FLOOD INUNDATION MAPPING USING REMOTE SENSING AND HYDRAULIC MODELING: A CASE STUDY OF THE AKÇAY SUB-BASIN

Abstract

This study investigates the flood event that occurred on 12–13 December 2022 in the Akçay Sub-Basin, located in the Western Mediterranean Basin of Türkiye, a region prone to flooding. The accuracy of flood inundation maps generated using the HEC-RAS 2D hydraulic model and Sentinel-1 SAR data was evaluated. Sentinel-1 imagery was processed on the Google Earth Engine platform, and approximately 379 hectares of land were identified as affected by the flood. The HEC-RAS model was calibrated using ground measurements and GPM-IMERG satellite precipitation data, with estimated flood depths ranging between 0.0016 and 2.1279 m. Additionally, soil moisture analysis with SMAP data revealed that surface and root zone saturation played a decisive role in flood development. A limited spatial agreement (26.17%) was observed between the flood inundation map derived from the HEC-RAS hydraulic model and the flood extent map generated from Sentinel-1 satellite imagery acquired two days after the flood event. The overall accuracy, sensitivity, and F1-score were calculated as 0.37, 0.34, and 0.36, respectively. These findings demonstrate that the integrated use of remote sensing data and hydraulic modeling approaches provides significant potential for identifying and analyzing the spatial extent of flash flood events.

Keywords

• GPM-IMERG
• HEC-RAS
• Sentinel-1
• SMAP
• Flood Inundation Mapping

TAŞKIN YAYILIM HARİTALAMASINDA UZAKTAN ALGILAMA VE HİDROLİK MODELLEME: AKÇAY ALT HAVZASI ÖRNEĞİ

Abstract

Bu çalışma, Türkiye’nin Batı Akdeniz Havzası’nda yer alan ve taşkına eğilimli bir bölge olan Akçay Alt Havzası’nda, 12–13 Aralık 2022 tarihlerinde meydana gelen taşkın olayını incelemekte; HEC-RAS 2B hidrolik modeli ve Sentinel-1 SAR verileri kullanılarak oluşturulan taşkın yayılım haritalarının doğruluğunu değerlendirmektedir. Sentinel-1 görüntüleri, Google Earth Engine platformunda işlenmiş ve yaklaşık 379 hektarlık alanın taşkından etkilendiği belirlenmiştir. HEC-RAS modeli, yer ölçümleri ve GPM-IMERG uydu yağış verileriyle kalibre edilmiş; tahmin edilen taşkın derinlikleri 0,0016–2,1279 m arasında hesaplanmıştır. Ayrıca SMAP verileriyle toprak nemi analiz edilmiş, yüzey ve kök bölgesi doygunluğunun taşkın gelişimi üzerinde belirleyici olduğu görülmüştür. HEC-RAS modelinden elde edilen taşkın yayılım haritası ile taşkın olayından 2 gün gecikmeli olarak Sentinel-1 uydu verileri kullanılarak türetilen taşkın yayılım haritası arasında sınırlı düzeyde mekansal uyum (%26,17) elde edilmiş; doğruluk, duyarlılık ve F1 skorları sırasıyla 0,37, 0,34 ve 0,36 olarak bulunmuştur. Elde edilen bulgular, uzaktan algılama verileri ile hidrolik modelleme yaklaşımlarının birlikte kullanılmasının, ani yağış kaynaklı taşkınların mekânsal yayılımının belirlenmesi ve değerlendirilmesinde önemli bir potansiyel sunduğunu ortaya koymaktadır.

Keywords

• GPM-IMERG
• HEC-RAS
• Sentinel-1
• SMAP
• Taşkın Yayılım Haritalaması

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