基于像元二分法的白龙江流域植被覆盖度与滑坡时空格局分析

Analysis on spatial-temporal patterns of the vegetation coverage and landslides in Bailongjiang River Basin based on the Dimidiate Pixel Model

白龙江流域影响滑坡形成的主要因素包括地质构造、地形地貌、水文、气象、植被和人工干扰等,其中地表植被作为滑坡形成的主要外在因素对滑坡的形成和发展具有重要的作用,已引起学术界的广泛关注.以植被覆盖度为主要度量指标,选择2002,2005,2008,2011年4个时段的遥感NDV I值,在改进像元二分法的基础上,探讨了近10年来该流域地表植被覆盖度及其变化特征,并分析了其与滑坡点空间格局的关系.结果表明:该流域植被覆盖度总体变化微弱,但区域内部植被覆盖度变化具有明显的空间异质性,其中低覆盖区域覆盖度呈明显的增加趋势;而历年来,该流域植被覆盖度高的地区滑坡点密度均较低,滑坡点占总滑坡的20.6%,空间分布呈离散状态,而植被覆盖度低的地区滑坡密度较高,滑坡点占总滑坡的34.5%,空间分布主要呈聚集状态,说明白龙江流域植被覆盖度与滑坡点密度呈现负相关关系,植被覆盖度的高低是滑坡发生的一个主要影响因素.研究表明,近10年来,该流域低植被覆盖区域的植被覆盖度增加较快,说明在国家实施退耕还林还草政策后,该流域植被恢复较快,生态脆弱程度减轻,这将为地方防治滑坡灾害的发生起到积极的推动作用.本研究结论可为全流域制定宏观尺度上的滑坡生态防治策略提供科学依据.

Bailongjiang River Basin is one of the high incidence areas of geologic hazards in China, where landslides are widely distributed, which has a serious harmful effect on people’s life, property and local economic development. The main factors affecting the formation of a landslide includes its geological structure, landform, hydrology, meteorology, vegetation and artificial interference, etc. As one of the main external factors for landslide formation, vegetation plays an important role in the formation and development of landslides, which has attracted extensive attention from academic circles. The characteristics of vegetation coverage and its variations in recent 10 years were discussed here, based on the dimidiate pixel model with N DV I in 2002, 2005, 2008, 2011, and then their correlation with landslide was analyzed. The results showed that the changes in vegetation coverage had been generally small but in the region, it presented an obvious spatial heterogeneity, meaning that the low coverage regions thereof showed a trend of obvious increases. And over the years, the density of landslides had been low in regions with a high vegetation coverage, which accounted for 20.6% of the total landslides; and the density of landslides was high in regions with a low vegetation coverage, which accounted for 34.5% of the total landslides. All above showed that there is a negative correlation between the vegetation coverage and the density of landslides in Bailongjiang River Basin, and the vegetation coverage is one of the main influence factors to the formation of a landslide. The research showed that in recent 10 years, the vegetation coverage have been increasing quickly in regions with a low vegetation coverage at first, which means that after the implementation of the policy of returning farmland to forest and grass, the vegetation has recovered quickly and the ecological environment improved, which will play a positive role in the prevention and control of local landslides. The conclusion of this research will provide a scientific basis for landslide prevention strategies in the whole river basin.