Forest fires in Algeria are ravaging an average of more than 32,000 hectares annually despite the prevention and control plan put in place. They are the most damaging factor of degradation of the forest and weigh heav...Forest fires in Algeria are ravaging an average of more than 32,000 hectares annually despite the prevention and control plan put in place. They are the most damaging factor of degradation of the forest and weigh heavily on the environment and the local economy. Conventional methods for fire prevention and control are time consuming and are not always reliable in view of the complexity and diversity of forest ecosystems. The main idea behind this study is to use the GIS and remote sensing for the development of a fire risk map of the Khoudida State Forest (Algeria). The approach adopted involves three parameters that control the fire behavior, which are: the top-morphology of the field, the combustibility of the plant cover and hazards. For each factor its correlation with risk was evaluated;the combination of the slope, altitude and exposure parameters in the topo-morphological index and the hazard map made it possible to evaluate the average risk for an area of more than 2132 hectares, 1521 hectares high and only 493 hectares, respectively 51.4%, 36.7% and 11.9%.展开更多
为了提升地质灾害易发性评价的精度,以浙江省杭州市富阳区为研究区,提出了考虑缓冲区优化策略的随机森林地质灾害易发性评价方法。首先,选取归一化植被指数、距道路距离、距断层距离、汛期降雨量、坡度、坡向、起伏度、距水系距离和岩性...为了提升地质灾害易发性评价的精度,以浙江省杭州市富阳区为研究区,提出了考虑缓冲区优化策略的随机森林地质灾害易发性评价方法。首先,选取归一化植被指数、距道路距离、距断层距离、汛期降雨量、坡度、坡向、起伏度、距水系距离和岩性共9个评价因子,通过多重共线性分析确保因子的独立性。其次,构建0.5、1、1.5、2 km 4种缓冲区范围,以随机采样方法生成负样本点,避免正负样本交叉污染,提高样本代表性和模型的区分能力,并增设一组无缓冲区的随机采样点作为参照。接着,采用随机森林算法对地质灾害易发性模型进行训练和测试,结果表明缓冲区优化策略能够显著提升模型预测精度,且缓冲区的设定存在最优边界。其中,1 km缓冲区对应的模型AUC(area under curve)值最高为0.815,表明该缓冲区设定下采集的负样本能够更加准确地区分地质灾害特征。最后,基于最优缓冲区与随机森林算法(random forest,RF)模型的易发性评价结果,高易发区主要集中在西北部和东南部的山区地带,且频率比随着易发性等级升高而不断增大,验证了这一方法的科学性,可为富阳区的地灾防治工作提供依据。展开更多
文摘Forest fires in Algeria are ravaging an average of more than 32,000 hectares annually despite the prevention and control plan put in place. They are the most damaging factor of degradation of the forest and weigh heavily on the environment and the local economy. Conventional methods for fire prevention and control are time consuming and are not always reliable in view of the complexity and diversity of forest ecosystems. The main idea behind this study is to use the GIS and remote sensing for the development of a fire risk map of the Khoudida State Forest (Algeria). The approach adopted involves three parameters that control the fire behavior, which are: the top-morphology of the field, the combustibility of the plant cover and hazards. For each factor its correlation with risk was evaluated;the combination of the slope, altitude and exposure parameters in the topo-morphological index and the hazard map made it possible to evaluate the average risk for an area of more than 2132 hectares, 1521 hectares high and only 493 hectares, respectively 51.4%, 36.7% and 11.9%.
文摘为了提升地质灾害易发性评价的精度,以浙江省杭州市富阳区为研究区,提出了考虑缓冲区优化策略的随机森林地质灾害易发性评价方法。首先,选取归一化植被指数、距道路距离、距断层距离、汛期降雨量、坡度、坡向、起伏度、距水系距离和岩性共9个评价因子,通过多重共线性分析确保因子的独立性。其次,构建0.5、1、1.5、2 km 4种缓冲区范围,以随机采样方法生成负样本点,避免正负样本交叉污染,提高样本代表性和模型的区分能力,并增设一组无缓冲区的随机采样点作为参照。接着,采用随机森林算法对地质灾害易发性模型进行训练和测试,结果表明缓冲区优化策略能够显著提升模型预测精度,且缓冲区的设定存在最优边界。其中,1 km缓冲区对应的模型AUC(area under curve)值最高为0.815,表明该缓冲区设定下采集的负样本能够更加准确地区分地质灾害特征。最后,基于最优缓冲区与随机森林算法(random forest,RF)模型的易发性评价结果,高易发区主要集中在西北部和东南部的山区地带,且频率比随着易发性等级升高而不断增大,验证了这一方法的科学性,可为富阳区的地灾防治工作提供依据。
