Unmanned Aerial Systems (UASs) are widely used for various applications, especially for large-scale mapping of flood plains. The Unmanned Aerial Vehicles (UAVs) act as a bridge to fill the gap between the satellite and the field scale, as they provide an alternative to temporal and spatial resolution to the satellite imagery and can be directly linked to the terrestrial measurements. In the study, UAV-derived point clouds are used to create very high-resolution surface models based on Structure from Motion (SfM) technique, which is applied for the creation of 3-D models from unstructured imagery and frequently used in conjunction with UAVs. Thus, seasonal hydrogeomorphological changes in the Bogacay River flood plain in Antalya Province have been evaluated by using fine resolution UAV-derived orthophotos and Digital Surface Models (DSMs). The monitored landscape changes were determined to have the utmost influence on the multihazard performance of the bridges, which are located on the study region. Further, in the light of this information, the seismic performance of reinforced concrete (RC) bridge infrastructure was determined via static pushover methods. In the study region, the scour depths were determined to reach maximum of 2.2 meters under the bridge piers. The scour-induced reduction in pile lateral displacement capacities was detected to deteriorate the seismic performance of the bridges.