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Abstract This work investigates the siphon break phenomenon associated with pipe leakage location. The present study is divided into two parts: (1) an unsteady three-dimensional (3D) computational fluid dynamics (CFD) model is developed to simulate the pressure head (water level) and discharge in the simulated siphon using the volume-of-fluid (VOF) technique under no-leakage condition and (2) using the model developed in the first part we investigated the siphon break phenomenon associated with pipe leakage location. The calculated results of transient water level and discharge rate at the simulated siphon for the no-leakage condition were in good agreement with the experimental measurements. In addition, the velocity, pressure fields, and phase fractions in the siphon pipe were analyzed in depth. The methodology and findings presented show that leakage above the hydraulic grade line and close to the top inverted U section of the siphon pipe ultimately leads to the siphon breakage, which is not the case for a leakage below the hydraulic grade line. It is also concluded that if leakage is above the hydraulic grade line and the leakage position is far away from the upper horizontal section of the siphon pipe, it may not lead to the immediate siphon breakage as ingested air gets removed with siphoning water, allowing it further time to cause complete siphon breakage. 

Wetlands play a significant role in flood mitigation. Remote sensing technologies as an efficient and accurate approach have been widely applied to delineate wetlands. Supervised classification is conventionally applied for remote sensing technologies to improve the wetland delineation accuracy. However, performing supervised classification requires preparing the training data, which is also considered time-consuming and prone to human mistakes. This paper presents a deterministic topographic wetland index to delineate wetland inundation areas without performing supervised classification. The classic methods such as Normalized Difference Vegetation Index, Normalized Difference Water Index, and Topographic Wetness Index were chosen to compare with the proposed deterministic topographic method on wetland delineation accuracy. The ground truth sample points validated by Google satellite imageries from four different years were used for the assessment of the delineation overall accuracy. The results show that the proposed deterministic topographic wetland index has the highest overall accuracy (98.90%) and Kappa coefficient (0.641) among the selected approaches in this study. The findings of this paper will provide an alternative approach for delineating wetlands rapidly by using solely the LiDAR-derived Digital Elevation Model.