Regional Frequency Analysis of Maximum Daily Rainfalls Based on L-Moment Approach

Abstract

The main goal of the study is to perform regional frequency analysis of maximum daily rainfalls selected for each year among daily rainfalls measured over Tokat region by using L-moment approach. Initially, using Runs and Mann-Whitney statistics to detect whether the conditions of randomness and homogeneity were implemented were applied to the maximum daily rainfalls. Thereafter, the most suitable distribution among the selected various statistical distributions whose parameters were predicted via L-moment approach for four hydrologic homogeneous regions of Tokat region, which was divided into four hydrologic homogeneous region as West-W, Central North-CN, Central South-CS and East-E, was determined according to the mean absolute deviation index (MADI) and mean square deviation index (MSDI) measures. The results of MADI and MSDI showed that the most suitable statistical distributions were, generalized logistic (GLO) for W and CN, generalized pareto (GPA) for CS, and generalized extreme value type I (GEV) for E.

Keywords

• Maximum rainfall, hydrologic homogeneous region, L-moment

L-Moment Yaklaşımı ile Maksimum Günlük Yağmurların Bölgesel Frekans Analizi

Öz

Bu çalışmanın ana amacı, Tokat bölgesinde ölçülen günlük yağmurlar arasından her yıl için seçilen maksimum günlük yağmurların bölgesel frekans analizini yapmaktır. Öncelikle, rasgelelik ve homojenlik şartlarının yerine getirilip getirilmediğini saptamak için Runs ve Mann-Whitney istatistikleri maksimum günlük yağmurlara uygulandı. Daha sonra, Batı-W, Orta Kuzey-CN, Orta Güney-CS ve Doğu-E olarak dört hidrolojik homojen bölgeye ayrılan Tokat bölgesinin bu homojen yöreleri için parametreleri L-moment yöntemi ile tahmin edilen seçilmiş değişik dağılımlar arasından en uygun olanı, “the mean absolute deviation index (MADI) ve mean square deviation index (MSDI)” ölçütlerine göre belirlendi. MADI ve MSDI sonuçları, W ve CN için genelleşmiş logistic (GLO), CS için genelleşmiş pareto (GPA) ve E için genelleşmiş extreme value type I (GEV)’in en uygun olasılık dağılım olduklarını gösterdi.

Anahtar Kelimeler

• Maksimum yağmur, hidrolojik homojen bölge, L-moment

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