Kahramanmaraş Şehri Sel ve Taşkınlarının Coğrafi Analizi ve Öngörüler
Bu çalışmada Kahramanmaraş’ta yaşanan sel ve taşkın olaylarının coğrafi analizlerinin yapılması ve geleceğe yönelik öngörülerde bulunulması amaçlanmıştır. Araştırma kapsamında; yüzey analizleri, hidrolojik ve morfometrik analizler, arazi kullanımındaki zamana bağlı değişimin izlenmesi çalışmaları yapılmıştır. Bu çalışmalar; MapInfo Professional 11.0 yazılımı ve 1/25000 ölçekli topografya haritalarından üretilen veritabanı kullanılarak yapılmıştır. Ayrıca günlük sıcaklık ve yağış rasatlarına dayalı Thornthwaite su bilançosu, yağış tipi ve yağışın mevsimsel değişimi, sıcaklık değişim özellikleri ve iklim analiz sonuçlarının lineer regresyon analizleri, regresyon denklemi ve r2 değerlerine dayalı yağış ve sıcaklık öngörüleri bu araştırma kapsamında gerçekleştirilen diğer analizlerdir. Morfometrik analiz sonuçlarına göre akarsu havzalarının sel ve taşkın duyarlılıklarına bakıldığında; Akdere ve Erkenez Çayı havzalarında yüksek risk, Karaçay, Cancığın Dere, Kerhan Çayı havzalarında orta seviyede risk ve İğdeliöz, Ağcalıdere ve Boğazdere havzalarında ise riskin daha düşük olduğu görülmüştür. Şehrin kuzey yönde gelişmesiyle, kuzeydeki geçirimliliği yüksek ve eğimli sahaların geçirimlilik özellikleri büyük oranda zayıflatılmıştır. Bu durum; şehir merkezi istikametindeki yüzeysel akışın hızının ve miktarının artmasının, şehir merkezinde yaşanan sellerin afete dönüşmesinin, afetlerin sıklık ve şiddet özelliklerinin artmasının önemli nedeni olarak görünmektedir.
Flashflood and Flood Geographical Analysis and Foresight in Kahramanmaraş City
In this study, our aim was to employ a geographical analysis of flood and flash flood events in Kahramanmaraş and make predictions for the future. Within the scope of the research; surface analyses, hydrological and morphometric analyses, and monitoring of time-based change studies in land use were conducted. A database was created by using MapInfo Professional 11.0 software and 1/25000 scale topography maps. Also, Thornthwaite water balance, rainfall types and its seasonal change, temperature change characteristics and linear regression analyses of climate analysis results, regression equation and rainfall and temperature predictions based on r2 values were other analyses carried out within the scope of this research. According to the results of the morphometric analysis, looking at the flood and flash flood sensitivity of the stream basins, high risk in Akdere, Erkenez Stream Basins, moderate risk in Karaçay, Cancığın, Kerhan Stream Basins and lower risk in the Basins of İğdeliöz, Ağcalıdere, Boğazdere were observed. An increase in impermeable grounds due to urbanization can encourage flood disasters by increasing the speed and amount of surface flow in the direction of the city center.
Kahramanmaraş city center is located between Ahır Mountain in the north (an extension of the Eastern Taurus), and the Kahramanmaraş Plain in the south. In the north of the city, Mount Ahır rises to 2000 meters, while in the south the altitude on the plain area drops to 430 meters. The geomorphology on which the city is located consists of hillside plots in the north and plains located in the south. This area is drained by the Akdere, Keklikdere, Cephanelik Cancığın, İğdeliöz ,Ağcalı, Boğazdere, Karaçay, Erkenez and Kerhan Streams, which take their sources from the high parts of Ahır Mountain. These drainage canals, which have roughly semi-parallel patterns, pass from high slopes to the plain with a slope fracture and merge into the Aksu River. The geomorphological, hydrographic, climatological, soil, and vegetation characteristics and methods of benefiting from the land and interventions in natural systems via projects have all caused floods and flash floods, which have turned into disasters with an increase in frequency and effect in Kahramanmaraş city. In this study, our aim was to conduct a geographical analysis of flood and flash flood disasters occurring in Kahramanmaraş city center, and to have foresights for the future. Within the scope of the research, MapInfo Professional 11.0, one of the software of Geographic Information Systems (GIS), was used for mapping, altitude, slope, and hydrological and morphometric analyses. Also, studies have been carried out to monitor the time-dependent change in land use. Additionally, Thornthwaite water balance, based on the climate data that belongs to Kahramanmaraş Meteorology Station’s daily temperature and rainfall observations provided by the General Directorate of Meteorology, seasonal change of rainfall type, temperature change characteristics and linear regression analyses of the climate analysis’ results were performed. Rainfall and temperature predictions were employed using the regression equation and r2 values. The oldest official registration for a flood and flash flood that caused the loss of life in the city center dates back to 1972. On April 15, 1972, a total of 31.3 mm of rainfall fell, and after 50 minutes of severe rainfall, a mass of water that was 5-6 meters high and 50-60 meters in width, occurred in the Akdere basin and caused a major flood disaster in the region. After this event, 5 people died in the village of Dereli, which is located in the Akdere Valley, 27 houses were filled with deposits and 80 small animals were destroyed by floodwaters. In the following years, there have been many floods and flash floods in the city center, where property damage occurred. The most recent flood occurred in 2018. On June 13, 2018, rainfall, measured at 17.8mm by the meteorological station in the city center, caused a serious flood. As a result of the flood, 3 people died and in some places, it damaged many homes, businesses and vehicles in the city center and in some places, the infrastructure of the city was also badly damaged. The maximum amount of rainfall per day was measured for the highest 100 units between 1959 and 2018. When looking at the distribution of the daily maximum rainfall numbers by months, it was observed that rainfall decreased mostly in December, January, February and November, respectively. It was observed that the amount of maximum daily rainfall was in December with 98.2 mm, in February with 94.2 mm, and in November with 72.0 mm. It was noted that 30 of the top 100 maximum rainfall events which were measured in this period, decreased in the period after 2000. It can be said that this condition indicates a change in the city’s rainfall regime. According to the results of morphometric analysis of the stream basins, the “highest risk” was seen in the Akdere and Erkenez Stream Basins when looking at flood and flashflood sensitivities. Both of the floods that caused the loss of life in the city center in 1972 and 2018, occurred within the borders of the Akdere Basin. The Karaçay, Cancığın, and Kerhan Stream Basins have a “moderate risk”, while in the Basins of İğdeliöz, Ağcalıdere and Boğazdere, a “low level of risk” was observed. With the development of the city in the north direction, the high and sloped areas of the city have been concreted. This causes an increase in the speed and quantity of water that are switched to the superficial flow towards the city center as a result of the rains. The role of urbanization in the north is significant in the occurrence of the flood in the city center. That is why the natural areas in the north of the city should be protected and the development of the city in a northerly direction should be prevented.
