The Utility of SMAP Soil Moisture and Freeze-Thaw Datasets as Precursors to Spring-Melt Flood Conditions: A Case Study in the Red River of the North Basin

Abstract

We evaluated NASA soil moisture active–passive (SMAP) soil moisture (SM) and freeze-thaw (FT) datasets for the utility to identify FT and SM conditions as precursors to a 2017 spring-melt flood event in the Red River of the North Basin. SMAP FT and SM datasets were analyzed at basin-scale and at specific North Dakota Agricultural Weather Network (NDAWN), National Oceanic and Atmospheric Administration (NOAA), and Red River of the North U.S. Geological Survey (USGS) stations prior to and during the observed flood. Results indicate that SMAP FT dataset had better agreement with NDAWN and NOAA air temperature measurements than with soil temperature. SMAP FT and SM were able to observe FT states and saturated soil conditions at basin-level and significant increases in SM content up to five days before USGS gauge height increase and the manifestation of the flood event. A Spearman's rank ( $R_{s}$ ) cross-correlation coefficient lag function was applied to SMAP SM and USGS river gauge heights and the strength of the relationship varied by location and lead time. Downstream locations near and in the flood area (North Grand Forks, Oslo, North Drayton) displayed moderate to strong relationships at 1-, 3-, and 4-day lead times ( R s = 0.67, 0.84, 0.71; p $R_{s}= 0.88; p ), well during the flood event recorded. This study suggests that SMAP SM and FT datasets can potentially provide useful information on surface state conditions to spring-melt floods in the Red River of the North Basin.