NSF Org:	EAR Division Of Earth Sciences
Recipient:	UNIVERSITY OF WASHINGTON
Initial Amendment Date:	October 31, 2022
Latest Amendment Date:	October 31, 2022
Award Number:	2303870
Award Instrument:	Standard Grant
Program Manager:	Justin Lawrence jlawrenc@nsf.gov  (703)292-2425 EAR  Division Of Earth Sciences GEO  Directorate for Geosciences
Start Date:	November 1, 2022
End Date:	October 31, 2025 (Estimated)
Total Intended Award Amount:	$49,443.00
Total Awarded Amount to Date:	$49,443.00
Funds Obligated to Date:	FY 2023 = $49,443.00
History of Investigator:	Erkan Istanbulluoglu (Principal Investigator) erkani@u.washington.edu
Recipient Sponsored Research Office:	University of Washington 4333 BROOKLYN AVE NE SEATTLE WA  US  98195-1016 (206)543-4043
Sponsor Congressional District:	07
Primary Place of Performance:	University of Washington 4333 Brooklyn Ave NE Seattle WA  US  98195-0001
Primary Place of Performance Congressional District:	07
Unique Entity Identifier (UEI):	HD1WMN6945W6
Parent UEI:
NSF Program(s):	XC-Crosscutting Activities Pro, Geomorphology & Land-use Dynam
Primary Program Source:	01002324DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):	7914
Program Element Code(s):	722200, 745800
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.050

ABSTRACT

Recent hot and dry summers have worsened wildfires in the western United States, broadening their impact well into the cool and wet slopes of coastal Pacific Northwest (PNW) that have rarely been burnt. Growing evidence suggests that drier climatic conditions and increasing wildfire size and severity could make cool and wet steep slopes of the PNW more susceptible to runoff-driven debris flows, landslides and rockslides. Because wildfires have been rare in coastal slopes, there is limited understanding with respect to their postfire geomorphic response. A recently burned Bolt Creek Fire within the North Cascade Range of Washington state produced high soil burn severity on steep forested slopes, where landslides and debris flows are dominant forms of geomorphic transport. Steep slopes and evidence of soil hydrophobicity present a perishable data collection opportunity for anticipated postfire runoff and geomorphic response during the fall and early winter, when most of the extreme precipitation events fall in the region. Runoff-driven debris flows are usually expected before soil infiltration rates improve with soil wetting and vegetation growth. This team will collect geospatial data using ground- and UAV-based lidar and aerial imagery, soil water repellency and vegetation states as soon as possible to establish baseline conditions, and following major storms that trigger geomorphic response. Digital Elevation Model (DEM) time series will be created to map erosion and deposition patterns using DEM differencing, and to test and refine existing debris flow models and data-driven landslide hazard mapping methods. The Washington Department of Natural Resources Landslide Hazard Program will collaborate with them in data collection and analysis. A female undergraduate student will participate in the surveys and data analysis, be trained by RAPID facility staff, develop skills for data post-processing and participate in DEM differencing and erosion mapping analysis.

Our current conceptual understanding of postfire landscape response suggests that, immediately after a wildfire, impacted areas are at high risk for flash floods and runoff-initiated debris flows. This high risk comes from progressive sediment bulking caused by infiltration-excess runoff on water-repellent hillslopes. While infiltration excess runoff-driven debris flow risk subsides within months as soil infiltration capacity recovers, saturation-driven landslide risk peaks within several years due to decaying tree roots losing tensile strength to hold soils. This conceptual framework, as well as early warning models for postfire debris flows have been largely developed and tested on observations and data acquired from inland regions of the Western United States and Southern California, where fires are more frequent and climate is drier than the coastal PNW. While runoff-driven debris flow events were rarely reported in the past, more recent evidence suggests growing risk for such events in the coastal PNW. The data set this team will develop will provide a rare opportunity to observe the nature of postfire geomorphic in coastal PNW. If runoff-driven debris flows occur, the data will provide the unique opportunity to study their initiation and transport mechanics, as inferred from topographic change and the characterization of the surrounding soil and vegetation. The data will also provide initial topographic conditions for studying landslides, which are anticipated within several years of root decay, but may in fact happen during the observational period under extreme rainfall. Rockfall observations in relation to vegetation and precipitation have been rare and their observations will contribute to the refinement of existing rockfall models.

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.

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