The Best Fit Flood Probability Distribution for Alibeyköy Basin in İstanbul, Türkiye

Öz

Determination of peak flow rates is crucial in reducing the economic and social impact of flood. Therefore, the investigation of various methods for estimating flood is of paramount importance. Flood frequency analysis can be used as a practical method in predicting the peak flow values as the flood peaks have return periods that are typically much larger than the recording length. In this study, 7 different probability distributions (normal (N), two-parameter lognormal (LN2), three-parameter lognormal (LN3), extreme value type I (Gumbel), generalized extreme value (GEV), Pearson Type III (P3) and Log-Pearson Type III (LP3)) are employed for flood frequency analysis of Alibeyköy Watershed using 44-years of measured annual maximum flow. K-S and PPCC tests are applied to determine the most suitable distributions to estimate the flood flow rate. Based on these tests, GEV and Gumbel distributions appear to be the most preferable distributions in flood flow estimation.

Anahtar Kelimeler

• flood frequency analysis
• probability distribution
• return period
• peak flow

Alibeyköy Havzası İçin En Uygun Taşkın Olasılık Dağılımı

Öz

Taşkın debisinin belirlenmesi, taşkının ekonomik ve sosyal etkisinin azaltılmasında önemli bir rol oynar. Hem kırsal hem de kentleşmiş alanlardaki taşkın hasarı ülke ekonomisini önemli ölçüde etkilemektedir. Bu nedenle, taşkın tahmini için çeşitli hesaplama yöntemlerinin araştırılması büyük önem taşımaktadır. Taşkın frekansı analizi, genellikle ölçülenden çok daha büyük olan geri dönüş dönemlerine karşılık gelen ve bir olasılık eğrisinin üst kuyruğunda taşkın zirveleri göründüğünden, taşkın büyüklüklerinin tahmin edilmesinde pratik bir yöntem olarak kullanılabilir. Bu analiz, özellikle akış verisi olmayan nehirler için çok önemlidir. Bu çalışmada 7 farklı olasılık dağılımı (normal (N), iki parametreli lognormal (LN2), üç parametreli lognormal (LN3), uç değer tip I (Gumbel), genelleştirilmiş uç değer (GEV), Pearson Tip III (P3 ) ve hidrolojik frekans analizinde yaygın olarak kullanılan Log-Pearson Tip III (LP3)), Alibeyköy Havzası taşkın frekans analizinde kullanılmıştır. Her bir olasılık dağılımı, Alibeyköy Havzası'ndaki bir ölçüm istasyonunda ölçülen yıllık maksimum akışlar kullanılarak geliştirilmiştir. Olasılık dağılımını elde etmek için 44 yıllık maksimum akış verileri kullanılmıştır. Daha sonra bu dağılımlar, T-yıllık taşkın tekrarlama aralıklarının (50, 100, 200 ve 500 yıl) tahmin edilmesinde kullanılmıştır. Son olarak, taşkın akış oranını tahmin etmek için en uygun dağılımları belirlemek için K-S ve PPCC uygunluk testleri yapılmıştır. Bu testlerin değerlendirmesine göre GEV ve Gumbel dağılımları taşkın akış tahmininde en tercih edilebilir dağılımlar olarak görünmektedir.

Anahtar Kelimeler

• taşkın frekans analizi
• olasılık dağılımı
• dönüş periyodu
• taşkın debisi

Kaynakça

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