Publication: Darlık havzasının jeomorfolojik gelişimi ve flüvyal süreçlerin etkisi
Abstract
Darlık havzasının jeomorfolojik gelişimi ve flüvyal süreçlerin etkisi Darlık Havzası, İstanbul (Şile) ile Kocaeli (Gebze–Dilovası) arasında, 336,76 km² alanlı ve akışını ağırlıkla Karadeniz yönüne veren bir sistemdir; yükselti 0–647 m arasında değişmekte, alanın önemli bölümü 127–192 m bandında yoğunlaşmaktadır. Havza, İstanbul–Sakarya zonları geçişinde yer almakta ve Sarıyer–Şile bindirmesi gibi yapısal unsurların kontrolündedir. Çalışmada 12,5 m SYM temelli CBS analitiği kullanılmış; Strahler dizini, 1 km² ızgara yaklaşımıyla drenaj yoğunluğu (Dd), boyuna profil ve jeoloji–hidrojeoloji–iklim katmanlarının entegrasyonu birlikte değerlendirilmiştir. Topoğrafyada eğim–bakı–nispi yükselti bileşenleriyle rölyefin mekânsal düzeni çıkarılmış; hipsometrik eğri/ integral üzerinden evrimsel yorum çerçevesi oluşturulmuştur. Drenaj ve morfometrik analizlerde Strahler hiyerarşisi, Dd’nin 1 km² ızgaralardaki dağılımı ile çatallanma oranı (Rb) ve uzunluk oranı (RL) tabloları kullanılarak ağın olgunluğu ve yapısal/ litolojik sınırlara duyarlılığı irdelenmiştir. Boyuna profil üzerinde ana kol boyunca eğim kırıkları ve potansiyel eğim kırıklıkları tespit edilip tartışılmıştır. Süreç alanları kapsamında aşındırma–taşıma–birikim zonları hem morfometrik çıktılar hem de saha gözlemleriyle ayrılmış; bu üçlü zonlama havzanın sediman bütçesini okumada temel alınmıştır. Havza genelinde ovalar, platolar, çentik ve tabanlı vadiler morfolojik birimler olarak sahadaki örnekleriyle eşleştirilip haritalanmıştır. Hidrojeoloji–iklim boyutunda geçirgenlik özellikleri, yıllık yağış–sıcaklık dağılımları ve Erinç/ De Martonne indisleriyle akış rejimi üzerinde iklim–litoloji etkisi değerlendirilmiştir. Tehlike–hassasiyet analizlerinde erozyon ve heyelan şiddeti haritaları ile duyarlı yamaçlar ve taşkın ovası parçaları belirlenmiştir. Antropojenik etkiler başlığında baraj rejimi, ormancılık ve özellikle madencilik kaynaklı arazi örtüsü değişimleri ile sediman/ iz element (Zn, Pb) ve organik kirleticiler (PAH/ PCB/ OCP) havza su kalitesi açısından risk unsurları olarak saptanmıştır. Nüfus/ yerleşme verileri (2007–2024) köy ölçeğinde incelenmiş; sanayi ve kentsel baskı odaklarının morfodinamik süreçlerle çakıştığı görülmüştür. Son olarak alt havzalar tanımlanmış ve süreç odaklı planlama için birim ölçekli müdahale olanağı ortaya konmuştur.
Geomorphological development of the darlik basin and the impact of fluvial processes The Darlık Basin, located between Istanbul (Şile) and Kocaeli (Gebze–Dilovası), covers an area of 336,76 km² and has a predominantly Black Sea-directed flow. Elevations range from 0–647 m, with a significant portion of the area concentrated in the 127–192 m range. The basin is located at the transition between the Istanbul–Sakarya zones and is controlled by structural elements such as the Sarıyer–Şile thrust. GIS analytics based on 27.5 m DEM were used in the study, and the Strahler index, drainage density (Dd) using a 1 km² grid approach, longitudinal profile, and the integration of geology, hydrogeology, and climate layers were evaluated together. The spatial configuration of the relief was determined using topographic components of slope, aspect, and relative elevation; an evolutionary interpretation framework was established using the hypsometric curve/ integral. Drainage and morphometric analyses used the Strahler hierarchy, the distribution of Dd on 1 km² grids, and bifurcation ratio (Rb) and aspect ratio (RL) tables to examine the network's maturity and sensitivity to structural/ lithological boundaries. Slope breaks and potential slope breaks along the main branch of the longitudinal profile were identified and discussed. Within the process areas, erosion, transport, and accumulation zones were distinguished using both morphometric data and field observations; this triple zoning was used as the basis for interpreting the basin's sediment budget. Throughout the basin, plains, plateaus, notches, and valleys with floors were mapped and matched with field examples as morphological units. The hydrogeology-climate dimension assessed the climate-lithology effect on the flow regime using permeability characteristics, annual precipitation-temperature distributions, and Erinç/ De Martonne indices. In hazard-vulnerability analyses, erosion and landslide intensity maps were used to identify susceptible slopes and flood plains. Under the heading of anthropogenic impacts, dam regime, land cover changes resulting from forestry and, particularly, mining, as well as sediment/ trace element (Zn, Pb) and organic pollutants (PAH/ PCB/ OCP) were identified as risk factors for basin water quality. Population/ settlement data (2007–2024) was examined at the village scale, revealing that industrial and urban pressure centers overlap with morphodynamic processes. Finally, sub-basins were defined, and the possibility of unit-scale intervention for process-oriented planning was demonstrated.
Geomorphological development of the darlik basin and the impact of fluvial processes The Darlık Basin, located between Istanbul (Şile) and Kocaeli (Gebze–Dilovası), covers an area of 336,76 km² and has a predominantly Black Sea-directed flow. Elevations range from 0–647 m, with a significant portion of the area concentrated in the 127–192 m range. The basin is located at the transition between the Istanbul–Sakarya zones and is controlled by structural elements such as the Sarıyer–Şile thrust. GIS analytics based on 27.5 m DEM were used in the study, and the Strahler index, drainage density (Dd) using a 1 km² grid approach, longitudinal profile, and the integration of geology, hydrogeology, and climate layers were evaluated together. The spatial configuration of the relief was determined using topographic components of slope, aspect, and relative elevation; an evolutionary interpretation framework was established using the hypsometric curve/ integral. Drainage and morphometric analyses used the Strahler hierarchy, the distribution of Dd on 1 km² grids, and bifurcation ratio (Rb) and aspect ratio (RL) tables to examine the network's maturity and sensitivity to structural/ lithological boundaries. Slope breaks and potential slope breaks along the main branch of the longitudinal profile were identified and discussed. Within the process areas, erosion, transport, and accumulation zones were distinguished using both morphometric data and field observations; this triple zoning was used as the basis for interpreting the basin's sediment budget. Throughout the basin, plains, plateaus, notches, and valleys with floors were mapped and matched with field examples as morphological units. The hydrogeology-climate dimension assessed the climate-lithology effect on the flow regime using permeability characteristics, annual precipitation-temperature distributions, and Erinç/ De Martonne indices. In hazard-vulnerability analyses, erosion and landslide intensity maps were used to identify susceptible slopes and flood plains. Under the heading of anthropogenic impacts, dam regime, land cover changes resulting from forestry and, particularly, mining, as well as sediment/ trace element (Zn, Pb) and organic pollutants (PAH/ PCB/ OCP) were identified as risk factors for basin water quality. Population/ settlement data (2007–2024) was examined at the village scale, revealing that industrial and urban pressure centers overlap with morphodynamic processes. Finally, sub-basins were defined, and the possibility of unit-scale intervention for process-oriented planning was demonstrated.