陆表切割密度(Land Dissection Density,LDD)的空间格局与陆地表面土壤侵蚀息息相关,国内相关研究主要基于流域或局地尺度分析黄土高原和东北地区的陆表切割情况,全国尺度上陆表切割情况仍未知。该文基于ALOS World 3D-30 m DEM数据和...陆表切割密度(Land Dissection Density,LDD)的空间格局与陆地表面土壤侵蚀息息相关,国内相关研究主要基于流域或局地尺度分析黄土高原和东北地区的陆表切割情况,全国尺度上陆表切割情况仍未知。该文基于ALOS World 3D-30 m DEM数据和全国二级流域数据,利用Geomorphons地形元素分类方法制成全国陆表切割密度分布图,并结合地貌区划分析各地貌区内不同等级切割密度的分布情况。结果显示:全国二级流域的陆表切割密度介于0~7 km/km^(2)之间,强烈切割(3~<5 km/km^(2))流域面积约占国土面积的0.54%;切割密度与流域地形因素密切相关,缓斜坡(2°<~5°)、高丘陵和小起伏山地(100~400 m)以及低海拔(<1000 m)地区是切割易发区;一级地貌大区间的切割密度空间格局差异显著,中度及以上切割(LDD≥2 km/km^(2))流域空间分布呈现出不同模式,体现了地貌区内外营力的共同作用;陆表切割易发生在受剥蚀外营力作用影响的二级地貌区,且不同等级切割密度在不同地貌类型上具有一定聚集性。研究结果可拓展现有陆表切割研究的空间尺度,为宏观层面的陆表切割现状和全国各地土壤侵蚀评估提供科学依据。展开更多
An inventory of topographic modifications is essential to addressing their impacts on hydrological and morphological processes in human-altered watersheds.However,such inventories are generally lacking.This study pres...An inventory of topographic modifications is essential to addressing their impacts on hydrological and morphological processes in human-altered watersheds.However,such inventories are generally lacking.This study presents two workflows for semi-automatic detection of linear earthen runoff and erosion control berms in rangelands using high-resolution topographic data.The workflows consist of initial object identification by applying either morphological grayscale reconstruction(MGR)or the Geomorphon(GEO)method,followed by identification refinements through filters based on objects’horizontal and vertical information.Three sites were selected within the Altar Valley,Arizona,in the southwestern United States.One site was used for developing workflows and optimizing filter thresholds,and the other two sites were used to validate workflows.The results showed that:1)The MGR-based workflow methodology could produce final precision and detection rates of up to 92%and 75%,respectively,and take less than 5 s for a 10.1 km^(2) site;2)The workflow based on the MGR method yielded greater identification accuracy than did the GEO workflow;3)Object length,orientation,and eccentricity were important characteristics for identifying earthen berms,and are sensitive to general channel flow direction and berm shape;4)Manual interrogation of topographic data and imagery can significantly improve identification precision rates.The proposed workflows will be useful for developing inventories of runoff and erosion control structures in support of sustainable rangeland management.展开更多
文摘An inventory of topographic modifications is essential to addressing their impacts on hydrological and morphological processes in human-altered watersheds.However,such inventories are generally lacking.This study presents two workflows for semi-automatic detection of linear earthen runoff and erosion control berms in rangelands using high-resolution topographic data.The workflows consist of initial object identification by applying either morphological grayscale reconstruction(MGR)or the Geomorphon(GEO)method,followed by identification refinements through filters based on objects’horizontal and vertical information.Three sites were selected within the Altar Valley,Arizona,in the southwestern United States.One site was used for developing workflows and optimizing filter thresholds,and the other two sites were used to validate workflows.The results showed that:1)The MGR-based workflow methodology could produce final precision and detection rates of up to 92%and 75%,respectively,and take less than 5 s for a 10.1 km^(2) site;2)The workflow based on the MGR method yielded greater identification accuracy than did the GEO workflow;3)Object length,orientation,and eccentricity were important characteristics for identifying earthen berms,and are sensitive to general channel flow direction and berm shape;4)Manual interrogation of topographic data and imagery can significantly improve identification precision rates.The proposed workflows will be useful for developing inventories of runoff and erosion control structures in support of sustainable rangeland management.
