| In the context of the development of the global warming and frequent human activities,permafrost degradation in the Qinghai-Tibet Plateau (QTP) is serious. Thermokarst lake, as one ofthe most typical thermal hazards, is also an important symbol of permafrost degradation. From theview of the aspects of environment and engineering, the effects of thermokarst lake to them aretypical and direct. In order to study thermokarst lakes in QTP in this thesis, a typical zone fromXiushuihe to Fenghuoshan along the Qinghai-Tibet Railway (QTR) and the Qinghai-TibetHighway (QTH) was selected to analyze the distribution and developing characteristics of thethermokarst lakes. From the perspective of disaster and geography, the works were based on theanalysis of aviation and spaceflight remote sensing data in different periods and monitoring thetypical zones. The conditions and factors influencing the thermokarst lake sensitivity, space-timeevolution characteristics of the thermokarst lakes were analyzed on the basis of GIS platform.Then the evaluation method of sensitivity was established and sensitivity evaluation of thethermokarst lakes was realized. In order to understand the space-time evolution laws of thethermokarst lakes more than40years, the development process of a typical lake, named BLH–A,and its development trend were studied through aviation images. The works might providereference for coordination and sustainable development planning and strategy implementationbetween the environment and local project in QTP. The main conclusions are as follows.(1) The processing methods on QuickBird satellite image data with a resolution of0.6m in2006and the SPOT-5satellite image data with a resolution of2.5m in2010in the study areawere discussed. Focusing on fusion, correct and mosaic processing methods on thermokarst lakedominance, a better interpretation method of thermokarst lake was explored. According to theinterpretation marks of the thermokarst lakes, remote sensing data was interpreted, andinformation of thermokarst lakes was obtained.(2) Six factors, including the type of permafrost, the ground temperature, vegetation type, soiltype, hydrogeological conditions and slope angle were selected to statistically analyze thedistribution of the thermokarst lake. After the analysis and evaluation of statistical results, usingthe mathematical statistics for the factors, the sensitive coefficient of each factor was calculatedand the results were evaluated. Finally, the sensitivity value of each factor was obtained through the average method. And the forming conditions of the thermokarst lakes were compared based onthe analysis of the sensitive factors. Then59comprehensive sensitivity coefficient indices indifferent geological environment in the study area were obtained, which provided the basis for thespace evolution analysis of the thermokarst lakes.(3) In order to investigate the developing trend of the thermokarst lakes, a lake located in theBeiluhe Basin (named BLH-A) was dynamically monitored through remote sensing and fieldinvestigation. According to remote sensing images in1969,1999,2006,2008and2010, the areaof the BLH–A was increasing with the growth of0.35%from1969to1999, and then the rateincreased with time. Under the background of the global climate warming, the area was growingfaster and faster over time: the growth rate was0.42%from1999to2006,0.44%from2006to2008, and0.49%from2008to2010. And the expansion trend of the lake was also increasing.From1969to1999the dilation rate of the lake was0.42m/a. After1999the rate was around0.6m/a, and was up to0.65m/a after2008. Through calculation, the BLH–A expanded51.8mtoward QTR in41years, which would do damage to the roadbed of QTR. This result wasconsistent with field monitoring data, which showed that the shore of the lake collapsed and fellback constantly. From August2007to October2010, all the monitoring points along the lakeshoredrew back more than0.6m, with the maximum of3.2m.(4) In order to analyze the evolvement law of Thermokarst Lake with the change of the timein41years from1969to2010, or before and after the Qinghai-Tibet highway and theQinghai-Tibet railway construction, combining with the geological environment sensitivity factorsand images of remote sensing dynamic monitoring project to Thermokarst Lake. The results showthat, during the41years, with increasing the PDmn, the total area of the thermokarst lakes and theannual growth rate increase accordingly. In addition, in the first30years, they grow slow;however, the number and the total area of the thermokarst lakes grow faster after the finishing ofthe Qinghai-Tibet railway construction. Moreover, the results forecast that the area of the totalthermokarst lakes will become doubling in the near50years, which is4.5%of the study area.After100years, the area will almost achieve five fold than that in2010, which could be10.0%ofthe study area. |
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