The design of open channels often requires the use of channel drop and/or energy dissipation structures to dissipate excess energy created by gravity. A drop structure, also known as a grade control, or over-fall , is typically built in streams to pass water to a lower elevation. In irrigation channels and storm-water systems, drops are used to offset the elevation difference between the channel slope and ground slope to control the longitudinal slope of channels to keep design velocities within acceptable limits. In addition, they serve other purposes such as erosion prevention. Energy loss is achieved through turbulent mixing in the pool. Providing methods to increase the efficiency of energy dissipation in vertical drops, optimized geometry of drops has been the interest of a number of former investigators. Among these, the grating and netting drop-type dissipators are reported as efficient measures to increase the head loss at the base of the vertical drops. These types of drops not only increase the efficiency of energy dissipation but also improve the air-entrainment into the water through falling different separate jets in the pool. Furthermore, flow in the upstream channel over the drops can be either sub- or supercritical, passes over a vertical fall (free over-fall) and descends into the downstream channel of the drop. Thus the upstream approach flow regime is a major issue in studying hydraulics of flow over the drops. In the present study, the characteristics of flow over netting drop-type dissipators were investigated based on numerical modeling. A range of velocity and depth of the supercritical approach flows was analyzed to examine the flow structure at the regions of the falling jets through the netting roof, the sliding jet and the pool. 3-D numerical modeling of flow through netting drop-type dissipators with upstream supercritical approach flow was performed using an open source Open Foam software. For modeling the water free-surface, the Volume of Fluid (VOF) method was applied. The netting dissipators were installed on the edge of the vertical drops and the effects of the upstream supercritical approach flow Froude number and the height of the drops on the hydraulic and hydrodynamic characteristics of flow at the pool were investigated. According to the former studies as well as based on a trial and error procedure among the different turbulent models, the k -? turbulent model was employed in the present study. The meshes size were minimized in three levels i.e. close to the dissipator, drop structure walls, and the interface between the water and air. Variation trends of several hydraulic or geometric characteristics of flow and length scales of the distributed/deflected jets and the supercritical flow aspects in the pool were simulated herein. Results were compared well with those of the former experimental investigations indicating that the present numerical modeling properly simulates the flow field and provides reliable outputs for the flow characteristics at the netting drop-type dissipators with the upstream supercritical approach flow. According to the results, hydraulic jump does not traire in the pool, however, an intense turbulent flow, shock waves and transverse waves were formed inside the pool moving downstream. It was shown that the dispersion/diffusion likewise mechanism inside the pool increases the velocity gradient as well as the momentum exchange and consequently, increases the energy dissipation. However, compared to the netting drop-type dissipators with the upstream subcritical approach flow, the efficiency of energy dissipation is reduced in the present study. Key words: Energy Dissipater, Hydraulic Jump, Netting, Vertical Drop, Numerical Modelling