Collaborative Research: RAPID: Typhoon Merbok in coastal western Alaska: Extent of flooding and impacts on plant communities and ecosystem function

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On September 16th, 2022, the Yukon-Kuskokwim (YK) Delta of western Alaska was hit by ex-Typhoon Merbok, a storm that many residents of the area described as the worst in their lifetime. The storm surge was several meters in height, and inland locations that normally do not flood under the highest tides of the year were inundated, resulting in extensive loss of homes, fishing boats, and subsistence cabins. This storm was unusual not only because of its size, but also its timing as the ground was not yet frozen or snow-covered. Since the Delta is flat, salty water extended for about a dozen or more miles inland, flooding Alaskan villages, hunting and fishing camps, and landscapes that are not acclimated to frequent floods. In this work, scientists will perform aerial and ground surveys to map the extent of the floods by looking for driftwood and other vegetation left behind by retreating water. Where driftwood is found, scientists will determine the amount of sediment deposited and measure pond salinity to test whether ponds switched from freshwater to salty water during the flood. The researchers will then set-up areas to observe longer-term effects of the floods on plants and the release of greenhouse gases to the atmosphere. As climate change contributes to larger and more frequent storms like Typhoon Merbok, understanding the consequences of them is becoming increasingly important to better prepare for the impacts of these storms on the landscape and the people who live in their path. This research consists of three components to address the extent and impact of Typhoon Merbok on the YK Delta region. First, researchers will conduct aerial and river surveys of drift lines and salinity along four rivers near Chevak, Alaska. For aerial surveys, transects ca. 30 km long and 2 km apart will be flown in mid-autumn 2022 with two observers photographing drift lines. All photographs will be geolocated. For river surveys, researchers will locate and sample debris, collect soil to quantity sediment deposition, and sample water bodies for salinity. Second, researchers will use high-resolution remotely-sensed imagery to locate fields of larger debris over a greater extent of the YK Delta. The elevation of debris from components one and two will be extracted from available LIDAR and structure-from-motion elevation models to determine the elevation of flood waters. Finally, researchers will establish monitoring plots to test hypotheses about impacts of the flooding, including evaluating changes to plant community composition, CO2 flux due to salt-kill, and CH4 flux due to suppression of methanogenesis by sulfates that occur in sea water. The project will produce valuable maps and data on the impacts of Merbok on the YK Delta Region, which will be made publicly available and be shared directly with local communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.