Small Regional Geohazards Susceptibility Mapping Based on Geomorphic Unit
Received date: 2014-03-27
Request revised date: 2014-07-20
Online published: 2015-01-15
Copyright
The assessment of geological disasters mainly includes susceptibility assessment, hazard assessment, vulnerability assessment and risk assessment. The first two just reflect the geological disasters’ nature characteristics and theirs’ dangerous levels, what’s more, the remaining additionally describe geological disasters’ social characteristics and social potential losses on the basis of the first two. Actually, the susceptibility and hazard assessment could trace back to the 1970s, meanwhile, with the rapid development of GIS technology and high precision geotechnical physical model after 1990s, the research about geological disasters’ dangerous levels also step into a rapid development stage. On the whole, susceptibility assessment of geological disasters statically reflect the probability of geological disasters’ occurrence in view of the basic geological environmental conditions (internal control factors). On the other way, hazard assessment of geological disasters additionally takes external factors (time probability etc.) into account and responds the probability of geological disasters’ occurrence. Thus it can be seen that susceptibility assessment is the most fundamental research work in hazard or risk assessment and directly describes geological disasters’ inoculation situation. Nowadays, with the popularization and deepening of regional geological disaster risk assessment and zoning work, in view of small area, especially for small mountainous area or small populated area, the susceptibility assessment to geological disasters becomes increasingly urgent and important. Based on the above situation, this article takes Wenchuan County surrounding area as the study object, taking grid unit and geomorphic unit as evaluation unit, using information value method and logistic regression method to take an analysis on the susceptibility zoning. According to the results of comparative analysis, in a small area, susceptibility zoning with geomorphic unit not only can better reflect the local comprehensive characters, make the evaluation results more close to the actual geological disasters distribution, but could get clear hierarchical level, and more effective for the application of the mathematical model. The conclusions is: in a small area, it will have a good applicability and plasticity for the susceptibility zoning which is based on the geomorphic unit and it is a beneficial attempt and inspiration for the geological disasters susceptibility mapping in the large scale.
TANG Chuan , MA Guo-chao . Small Regional Geohazards Susceptibility Mapping Based on Geomorphic Unit[J]. SCIENTIA GEOGRAPHICA SINICA, 2015 , 35(1) : 91 -98 . DOI: 10.13249/j.cnki.sgs.2015.01.91
Fig.1 The units in study area图1 研究区单元划分 |
Table 1 Factor classification and index calculation (grid unit)表1 因子分级与指标计算(栅格单元) |
评价因子 | 分级 | Si(km2) | Si/S (%) | Ni(km2) | Ni/N(%) | Ni/Si | I1 | I2 |
---|---|---|---|---|---|---|---|---|
坡度(°) | 0-15 | 3.646 | 12.76 | 0.156 | 6.13 | 0.0428 | -0.7326 | 0.1044 |
15-30 | 10.165 | 35.57 | 0.406 | 15.96 | 0.0399 | -0.8014 | 0.0974 | |
30-45 | 11.605 | 40.61 | 1.284 | 50.47 | 0.1106 | 0.2175 | 0.2699 | |
>45 | 3.164 | 11.07 | 0.698 | 27.44 | 0.2206 | 0.9076 | 0.5381 | |
高程(m) | 1320-1630 | 9.415 | 32.94 | 1.531 | 60.18 | 0.1626 | 0.6026 | 0.5005 |
1630-1985 | 9.178 | 32.11 | 0.509 | 20.01 | 0.0555 | -0.4731 | 0.1707 | |
1985-2408 | 6.894 | 24.12 | 0.315 | 12.38 | 0.0457 | -0.6669 | 0.1406 | |
2408-3200 | 3.093 | 10.82 | 0.189 | 7.43 | 0.0611 | -0.3762 | 0.1881 | |
距河流距离(m) | <500 | 7.026 | 24.58 | 1.262 | 49.61 | 0.1796 | 0.7020 | 0.7484 |
>500 | 21.554 | 75.42 | 1.282 | 50.39 | 0.0595 | -0.4032 | 0.2478 | |
距断层距离(km) | >1 | 4.371 | 15.29 | 0.25 | 9.83 | 0.0572 | -0.4423 | 0.3813 |
<1 | 24.209 | 84.71 | 2.294 | 90.17 | 0.0948 | 0.0625 | 0.6317 | |
地表形态 | 凸 | 16.532 | 57.84 | 1.149 | 45.17 | 0.0695 | -0.2474 | 0.3658 |
凹 | 12.048 | 42.16 | 1.395 | 54.83 | 0.1158 | 0.2630 | 0.6094 | |
工程岩组 | 软弱岩体 | 9.567 | 33.47 | 1.787 | 70.24 | 0.1868 | 0.7412 | 0.6441 |
较软弱岩体 | 11.198 | 39.18 | 0.516 | 20.28 | 0.0461 | -0.6584 | 0.1589 | |
较坚硬岩体 | 4.007 | 14.02 | 0.099 | 3.89 | 0.0247 | -1.2817 | 0.0852 | |
坚硬岩体 | 3.808 | 13.32 | 0.142 | 5.58 | 0.0373 | -0.8701 | 0.1286 |
Table 2 Factor classification and index calculation (geomorphic unit)表2 因子分级与指标计算(地貌单元) |
评价因子 | 分级 | Si(km2) | Si/S (%) | Ni(km2) | Ni/N(%) | Ni/Si | I1 | I2 |
---|---|---|---|---|---|---|---|---|
平均坡度(°) | 0-15 | 1.891 | 6.62 | 0.027 | 1.06 | 0.0143 | -1.830 | 0.0398 |
15-30 | 11.487 | 40.19 | 0.732 | 28.77 | 0.0637 | -0.334 | 0.1776 | |
30-45 | 14.289 | 50.00 | 1.633 | 64.19 | 0.1143 | 0.250 | 0.3185 | |
>45 | 0.913 | 3.19 | 0.152 | 5.97 | 0.1665 | 0.626 | 0.4640 | |
相对高差(m) | 0-250 | 2.438 | 8.53 | 0.051 | 2.00 | 0.0209 | -1.448 | 0.0513 |
250-500 | 9.982 | 34.93 | 0.900 | 35.38 | 0.0902 | 0.013 | 0.2212 | |
500-750 | 11.618 | 40.65 | 1.159 | 45.56 | 0.0998 | 0.114 | 0.2448 | |
750-1000 | 3.335 | 11.67 | 0.308 | 12.11 | 0.0924 | 0.037 | 0.2266 | |
>1000 | 1.207 | 4.22 | 0.126 | 4.95 | 0.1044 | 0.159 | 0.2561 | |
地貌形态 | 平 | 0.887 | 3.10 | 0.017 | 0.67 | 0.0192 | -1.536 | 0.0975 |
凹 | 11.904 | 41.65 | 0.836 | 32.86 | 0.0702 | -0.237 | 0.3574 | |
凸 | 15.789 | 55.24 | 1.691 | 66.47 | 0.1071 | 0.185 | 0.5450 | |
距河流距离 | <500 m的单元 | 2.487 | 8.70 | 0.136 | 5.35 | 0.0547 | -0.487 | 0.1983 |
两者间的单元 | 9.287 | 32.49 | 1.615 | 63.48 | 0.1739 | 0.670 | 0.6305 | |
>500 m的单元 | 16.806 | 58.80 | 0.793 | 31.17 | 0.0472 | -0.635 | 0.1711 | |
距断层距离 | <1 km的单元 | 17.756 | 62.13 | 1.925 | 75.67 | 0.1084 | 0.197 | 0.4238 |
两者间的单元 | 9.925 | 34.73 | 0.535 | 21.03 | 0.0539 | -0.502 | 0.2107 | |
>1 km的单元 | 0.899 | 3.15 | 0.084 | 3.30 | 0.0934 | 0.049 | 0.3653 | |
工程岩组 | 软弱岩体 | 14.837 | 51.91 | 1.850 | 72.72 | 0.1247 | 0.337 | 0.4073 |
较软弱岩体 | 0.811 | 2.84 | 0.055 | 2.16 | 0.0678 | -0.272 | 0.2216 | |
较坚硬岩体 | 8.497 | 29.73 | 0.283 | 11.12 | 0.0333 | -0.983 | 0.1088 | |
坚硬岩体 | 4.435 | 15.52 | 0.356 | 13.99 | 0.0803 | -0.103 | 0.2622 |
注:表1-2中,Si、S、Ni、N均与公式3-4相对应;I1、I2分别指信息量值与逻辑回归指标值,I2是由Ni/ Si线性归一化所得。 |
Table 3 Logistic regression coefficient表3 逻辑回归系数 |
单元格式 | 常数项 | 坡度 | 工程岩组 | 地貌形态 | 距河流距离 | 距断层距离 | 相对高差/高程 |
---|---|---|---|---|---|---|---|
栅格单元 | -5.950 | 3.720 | 1.990 | -0.338 | 1.185 | 1.755 | 2.728 |
地貌单元 | -1.849 | 6.614 | 2.328 | -2.539 | 3.971 | -1.111 | -1.643 |
Fig.2 The susceptibility zoning in study area图2 研究区易发性分区 |
Fig.3 The comparison of regional assessment图3 区域评价比较 |
Fig.4 Actual geological disasters distribution proportion图4 已发地质灾害分布比例 |
Fig.5 The statistics of susceptibilityzoning图5 易发分区统计 |
The authors have declared that no competing interests exist.
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