In Juneau, Alaska, the Mendenhall Glacier has been producing glacier outburst floods sourced from the Suicide Basin since 2011. In 2023 and 2024, the outburst floods were significantly larger than previously experienced and caused damage to hundreds of homes in the densely populated Mendenhall Valley. During the 2024 event the Mendenhall River gauge crested at 15.99 feet, the largest flow within the Mendenhall River system in historical record. This triggered state and national disaster declarations, and concerns of even larger releases in the future. It was determined that a new model was needed to create updated flood inundation maps that account for these historic outburst events and predict future hazards as the glacier recedes up the valley toward Suicide Basin
In September 2024, the Alaska Department of Transportation and Public Facilities, as part of a multi-agency response team, solicited imagery and LiDAR data collection of the Mendenhall Valley to produce an updated orthoimage and digital elevation model for the flood modeling team. The state agencies desired the river level to be below 1,500 cfs during the data collection and the fieldwork completed by November 1. The Elevate team won the solicitation for this important collection and went to work planning for an unusual Fall-timed data collection. In coastal, southeast Alaska data collections are generally targeted for spring and summer months with more daylight and less cloud cover and rain . Already into Fall, this project pushed the limits of what would be possible before the Alaskan winter set it.
In mid October client-provided ground control targets were in place and they gave Elevate the notice to proceed with collection. The Elevate field team are experts in coastal Alaska weather and had already been putting together a payload and aircraft package to be able to collect the entire 7,500 acres of imagery and LiDAR in a single day with only a few hours of usable daylight. The team saw an opportune weather window approaching on October 20 and 21. As the weather window got close, the National Weather Service began issuing alerts that sensing instruments in Suicide Basin were hinting at the possibility of another glacial outburst flood. Sure enough, the basin released again and the river climbed rapidly to a peak in the early morning hours of October 21. The Elevate team decided to make use of the good weather regardless and were able to collect both imagery and LiDAR from the entire area on October 21. The Elevate team continued watching for another window through the rest of the month to recollect the river corridor and lakeshore when the river level came back down. The next window came on October 31 and November 1. A trace of precipitation fell on both days and a fog engulfed the area throughout the day. The team was able to find a thread of fog-free area over portions of the river each evening just as civil twilight was ending and fog began to engulf the runway at Juneau International Airport. This completed the entire area of data collection, including the low-water requirement, just as Juneau went into another multi-week stretch of rain and snow and into winter.
