The Willow Creek Reservoir near Augusta, Montana provides an essential supply of water for farmers and ranchers along the Rocky Mountain Front. The reservoir is dammed by an earthen structure, protecting farms, ranches, roads, bridges, and utilities that lie along the floodplain downstream.
In June of 2018, record rainfall and flooding in the Sun River Basin pushed water levels at the reservoir to concerning levels. As reservoir levels increased to the crest of the emergency spillway, which had not been tested since 1964, the Bureau of Reclamation and Greenfields Irrigation District mobilized to ensure that spill water did not erode the earthen emergency spillway and send additional water into the already overwhelmed rivers.
To aid in their emergency response planning, Reclamation needed to safely collect a large amount of aerial data regarding current conditions at the spillway site in a short period of time. DJ&A has long supported the Reclamation’s survey and mapping needs, completing more than 260 projects for Reclamation since 1995. Due to this longstanding working relationship, Reclamation called upon DJ&A to see if they could complete this emergency project within 24 hours.
Within 24 hours of a phone call, crews arrived on-site and deployed a Vapor 55 UAV equipped with a Riegl VUX-1 LR system to acquire LiDAR data at a density of 200+ ppsm and ortho-rectified mosaic images of the corridor. Deliverables included reference images of the spillway, an orthomosaic of the corridor, and 1-ft contour mapping in Civil3D and AutoCAD format in compliance with USBR drafting standards.
- UAV LiDAR data acquisition of spillway corridor (approximately 200 acres)
- LiDAR data processing services
- Point cloud classification and bare earth processing
- Ortho-rectified imagery acquisition
- Aerial acquisition of reference imagery
- Orthomosaic generation
- Integration of existing data into the final topographic mapping
- Delivery of 1-ft contour mapping in Civil3D and AutoCAD format in compliance with USBR drafting standards
For a project of this size (roughly 180 acres), the use of an unmanned aerial vehicle allowed data collection from a complex and dangerous floodplain to be completed in a time- and cost-efficient manner, without putting human lives in danger or sacrificing the quality of the data collected.
This project relied upon cutting-edge aerial LiDAR and orthophotography technology. By integrating Survey Grade GPS with an Inertial Measurement Unit (IMU), the LiDAR data and photos could be controlled to a high level of accuracy based on the trajectory of the UAV. This method of data collection is far more efficient, yet just as precise as alternative collection methods, such as terrestrial LiDAR.
Additionally, the low weight of the UAV system allowed for orthophotography to be captured simultaneously during the flight. With a resolution of 1 inch, the orthophotography images captured from DJ&A’s UAV were far more precise than what could have been acquired from a plane.