贵南铁路建设对荔波-环江喀斯特世界自然遗产地地貌价值的影响

基于"3S"技术,结合水文、地质地貌等野外考察,围绕喀斯特水动力效应、地貌响应及缓冲区的缓冲作用进行分析,探讨了贵南铁路对荔波-环江喀斯特世界自然遗产地地貌价值的影响。结果表明:1)贵南铁路线路穿过荔波-环江喀斯特的缓冲区,未穿过遗产地,对遗产地地貌价值无直接影响;2)线路以桥梁、隧道、路基的形式穿过缓冲区,以桥梁形式跨过遗产地上游地表河与地下河,河中不设桥墩,基本不影响遗产地上游水质水量;缓冲区的九万大山二号隧道可能使缓冲区隧区降深漏斗带内地下水位降低,但对遗产地的水文地质条件和喀斯特作用过程的影响极小;位于缓冲区的路基出露处均为非喀斯特地貌,不影响遗产地喀斯特地貌;3)遗产地大、小七孔与茂兰-环江2个片区分属不同的水文地质单元,无统一的地下水水力联系,贵南铁路对遗产地2个片区之间地下水水力联系及喀斯特作用过程无影响;4)线路将影响缓冲区的13个峰丛洼地共计面积5.32 km2,占缓冲区总面积的1.22%,基本不影响缓冲区的缓冲作用。

Impact of Guinan Railway Construction on the Geomorphologic Value of the Libo-Huanjiang Karst World Heritage Site

The relationship between protection of an outstanding universal value and regional development and utilization has always been an important aspect of World Heritage protection and management. As an important component of South China Karst, the Libo-Huanjiang karst World Heritage property was listed on the World Heritage list for its outstanding geomorphologic and aesthetic value, meaning that it should be protected by all the world. Its outcropped carbonate rocks developed in different geological ages and formed remarkable fengcong (cone karst) and fenglin (tower karst), which shows the change and evolution of landform between fengcong and fenglin. Guinan Railway, from Guiyang to Nanning in China, which will pass through the buffer zone of Libo-Huanjiang karst, is planning to be constructed for the display and community development of the world heritage property, as well as the poverty alleviation of the buffer zone (as peripheral coordination area of a world heritage property to reduce the adverse effects caused by human activities outside the area). The area of the property and its buffer zone are 366.47 km2 and 479.28 km2, respectively. This study used 3S technology and field studies to assess the impact of Guinan Railway construction on the hydrology, geology, and landforms of the area with regard to its geomorphologic value and the potential effects of the buffer zone. The results indicated that: 1) Carbonate rocks are continuously distributed throughout the property and its buffer zone; karst systems are obvious and support many springs. Underground rivers are mainly distributed in fengcong-valley, fenglin-valley, and depression landscapes. The area’s special hydrogeological conditions are represented by typical geomorphological types such as fengcong karst and fenglin karst as well as active groundwater features. 2) The Guinan Railway will pass through the buffer zone of the property, though not through the property itself, so will not directly influence its geomorphological value. The Chaoyang Tunnel will be located within the upper reach of the buffer zone, and the its capture rate of the Di’e River during construction is expected to be 0.88%. Although this is predicted to have little effect on groundwater flow diversion from the Di’e River, monitoring and management of the Chaoyang Tunnel will be indispensable. 3) The railway route is designed to cross the buffer zone via bridges, tunnels, and subgrades. All the bridges are designed to cross rivers without support piers, avoiding impacts to water quality and quantity. The Jiuwandashan No.2 Tunnel may reduce the groundwater level within its cone of depression, but would have little influence on the property’s hydrogeological conditions and karst processes. The exposed subgrades will cross non-karst landforms, having no effect on karst landforms within the property. 4) The hydrogeological units of the Da-xiaoqikong and Maolan-Huanjiang components, the two parts of Libo-Huanjiang karst, are different, with no unified groundwater hydraulic connection, so the Guinan Railway would not affect groundwater hydraulic connections and karst processes. 5) The railway route would affect 13 fengcong-depression sites with an area of 5.32 km², accounting for 1.22% of the total area of the buffer zone. Therefore, it would have little influence on the zone’s buffering effect.6) The existence of the buffer zone protects the geomorphologic value of the property from potential impacts of Guinan Railway construction, as a buffer zone is meant to do. However, due to unique connections between changes in karst water environments and karst landform evolution, further research on the hydrogeological processes at karst-related natural World Heritage sites and the evolution of karst landforms is still needed. In addition, the monitoring and management of railway projects during the construction and operation periods should be strengthened.