekilde analiz edilmesi gerektiğini göstermiştir.
This study investigates the flood disaster that occurred due to the sudden flooding on September 25, 2014 in the Ilıcalar, located in the Başlamış neighborhood of Erzin district of Hatay. The study’s primary purpose is to reveal the geomorphological, climatologicalhydrographic, and anthropological factors that caused the flooding of Ilıcalar and explain the adverse effects of inefficient land use. It also aims to determine the problems arising from the fact that the structure of the place and its geographical conditions are not considered in selecting the settlements’ location with the example of Ilıcalar.
In this study, a 1/100.000 scale geology map has been obtained from the General Directorate of Mineral Research and Exploration to explain the research area’s lithological and tectonic features. The research area’s geomorphological features have been explained with a 1/25.000 scale topography map obtained from the General Directorate of Map. Besides, ALOS PALSAR DEM (Digital Elevation Model) with 12.5 m resolution has been used to show the topography in more detail. These data have been converted to point elevation data (Raster to Point); thus, the pixel-based cumulative percentage of the field’s elevation values, i.e., the hypsometric curve graph, has been produced.
Annual, daily, and hourly precipitation data provided by the General Directorate of Meteorology have been used to reveal the climatic features. In addition, NOAA National Oceanic and Atmospheric Department) HYSPLIT (The Hybrid Single Particle Langrangian Integrated Trajectory Model) model has been used. Schreiber’s monthly precipitation calculation formula has also been used to calculate the situation of heavy rain. It started in the evening hours on September 24, 2014 and continued until the first hours of the morning on September 25, 2014, throughout the basin. For this process, using DEM data, a total of 9.939-point elevation data randomly selected within the research area’s boundaries have been produced. The Inverse Distance Weighting interpolation method has been applied to the data obtained from the Erzin-Yeşilkent meteorology station.
The stream data in the Gökgöldere (Sarıçay) basin have been obtained using the Hydrology plugin in the Spatial Analyst Tools module of ArcMap 10.5 software using ALOS PALSAR DEM data. The research area’s river density has been determined by using the total length data and basin area data of these streams. It has been revealed how anthropogenic factors triggered the flood disaster with the help of the observations made in the research area and the images taken with Unmanned Aerial Vehicles.
Since the forest cover had been heavily destroyed in the months/years before the flood disaster, it has been considered necessary to determine vegetation change over the years. The Normalized Difference Vegetation Index (NDVI) analysis has been applied for this purpose. Landsat 5 (August 15, 2005), Landsat 5(August 29, 2010) Landsat 8 (August 24, 2014) satellite images; Landsat 8 Band 5 (Near Infrared), and Band 4 (Red); Landsat 5 8 Band 4 (Near Infrared) and Band 3 (Red) data have been used for this index. NDVI is found by proportioning the difference and sum of near infrared and red bands. It significantly removes the different enlightenment characteristics and shadow effects caused by the sun and perspective (Sellers, 1985; Melesse ve Jordan, 2003; Holben ve Frasher, 1984; Schultz ve Engman, 2000; Sotomayor, 2002; Özdemir, 2007; Canpolat, 2014). At the last stage of this study, a semi-structured interview method has been conducted with the disaster witnesses to explain the effects of the flood disaster.
The following findings are obtained from this study: The amount of precipitation measured by General Directorate of Meteorology for Erzin on September 25, 2014 is 69.6 mm. In addition to the sudden and downpour precipitation that lasted for 4–5 hours, the high slope values increased the water’s mass heading toward the valley in a short time. The valley, which narrowed very close to the Ilıcalar, was filled with rubble, tree trunk, and branches dragged by the Sarı Çay. Then, a natural embankment was formed. As a result of the increase in precipitation, this set was destroyed with water pressure accumulated. Thus, the structures built in the stream bed were submerged. As a result of the flood, five people died, 14 residences and 42 workplaces have been adversely affected. These negative results of the flood revealed that the geographical conditions should be analyzed well in the settlements’ site selection.