Hasanlar Dam and Hydroelectric Power Plant are located on Küçük Melen Creek in the Western Black Sea Basin of Turkey. The dam was constructed in 1974 to provide domestic water needs of the Düzce Province, to supply irrigation water need, to control and mitigate floods and to produce hydroelectric power. This dam has been subjected to severe sedimentation since its construction in 1974. Therefore, bathymetric field survey studies were conducted to determine storage loss in the Hasanlar Dam reservoir by sedimentation. Bathymetric survey data from the reservoir site of the Hasanlar Dam were obtained in 1979, 1999 and 2014. Analysis of the bathymetric data, GIS and remotes sensing techniques showed that storage loss in reservoir active volume between 1974 and 1999 was 24% and between 1974 and 2014 storage loss was 26%. Analysis of the bathymetric maps also showed that sediment accumulation is severe near and around the dam body and the spillway whose discharge capacity was decreased by sediment accumulation. This is extremely critical because the flood of May 1998 caused the high risk of collapse of dam due to reduced capacity of the spillway. Remote sensing technique was used to determine the future deposition of sediment in the reservoir. For this purpose, 35 points in the reservoir area were determined by comparing the relative water depths and actual water depths using satellite image of the bathymetry in July 2017 and Lake Observation Station. High correlation (R 2 = 0.833) was calculated by using logarithmic nonlinear regression analysis between actual and relative water depths for those 35 control points. The average of absolute values of differences between the estimated and actual water depths was found as 1.06 m, and RMSE was calculated as 1.25 m. This analysis shows that in the future, remote sensing data can be used in the studies of determining the depth of water and the total sediment thickness. In addition, the volume of the entire reservoir can be predicted by measuring the actual water depth only at those 35 control points without making a bathymetric map of the whole dam reservoir.

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Water depth data of a reservoir is used in calculation of water volume storage and sedimentation volume in reservoirs. The goal of this study is to examine the recent developments in sediment accumulation in Berdan Dam Reservoir as of the year 2019, to examine the risks caused by sedimentation in terms of sustainability within the framework of dam safety principles and to assess the possibilities of using remote sensing data to determine bathymetric water depths. In this study, the water depth of Berdan Dam Reservoir is investigated to determine bathymetric elevations of the reservoir by using the Log Ratio Transformation (LRT) method which is developed by the US National Oceanic and Atmospheric Admisinistration (NOAA). 25 control points were used for calibration of water depth. The depths of these points were selected from the July 2019 bathymetric map of Berdan Dam Reservoir with a depth difference of 1 m between the points. As remote sensing data, archive scanning was performed by considering the date of the bathymetric map and cloudlessness, the image of Sentinel-2 dated 28 July 2019 was selected and analyzed. As a result, high correlation was found between the predicted water depths and surveyed water depths by using logaritmic nonlinear regression analysis for chosen 25 control points. The regression value between the average bathymetric elevations was found to be 0.944 and the root mean square error (RMSE) was calculated as 1.70 m.