基于Google Earth Engine的玉米洪涝灾害精细化评估以河北省保定市“23·7”强降水过程为例

Refined evaluation of maize flood disaster based on Google Earth Engine: A case study of the “23·7” heavy precipitation process in Baoding City, Hebei Province

  • 摘要: 快速准确的大范围精细化评估对粮食生产、农业保险和防灾减灾具有重要意义。本文选取保定市“23·7”(受2023年7月29日至8月2日强降雨影响, 形成的海河流域性特大洪水)暴雨洪涝过程为研究对象, 依托Google Earth Engine平台研究玉米受灾情况的快速评估方法, 选用Landsat卫星数据, 验证归一化植被指数(NDVI)和增强型植被指数(EVI2)与玉米产量相关性, 根据植被指数差值进行玉米受灾范围提取, 同时结合Sentinel-2数据, 利用遥感影像监督分类和自然断点技术, 进行玉米绝产、减产等级划分, 实现大范围玉米灾损的快速评估。研究结果表明: 1)基于相关性分析验证, NDVI与玉米实际产量存在明显正相关, 相关性系数为0.84 (P<0.01), 可用于玉米产量反演。2)基于植被光谱特征分析, 保定市境内存在不同程度的玉米减产, 其中东部减产相对严重, 中部和南部相对较轻。3)通过阈值分类结果统计, “23·7”暴雨洪涝过程造成保定市4.5万hm2玉米绝产, 绝产面积约占农田总面积5%, 减产面积约占总农田面积66%。本文为强降雨导致的玉米受灾情况评估和灾损分布制图提供了一个快速可靠的方法框架, 可为大面积农作物精细化评估提供方法参考和案例支持。

     

    Abstract: In light of the frequent occurrence of extreme weather events, the assessment of agricultural disasters caused by large-scale flooding is crucial for food production, agricultural insurance, and disaster prevention and mitigation. From July 29 to August 1, 2023, Baoding City experienced significant rainfall and flooding (23.7 flood disaster), resulting in substantial losses. This study focused on this event, aiming to develop a rapid assessment method for maize disaster damage using remote sensing technology, specifically leveraging the Google Earth Engine (GEE) platform. The goal is to provide a scientific basis for agricultural disaster management and post-disaster recovery. Relying on the GEE platform, the study utilized Landsat satellite data and agricultural statistics from 2016 to 2020. It examined the correlation between two vegetation indices of NDVI (normalized difference vegetation index) and EVI2 (enhanced vegetation index) and maize yield. The range of maize damage was delineated by analyzing the difference in vegetation indices between normal and disaster years. Furthermore, Sentinel-2 data was incorporated to classify maize yield extinction and reduction grades in the affected areas using supervised classification of remote sensing images and the natural breakpoint technique. The study ultimately assessed the extent of maize damage in Baoding City. The results indicated that: 1) NDVI was strongly positively correlated with maize yield, with a correlation coefficient of 0.84 (P<0.01), demonstrating its suitability for maize yield inversion. 2) Spectral analysis revealed varying degrees of maize yield reduction across Baoding. The eastern part of the city (Zhuozhou and Gaobeidian) experienced the most severe yield reductions, while the central and southern parts of the city were less affected. 3) The “23-7” flood disaster caused maize yield extinction over an area of 45 000 hectares in Baoding, representing about 5% of the total farmland. Additionally, approximately 66% of the farmland experienced yield reductions, highlighting the widespread impact of the disaster. This study underscored the importance of leveraging remote sensing technology and cloud-based platforms like GEE for improving agricultural resilience in the face of increasing climate variability and extreme weather events, and provides a rapid and reliable methodological framework for assessing maize damage from heavy rainfall and mapping damage distribution. It offers valuable insights for large-scale crop damage assessments and serves as a reference for future disaster response efforts.

     

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