Abstract
An accurate flood detection method is essential for obtaining areas of irrigated rice fields affected by flooding. This paper aims to distinguish between rice fields with flooding and rice fields with agronomic inundation using MODerate resolution Imaging Spectroradiometer (MODIS) 8 day 500 m spatial resolution (MOD09A1) imageries over irrigated rice fields with complex cropping patterns in West Java. Over the past decade, Enhanced Vegetation Index (EVI) ≤ 0.1 derived from moderate resolution remote sensing imageries has been used for detecting flooding in irrigated rice fields. Without additional farming information, this paper argues that EVI ≤ 0.1 cannot estimate flood areas correctly, given the existence of both hazardous flooding and non-hazardous agronomic inundation in irrigated rice fields. Adding a threshold of 40-day duration representing land preparation and transplanting activities enables EVI ≤ 0.1 to distinguish between agronomic inundation and flooding in irrigated rice fields. The difference in the Start of Season (SOS) between the wet planting season 2013/2014 and long-term average (2000–2015) shows that the Overall Accuracy (OA) and F1 scores are 75.96% and 81.74%, respectively. The confusion matrix using the respondents’ reports shows OA of 80.5% and Kappa of 60.16%. The quality of flood maps is partly influenced by environmental processes, human decisions, and mixed pixels.
Highlights
Surface water detected during the dry planting season 2014 was rice fields with agronomic inundation as no flood events were reported by farmers, extension officers, and water managers
This finding provides evidence that Enhanced Vegetation Index (EVI) ≤ 0.1 is not able to discriminate between hazardous flooding and non-hazardous agronomic inundation in irrigated rice fields in the study area
This study has successfully proposed a relatively simple method to distinguish between hazardous flooding and non-hazardous agronomic inundation using time-series MOD09A1 in irrigated rice fields with complex cropping patterns
Summary
Spectral indices are a single band or combination of bands that can distinguish target objects as a consequence of specific physical differences captured in spectral behavior. Water indices, such as NDWI (Normalized Difference Water Index) [7,8,9] or MLSWI (Modified Land Surface Water Index) [10], are commonly used as tools to detect water bodies on the earth’s surface. Studies have been conducted on constructing EVI with two bands, using only red and near-infrared wavelengths, to respond to this limitation [18]
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