Rapid Flood Progress Monitoring in Cropland with NASA SMAP

Abstract

Research in different agricultural sectors, including in crop loss estimation during flood and yield estimation, substantially rely on inundation information. Spaceborne remote sensing has widely been used in the mapping and monitoring of floods. However, the inability of optical remote sensing to cloud penetration and the scarcity of fine temporal resolution SAR data hinder the application of flood mapping in many cases. Soil Moisture Active Passive (SMAP) level 4 products, which are model-driven soil moisture data derived from SMAP observations and are available at 3-h intervals, can offer an intermediate but effective solution. This study maps flood progress in croplands by incorporating SMAP surface soil moisture, soil physical properties, and national floodplain information. Soil moisture above the effective soil porosity is a direct indication of soil saturation. Soil moisture also increases considerably during a flood event. Therefore, this approach took into account three conditions to map the flooded pixels: a minimum of 0.05 m3m−3 increment in soil moisture from pre-flood to post-flood condition, soil moisture above the effective soil porosity, and the holding of saturation condition for the 72 consecutive hours. Results indicated that the SMAP-derived maps were able to successfully map most of the flooded areas in the reference maps in the majority of the cases, though with some degree of overestimation (due to the coarse spatial resolution of SMAP). Finally, the inundated croplands are extracted from saturated areas by Spatial Hazard Zone areas (SHFA) of Federal Emergency Management Agency (FEMA) and cropland data layer (CDL). The flood maps extracted from SMAP data are validated with FEMA-declared affected counties as well as with flood maps from other sources.

Operational Flood Mapping Using Multi-Temporal Sentinel-1 SAR Images: A Case Study from Bangladesh

“…Due to the high level of cloud contamination during the monsoon time, cloud-free Landsat images identification was difficult for flood mapping [85]. For Bangladesh, one of the best opportunities for operational flood mapping comes from Sentinel-1 imaging as it is publically available [63]. In Bangladesh, the agriculture sector is greatly impacted by floods, despite conventional flood management systems paying very limited attention to this sector [63].…”

“…Box plots were used to show the statistical distribution of the data. A distinct separable backscatter value for water and other classes was used for image classification [44,63].…”

A Systematic Review on Case Studies of Remote-Sensing-Based Flood Crop Loss Assessment

“…Similarly, crop loss assessment models based on the soil-water balance can benefit from the recent launch of NASA's Soil Moisture Active Passive (SMAP) mission. Rapid flood progress monitoring in cropland using soil saturation can be mapped using SMAP data [58,118].…”

“…Although no use of Sentinel-1 data was reported in these selected case studies, there is a high possibility of the use of Sentinel-1 in the near future because of the free-of-charge availability. Sentinel-1 provides C-band SAR data with multiple polarization, which is suitable for both flood mapping and crop condition monitoring [58].…”

High-Frequency Variations in Pearl River Plume Observed by Soil Moisture Active Passive Sea Surface Salinity

“…Remote sensing offers a unique method to study the sea surface salinity (SSS) associated with various oceanic and climatological phenomena [28][29][30]. Launched in January 2015, NASA's Soil Moisture Active Passive (SMAP) platform and mission provide unique and complementary observations to study floods and discharged freshwater in coastal estuarine regions [31,32]. Using in situ salinity data, Tang et al [33] validated the SMAP SSS and suggested that the SMAP can track large salinity changes occurring within a month.…”