文章基于归一化水体指数(normalized difference water index,NDWI),利用2014—2023年Landsat8-OLI和Sentinel-2卫星遥感数据制作哈素海水域面积图像,对2014—2023年哈素海水域面积变化及其与气象因素关系进行研究。结果表明:哈素海水...文章基于归一化水体指数(normalized difference water index,NDWI),利用2014—2023年Landsat8-OLI和Sentinel-2卫星遥感数据制作哈素海水域面积图像,对2014—2023年哈素海水域面积变化及其与气象因素关系进行研究。结果表明:哈素海水域整体面积多年维持在30 km^(2)左右,明水区与水生植物覆盖区(主要是芦苇)各占一半。从2015年起,在积极的人工干预下,水域面积从2014年的12.87 km^(2)增加到2023年的15.43 km^(2)。气象要素与哈素海水域小气候产生相互作用:一是降水、高温(蒸发)等因素对哈素海水域面积变化有较大影响;二是哈素海具有平缓极端气温,增加相对湿度和降水量的作用;三是哈素海对区域风速有一定影响,水域内风速较周边陆地偏大。展开更多
以位于我国不同地区的15个湖泊为研究区域,基于高分一号(GF-1)卫星遥感影像计算归一化水体指数(normalized difference water index,NDWI),在此基础上分别采用迭代法、大津法和直方图双峰法选取分割阈值及提取水体信息,并分析3种方法的...以位于我国不同地区的15个湖泊为研究区域,基于高分一号(GF-1)卫星遥感影像计算归一化水体指数(normalized difference water index,NDWI),在此基础上分别采用迭代法、大津法和直方图双峰法选取分割阈值及提取水体信息,并分析3种方法的阈值选取结果及水体信息提取结果。研究结果表明:迭代法与大津法选取的阈值相近,与直方图双峰法选取的阈值相差较大;迭代法选取阈值的效率较高;直方图双峰法的提取精度最优,其提取的水域面积与参考面积拟合的效果最好。该研究可为GF-1影像的精准水体提取提供自适应阈值分割方法的选取策略。展开更多
The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography,which primarily consists of steep slopes and mountainous areas.Further...The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography,which primarily consists of steep slopes and mountainous areas.Furthermore,climate change frequently exposes this basin to drought,which negatively affects soil and water conservation.However,recent studies have rarely shown how soil reacts to drought,such as soil erosion.Therefore,the purpose of this study is to evaluate the relationship between drought and soil erosion in the Langat River Basin.We analyzed drought indices using Landsat 8 satellite images in November 2021,and created the normalized differential water index(NDWI)via Landsat 8 data to produce a drought map.We used the revised universal soil loss equation(RUSLE)model to predict soil erosion.We verified an association between the NDWI and soil erosion data using a correlation analysis.The results revealed that the southern and northern regions of the study area experienced drought events.We predicted an average annual soil erosion of approximately 58.11 t/(hm^(2)·a).Analysis of the association between the NDWI and soil erosion revealed a strong positive correlation,with a Pearson correlation coefficient of 0.86.We assumed that the slope length and steepness factor was the primary contributor to soil erosion in the study area.As a result,these findings can help authorities plan effective measures to reduce the impacts of drought and soil erosion in the future.展开更多
2022年6月北江流域遭遇百年一遇特大洪水,对下游江心洲的形态与植被覆盖产生了显著影响。研究基于2022年多时相哨兵2号遥感影像及实测河道地形数据,结合归一化差分水体指数(Normalized Difference Water Index,NDWI)和归一化差分植被指...2022年6月北江流域遭遇百年一遇特大洪水,对下游江心洲的形态与植被覆盖产生了显著影响。研究基于2022年多时相哨兵2号遥感影像及实测河道地形数据,结合归一化差分水体指数(Normalized Difference Water Index,NDWI)和归一化差分植被指数(Normalized Difference Vegetation Index,NDVI),分析了北江下游芦苞浅段5个江心洲的平面形态、断面地形、NDVI均值及植被覆盖的年内演变特征。结果表明:洪水期间各江心洲面积与周长均显著减小,其中未建土堤的中间洲、芦苞洲和太监洲面积减少幅度更大,分别达55.4%、69.0%和66.4%。河道断面地形显示洪水后主河槽以轻微淤积为主,江心洲高程未发生显著变化。建堤江心洲(邓塘洲、四姓洲)堤内植被受洪水影响较小,NDVI均值在洪水后仍保持较高水平,而江心洲堤外及未建堤江心洲植被面积普遍减少32.5%~74.4%。研究分析了特大洪水对北江下游芦苞浅段江心洲形态及植被覆盖的差异化影响,为区域河道治理与生态修复提供了科学依据。展开更多
文摘以位于我国不同地区的15个湖泊为研究区域,基于高分一号(GF-1)卫星遥感影像计算归一化水体指数(normalized difference water index,NDWI),在此基础上分别采用迭代法、大津法和直方图双峰法选取分割阈值及提取水体信息,并分析3种方法的阈值选取结果及水体信息提取结果。研究结果表明:迭代法与大津法选取的阈值相近,与直方图双峰法选取的阈值相差较大;迭代法选取阈值的效率较高;直方图双峰法的提取精度最优,其提取的水域面积与参考面积拟合的效果最好。该研究可为GF-1影像的精准水体提取提供自适应阈值分割方法的选取策略。
文摘The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography,which primarily consists of steep slopes and mountainous areas.Furthermore,climate change frequently exposes this basin to drought,which negatively affects soil and water conservation.However,recent studies have rarely shown how soil reacts to drought,such as soil erosion.Therefore,the purpose of this study is to evaluate the relationship between drought and soil erosion in the Langat River Basin.We analyzed drought indices using Landsat 8 satellite images in November 2021,and created the normalized differential water index(NDWI)via Landsat 8 data to produce a drought map.We used the revised universal soil loss equation(RUSLE)model to predict soil erosion.We verified an association between the NDWI and soil erosion data using a correlation analysis.The results revealed that the southern and northern regions of the study area experienced drought events.We predicted an average annual soil erosion of approximately 58.11 t/(hm^(2)·a).Analysis of the association between the NDWI and soil erosion revealed a strong positive correlation,with a Pearson correlation coefficient of 0.86.We assumed that the slope length and steepness factor was the primary contributor to soil erosion in the study area.As a result,these findings can help authorities plan effective measures to reduce the impacts of drought and soil erosion in the future.
