Rapid Flood Progress Monitoring in Cropland with NASA SMAP

Md Rahman,Li Lin,Junmei Tang,Chen Zhang,Eugene Yu,Liping Di

doi:10.3390/rs11020191

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.

Highlights

Floods are one of the most common, devastating natural hazards around the world considering its scale and impact [1,2,3,4]
Recent examples are Hurricane Harvey-induced flood, and Hurricane Irma-induced flood in 2017, which accounted for a million-dollar crop loss in the south-eastern parts of the United States (US) [13,14]; the Mid-Atlantic river flood in 2012 caused a multimillion-dollar crop loss in the east coast [15]; the Mississippi River flood in 2011 accounted for more than sixty million dollars in the catchment of this river [16]
Since this study investigated five flood events as case studies, the findings of this study are presented in separate sections as follow

Summary

Introduction

Floods are one of the most common, devastating natural hazards around the world considering its scale and impact [1,2,3,4]. It is considered the number one natural hazard in the United States (US) [5]. The agriculture sector is one of the most vulnerable sectors to flooding mainly for two reasons: croplands are outside of the coverage of conventional hazard management systems, and the vast spatial scale of croplands [9]. Almost every year flooding causes significant crop damage over large agriculture area in the US [10,11,12]. Rapid flood progress monitoring is crucial for rapid crop loss assessment, crop condition monitoring, crop insurance, and policy making

Objectives

Methods

Results