Abstract
Abstract. A flood, one of the most devastating natural disasters in the world, occurs when water inundates land that's normally dry. Although floods can develop in many ways, river floods (i.e. overflow by rivers or river banks) are the most common. Turkey is one of the flood-affected countries with its 20 main basins in 8 regions. One of the most aggrieved basins in Turkey is the Maritsa river basin in in Eastern Balkans, which also contains the natural border regions with Greece and Bulgaria. 65% of the Maritsa River basin, which originates from the Rila Mountains and joins the Arda and Tundzha rivers, is located in Bulgaria. When the melting snow flow or precipitation in the basin increases, the Maritsa River overflows from the slopes to the Edirne Plain and from time to time exceeds the capacity of the bed, causing floods. On the other hand, since the water level in the dams and reservoirs was kept at the highest level for production purposes, the flood repeat interval increased in the region, since 2000s. Today, it is possible to monitor and evaluate the damages of flood by obtaining very reliable information with space technology. Especially, microwave SAR images that can penetrate clouds, are of great importance in flood mapping because they provide immediate information on the extent of inundation and support the evaluation of property and environmental damages. In this study, rapid flood risk assessment in the region was performed using Landsat 8 and Sentinel 2 Normalized Difference Water Index (NDWI) time series images, and calibrated Sentinel 1 SAR images produced on Google Earth Engine (GEE) platform for 2015-2018 period. GEE is a cloud-based platform that facilitates access to high-performance computing resources to handle very large geographic data sets. The results were compared and verified using meteorological data, riverbed flow data, and digital media news. The results showed that the most affected areas were consistent with the highest measured flow rates and the magnitude of flood damages caused by two main causes in the basin (i.e. opening of shutters in Bulgarian dams or local excessive rainfall) was very different (approximately 8 times larger) from each other.
Highlights
Floods, which have serious environmental and social impacts worldwide, have been mostly caused by climate-related factors such as severe spring snowmelt and heavy rainfall in the last decade (CRED, 2015).operations of the Bulgarian dams without causing economic loss (Sezen, 2007).Turkey is one of the countries affected by the floods with its 20 main basins in eight regions
One of the most aggrieved basins in Turkey is the Maritsa (Meriç in Turkish) river basin, located in Eastern Balkans containing the natural boundary regions with Greece and Bulgaria (INWEB, 2019). River floods in this basin where three rivers meet are among the most common examples, due to excessive rainfall or snowmelt as well as uncontrolled water released from existing dams in Bulgaria and insufficient riverbed cross-sections
After 1994, with the privatization of dams and hydroelectric power generation, the water level in the reservoirs was kept at the highest level for production purposes and the flood recurrence interval increased after this date (Yildiz, 2011)
Summary
Floods, which have serious environmental and social impacts worldwide, have been mostly caused by climate-related factors such as severe spring snowmelt and heavy rainfall in the last decade (CRED, 2015).operations of the Bulgarian dams without causing economic loss (Sezen, 2007).Turkey is one of the countries affected by the floods with its 20 main basins in eight regions. One of the most aggrieved basins in Turkey is the Maritsa (Meriç in Turkish) river basin, located in Eastern Balkans containing the natural boundary regions with Greece and Bulgaria (INWEB, 2019). River floods in this basin where three rivers meet (biggest tributaries, Tundzha and Arda Rivers, joining in Maritsa in Edirne) are among the most common examples, due to excessive rainfall or snowmelt as well as uncontrolled water released from existing dams in Bulgaria and insufficient riverbed cross-sections. Uncontrolled water released from existing dams directly overflows on the Maritsa River, causing serious transboundary floods in Edirne. Research studies have shown that, especially after 2005, floods, occurred very often, can be prevented with proper implementations and
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