Use of Unmanned Aircraft Images in Urban Drainage Projects

In drainage systems projects there are great uncertainties in estimating flows, especially due to the lack of information to characterize the land surface (land use, topography, etc.) due to the difficulties and high costs to involved. An alternative for the acquisition of information of this nature is the use of mappings made by unmanned aerial vehicles (UAVs), that can produce high spatial resolution images of the order of a few centimetres. The interpretation of these data in GIS allows a greater number of analyses and adds greater reliability in the projected structures. This study evaluated the feasibility of the use of data from a UAV in the development of a drainage network project of a typical apartment block in the city of Santa Maria - RS, considering different spatial resolutions in the analysis. The results showed that the surface characterization generated by the UAV was suitable for the design of the drainage systems, justifying its application by the agility in the mapping and the level of detail obtained in the drainage networks. However, the resolution of the image proved to be a determinant factor for the accuracy of the flow estimation, and as the resolution was reduced, significant differences were identified in the estimated flow rates indicating the resolution limit of 1,5m pixels in microdrainage.