Assessment of gully development using geomorphic change detection between pre- and post-urbanization scenarios

Urbanization processes have caused changes in the runoff behavior, especially by impervious surfaces produced by paving and buildings. Impermeable surfaces prevent the infiltration of rainwater, increasing the volume and speed of runoff. Besides, inadequate urban planning coupled with heavy rains promotes the evolution of erosion processes, especially in peri-urban areas. This research aims to identify spatial patterns of geomorphic change in the gully areas due to urbanization in the city of Jacarei (SP). The methodology has the following steps: (1) elaboration of the Digital Elevation Model (DEM) from stereophotogrammetric techniques; (2) elaboration of the pre- and post-urbanization DEM; (3) extraction of contributing area using the D-Infinity method and of the topographic indices (topographic wetness, stream power, and compound topographic); and (4) calculate the difference between the pre- and post-urbanization topographic attributes. The preparation of the pre- and post-urbanization DEM used the MATCH-T DSM and DTMaster modules, both belonging to the INPHO system. Photogrammetric techniques allow the generation of digital models suitable for hydrological studies. The urbanization exposed an evident influence on the triggering of erosion, evidencing an increase of all topographic indices in areas that develop gullies.