This study aims to evaluate the performance and effectiveness of six spectral water indices - derived from Multispectral sentinel-2 data - to detect soil moisture and inundated area in arid regions to be used as an indicator of mudflow phenomena to predict high-risk areas. Herein, the validation of the performance of spectral indices was conducted using threshold method, spectral curve performance, and soil-line method. These indirect validation techniques play a key role in saving time, effort, and cost, particularly for large-scale and inaccessible areas. It was observed that the Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (mNDWI), and RSWIR indices have the potential to detect soil moisture and inundated areas in arid regions. According to the temporal spectral curve performance, the spectral characteristics of water and soil moisture were distinct in the Near infrared (NIR) and Short-wave Infrared (SWIR1,2) bands. However, the rate and degree differed between these bands, depending on the amount of water in the soil. Furthermore, the soil line method supported the appropriate selection of threshold values to detect soil moisture. However, the threshold values varied with location, time, season, and between indices. We concluded that considering the factors influencing the behavior of water and soil reflectivity could support decision-makers in identifying high-risk mudflow locations.

中文翻译：

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使用多光谱哨兵 2 数据检测水指数的潜力和有效性，以检测土壤湿度作为干旱地区泥石流发生的指标


本研究旨在评估源自多光谱哨兵 2 数据的六种光谱水指数的性能和有效性，以检测干旱地区的土壤湿度和淹没面积，并将其用作泥石流现象的指标来预测高风险地区。这里，采用阈值法、光谱曲线性能和土线法对光谱指数的性能进行验证。这些间接验证技术在节省时间、精力和成本方面发挥着关键作用，特别是对于大规模和难以到达的区域。据观察，归一化水分指数（NDWI）、修正归一化水分指数（mNDWI）和RSWIR指数具有检测干旱地区土壤湿度和淹没面积的潜力。从时间光谱曲线表现来看，水和土壤湿度在近红外（NIR）和短波红外（SWIR1,2）波段的光谱特征明显。然而，这些带之间的速率和程度有所不同，具体取决于土壤中的水量。此外，土壤线法支持适当选择阈值来检测土壤湿度。然而，阈值随地点、时间、季节以及指数之间的变化而变化。我们的结论是，考虑影响水和土壤反射率行为的因素可以支持决策者识别高风险泥石流位置。