An important achievement is the invention and development of techniques for measurement of velocities in hydraulic engineering applications. Knowledge of the technological advances in digital cameras with high resolution and high speed are extremely useful to measure relevant predictive parameters in the environment. Here we present some advances in image processing techniques, these can be used in hydraulic hazard predictions therefore, providing a tremendous potential to measure the behavior of the water surface flow. This technique was performed at the Laboratory of Hydraulics Department of Hydraulic, Maritime and Environmental Universidad Pol ytechnic de Catalonia, (UPC Barcelona Tech) where we used a water flow platform with dimensions of 5.5 m long and 4 m wide allowing a zone of useful measurements of 5.5m x 3m, where the width is similar of a typical urban road. The platform allows to modify the slopes longitudinal at angles between 0% and 10% and transversal slopes of between 0% and 4%. And there is also the possibility of a range of flows. In the experiments discussed here we used flow rates up to 200 l/s [1]. In addition, a camera high resolution 1280 x 1024 pixels with maximum speed of 488 frames per second. A novel technique using particle image velocimetry to measure surface flow velocities has been developed and validated with the experiments assays with the grate inlets. In this case, the Methodology carried out can become a useful tools to understand the hydraulics behavior of the flow approaching the inlet where the traditional measuring equipment have serious problems and limitations.