Low-altitude airborne surveys for hydrologic studies: lessons learned and a path forward

Abstract:

In 2018, the U.S. Geological Survey (USGS) Hydrogeophysics Branch initiated a demonstration and evaluation of the application of small unoccupied aircraft systems (sUAS) to USGS hydrologic studies. sUAS surveys were flown in support of USGS studies across the Nation involving a range of hydrologic frameworks and scientific questions. Airspace and field sites ranged from remote mountain regions to major urban corridors. Traditional visible light cameras as well as multispectral and thermal infrared sensors were mounted on a portable sUAS. The resulting data were used to derive orthomosaics, digital surface models, and video products for integration into larger hydrologic studies. Applications included mapping and characterization of vegetation to inform the groundwater component of basin-scale water budgets and to assess vegetation stress due to water quality and availability. Data were also used to locate and characterize groundwater seeps that affect aquatic habitats or that act as pathways for contaminants to a drinking water supply. An overview and outcomes of these case studies will be presented.

Our results indicate that existing off-the-shelf sensors mounted on commercially available multi-rotor portable sUAS can provide valuable qualitative and quantitative data on near-surface hydrogeological processes. However, challenges and important considerations remain in the use of sUAS for routine operational hydrologic surveys, and it is important that environmental site managers and field teams have a realistic understanding of the data collection and processing realities when planning and implementing studies. The adaptation of traditional geophysical methods to sensors that can be mounted on sUAS faces significant technical obstacles; but lessons learned from existing sUAS geoscience field work can be used to identify tools needed to meet current scientific needs and to prioritize and inform efforts to expand the use of low-altitude sUAS automated geophysical surveys using for routine operations. A summary of our findings – including lessons learned, key considerations, and future directions – will be presented