| The Palongzangbu basin of southeastern Tibet influenced by the Indian Ocean air current and southwest monsoon, valley marine glacier developed, and regional geological structure is complex, fault developed, earthquake is frequent. Because of the high temperature and rainfall, glacial debris flow developed in the basin,and they caused serious property losses, washed out road18, such as Guxiang gully,Midui gully, Peilong gully etc.. On the basis of previous studies, sensing images is remote to extract information of debris flow through multi-source for studying the characteristics of typical gully. Disaster chain model of debris flow is studied from the perspective of remote sensing, and then it can provide data and theoretical for the basis early warning forecast of Palongzangbu basin.This thesis is based on the ministry of land and resource’s research which is disaster chain distribution law and risk of southeast of qinghai-tibet plateau area. Depend on field investigation and indoor analysis of remote sensing, the analysis of debris flow disaster chain in Palongzangbu based on remote sensing is finished, conclusion is as follows:(1) According to Palongzangbu debris flow disaster chain research, the study area’s topography and geomorphology, geological environment, climate conditions are analyzed in this paper, combined the technology of RS and GIS platform of integral information extraction and analysis, on the basis of the overall research to analysis the typical debris flow for further, for Palongzangbu debris flow disaster chain research provides remote sensing perspective of new ideas.(2) Compared to three periods of remote sensing classification results in the study area, using the ARCGIS statistical analysis shows that in the TM images of study area in1988, the glacier area of3556.72km2, glacial lake number65, glacial lake area of6.11km2; ETM+image in2002, the glacier area of3193.09km2, lake number84, glacial lake area of5.64km; TM images in2010, the glacier area of2381.47km2, lake number112, glacial lake area of7.26km2. Glacier area from1988to2002reduced363.63km2, shrink rate is25.97km2/a,during2002-2010glacier area reduced811.62km2, annual retreat rate is101.45km2/a, overall was accelerated glacier retreat; glacial lake number from1988in65to112,1988, the area of the glacial lake in1988from6.11km2to5.64km2of2002, to the glacial lake area of growth in2010to7.26km2, glacial lake is not only accelerating state from the number to the area.(3) Base on the study of the glaciers and glacial lake changes in the study area, using ARCGIS platform to identify and statistics glacier and glacial lake which in the debris flow basin, In October1998TM remote sensing image, the debris flow basin glacier area of2068.50km2, glacial lake number43, the lake area of3.59km2; Around November2002ETM+image, debris flow basin glacier area of1187.95km2,glacial lake number46, the lake area of2.49km2;around November2010TM image, the debris flow basin glacier area of868.05km2,glacial lake number78, the lake area of3.33km2. From the point of glacier and the lake area of distribution, glaciers in left bank and right bank in many years to maintain basic balance; But the glacial lake distribution, the left bank of area the lake area and the number is greater than the right bank.(4) Compare glacier and the lake classification data from1988to2002, after14years, lake number increased from43to46, increased by2.5%, and lake area is also reduced from3.59km2to3.59km, reduced by40.16%; Glacier area reduced from2068.50km2to1187.95km2, decrease rate was42,57%, and the average withdrawal rate62.90km2/a. Compare2002to2010glacier and the lake supervised classification result, after8years, glacial lake number increased from46to78, increased by58.24%, glacial lake area increased from2.49km2to2.49km2increased by33.57%; Glacier area reduced from1187.95km2to868.05km2, decreased by26.93%, annual average withdrawal rate is39.90km2/a. From1988to2010between22years of glacier and the lake data analysis, glacier has decreased by1200.44km2, decreased by54.57%, annual average withdrawal rate is58.03km2/a; the lake number increased from43to78, increased by81.40%, the lake area from reduced3.59km2to3.33km2, fell by7.24%. Debris flow basin glacier change trend with the entire study area glaciers have almost the same change trend, all showed a trend of shrinking; glacial lake area change tendency in debris flow basin was increased after the first reduce the trend, is also consistent with the change in the study area.(5) Base on the three periods of remote sensing of the glaciers and glacial lake change analysis in the study area and debris flow, during22years glacier area constantly shrinking back in Palongzangbu basin of Tibetan southeastern, quantity and area of the lake has a tendency to increase, with the further effect of global warming and the Indian Ocean warm current, predict Palongzangbu basin glaciers will retreat further, lake of number and area will gradually increase, coupled with the influence of the heavy rain and high temperature, outbreak of debris flow is likely to further increase in the future of Palongzangbu basin.(6) Useing high resolution remote sensing interpretation, the study area with a total area of16021.12km2, interpretation found121debris flow gully, debris flow basin area of5639.55km2, accounting for35.2%of the entire study area, the overall study area belongs to the debris flow development area. By comparing debris flow gully in the Palongzangbu basin,64debris flow gully in the left bank, the right have of57debris flow gully, according to the basin area, fan area, long of gully for analysis, found that on the left bank were greater than the right, the description on the left bank debris flow is bigger than the left bank.(7)In this paper, using the ARCGIS platform to interpretation strong frost weathering zone, glacial till, rock fall and landslide source in the121debris flow gully, compared with strong frost weathering zone, rock fall and landslide source on both sides of the distribution is uniform in the Palongzangbu basin, no obvious difference; But glacial till interpretation with a total area of157.24km2, accounting for2.8%of the debris flow basin area, including the study area on the left bank interpretation in the basin is101.48km2, accounting for64.5%of the total area of glacial till, the interpretation results same to the glacier and glacial lake results corresponds to the supervised classification, proved Palongzangbu basin glacier in left bank is more activity than the right bank, strong glaciers formed more glacial till.(8) This paper has chosen three typical debris flow gully in detail of remote sensing information extraction, including Midui gully and Peilong gully are typical glacial lake outburst debris flow, Tianmo gully is a typical snowmelt and rainfall debris flow,compare four remote sensing images of glacial lake in the Midui gully the lake area from1988to2002reduced0.02km2, decrease is mainly due to glacial lake break in July1988caused outbreak of debris flow, after the lake has been reduced, in November2002to February2002lake by the previous two gradually combined into one, increasing the area of the lake, the lake area is the growth rate of 9090.91m2/a, further as temperatures rise, glaciers continue to shrink, lake area will be further expanded, Midui gully will further increase the risk of outbreaks.(9) By remote sensing information extraction and analysis of the typical debris flow gully, to divided debris flow disasters chain in Palongzangbu basin into two categories:glacial lake outbreak debris flow disaster chain and snowmelt and rainfall debris flow disaster chain. Including glacial lake outbreak debris flow disaster chain process:high temperature and rainfall->(ice-fall,avalanche formation temporarily lake or collapse directly into the lake)-> lake dam break caused floods-> glacial sediment, rock fall, landslide and channel source-> outbreak debris flow-> the fan oppression even blocked off river and formed dammed lake-> dammed lake break caused floods; Snowmelt and rainfall debris flow disaster chain process:rainfall, local temperature mutations->(ice-fall,avalanche not blocking channel)-> floods-> glacial sediment, rock fall, landslide and channel source-> outbreak debris flow-> the fan oppression even blocked off river and formed dammed lake-> dammed lake break caused floods. |
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